NOC-AE-07002240, Supplement 3 to the Response to Generic Letter 2004-02

Supplement 3 to the Response to Generic Letter 2004-02

ML080700338
Person / Time
Site:	South Texas
Issue date:	02/29/2008
From:	Rencurrel D Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
D43.02, GL-04-002, NOC-AE-07002240, TAC MC4719, TAC MC4720
Download: ML080700338 (72)

Text

Attachments 1-5 Not for Public Disclosure per 10CFR2.390 Nuclear Operating Company South Texas Pro/ect Electric GeneratingStation PR. Box 289 Wadsworth, Texas 77483 February 29, 2008 NOC-AE-07002240 10CFR50.54(f) 10CFR2.390 File No. D43.02 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 and 2 Docket Nos. STN 50-498 and STN 50-499 Supplement 3 to the Response to Generic Letter 2004-02 (TAC Nos. MC4719 and MC4720)

References:

1. Letter dated November 21, 2007, from William H. Ruland, NRC, to Anthony Pietrangelo, NEI, "Revised Content Guide for Generic Letter 2004-02 Supplemental Responses"(ML073110269, ML073110278)

2. Letter dated December 13, 2007, from David W. Rencurrel, STPNOC, to NRC Document Control Desk, "Supplement to Request for Extension for Final Response to Generic Letter 2004-02 and Implementation of Revised Design Basis for ECCS Sump (TAC Nos. MC4719 and MC4720)" (ML073580125, NOC-AE-07002249)

3. Letter dated December 19, 2007, from Mohan C. Thadani, NRC, to James J.

Sheppard, STPNOC, "South Texas Project, Units 1 And 2 - Approval Of Extension Request For Corrective Actions Re: Generic Letter 2004-02, "Potential Impact Of Debris Blockage On Emergency Recirculation During Design Basis Accidents At Pressurized Water Reactors," (TAC NOS. MC4719 AND MC4720), (ML073520076)

STP Nuclear Operating Company (STPNOC) submits this supplemental response to Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors." The enclosed response was prepared using the content guidance of Reference 1 with intent of allowing the NRC to close most of the sump debris blockage issues identifiedin GL 2004-02 for STP Units 1 and 2. Final closure is not expected until completion of testing and finalization of the design basis as described in Reference 2. As stated in Reference 2 and approved in Reference 3, STPNOC will submit a letter by June 30, 2008, verifying completion of all GL2004-02 corrective actions and confirming compliance with the regulatory requirements listed in GL2004-02.

The enclosure identifies some responses where supplemental information is to be provided. This information generally depends on the completion of the STP sump strainer testing and integration of the test results into the design. The responses will be updated with the verification letter described above.

The specific items are identified in a list of committed responses in the enclosure.

Povcerr evl-tiII'&

STI 32229932 Attachments 1-5 Not for Public Disclosure per 10CFR2.390 00ma~) (e cuef#.

,'IJ

NOC-AE-07002240 Page 2 of 3 STPNOC requests that Attachments 1 - 5 to the enclosure be withheld from public disclosure in accordance with IOCFR2.390.

If you have any questions concerning the content of this supplemental response, please contact Mr. A. W.

Harrison at (361) 972-7298, or me at (361) 972-7867.

I state under penalty of perjury that the foregoing is true and correct.

Executedon __________

avdyW Ren~curre Vice President, Engineering & Strategic Projects Awh/

Enclosure:

Supplement 3 to the Response to Generic'Letter 2004-02

NOC-AE-07002240 Page 3 of 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 760,11-8064 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Thad Hill Senior Project Manager Eddy Daniels U.S. Nuclear Regulatory Commission Marty Ryan One White Flint North (MS 7 D1) Robert Bailey 11555 Rockville Pike Steve Winn Rockville, MD 20852 NRG South Texas LP Senior Resident Inspector Ed Alarcon U. S. Nuclear Regulatory Commission J. J. Nesrsta P. 0. Box 289, Mail Code: MN1 16 R. K. Temple Wadsworth, TX 77483 Kevin Pollo City Public Service C. M.,Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs Road C. Kirksey Austin, TX 78704 City of Austin Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189

Enclosure NOC-AE-07002240 Enclosure Supplement 3 to the Response to Generic Letter 2004-02 STI 32229932 Attachments 1-5 Not for Public Disclosure per 10CFR2.390

Enclosure NOC-AE-07002240 Page 1 of 63

1. Overall Compliance Upon review of the requirements listed in Generic Letter (GL) 2004-02, STP Nuclear Operating Company (STPNOC) performed an evaluation of the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) recirculation functions. The evaluation demonstrated that modifications were needed to establish the new design basis. STPNOC has implemented these modifications to meet the required schedule as discussed below.

Plant hardware modifications developed in response to issues identified in GL2004-02 are installed in STP Units 1 and 2 and are supporting compliance with the current design and licensing basis regulatory requirements for long term cooling following a design basis loss of coolant accident. Similarly implementation is complete for STPNOC plant administrative procedures and processes needed to support the GL2004-02 hardware modifications and revised operating practices, as well as to support the assumptions, initial conditions and conclusions of GL2004-02 related evaluations, including evaluations of design basis accident debris generation and transport, sump strainer performance, impact of chemical effects and downstream effects of debris. Since hardware, operating procedures and administrative controls required to support actions taken in response to issues identified in GL2004-02 are already implemented at STP, STPNOC has high confidence that if an accident of the type described in GL2004-02 were to occur at STP, plant systems and plant operators would respond in a manner consistent with the intent of the GL2004-02 corrective actions, including conformance with the regulatory requirements listed in GL2004-02.

While STPNOC's confidence in expected operator and plant response to an accident is high, the plant design and licensing basis can not be changed until all regulatory requirements affecting associated change processes are complete. Consequently, STPNOC requested an extension to June 30, 2008 to allow full completion of 10CFR50, Appendix B activities to support completion of chemical effects head loss testing, preparation of the associated test report and changing the plant design and licensing bases to be in compliance with actions taken in response to issues identified in GL2004-02 (Reference 2 to the cover letter). The NRC approved the request in Reference 3 to the cover letter.

2. General Description of and Schedule for Corrective Actions STPNOC will implement sump design modifications to meet the required schedule as discussed below.

The design basis and licensing basis for the plant will be updated to reflect the corresponding changes due to the new regulatory requirements.

For the sump performance evaluation, STPNOC joined with other plants in the Strategic Teaming and Resource Sharing (STARS)/ Utilities Service Alliance (USA) group to engage a contractor team headed by Westinghouse Electric Co. along with Alion Science and Technology and Enercon Services, Inc.

Sump evaluation activities include the following:

• Containment walkdowns

• Debris generation and transport analysis

• Calculation of required and available net positive suction head (NPSH)

• Screen requirements

• Screen structural analyses

• Potential or planned design/operational/procedural modifications

• Downstream effects evaluation 0 Upstream effects evaluation

• Chemical effects evaluation

Enclosure NOC-AE-07002240 Page 2 of 63 STPNOC also joined with other plants in the STARS/USA group to contract with Performance Contracting Inc. (PCI) to provide an advanced design sump strainer for each respective plant. The new sump strainer has replaced the original sump screens for STP. Laboratory testing is being performed by PCI (Alden Research Laboratory and Areva NP are the sub-contractors for this testing) to demonstrate acceptability of the new sump strainer design.

STPNOC will be in full compliance with the regulatory requirements discussed in the applicable regulatory requirements section of GL2004-02 by June 30, 2008, as discussed in Reference 2 to the cover letter.

A three-dimensional computational fluid dynamics (CFD) analysis for debris transport was performed to define the debris loading on the sump strainers and also determine the need to install any debris interceptors. It was determined that debris interceptors were not required.

A revision to the sump water level calculation was prepared to support the CFD analysis and to address the items identified in the upstream effects evaluation that was prepared by Enercon.

A latent debris walkdown inside containment was performed to validate the conservative assumptions used for latent debris in the debris generation analysis.

The design for the new sump strainers will be validated by testing. The test goals are to demonstrate that the thin-bed effect is not a concern and that the head loss due to the STP plant-specific debris loading is acceptable. The testing scheduled for February 2008 is complete and will be discussed later in the response letter due June 30, 2008.

Coatings testing was conducted by Westinghouse to demonstrate that the zone of influence (ZOI) for coatings may be defined using a radius of 5D (5 times the diameter of the break pipe). This result is used to reduce the debris loading on the sump and to demonstrate margin for the new sump strainer design.

The following plant modifications were implemented in Unit 1 during the Fall 2006 refueling outage and in Unit 2 during the Spring 2007 refueling outage:

• Remove existing sump screens from each of the three emergency sumps.

• The vortex breakers will remain in place.

• Install new emergency sump strainer modules by bolting the support frame to the floor.

Modules are bolted to the frame.

3. Specific Information Regarding Methodology for Demonstrating Compliance Content Guide Item 3.a - Break Selection The objective of the break selection process is to identify the break size and location thatpresent the greatest challenge to post-accidentsump performance.

• Describe andprovide the basisfor the break selection criteria used in the evaluation.

• State whether secondary line breaks were considered in the evaluation (e.g., main steam and feedwater lines) and briefly explain why or why not.

• Discuss the basisfor reachingthe conclusion that the break size(s) and locations chosen present the greatest challenge to post-accidentsump performance.

Enclosure NOC-AE-07002240 Page 3 of 63 Content Guide Item 3.a - Break Selection

• Describe andprovide the basisfor the break selection criteria used in the evaluation.

Response

In the debris generation calculation various breaks were evaluated in the Reactor Coolant System (RCS) and connected piping.

Break selection consists of determining the size and location of the high energy line breaks (HELB) that produce debris and potentially challenge the performance of the sump screen. The break selection process evaluated a number of break locations to identify the location that is likely to present the greatest challenge to post-accident sump performance. The debris inventory and the transport path were considered when making this determination.

Regulatory guidance recommends that a sufficient number of breaks bounding variations in debris size, quantity, and type be identified. STP evaluated a number of break locations and piping systems, and considered breaks that rely on recirculation to mitigate the event. The following break locations were considered.

Break Criteria 1 - Breaks in the RCS with the largest potential for debris Break Criteria 2 - Large breaks with two or more different types of debris Break Criteria 3 - Breaks in the most direct path to the sump Break Criteria 4 - Medium and large breaks with the largest potential particulate debris to fibrous insulation ratio by weight Break Criteria 5 - Breaks that generate an amount of fibrous debris that, after transport to the sump screen, could form a uniform thin bed (i.e., usually 1/8" thick) that could subsequently filter sufficient particulate debris to create a relatively high head loss referred to as the "thin-bed effect".

This spectrum of breaks is consistent with that recommended in the NRC's Safety Evaluation Report (SER) for the Nuclear Energy Institute (NEI) Guidance Report (GR), NEI 04-07, "Pressurized Water Reactor Sump Performance Evaluation Methodology." It is also consistent with regulatory position 1.3.2.3 of Regulatory Guide 1.82, "Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident," Revision 3.

Locations were selected for the breaks that produce the maximum amount of debris and also the worst combination of debris mixes with the possibility of being transported to the sump screen. Section 3.3.5.2 of the SER advocates break selection at 5-ft intervals along a pipe in question but clarifies that "the concept of equal increments is only a reminder to be systematic and thorough". It further qualifies that recommendation by noting that a more discrete approach driven by the comparison of debris source term and transport potential can be effective at placing postulated breaks. The key difference between many breaks (especially large breaks) is not the exact location along the pipe, but rather the envelope of containment material targets that is affected.

A small break loss of coolant accident (SBLOCA) inside the secondary shield wall was evaluated for STP. The debris generated by the SBLOCA is less than the debris generated by the large break loss of coolant accident (LBLOCA); however the containment water level at the time of recirculation would be less than the water level caused by the LBLOCA which results in higher average fluid velocities and increases the transportation of debris to the containment sump For SBLOCAs outside the secondary shield wall, SER Section 3.3.5.2 stipulates the need to evaluate breaks in RCS-attached piping beyond isolation points is contingent upon the determination that

Enclosure NOC-AE-07002240 Page 4 of 63 recirculation would not be required should a break occur in these sections. The debris generation analysis for STP considered the failure of a single isolation valve inside the secondary shield wall and includes SBLOCAs outside the secondary shield wall in the spectrum of events evaluated to ensure these would not be limiting Breaks in the RCS with the largest potential for debris (Break Criterion 1)

The break with the largest potential for debris generation is the largest break in an area with the largest concentration of debris source material. For STP, there were seven possible break locations that have the potential to generate the largest concentration of debris:

1. 29" hot leg (LBLOCA) located inside the steam generator compartment inside the secondary shield wall.

2. A hot leg line break in the other compartment was also evaluated since the layout of the STP containment is such that the steam generator compartments each contain two RCS loops.

3. 31" ID RCS cross-over line (LBLOCA), located inside the steam generator compartment inside the secondary shield wall.

4. RCS Nozzle (LBLOCA) in the reactor vessel cavity.

5. 12" residual heat removal (RHR) pump suction line from the RCS hot leg (SBLOCA), located outside the secondary shield wall, but inside the RHR pump/heat exchanger compartment.

6. 8" SI pump discharge line to the RCS hot leg (SBLOCA), located outside the secondary shield wall.

7. 4" chemical and volume control system (CVCS) letdown line (SBLOCA) from the RCS Loop 3 cross-over pipe inside the steam generator (SG) compartment. This break was analyzed because it is the largest pipe break postulated that allows the control room operators time to isolate the safety injection (SI). accumulators before they discharge into the RCS.

Large breaks with two or more different types of debris (Break Criterion 2).

The debris generated by the RCS hot leg line break and the reactor vessel cavity nozzle break discussed in Break Criterion 1 bound the break under criterion 2I The types of insulation debris within the primary shield wall are reflective metal insulation (RMI) and Marinite, and the types of insulation within the secondary shield wall are NUKONTM, Thermal-Wrap and Microtherm.

Breaks with the most direct path to the sump (BreakCriterion 3).

The 12" RHR pump suction lines (A, B and C) from the RCS hot legs have second isolation valves that are located outside the secondary shield wall presenting a potential for direct transport to the sump..

Though these isolation valves are inside the RHR pump/heat exchanger rooms, which are separated from the area where the containment sumps are located and therefore to do not provide a direct path to the sumps, a break in this line was included in the STP analyses. The "A" and ."B" SI system discharge lines to the RCS hot legs also have isolation valves outside the secondary shield wall but are located on the opposite side of containment away from the sump. A break in these lines was also included in the analysis.

Large breaks with the largest potential particulate debris to fibrous insulation ratio by weight (Break Criterion 4).

The types of insulation identified within the containment are RMI, NUKONTM, Thermal-Wrap, Microtherm and Marinite. Since STP has a very limited quantity of particulate type insulation with respect to the fibrous insulation, and this particulate insulation is affected by the LBLOCAs evaluated in

Enclosure NOC-AE-07002240 Page 5 of 63 accordance wvith Break Criterion 1, large breaks with the largest potential particulate debris to fibrous insulation ratio is bounded by Break Criterion 1.

Breaks that generate a "thin bed" - high particulate with 1/8" fiber bed (Break Criterion 5)

Break Criterion 5 postulates a scenario that could generate an amount of fibrous debris that, after its transport to the sump screen, could form a uniform thin bed that could subsequently filter sufficient particulate debris to create a relatively high head loss referred to as "the thin-bed effect" (TBE). The quantity of fiber needed to form a thin bed is the quantity of fiber that would form a 1/8" thick uniform debris bed on the entire surface area of the sump screen.

The STP Debris Accumulation and Head Loss Analysis does consider a thin fibrous bed on the sump screens. The STP containment contains a large quantity of fibrous insulation, which is postulated to become transportable debris due to a LBLOCA. Therefore, the analysis does consider a thin fibrous debris bed as well as the maximum fibrous debris bed.

Content Guide Item 3.a - Break Selection

• State whether secondary line breaks were considered in the evaluation (e.g., main steam and feedwater lines) and briefly explain why or why not.

Response

The large main steam and feedwater line breaks were not evaluated since recirculation is not required under the plant licensing basis for STP.

Content Guide Item 3.a - Break Selection

• Discuss the basisfor reachingthe conclusion that the break size(s) and locationschosen present the greatestchallenge to post-accidentsump performance.

Response

A postulated LBLOCA of the Loop "C" hot leg at the steam generator generates the maximum possible quantity of fibrous debris at STP. This break also produces some Microtherm insulation debris. These LBLOCA debris quantities are significant due to the large zones of influence (ZOI). One other LBLOCA case analyzed is in the RCS hot leg at the reactor vessel nozzle. This break produced Marinite insulation debris and significantly less fibrous insulation debris. This break also produces RMI insulation debris and Microtherm insulation debris. The make up of the total debris generated by these two breaks were different enough to warrant separate transport and head loss analysis to ensure that the head loss at the Containment Sump is thoroughly evaluated.

Content Guide Item 3.b Debris Generation/Zoneof Influence (ZOI) (excluding coatings)

The objective of the debris generation/ZOIprocess is to determine,for each postulated break location:

(1) the zone within which the breakjetforces would be sufficient to damage materialsand create debris; and (2) the amount of debris generatedby the breakjetforces.

• Describe the methodology used to determine the ZOIsfor generatingdebris. Identify which debris analyses used approved methodology default values. For debris with ZOIs not defined in the guidance report/SE, or if using other than default values, discuss method(s) used to determine ZO0 and the basisfor each.

• Provide destruction ZOIs and the basisfor the ZOIsfor each applicabledebris constituent.

Enclosure NOC-AE-07002240 Page 6 of 63 0 Identify if destruction testing was conducted to determine ZOIs. If such testing has not been previously submitted to the NRCfor review or information, describe the test procedure and results with reference to the test report(s).

• Provide the quantiot of each debris type generatedfor each break location evaluated. If more thanfour break locations were evaluated,provide data only for thefour most limiting locations.

0 Provide total surface area of all signs, placards,tags, tape, and similarmiscellaneous

-materialsin containment.

Response

As noted in section 3.4.2.2 of the SER, the debris generation analysis considers the ZOI to be defined based on the material with the lowest destruction pressure. Refinements in the STP analysis include debris-specific (insulation material specific) and non-spherical ZOIs. The debris-specific refinements, as endorsed in SER Section 4.2.2.1.1, provide relief as long as there are two or more district types of insulation within the break location. In the STP containment, there are two or more distinct types of insulation and a debris-sliecific refinement is beneficial in this analysis. The destruction pressures and associated ZOI radii for the insulating materials in the STP containment are listed in Table 1.

Table I - Destruction Pressures and ZOI Radii for Potential Debris Sources Destruction ZOI Radius Insulation Types (Radius/Break Reference/Basis sPressure (psi) Diameter)

Transco RMI 114 2.0 SER Table 3.2 NUKONTM 6 17 SER Table 3.2 Thermal-Wra'p 6 17 Assumed the same as NUKONTM based on GR 3.4.3.3.1 Marinite 114 2.0 See discussion below Microtherm(1) 2.4 28.6 See discussion below Marinite The SER does not recommend a destruction pressure or ZOI for this material and insufficient data exists on its material properties and destruction pressure. However, since this insulation is covered with 3/16" stainless steel plate, the destruction pressure was assumed to be equivalent to that of RMI. This destruction pressure is 114 psig, which corresponds to a ZOI of 2.0D.

Microtherm The material specifications for Microtherm were insufficient to determine an appropriate destruction pressure and ZOI. Therefore, the lowest destruction pressure (Min-K at 2.4 psi) and the greatest ZOI (also Min-K at L/D of 28.6) identified in Table 3-2 of the SER were utilized in the STP analysis.

Robust barriers, i.e., structures and equipment that are impervious to jet impingement, are assumed to prevent further expansion of the break jet. The volume of a spherical ZOI with a radial dimension extending beyond robust barriers such as walls or encompassing a large component such as a tank or

Enclosure NOC-AE-07002240 Page 7 of 63 steam generator is truncated by the barrier. The SER stipulates that deflection/reflection need not be considered but "shadow" surfaces of components should be included in the analysis.

ZOIs were not applied within the primary shield wall due to the relatively small area between the reactor vessel and the primary shield wall. All of the insulation material within the primary shield wall was considered to be destroyed by a LBLOCA within the primary shield wall.

The debris generation analysis identified a LBLOCA break in the Loop C 29" hot leg Line break at the steam generator and the RCS hot leg line break at a nozzle in the reactor cavity as the two limiting breaks in the RCS. The debris quantities for these two breaks as well as Loop A hot leg and the 4" CVCS letdown line are presented in Table 2.

Table 2 - Summary of Debris Generation for Breaks in the RCS Loop "A" hot leg Loop "C" hot leg RCS hot leg Nozzle 4" CVCS Letdown Insulation Type Line Break Line Break Line Break Pipe Break (SBLOCA)

Marinite 0 0 15.2 ft3 0 RMI 0 0 24,493 ft2 0 NUKONTM 838.9 ft 3

908.3 ft 3 424.9 ft 3 212.5 ft 3

Thermal-Wrap 1400.0 ft 3

1400.0 ft 3

85.1 ft3 42.6 ft3 Microtherm 2.6 ft 3 2.3 ft3 0.9 ft3 0 The breaks associated with the potential for direct transport to the sump (Break Criterion 3) resulted in a limiting NUKONTM debris generation of 70.5 ft3 for the 12" RHR suction lines and 31.2 ft3 for the 8" SI pump discharge lines.

Miscellaneous Solid Debris The STP debris generation analysis does recognize the presence of miscellaneous solid object debris sources, such as equipment labels and tags, and plastic signs. As suggested by the GR, this miscellaneous solid object debris source is bounded by 100 ft2 , andincludes an allowance of 14 ft2 for 100 equipment clearance order (ECO) tags (size of 4" x 5") and 2 ft2 for ty-wraps.

Content Guide Item 3c. Debris Characteristics The objective of the debris characteristicsdeterminationprocess is to establish a conservative debris characteristicsprofilefor use in determining the transportabilityof debris and its contributionto head loss.

" Provide the assumed size distributionfor each type of debris.

" Provide bulk densities (i.e., including voids between thefibers/particles)and material densities (i.e., the density of the microscopicfibers/particlesthemselves) forfibrous and particulatedebris.

• Provide assumed specific surface areasforfibrousandparticulatedebris.

• Provide the technical basisfor any debris characterizationassumptions that deviatefrom NRC-approved guidance.

Enclosure NOC-AE-07002240 Page 8 of 63 The debris sources for STP include insulation, coatings, and latent debris. The insulation debris types include RMI, NUKONTM, Thermal-Wrap, Microtherm and Marinite. The RMI is located on the reactor vessel inside the primary shield wall. The NIJKONTM is located on various piping and equipment throughout containment. The Thermal-Wrap is installed on the steam generators. Marinite is installed on the reactor vessel nozzles. The Microtherm is used on some piping in the secondary shield wall penetrations. The characteristics of the insulation debris materials are discussed in this section as the characteristics of the other debris types (e.g., coatings and latent) are included elsewhere Content Guide Item 3c. Debris Characteristics

• Provide the assumed size distributionfor each type of debris.

Response

As recommended by Section 4.2.4 of the SER, a four-size distribution for low density fiberglass (LDFG) insulation material inside the ZOI of a postulated break is used in the STP debris generation analysis. The distribution categorizes destroyed insulation debris as fines, small pieces, large pieces and intact blankets.

Fines are defined as individual fibers, small pieces are smaller than 6" on a side, large pieces are greater than 6" on a side and intact blankets are large pieces that are still protected by the covering, thereby preventing further erosion. Table 3 summarizes the LDFG size distributions.

Table 3 - LDFG Debris Size Distribution Within Each Sub-Zone Size 18.6 psi ZOI 10.0 - 18.6 psi ZOI 6.0 - 10.0 psi ZOI (7.0 L/D) (11.9 - 7.0 L/D) (17.0 - 11.9 L/D)

Fines (Individual Fibers) 20% 13% 8%

Small Pieces (<6" on a Side) 80% 54% 7%

,Large Pieces (>6" on a Side) 0% 16% 41%

Intact (covered) Blankets 0% 17% 44%

Table 4 summarizes the other potential debris sources in the STP containment and the associated debris size distributions from Table 3-3 of the SER. Materials for which debris generation is not known well enough to conservatively estimate debris size distribution will assume maximum destruction as 100%

fines.

Table 4 - Debris Size Distribution Material Percentage Percentage I Small Fines[ Large Pieces Within the ZOI RMI 75 25 Marinite 100 0 Microtherm 100 0 Outside the ZOI Covered Undamaged 0 0 Insulation

Enclosure NOIC-AE-07002240 Page 9 of 63 Content Guide Item 3c. Debris Characteristics

• Provide bulk densities (i.e., including voids between thefibers/particles)and material densities (i.e., the density of the microscopicfibers/particlesthemselves)for fibrous and particulatedebris.

Response

Table 5 and Table 6 provide a summary of the as-fabricated densities, microscopic densities, and dimensions for applicable debris types at STP. Characteristics associated with coatings will be further discussed later in this report.

Table 5 - Fibrous Material Characteristics As-Fabricated Microscopic Characteristic Debris Material Density Density Diameter (lb/ft3 ) (lb/ft3 ) (jim)

NUKON TM 2.4 175 7 jm Thermal-Wrap 2.4 159 5.5 jim Table 6 - Particulate Debris Characteristics As-Fabricated Microscopic Characteristic Debris Material Density Density Diameter (lb/fl3) (lb/ft3) (Gm)

Marinite (1) 14.5 144 5 Microtherm 15 187 2.5 to 20 The material characteristics for Marinite are assumed to be the same as those identified for Calcium Silicate due to their similar appearances.

Content Guide Item 3c. Debris Characteristics

• Provide assumed specific surface areasforfibrousandparticulatedebris.

Response

The specific surface area (Sv) was only used for preliminary analytically determined head loss values across a debris laden sump screen using the correlation given in NUREG/CR-6224. Since the head loss across the installed sump screen is determined via testing, these values are not used in the design basis for STP. Therefore, these values, are not provided as part of this report.

Enclosure NOC-AE-07002240 Page 10 of 63 Content Guide Item 3c. Debris Characteristics

• Provide the technical basisfor any debris characterizationassumptions that deviatefrom NRC-approved guidance.

Response

There are no such assumptions that differ from the guidance.

Content Guide Item 3d. Latent Debris The objective of the latent debris evaluationprocess is to provide a reasonable approximation of the amount and types of latent debris existing within the containment and its potentialimpact on sump screen head loss.

• Provide the methodology used to estimate quantity and composition of latent debris.

0 Provide the basisfor assumptions used in the evaluation.

0 Provide results of the latent debris evaluation, including amount of latent debris types and physical datafor latent debris as requestedfor other debris under c. above.

0 Provide amount of sacrificialstrainersurface areaallotted to miscellaneous latent debris.

Response

The latent debris at STP has been evaluated through containment condition assessments. Containment walkdowns were completedfor Unit 1 and for Unit 2. The conditions were completed in accordance with the guidance of NEI 02-01, "Condition Assessment Guidelines, Debris Sources Inside Containment,"

Revision 1. The quantity and composition of the latent debris was evaluated by extensive sampling for latent debris (dirt/dust and latent fiber) considering the guidance in NEI 04-07, Volume 2.

Samples were taken to determine the latent debris mass distribution per unit area, referred to as latent debris density (e.g. 1bm/1000 ft2) of representative surfaces throughout containment including vertical surfaces such as the liner and walls. These debris densities were then applied to all of the surface areas inside containment to calculate the total amount of latent debris inside containment.

The latent debris density was estimated by weighing sample bags before and after sampling, dividing the net weight increase by the sampled surface area, and converting the result to a density (e.g. lbm/1000 ft2).

Samples were taken for Unit 1. The visual assessments and walkdowns supported that there were no significant differences between the Units that would affect the quantity or types of latent debris.

Therefore, the samples taken are representative of both Units.

The results of the latent debris calculation conservatively determined the debris loading to be less than 160 lbm in each containment. Therefore, it was elected to use a conservative bounding value of 200 lbm for the latent debris source term in containment.

Visual examination of the debris showed very low fiber content. In lieu of analysis of samples, conservative values for debris composition properties were assumed as recommended by NEI 04-07 Volume 2. This results in a very conservative estimate of fiber content. The particulate / fiber mix of the latent debris will be assumed to be 15% fiber. The latent debris source term value incorporated into the STP analysis is presented in Table 7.

Enclosure NOC-AE-07002240 Page 11 of 63 Table 7 - Latent Debris Source Term Latent Debris Type Mass (ibm) Density (lbm/ft3) Characteristic Size (ft)

Dirt and Dust 170 169 5.67E-05 Latent Fiber 30 175 2.3 E-05 The containment condition assessments also included the identification of miscellaneous solid objects such as labels and tags. Qualified tags attached with stainless steel wires were found for much of the equipment. Unqualified items were identified and removed. The total surface area for any remaining debris of this type was determined to be much less than 100 ft2. Therefore, as suggested by NEI 04-07, this miscellaneous solid object debris source is bounded by the 100 ft2 that was implemented in the STP debris generation and transport analyses.

A sacrificial area of 200 ft2 of strainer surface per strainer was designated as a penalty for miscellaneous latent debris including labels and tags. STP has identified tags and labels which are qualified and which have been shown to not transport to the emergency sump strainers (ac ceptable labels).

Content Guide Item 3e. Debris Transport The objective of the debris transportevaluationprocess is to estimate the fraction of debris that would be transportedfrom debris sources within containment to the sump suction strainers.

• Describe the methodology used to analyze debris transportduring the blowdown, washdown, pool-fill-up, and recirculationphases of an accident.

• Provide the technical basisfor assumptions and methods used in the analysis that deviate from the approved guidance.

• Identify any computationalfluiddynamics codes used to compute debris transportfractions during recirculationand summarize the methodology, modeling assumptions, and results.

• Provide a summary of, and supportingbasisfor, any credit taken for debris interceptors.

• State whetherfine debris was assumed to settle andprovide basisfor any settling credited.

" Provide the calculateddebris transportfractions and the total quantitiesof each type of debris transportedto the strainers.

Content Guide Item 3e. Debris Transport

• Describe the methodology used to analyze debris transportduring the blowdown, washdown, pool-fill-up, and recirculationphases of an accident.

Response

The methodology used in the transport analysis is based on the NEI 04-07 guidance report (GR) for refined analyses as modified by the NRC's safety evaluation report (SER), as well as the refined methodologies suggested by the SER in Appendices III, IV, and VI. The specific effect of each of the four modes of transport was analyzed for each type of.debris generated. These modes of transport are:

• Blowdown transport- the vertical and horizontal transport of debris to all areas of containment by the break jet.

" Washdown transport- the vertical (downward) transport of debris by the containment sprays and break flow.

Enclosure NOC-AE-07002240 Page 12 of 63

• Poolfill-up transport- the transport of debris by break and containment spray flows from the refueling water storage tank (RWST) to regions that may be active or inactive during recirculation.

" Recirculation transport- the horizontal transport of debris from the active portions of the recirculation pool to the sump screens by the flow through the emergency core coolant system (ECCS).

The logic tree approach was then applied for each type of debris determined from the debris generation calculation. The logic tree shown in Figure 1 is somewhat different than the baseline logic tree provided in the GR. This departure was made to account for certain non-conservative assumptions identified by the SER including the transport of large pieces, erosion of small and large pieces, the potential for washdown debris to enter the pool after inactive areas have been filled, and the direct transport of debris to the sump screens during pool fill-up. Also, the generic logic tree was expanded to account for a more refined debris size distribution. (Note that some branches of the logic tree may not be required for certain debris types).

Enclosure NOC-AE-07002240 Page 13 of 63 Retained on Structures Remains intact Upper Transport Containment Erodes to Fines Washed Down S d m n Remains intact Transport Sediment Actie Pol Seimen IrErodes to Fines Remains intact Retained onI Structures Remains intact Upper Transport ActivenPool Erodes to Fines Washed Down S d m n Remains intact Transport Sediment Active Pool Erodes to Fines Sediment I Remains intact

Enclosure NOC-AE-07002240 Page 14 of 63 The basic methodology used for the South Texas Project transport analysis is shown below:

1. Based on many of the containment building drawings, a three-dimensional model was built using computer aided design and drafting (CADD) software.

2. A review was made of the drawings and CADD model to determine transport flow paths.

Potential upstream blockage points including screens, fences, grating, drains, etc. that could lead to water holdup were addressed.

3. Debris types and size distributions were gathered from the debris generation calculation for each postulated break location.

4. The fraction of debris blown into upper containment was determined based on the relative volumes of upper and lower containment.

5. The quantity of debris washed down by spray flow was conservatively determined.

6. The quantity of debris transported to inactive areas or directly to the sump screens was calculated based on the volume of the inactive and sump cavities proportional to the water volume at the time these cavities are filled.

7. Using conservative assumptions, the locations of each type/size of debris at the beginning of recirculation was determined.

8. A computerized flow dynamics (CFD) model was developed to simulate the flow patterns that would occur during recirculation.

9. A graphical determination of the transport fraction of each type of debris was made using the.

velocity and turbulent kinetic energy (TKE) profiles from the CFD model output, along with the determined initial distribution of debris.

10. The recirculation transport fractions from the CFD analysis were gathered to input into the logic trees.

11. The effects of erosion on the LOCA generated debris were evaluated to determine the potential significance.

12. The overall transport fraction for each type of debris was determined by combining each of the previous steps in logic trees.

BLOWDOWN TRANSPORT The fraction of blowdown flow to various regions was estimated using the relative volumes of containment. Fine debris would be suspended and carried by the blowdown flow. Small and large piece debris would also be carried by the high velocity blowdown flow in the vicinity of the break. However, in areas farther away from the break that are not directly affected by the blowdown, this debris would likely fall to the floor.

The volumes for the upper containment (including the refueling canal and areas above the operating deck) and for lower containment (including the open area inside the steam generator and pump enclosures, the area inside the secondary shield wall, and the annulus area below the operating deck) were determined from the CADDmodel. Because the debris was assumed to be carried with the blowdown flow, the flow split is then proportional to the containment volumes. This resulted in a transport fraction for the fine debris to upper containment of 69%.

The drywell debris transport study (DDTS) 1 testing provides debris holdup values for blowdown occurring in a wetted and highly congested area. Values associated with grating being present in the D.V. Rao, et al., "Drywell Debris Transport Study: Experimental Work", NUREG/CR-6369, Volume 2, September 1999.

Enclosure NOC-AE-07002240 Page 15 of 63 blowdown flowpath were utilized in the STP blowdown analysis. The DDTS also presents values for holdup when blowdown travels a flow path with 900 turn(s). Although 90' turns might not have to be negotiated by debris blown to upper containment at STP, significant bends would have to be made.

Therefore, it was estimated that 5% (versus the 17% value in the study) of the small fiberglass debris blown upward would be trapped due to changes in flow direction.

Additional guidance was incorporated into the analysis through use of the Boiling Water Reactor (BWR)

Utility Resolution Guide (URG). The guidance from this document indicates that grating would trap approximately 65% of the small RMI debris blown toward it.

Table 8 and Table 9 show the transport fractions for each type/size of debris to upper containment and to the containment pool due to the blowdown forces for breaks inside the steam generator compartments.

Table 10 through Table 13 show the blowdown transport fractions for the break inside the reactor cavity and the small breaks outside the secondary shield wall. Note that debris outside the ZOI is not affected by the blowdown, and therefore the transport fraction for this debris would be 0%.

Table 8 - Blowdown transport fraction of debris to upper containment (Cases 1 and 5)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 69% 460/. 0% 0%

Microtherm TM (Case 1) 69% NA NA NA Qualified Coatings (inside ZOI) 69% NA NA NA

'Unqualified Coatings 0% NA NA NA

"(outside ZOI),

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 9 - Blowdown transport fractions of debris to containment pool (Cases 1 and 5)

Debris Type Fines Small Pieces Unjacketed Jacketed D Large Pieces Large Pieces LDFG 31% 20% 0% 0%

MicrothermTM (Case 1) 31% NA NA NA Qualified Coatings (inside ZOI) 31% NA NA NA Unqualified Coatings. .0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA

Enclosure NOC-AE-07002240 Page 16 of 63 Table 10 - Blowdown transport fractions of debris to upper containment (Case 2)

Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI NA 0% 0% NA LDFG 69% 46% 0% 0%

MariniteTM 0% NA NA NA Qualified Coatings (inside ZOI) 0% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 11 - Blowdown transport fractions of debris to containment pool (Case 2)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces Stainless Steel RMI NA 100% 100% NA LDFG 31% 20% 0% 0%

MariniteiM .100% NA NA NA Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 12 - Blowdown transport fractions of debris to upper containment (Cases 3 and 4)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 0% 0% 0% .0%

Qualified Coatings (inside ZOI) 0% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA

Enclosure NOC-AE-07002240 Page 17 of 63 Table 13 - Blowdown transport fractions of debris to containment pool (Cases 3 and 4)

D Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 100% 100% 100% 100%

Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA WASHDOWN TRANSPORT During the washdown phase, debris in upper containment could be washed down by the containment sprays. For STP, some small piece debris as well as all large pieces would be held up by grating.

The debris blown to upper containment was assumed to be scattered around and a reasonable approximation of the washdown locations was made based on the spray flow split in upper containment.

This resulted in the following washdown split of 26% of the containment sprays were estimated to flow directly into the steam generator compartments, 31% were estimated to flow into the steam generator compartments via the refueling canal (28.5%) and cable tray chase (2.7%), and the remaining 43% of the sprays were estimated to flow into the annulus.

Multiple levels of grating are present in the STP Containment. The results of the DDTS testing showed that approximately 40-50% of small fiberglass debris landing on grating would be washed through the grating due to spray flows. (Note that the spray flow at the plant is on the lower end of the 1 to 12 gpm/ft2 spray flow used in the testing). Holdup of small pieces of fiberglass debris was credited at each level of grating that washdown flow passed through. Credit was also taken for holdup of small pieces of RMI on grating based on the BWR URG, which indicates that the retention of small RMI debris on grating is approximately 29%.

The following tables show the fraction of debris in upper containment and the steam generator compartments that would be expected to transport to the pool floor inside and outside the secondary shield wall.

Table 14 - Washdown transport fractions of debris from upper containment to the annulus Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 43% 3% 0% 0%

MicrothermTM (Case 1) 43% NA NA NA Qualified Coatings (inside ZOI) 43% NA NA NA Unqualified Coatings NA NA NA NA (outside ZO0)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA

Enclosure NOC-AE-07002240 Page 18 of 63 Table 15 - Washdown transport fractions of debris from upper containment directly to the steam generator compartments Fines Small Pieces Unjacketed Jacketed Debris Type Large Pieces Large Pieces LDFG 26% 7% 0% 0%

MicrothermTM (Case 1) 26% NA NA NA Qualified Coatings (inside ZOI) 26% NA NA NA Unqualified Coatings N NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA Table 16 - Washdown transport fractions of debris from upper containment to the steam generator compartments via the canal drains and cable tray chase Unjacketed Jacketed Fines Small Pieces Large Pieces Large Pieces LDFG 31% 16% 0% 0%

MicrothermTM (Case 1) 31% NA NA NA

,Qualified Coatings (inside ZOI) 31% NA NA NA Unqualified Coatings NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA Table 17- Washdown transport fractions of debris in the steam generator compartments at the end of the blowdown phase Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces LDFG 100% 50% 0% 0%

MicrothermTM (Case 1) 100% NA NA NA Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA

Enclosure NOC-AE-07002240 Page 19 of 63 POOL FILLUP TRANSPORT During pool fill-up, the flow of water transports insulation debris from the break location to all areas of the recirculation pool. Some of the debris was assumed to transport to inactive areas of the pool and some was assumed to transport directly to the sump screens as the emergency sump cavities are filled. The cavities considered for pool fill up transport include the containment sump, the elevator pit, and the three ECCS sumps. Other potentially inactive areas where debris could be held up including the secondary normal sump were conservatively assumed to be negligible and were not credited.

Assuming that fine debris is uniformly distributed in the pool, and the water entering the pool from the break and sprays is clean (i.e. washdown of debris in upper containment occurs after inactive cavities have been filled), the transport to each of the inactive cavities was calculated for STP. (Note that the assumption that debris washdown occurs after inactive cavities have been filled is consistent with the requirements of the SER Section 3.8.

Table 18 - Pool fill-up transport fractions of debris to the two active sumps Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 8% 0% 0% 0%

MariniteTM (Case 2) 8% NA NA NA MicrothernTM (Case 1) 8% NA NA NA Qualified Coatings (inside ZOI) 8% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 8% NA NA NA Latent Fiber 8% NA NA NA Table 19 - Pool fill-up transport fractions of debris to the inactive sump Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 4% 0% 0% 0%

MariniterM (Case 2) 4% NA NA NA MicrothermTM (Case 1) 4% NA NA NA Qualified Coatings (inside ZOI) 4% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 4% NA NA NA Latent Fiber 4% NA NA NA

Enclosure NOC-AE-07002240 Page 20 of 63 Table 20 - Pool fill-up transport fractions of debris to the inactive cavities Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 13% 0% 0% 0%

MariniteTM (Case 2) 13% NA NA NA MicrothermTM (Case 1) 13% NA NA NA Qualified Coatings (inside ZOI) 13% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 13% NA NA NA Latent Fiber 13% NA NA NA RECIRCULATION TRANSPORT The recirculation pool debris transport fractions were determined through CFD modeling. To accomplish this, a three-dimensional CADDmodel was imported into the CFD model, flows into and out of the pool were defined, and the CFD simulation was run until steady-state conditions were reached. The result of the CFD analysis is a three-dimensional model showing the turbulence and fluid velocities within the pool. By comparing the direction of pool flow, the magnitude of the turbulence and velocity, the initial location of debris, and the specific debris transport metrics (i.e. the minimum velocity or turbulence required to transport a particular type/size of debris), the recirculation transport of each type/size of debris to the sump screens was determined.

A diagram showing the significant parts of the CFD model is shown below. The sump mass sink, the

.various direct and wash spray regions, and the combined break and spray wash regions are highlighted.

Enclosure NOC-AE-07002240 Page 21 of 63 Modeled Wash Spray

. Regions Combined Case 4b Break Flow with Spray Flow.

Figure 2 - Diagram of significant features modeled Flow-3D Version 9.0 developed by Flow Science Incorporated was used for the CFD modeling. The key CFD modeling attributes/considerations included the following:

ComputationalMesh:

A rectangular mesh was defined in the CFD model that was fine enough to resolve important features, but not so fine that the simulation would take prohibitively long to run. A 6-inch cell length was chosen as the largest cell size that could reasonably resolve the concrete structures that compose the containment floor. For the cells right above the containment floor, the mesh was set to 3 inches tall in order to closely resolve the vicinity of settled debris. To further define specific objects, node planes were placed at the edges of key structures including the top of the sump curb, and the edges of the break and spray mass source obstacles.

Modeling of Containment Spray Flows:

From consideration of various plan and section drawings, as well as the containment building CADDmodel, it was judged that spray water would drain to the pool through numerous pathways. Some of these pathways included: the steam generator compartments through the open area above the steam

Enclosure NOC-AE-07002240 Page 22 of 63 generators, into the refueling canal and through the refueling canal drains, and into the annulus through the various open sections of grating. The sprays were introduced near the surface of the pool.

Modeling of Break Flow.

STP breaks were modeled at the break location which was not directly above the recirculation pool and consideration of the additional free fall energy was not necessary. The break flow falls onto the floor at the associated elevation and then drains through various paths to the recirculation pool. This break flow was combined with the spray flow and introduced to each region where flow occurs near the surface of the pool.

Modeling of the Emergency Sump:

The emergency sumps at STP consist of three sumps. To bound the transport analysis, the worst case scenario (two sumps operating) was modeled. The two outer sumps were chosen as the active sumps since debris would be more likely to transport to the outer sumps. The mass sink used to pull flow from the CFD model was defined within the two sump cavities. A negative flow rate was set for the sump mass sink, which tells the CFD model to draw the specified amount of water from the pool over the entire exposed surface area of the mass sink obstacle.

Turbulence Modeling:

Several different turbulence modeling approaches can be selected for a Flow-3D calculation. The approaches are (ranging from least to most sophisticated):

• Prandtl mixing length

• Turbulent energy model

• Two-equation k-s model

• Renormalized group theory (RNG) model

• Large eddy simulation model The RNG turbulence model was judged to be the most appropriate for this CFD analysis due to the large spectrum of length scales that would likely exist in a containment pool during emergency recirculation.

The RNG approach applies statistical methods in a derivation of the averaged equations for turbulence quantities (such as turbulent kinetic energy and its dissipation rate). RNG-based turbulence schemes rely less on empirical constants while setting a framework for the derivation of a range of models at different scales.

Steady-State Metrics:

The CFD models were started from a stagnant state at a defined pool depth and run long enough for steady-state conditions to develop. A plot of mean kinetic energy was used to determine when steady-state conditions were reached. Checks were also made of the velocity and turbulent energy patterns in the pool to verify that steady-state conditions were reached.

Debris TransportMetrics:

Metrics for predidting debris transport have been adopted or derived from data. The specific metrics are the turbulent kinetic energy (TKE) necessary to keep debris suspended, and the flow velocity necessary to tumble sunken debris along a floor. The metrics utilized in the STP transport analysis originate from the sources below:

1) NUREG/CR-6772 Tables 3.1, 3.2 & 3.5,

2) NUREG/CR-6808 Table 3.2 and Figure 5-2, or

3) Calculated using Stokes' Law using water properties at 1200 F.

Enclosure NOC-AE-07002240 Page 23 of 63 Graphical Determination of Debris Transport Fractions The following steps were taken to determine what percentage of a particular type of debris could be expected to transport through the containment pool to the emergency sump screens.

• Colored contour velocity and TKE maps indicating regions of the pool through which a particular type of debris could be expected to transport were generated from the Flow-3D results in the.

form of bitmap files.

• The bitmap files were overlaid on the initial debris distribution plots and imported into AutoCAD with the appropriate scaling factor to convert the length scale of the color maps to feet.

" For the uniformly distributed debris, closed polylines were drawn around the contiguous areas where velocity or TKE was high enough that debris could be carried in suspension or tumbled along the floor to the sump screens.

• The areas within the closed polylines were determined utilizing an AutoCAD querying feature.

• The combined area within the polylines was compared to the debris distribution area.

• The percentage of a particular debris type that would transport to the sump screens was estimated based on the above comparison.

Plots showing the TKE and the velocity magnitude in the pool were generated for each case to determine areas where specific types of debris would be transported. The limits on the plots were set according to

,the minimum TKE or velocity metrics necessary to move each type of debris. The overlying yellow areas represent regions where the debris would be suspended, and the red areas represent regions where the debris would be tumbled along the floor. The yellow TKE portion of the plots is a three-dimensional representation of the TKE. The velocity portion of the plots represents the velocity magnitude just above the floor level (1.5 inches), where tumbling of sunken debris could occur. Directional flow vectors were also included in the plots to determine whether debris in certain areas would be transported to the sump

screens or transported to quieter regions of the pool where it could settle to the floor.

The following figures and discussion are presented as an example of how the transport analysis was performed for a single debris type - Small Piece Stainless Steel RMI. This same approach was utilized for other debris types analyzed at STP.

Figure 4 and Figure 5 show that the turbulence in the pool is only high enough to suspend small RMI debris in the vicinity of the location where break and spray flow from the steam generator compartments enters the pool.

As shown in Figure 3, the small RMI debris was assumed initially to be uniformly distributed inside the secondary shield wall and in the vicinity of the sump screens. This area was overlaid on top of the plot showing tumbling velocity and flow vectors to determine the recirculation transport fraction. The area where small pieces of RMI would transport'within the initial distribution area is 1,872 ft2 , as shown in Figure 6. Since the initial distribution area was determined to be 5,977 ft2 the recirculation transport fraction for small pieces of RMI is 31%.

Enclosure NOC-AE-07002240 Page 24 of 63 Initial Distribution of Small and Large Piece Debris For mCases 1, 2, and 5 ZO 1 5,977 fl 2 Figure 3 - Distribution of small & large piece debris in lower containment

Enclosure NOC-AE-07002240 Page 25 of 63 Figure 4 - TKE and velocity with limits set at suspension/tumbling of small pieces of stainless steel RMI

Enclosure NOC-AE-07002240 Page 26 of 63 Figure 5 - 3D view of TKE and velocity with limits set at suspension/tumbling of small pieces of stainless steel RMI

Enclosure NOC-AE-07002240 Page 27 of 63 M- Velocity' Ž 0.28 ft/s Floor area where small RMI in lower o ntainm ent would transport to the sumps 1872 ft2 2 2 TKE k 0.21 ft /s Figure 6 - Floor area where small RMI would transport to the sumps This same analysis was applied for each debris type (grouping was performed as applicable) evaluated at STP. Recirculation pool transport fractions were identified for each debris type associated with the location of its original distribution. This includes a transport fraction for debris: 1) not originally blown into upper containment, 2) washed down inside the secondary shield wall, and 3) washed down into the annulus.

Enclosure NOC-AE-07002240 Page 28 of 63 Content Guide Item 3e. Debris Transport

• Provide the technical basisfor assumptions and methods used in the analysis that deviate from the approved guidance.

Response

Debris erosion is the only area where the debris transport analysis deviates from the regulatory guidance.

The guidance specifies that an erosion fraction of 90% should be used for fiberglass debris. However, as described in the justification below, an erosion fraction of 10% was used for fiberglass debris in the recirculation pool.

The only insulation debris with thepotential for erosion at STP is the unjacketed small and large pieces of NukonTM and Thermal-WrapTM fiberglass.

Tests performed as a part of the drywell debris transport study (DDTS) have indicated that the erosion of fibrous debris is significantly different for debris directly impacted by containment sprays versus debris directly impacted by break flow. The erosion of large pieces of fibrous debris by containment sprays was found to be less than 1%, whereas the erosion due to the break flow was much higher. Due to differences in the design of PWR nuclear plants compared to the boiling water reactor (BWR) nuclear plants, the results of the erosion testing in the DDTS are only partially applicable. In a BWR plant, a LOCA accident would generate debris that would be held up below the break location on grating above the suppression pool. In STP, however, the break would generate debris that would either be blown to upper

-containment or blown out away from the break. Most of the debris would not be hung up directly below the break flow where it would undergo the high erosion rates suggested by the DDTS. Any debris blown

.to upper containment that is not washed back down, however, would be subject to erosion by the sprays.

Based on the results of the DDTS testing, a 1%,erosion factor was applied for small and large piece fibrous debris held up in upper containment. This is consistent with the approach taken for the pilot plant

'in the SER (Appendix VI). The erosion mechanism for debris in the pool is somewhat different than what

• wastested in the DDTS. The SER (Appendix III) describes erosion tests that indicated that the erosion

,rate of fibrous debris could be on the order of 0.3 percent of the current debris per hour for a pool with a 16-inch depth (compared to 2 percent per hour for a pool with a 9-inch depth). Using the following equation, this gives a total erosion of 7% after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and 89% after 30 days.

Number fe-oded 1 rate)OJHours where:

feroded = total fraction of debris eroded rate = erosion rate of current debris per hour Number ofHours = Number of hours debris is subject to erosion The SER points out substantial uncertainties associated with the erosion testing including the following:

• The integral debris transport tests lasted 3 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Therefore, the question remains whether the erosion rate tapers off with time. In addition, it is not certain that all of the end-of-test debris accumulation was the result of erosion products.

Enclosure NOC-AE-07002240 Page 29 of 63

• The test results include the usual variances in test data, such as flow and depth control and debris collection.

• Although the test series was designed to approximate the flow and turbulence characteristics of the volunteer-plant sump pool, the tank characteristics may have been significantly different than those at the plant. The difference in the erosion rates between the 9-inch and 16-inch pool depths in the integrated tests clearly illustrates the effect of pool turbulence on fibrous debris erosion.

" The geometry of the volunteer-plant sump pool is larger and more complex than that of the test tank used in the integrated tests.

" The long-term tests did not study large-piece debris.

Since the test data showed in general that the erosion consisted primarily of small, loosely attached pieces of fiber breaking off from larger pieces, it is considered reasonable to assume that erosion would taper off after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. To be conservative, however, the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> erosion was rounded up to 10%. This erosion fraction was applied for both small and unjacketed large fiberglass pieces in the containment pool.

Content Guide Item 3e. Debris Transport

• Identify any computationalfluiddynamics codes used to compute debris transportfractions during recirculationand summarize the methodology, modeling assumptions, and results.

Response

See response in subsection above for first bullet.

Content Guide Item 3e. Debris Transport

• Provide a summary of and supportingbasisfor, any credit takenfor debris interceptors.

Response

Debris interceptors are not integrated into the STP debris transport analysis Content Guide Item 3e. Debris Transport

• State whetherfine debris was assumed to settle andprovide basisfor any settling credited.

Response

Debris settling is not credited for the STP debris transport analyses. The analysis is a model of transport to the sump.

Content Guide Item 3e. Debris Transport

• Provide the calculateddebris transportfractions and the total quantitiesof each type of debris transportedto the strainers.

Enclosure NOC-AE-07002240 Page 30 of 63

Response

Transport logic trees were developed for each size and type of debris generated. These trees were used to determine the total fraction of debris that would reach the sump screen in each of the postulated cases.

The postulated cases include; a break in the Loop C hot leg, a break in reactor cavity, breaks in the RHR and SI pump suction and discharge lines of Loops A and B, a break in the RHR pump suction line of Loop C, and a break in the CVCS letdown line.

Table 21 - Case 1 (Loop C hot leg) debris transport fractions and debris amounts

~Debris DersDebris Debris Debris Type Debris Size Transport Generated AtSubip Fraction Fines 95% 329.2 ft3 312.7 ft3 3

Small Pieces 36% 1238.2 ft 445.8 ft3 LDFG (<6")

Large Pieces LD6" 1% 358.6 ft3 3.6 ft

(>6")

Intact Pieces 0% 382.5 ft Oft3

(>6")

MicrothermTM Total (Fines) 95% 2.3 ft3 2.2 ft3 Qualified Coatings Total (Fines) 95% 586lb 556.7 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb 3278lb (outside ZOI)

Dirt/Dust Total (Fines) 83% '170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb

Enclosure NOC-AE-07002240 Page 31 of 63 Table 22 - Case 2 (Reactor cavity) debris transport fractions Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Small Pieces 31% 18,370 ft2 5694.7 ft2

(<4")

RMI Large Pieces 31% 6,123 ft2 1898 ft2

(>4")

Fines 95% 305.9 ft3 290.6 ft3 Small Pieces 36% NA NA

(<6")

LDFG Large Pieces 1% 204.1 ft 3 2.0 ft3

(>6")

Intact Pieces 0% NA NA

(>6")

Marinite Total (Fines) 83% 15.2 ft3 12.6 ft3 MicrothermTM Total (Fines) 95% 0.9 ft3 0.86 ft3 Qualified Coatings Total (Fines) 83% 586lb 486.4 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278 lb 3278 lb Dirt/Dust Total (Fines) 83% 170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb Table 23 -RHR suction line of Loops A (bounding for suction lines) debris transport amounts Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 42.3 ft3 '42.3 ft3 Small Pieces 76% 0 ft3 0ft3

(<6")

LDFG (NukonTM)

Large Pieces 22% 28.2 ft3 6.20 ft3

(>6")

Intact Pieces 13% 0ft3 0ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI) 586 lb 586_lb Unqualified 100%

Coatings Total (Fines) 3278 lb 3278 lb (outside ZOI)

-Dirt/Dust Total (Fines) 100% 170 lb 170 lb 100% 30 lb 30 lb Latent Fiber Total (Fines)

Enclosure NOC-AE-07002240 Page 32 of 63 Table 24 -SI Discharge line of Loops B (bounding for discharge lines) debris transport amounts Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 18.7 ft3 18.7 ft3 Small Pieces 76% 0 ft3 0 ft3

(<6")

LDFG (NukonTM) Large Pieces 22% 12.5 ft 2.75 ft

(>6")

Intact Pieces 13% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI) Totl_(ins)_00%58 lb_586_lb Unqualified quaifide Coatings COatiTotal (Fines) 100% 3278 lb. 3278 lb (outside ZOI)_________ ________ ___ ______

Dirt/Dust Total (Fines) 100% 170 lb 170 lb Latent Fiber Total (Fines) 100% 30 lb 30 lb Table 25 - RHR pump suction line of Loop C debris transport fractions Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 41 ft3 41 ft 3 Small Pieces 100% 0 ft3 0 ft3

(<6")

LDFG Large Pieces 100% 27.3 ft3 27.3 ft3

(>6")

Intact Pieces 100% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb 3278lb (outside ZOI) Ttl(ns10328b27l Dirt/Dust Total (Fines) 100% 170 lb 170 lb Latent Fiber Total (Fines) 100% 30 lb 30 lb

Enclosure NOC-AE-07002240 Page 33 of 63 Table 26 - CVCS letdown line debris transport fractions Debris Debris Debris Debris Type Debris Size Transport Generated At Sump Fraction Fines 95% 153.1 ft3 145.4 ft3 3

Small Pieces 17% 0 ft 0 ft3

(<6")

LDFG (NukonTM) Large Pieces 1% 102.0 ft3 1.02 ft3

(>6")

Intact Pieces 0% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 95% 586lb 556.7 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb' 3278lb (outside ZOI)

Dirt/Dust Total (Fines) 83% 170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb Content Guide Item 3f Head Loss and Vortexing The objectives of the head loss and vortexing evaluations are to calculate head loss across the sump strainerand to evaluate the susceptibility of the strainerto vortexformation.

" Provide a schematic diagram of the emergency core cooling system (ECCS)and.containment spray systems (CSS).

" Provide the minimum submergence of the strainerunder small-breakloss-of-coolant accident (SBLOCA) and large-breakloss-of-coolant accident (LBLOCA) conditions.

" Provide a summary of the methodology, assumptions and results of the vortexing evaluation.

Provide basesfor key assumptions.

" Provide a summary of the methodology, assumptions, and results ofprototypical head loss testingfor the strainer,including chemical effects. Provide basesfor key assumptions.

• Address the ability of the design to accommodate the maximum volume of debris that is predictedto arrive at the screen.

" Address the ability of the screen to resist the formation of a "thin bed" or to accommodate partialthin bed formation.

" Provide the basisfor the strainerdesign maximum head loss.

• Describe significantmargins and conservatisms used in the head loss and vortexing calculations.

• Provide a summary of the methodology, assumptions,basesfor the assumptions, and results for the clean strainerhead loss calculation.

• Provide a summary of the methodology, assumptions,basesfor the assumptions, and results for the debris head loss analysis.

" State whether the sump is partiallysubmerged or vented (i.e., lacks a complete water seal over its entire surface)forany accident scenarios and describe what failure criteria in addition to loss of net positive suction head (NPSH) margin were applied to addresspotential inability to pass the requiredflow through the strainer.

• State whether near-field settling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used tojustify near-field credit.

• State whether temperature/viscositywas used to scale the results of the head loss tests to

Enclosure NOC-AE-07002240 Page 34 of 63 actualplant conditions.If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

State whether containment accidentpressure was credited in evaluatingwhetherflashing would occur across the strainersurface, and if so, summarize the methodology used to determine the available containmentpressure.

Content Guide Item 3f Head Loss and Vortexing

• Provide a schematic diagram of the emergency core cooling system (ECCS)and containment spray systems (CSS).

Response

See Figure 7 below for schematic with elevation layout.

STP SAFETY, INJECTION AND CONTAINMENT SPRAY TRAIN A LAYOUT EL. _(,25'

-TRAIN A TRAIN B R*AIN C Figure 7 - ECCS Schematic Content Guide Item 3f. Head Loss and Vortexing 0 Provide the minimum submergence of the strainerunder small-break loss-of-coolantaccident (SBLOCA) and large-breakloss-of-coolant accident (LBLOCA) conditions.

Response

For the SBLOCA low water condition, the strainer has /2 in. submergence. For the LBLOCA at the start of recirculation, the minimum water level provides the strainer with 10 in. submergence.

Enclosure NOC-AE-07002240 Page 35 of 63 Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions and results of the vortexing evaluation.

Provide basesfor key assumptions.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions, and results ofprototypical head loss testingfor the strainer,including chemical effects. Provide basesfor key assumptions.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Address the ability of the design to accommodate the maximum volume of debris that is predicted to arrive at the screen.

Response

This information will be provided in a later supplemental response.

'ContentGuide Item 3f Head Loss and Vortexing

• Address the ability of the screen to resist the formation of a "thin bed" or to accommodate partialthin bedformation.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide the basisfor the strainerdesign maximum head loss.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Describe significant margins and conservatisms used in the head loss and vortexing calculations.

Enclosure NOC-AE-07002240 Page 36 of 63

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f.Head Loss and Vortexing

• Provide a summary of the methodology, assumptions,bases for the assumptions, and results for the clean strainerhead loss calculation.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions, basesfor the assumptions, and results for the debris head loss analysis.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f HeadLoss and Vortexing

• State whether the sump is partiallysubmerged or vented (i.e., lacks a complete'water seal over its entire surface)for any accident scenariosand describe what failure criteriain addition to loss of net positive suction head (NPSH)margin were applied to addresspotential inability to pass the requiredflow through the strainer.

Response

The strainers are fully submerged for SBLOCA and LBLOCA conditions.

Content Guide Item 3f Head Loss and Vortexing

• State whether near-fieldsettling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used to justify near-field credit.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• State whether temperature/viscosity was used to scale the results of the head loss tests to actualplant conditions. If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

Response

This information will be providedin a later supplemental response.

Enclosure NOC-AE-07002240 Page 37 of 63 Content Guide Item 3f Head Loss and Vortexing 0 State whether containment accidentpressure was credited in evaluatingwhetherflashing would occur across the strainersurface, and if so, summarize the methodology used to determine the available containmentpressure.

Response

Containment accident pressure is not credited.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

The objective of the NPSH section is to calculate the NPSH marginfor the ECCS and CSS pumps that would exist during a loss-of-coolantaccident (LOCA) consideringa spectrum of break sizes.

" Provide applicablepumpflow rates, the total recirculationsumpflow rate, sump temperature(s),

and minimum containment water level.

" Describe the assumptions used in the calculationsfor the above parametersand the sources/bases of the assumptions.

• Provide the basisfor the requiredNPSH values, e.g., threepercent head drop or other criterion.

• Describe how friction and otherflow losses are accountedfor.

• Describe the system response scenariosfor LBLOCA and SBLOCA 's.

• Describe the operationalstatusfor each ECCS and CSSpump before and after the initiation of recirculation.

• Describe the singlefailure assumptions relevant to pump operationand sump performance.

• Describe how the containment sump water level is determined.

• Provide assumptions that are included in the analysis to ensure a minimum (conservative) water level is used in determiningNPSH margin.

" Describe whether and how the following volumes have been accountedfor in pool level calculations: empty spraypipe, water droplets, condensation and holdup on horizontaland vertical surfaces. If any are not accountedfor, explain why.

" Provide assumptions (and their bases) as to what equipment will displace water resulting in higher pool level.

" Provide assumptions (and their bases) as to what water sourcesprovide pool volume and how much volume is from each source.

• If credit is taken for containment accidentpressure in determining availableNPSH,provide description of the calculationof containment accidentpressure used in determining the available NPSH.

" Provide assumptions made which minimize the containment accidentpressure and maximize the sump water temperature.

" Specify whether the containment accidentpressure is set at the vaporpressurecorrespondingto the sump liquid temperature.

• Provide the NPSH margin resultsforpumps taking suction from the sump in recirculationmode.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide applicablepumpflow rates, the total recirculationsumpflow rate, sump temperature(s),

and minimum containment water level.

Enclosure NOC-AE-07002240 Page 38 of 63

Response

The design flow per sump for LBLOCA is 7,020 gpm. Two of the three sumps are assumed to be operating due to single failure of the diesel for the third train. The flows for the pumps in each operating train are:

LHSI 2,800 gpm HHSI 1,620 gpm CS 2,600 gpm The sump temperature at start of recirculation is 267 degrees F.

The minimum containment water level at start of recirculation is 38 in. off the floor.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the assumptions used in the calculationsfor the above parametersand the sources/bases of the assumptions.

Response

The SI pump flow rates are the maximum values given in the Technical Specifications. The CS pump flow rate is based on calculated maximum flows when two trains are operating. The sump temperature is from the containment LOCA pressure-temperature analysis which maximizes the sump temperature by using the maximum temperatures for cooling water to the heat exchangers and for the water of the ultimate heat sink. The containment water level was determined using conservative input values for the pool contributions and conservatively accounting for items such as holdup in locations in the containment, filling of empty pipe, water in transit, steam holdup, etc.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide the basisfor the requiredNPSH values, e.g., three percent head drop or other criterion.

Response

Westinghouse supplied the LHSI, HHSI, and CS pumps to STP from Pacific Pumps. The required NPSH values are based on input from Westinghouse and are as follows:

LHSI 16.5 ft. HHSI 16.1 ft. CS 16.4 ft.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe howfriction and otherflow losses are accountedfor.

Response

The strainer modification did not change the piping friction losses used in the NPSH calculation. The friction losses are based on the maximum flows of the SI and CS pumps.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the system response scenariosfor LBLOCA and SBLOCA 's.

Enclosure NOC-AE-07002240 Page 39 of 63

Response

For LBLOCA the Safety Injection Pumps and the Containment Spray Pumps start automatically and take suction from the Refueling Water Storage Tank. When the tank is drawn down, the pumps' suction is automatically switched over to the containment sumps for the recirculation mode. The HHSI and CS Pumps may be turned off later in the post-accident mitigation per the emergency operating procedures.

For SBLOCA the HHSI Pump is used to for the core cooling function during the injection and the recirculation phases. The CS pump is also assumed to be in operation due to automatic actuation by reaching the containment pressure set point..

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the operationalstatusfor each ECCS and CSSpump before and after the initiation of recirculation.

Response

Both before and after the initiation of recirculation, two Trains are operating. Each Train consists of one HHSI, one LHSI, and one CS pump. Each Train has its own containment sump with strainer.

Content Guide Item 3g. Net PositiveSuction Head (NPSH)

• Describe the singlefailure assumptions relevant to pump operationand sump performance.

Response

The STP design has three safety Trains each with its own containment sump. The sump performance analysis is based on a single failure that results in two Trains operating to handle the debris generated.

Content Guide Item 3g. Net PositiveSuction Head (NPSH)

• Describe how the containment sump water level is determined.

Response

The Containment Water Level Calculation analyzed multiple high-energy line break cases including large break and small break LOCA's chosen to encompass a wide range of potential break sizes and locations.

The breaks were analyzed at various times throughout the event including at the start of recirculation, at suspension of containment sprays and at the end of the event. The following methodology was used to.

develop the Containment Water Level Calculation:

1. A correlation was developed for the relationship between containment water level and the containment volume as a function of elevation using information from existing STP calculations. The correlation between containment volume and water level developed in the Water Level Calculation assumes equalization of water level between all areas of containment at the (-) 1 '-3" elevation including internal compartments (e.g., incore instrument room, reactor cavity and elevator shaft). The volume inside the accumulator skirts is only credited as a displacement volume for the small break LOCA case in which the water level does not reach the service way openings preventing this volume from filling. The correlation also includes all volumes below the (-)11 '-3" elevation (e.g., elevator shaft, normal sump, secondary normal sump, emergency sumps, incore instrument room sump and drain lines).

Enclosure NOC-AE-07002240 Page 40 of 63

2. The quantity of water added to containment from the Refueling Water Storage Tank, SI Accumulators, and the Reactor Coolant System was determined for each of the breaks considered.

3. The quantity of water diverted from the containment sump was determined. The following effects were considered:

• Steam holdup in the containment atmosphere

" Additional mass of water that must be added to the RCS due to the increase in the water density at the lower sump water temperature versus the RCS temperature prior to the LOCA

" Water volume required to fill the RCS steam space as condensation occurs

" Condensation on containment surfaces

• Water volume required to fill the Safety Injection and Containment Spray Piping that is empty prior to the LOCA

" Water in transit from the Containment Spray nozzles and the break location to the Containment Sump

" ECCS leakage outside of containment

• Miscellaneous hold-up volumes throughout containment

4. Given the net mass of water added to the containment floor based on items 2 and 3 listed above, the post-LOCA containment water level was then calculated using the correlation developed in item 1.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions that are included in the analysis to ensure a minimum (conservative) water level is used in determiningNPSH margin.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe whether and how the following volumes have been accountedfor in pool level calculations:empty spraypipe, water droplets, condensation and holdup on horizontal and vertical surfaces. If any are not accountedfor, explain why.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions (and their bases) as to what equipment will displace water resulting in higherpool level.

Response

See subsection immediately above.

Enclosure NOC-AE-07002240 Page 41 of 63 Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions (and their bases) as to what water sourcesprovidepool volume and how much volume is from each source.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• If credit is taken for containment accidentpressure in determining availableNPSH,provide description of the calculationof containment accident pressure used in determining the available NPSH.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions made which minimize the containment accidentpressureand maximize the sump water temperature.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Specify whether the containment accidentpressure is set at the vaporpressurecorrespondingto the sump liquid temperature.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide the NPSH margin resultsfor pumps taking suction from the sump in recirculationmode.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation The objective of the coatings evaluation section is to determine the plant-specific ZOI and debris characteristicsfor coatingsfor use in determining the eventual contribution of coatings to overall head loss at the sump screen.

Enclosure NOC-AE-07002240 Page 42 of 63

• Provide a summary of type(s) of coatingsystems used in containment, e.g., Carboline CZ ))

InorganicZinc primer,Ameron 90 epoxy finish coat.

- Describe andprovide basesfor assumptions made in post-LOCA paint debris transport analysis.

• Discuss suction strainerhead loss testing performed as it relates to both qualified and unqualified coatings and what surrogatematerial was used to simulate coatings debris.

• Provide basesfor the choice of surrogates.

• Describe andprovide basesfor coatings debrisgeneration assumptions. Forexample, describe how the quantity ofpaint debris was determined based on ZOI size for qualified and unqualified coatings.

-Describewhat debris characteristicswere assumed, i.e., chips, particulate,size distributionand provide basesfor the assumptions.

- Describe any ongoing containment coating condition assessmentprogram.

Content Guide Item 3.h - CoatingsEvaluation

• Provide a summary of type(s) of coating systems used in containment, e.g., Carboline CZ 11 InorganicZinc primer,Ameron 90 epoxy finish coat.

Response

The qualified coatings inside the Unit 1 and Unit 2 Reactor Containments are detailed in STP calculations. There are various types of qualified coatings used in the containment including Ethyl Silicate Inorganic Zinc (IOZ), Epoxy System, Phenolic Epoxy, Clear Sealer, Alkyd, Baked Enamel and Epoxy Intumescent.

The unqualified coatings inside the Unit 1 and Unit 2 Reactor Containments are detailed in STP calculations. There are various types of unqualified coatings used in the containment including IOZ, Epoxy System, Phenolic Epoxy, Alkyd and Baked Enamel.

The following is a brief summary of specific equipment and their coatings; the concrete walls are coated with an Epoxy System, the equipment (valves) are coated with IOZ, whip restraints are coated with Epoxy, the equipment supports are coated with IOZ, the pipe supports are coated with both Polyamide Primer (an epoxy coating) and IOZ.

Content Guide Item 3.h - CoatingsEvaluation

• Describe andprovide basesfor assumptions made in post-LOCA paint debris transportanalysis.

Response

The methodology utilized for the STP debris transport analysis is described above in another section. The transport of containment coatings was included in the analyses. In addition to the methodology described above, the following key attributes apply and are intended to describe and provide the bases for assumptions made in post-LOCA paint debris transport analysis.

1. It was assumed that the settling velocity of fine debris (insulation, dirt/dust, and paint particulate) can be calculated using Stokes' Law. This is a reasonable assumption since the particulate debris is generally spherical and would settle slowly (within the applicability of Stokes' Law).

Enclosure NOC-AE-07002240 Page 43 of 63

2. It was assumed that the unqualified coatings would be uniformly distributed in the recirculation pool. This is a reasonable assumption since the unqualified coatings are scattered around containment in small quantities.

3. Both the qualified coatings (inside the ZOI) and the unqualified coatings were conservatively assumed to fail as 10 micron particulate in the debris generation analysis.

The results of debris transport are included in the section above and include the associated values for the transport of coatings debris both within and outside the ZOI. A review of Table 21 through Table 26 identify that for the bounding LOCA analyses, coating debris transports as fines and 83% - 100% are transported to the screen, depending on the case.

Content Guide Item 3.h - Coatings Evaluation

• Discuss suction strainerhead loss testing performedas it relates to both qualified and unqualified coatings and what surrogatematerial was used to simulate coatings debris.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation

• Provide basesfor the choice of surrogates.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation

- Describe andprovidebasesfor coatings debris generation assumptions.For example, describe how the quantity ofpaint debris was determined based on ZOI size for qualified and unqualified.

coatings.

Response

The methodology utilized for the STPEGS debris generation analyses is described in sections above. The generation of containment coating debris was included in the analyses. In addition to the methodology described in these sections, the following key attributes apply and are intended to describe and provide the bases for coatings debris generation assumptions for STPEGS, and describe how the quantity of paint debris was determined based on ZOI size for qualified and unqualified coatings.

All coatings, qualified and unqualified, within the ZOI are assumed to fail and generate debris in the form of 10ýtm spherical particles, which is equivalent in size to the average zinc particle in inorganic zinc (IOZ) coatings or the pigment used in epoxy coatings.

Qualified Coatings The assumption made for coatings in the zone of influence (ZOI) of the LOCA is based on testing performed on representative coating systems. A spherical ZOI of 5D for qualified coatings was selected based on refined analysis in WCAP-16568-P, "Jet Impingement Testing to Determine the Zone of Influence (ZOI) for DBA Qualified/Acceptable Coatings", Revision 0. This was developed and

Enclosure NOC-AE-07002240 Page 44 of 63 performed in order to identify an appropriate ZOI for DBA-Qualified / Acceptable coating systems less than the 1OD ZOI mandated by the NRC SER on NEI 04-07. The results of this program demonstrate that a ZOI radius of 5D should be used for epoxy and untopcoated inorganic zinc coatings.

Per NEI 04-07, qualified coatings within the ZOI are assumed to fail as a result of impingement and post-accident environmental conditions. Qualified coatings outside the ZOI are assumed to remain intact. In order to determine the amount of qualified coatings that fail, a 3 dimensional model of the containment to calculate the areas of specific surfaces (i.e. floors, walls, equipment, etc.) within the ZOI. Plant documentation identifying coating types and applications were then used to determine the associated volume, weight and density of coatings. The density and weight of each of the various qualified coatings is listed in Table 27.

Unqualified Coatings Per NEI 04-07, all unqualified coatings inside and outside the ZOI are assumed to fail as a result of impingement and post-accident environmental conditions. The amount of unqualified coatings that will fail was determined in a similar manner. However, the weight of the applied coatings are determined based on a theoretical coating spread rates (sq. ft. per gallon @ 1 mil thickness) instead of specific vendor coating spread rates. The density and weight of each of the various unqualified coatings is listed in Table 28.

STP request for additional information (RAI) #26 is addressed by WCAP-16568-P.

Table 27 - Failed Qualified Coating Debris Source Term Type of Coating Density Weight (1b)

(lb/ft_) Weight (lb)

Epoxy 94 23 IOZ 457 553 Polyamide Primer 94 10

Enclosure NOC-AE-07002240 Page 45 of 63 Table 28 - Failed Unqualified Coating Debris Source Term Type of Coating (lb/ft3)

Density Wegt(b Weight (ib)

Epoxy 94 1,815 Alkyd 98 310 IOZ 457 884 Baked Enamel 98 269 Table 29 - Total Failed Qualified and Unqualified Coating Debris Source Term Type of Coating (lb/ft3)Wegt(b Weight (lb)

Density Epoxy 94 1,838 IOZ 457 1,437 Alkyd 98 310 Baked Enamel 98 269 Polyamide Primer 94 10 Content Guide Item 3.h - CoatingsEvaluation

• Describewhat debris characteristicswere assumed, i.e., chips, particulate,size distributionand provide basesfor the assumptions.

Response

See section above.

Content Guide Item 3.h - CoatingsEvaluation Describe any ongoing containment coating condition assessmentprogram.

Enclosure NOC-AE-07002240 Page 46 of 63

Response

STPNOC periodically conducts condition assessments of coatings inside containment. Coating condition assessments are conducted as part of the structures monitoring program. Visual inspection of coatings in containment is intended to characterize the condition of the coating systems. If localized areas of degraded coatings are identified, those areas are evaluated and scheduled for repair/replacement as necessary.

Content Guide'Item 3.i Debris Source Term The objective of the debris source term section is to identify any significant design and operationalmeasures taken to control or reduce the plant debris source term to prevent potential adverse effects on the ECCS and CSS recirculationfunctions.

• Provide the information requested in GL 04-02 Requested Information Item 2.69 regarding programmaticcontrols taken to limit debris sources in containment.

GL 2004-02 Requested Information Item 2(l) A description of the existing or planned programmaticcontrols that will ensure that potential sources of debris introduced into containment (e.g., insulations,signs, coatings, andforeign materials) will be assessedfor potential adverse effects on the ECCS and CSS recirculationfunctions. Addressees may reference their responses to GL 98-04, "Potentialfor Degradationof the Emergency Core CoolingSystem and the Containment Spray System after a Loss-of-Coolant Accident Because of Construction and Protective CoatingDeficiencies and ForeignMaterialin Containment,"to the extent that their

responses address these specificforeign material control issues.

In responding to GL 2004 Requested Information Item 209, provide the following:

• A summary of the containment housekeepingprogrammaticcontrols in place 'to control or reduce the latent debris burden. Specificallyfor RMI/low-fiber plants, provide a description ofprogrammatic controls to maintain the latent debrisfiber source term into the future to ensure assumptions and conclusions regardinginability toform a thin bed offibrous debris remain valid.

" A summary of theforeign material exclusion programmaticcontrols in place to control the introduction offoreign materialinto the containment.

• A description of how permanentplant changes inside containment areprogrammatically controlled so as to not change the analyticalassumptions and numerical inputs of the licensee analyses supportingthe conclusion that the reactorplant remains in compliance with 10 CFR 50.46 and relatedregulatory requirements.

• A descriptionof how maintenance activities includingassociated temporary changes are assessed and managed in accordancewith the Maintenance Rule, 10 CFR 50.65.

If any of the following suggested design and operationalrefinements given in the guidance report (guidancereport, Section 5) and SE (SE, Section 5.1) were used, summarize the applicationof the refinements.

• Recent or planned insulation change-outs in the containment which Will reduce the debris burden at the sump strainers

• Any actions taken to modify existing insulation (e.g., jacketing or banding)to reduce the debris burden at the sump strainers.

• Modifications to equipment or systems conducted to reduce the debris burden at the sump strainers

Enclosure NOC-AE-07002240 Page 47 of 63 Actions taken to modify or improve the containment coatingsprogram Content Guide Item 3.i Debris Source Term

• A summary of the containment housekeeping programmaticcontrols in place to control or reduce the latent debris burden. Specificallyfor RMI/low-fiber plants,provide a description ofprogrammatic controls to maintain the latent debrisfiber source term into the future to ensure assumptions and conclusions regardinginability to form a thin bed offibrous debris remain valid.

Response

During outages, STPNOC maintains containment cleanliness by adherence to the housekeeping procedure. Containment cleanliness is emphasized by the reactor containment building coordinators and the work supervisors. Prior to containment closeout at the end of the outage, the building coordinators oversee the cleanup of the containment work areas to achieve the goal of no loose debris.

Content Guide Item 3.i Debris Source Term

• A summary of the foreign material exclusion programmaticcontrols in place to control the introductionofforeign materialinto the containment.

Response

STPNOC uses a procedure to maintain containment integrity with respect to potential sump debris sources. This procedure provides guidance for a visual inspection of the affected areas inside containment at the completion of each containment entry when containment integrity has been established to verify that no loose debris is present that could be transported to the emergency sump and cause restriction of pump suction during LOCA conditions.

STPNOC has a procedure that governs signs and labels that contains the requirements for labeling inside containment. These requirements are used to minimize potential sump debris items.

Content Guide Item 3.i Debris Source Term

• A description of how permanentplant changes inside containmentare programmatically controlled so as to not change the analyticalassumptions and numerical inputs of the licensee analyses supportingthe conclusion that the reactorplant remains in compliance with 10 CFR 50.46 and relatedregulatoryrequirements

Response

Insulation replacement inside containment is either a like-for-like replacement as a maintenance activity

("rework") or is a modification with a design change that has been approved by STPNOC Engineering.

The STPNOC design change process ensures that new insulation material that differs from the initial design is evaluated.

The STPNOC design change process also calls for evaluations of added metals such as aluminum that could contribute to post-LOCA chemical effects in the sump water. The process looks at coatings that are to be used inside containment. Impacts to post-LOCA recirculation flow paths and recirculation sump debris impact on internals of fluid containing components are part of the design change evaluation process described in the procedure.

Enclosure NOC-AE-07002240 Page 48 of 63 Content Guide Item 3.i Debris Source Term A description of how maintenance activities including associatedtemporary changes are assessed and managed in accordancewith the MaintenanceRule, 10 CFR 50.65.

Response

Maintenance activities inside containment are subject to the cleanliness requirements that are given in the containment integrity surveillance procedure. The temporary change process also calls for an evaluation of items installed inside containment.

Content Guide Item 3.i Debris Source Term

• Recent orplannedinsulation change-outs in the containment which will reduce the debris burden at the sump strainers

• Any actions taken to modify existing insulation (e.g., jacketing or banding) to reduce the debris burden at the sump strainers

" Modifications to equipment or systems conducted to reduce the debris burden at the sump strainers

Response

STPNOC did not perform (and does not plan to perform) any insulation change outs or modifications to insulation banding or jacketing to reduce the potential insulation debris source term. No modifications to components or to systems were made to reduce the debris burden at the sump strainers.

Content Guide Item 3.i Debris Source Term

• Actions taken to modify or improve the containment coatingsprogram

Response

The sump performance evaluation did not result in any changes to the containment coatings program.

Content Guide Item 3.J Screen Modification Package The objective of the screen modificationpackage section is to provide a basic description of the sump screen modification.

• Provide a descriptionof the majorfeatures of the sump screen design modification.

• Provide a list of any modifications, such as reroute ofpiping and other components, relocationof supports, additionof whip restraintsand missile shields, etc., necessitated by the sump strainermodifications.

Content Guide Item 3.J Screen Modification Package

• Provide a descriptionof the majorfeatures of the sump screen design modification

Response

There is no change to the three independent sump pits. The sump screen above the pit has been removed; and now each sump has its own new strainer. There are no shared components between trains.

The new strainer assemblies for each of the 3 emergency sumps consist of two 5-module assemblies, one 4-module assembly, and one 6-module assembly. Each module is made up of eleven strainer disks. The strainer consists of stainless steel perforated plate with 0.095 in. diameter openings. Flow leaving the

Enclosure NOC-AE-07002240 Page 49 of 63 strainer assembly enters a four inlet plenum box (one inlet for each strainer assembly). The plenum box collects the flow from the strainer assemblies and directs it downward directly into the sump pit. An access cover is provided on the plenum box for internal inspection of the sump structures, vortex suppressor, and the strainer assemblies. The sump pit is now covered with a sump cover plate that prevents material from falling directly into the pit without passing through the strainer assemblies.

The new strainers have a surface area of 1,818.5 sq ft per sump. The old screens had a surface area of 155.4 sq ft per sump. For the design flow of 7,020 gpm per sump, the new strainers have a flow velocity of 0.009 ft/sec.

See the attached figures for the old screen design and the new strainer, design.

Content Guide Item 3.J Screen ModificationPackage

• Provide a list of any modifications, such as reroute ofpiping and other components, relocation of supports, addition of whip'restraintsand missile shields, etc., necessitated by the sump strainermodifications.

Response

There are no high energy lines in the area of the emergency sumps except for the High Head Safety Injection lines which are used for accident mitigation and are not assumed to be the accident initiator. No piping reroutes were needed for installation of the new sump strainers. No component relocations or additions were necessitated by the new strainer installation.

Content Guide Item k. Sump StructuralAnalysis The objective of the sump structuralanalysis section is to verify the structuraladequacy of the sump strainerincluding seismic loads and loads due to differentialpressure, missiles, andjet forces.

Provide the information requested in GL 2004-02 Requested Information Item 2(d)(vii).

• GL 2004-02 Requested Information Item 2(d)(vii) Verification that the strength of the trash racks is adequate to protect the debris screensfrom missiles and other large debris. The submittal should also provide verification that the trash racks and sump screens are capable of withstanding the loads imposed by expandingjets, missiles, the accumulation of debris, andpressure differentials caused by post-LOCA blockage underflow conditions

" Summarize the design inputs, design codes, loads, and load combinations utilizedfor the sump strainerstructuralanalysis.

" Summarize the structuralqualificationresults and design marginsfor the various components of the sump strainerstructuralassembly.

" Summarize the evaluationsperformedfor dynamic effects such as pipe whip, jet impingement, and missile impacts associatedwith high-energy line breaks (as applicable).

0 If a backflushingstrategy is credited,provide a summary statement regardingthe sump strainerstructuralanalysis consideringreverseflow.

Content Guide Item k. Sump StructuralAnalysis

• Summarize the design inputs, design codes, loads, and load combinations utilizedfor the sump strainerstructuralanalysis.

Enclosure NOC-AE-07002240 Page 50 of 63

Response

The strainer components are designed in accordance with the AISC "Specification for the Design, Fabrication, and Erection of Structural Steel for Buildings, 7th Edition" with Supplement Numbers 1, 2 and 3; and SEI/ASCE 8-02, "Specification for the Design of Cold-Formed Stainless Steel Structural Members". The acceptance criteria are primarily in accordance with these codes. In circumstances where these specifications do not provide adequate guidance for a particular component, other codes, specifications or standards are used for guidance. For instance, the strainers are made from stainless steel materials. The AISC Specification does not specifically cover stainless steel materials. Therefore, ANSE/AISC N690-1994, "Specification for the Design, Fabrication, and Erection of Steel Safety Related Structures for Nuclear Facilities", is used to supplement the AISC Specification in any areas related specifically to the structural qualification of stainless steel. Note that only the allowable stresses are used from this Specification and load combinations and allowable stress factors for higher service levels are not used.

For the perforated plates, the equations from Appendix A, Article A-8000 of the ASME B&PV Code,Section III, 1998 Edition are used instead of the AISC code. A-8000 is deemed more appropriate because it is written specifically for perforated plates.

The strainer also has several components made from thin gage sheet steel, and cold formed stainless sheet steel. SEI/ASCE 8-02, "Specification of the Design of Cold-Formed Stainless Steel Structural Members", is used for certain components where rules specific to thin gage and cold form stainless steel are applicable. The rules for Allowable Stress Design (ASD) as specified in Appendix D of this specification are used. This is further supplemented by the AISC Specification where the ASCE Specification is lacking specific guidance. Finally, guidance is also taken from AWS D1.6, "Structural Welding Code - Stainless Steel", as it relates to the qualification of stainless steel welds.

The new strainers are designed for loads due to weight, pressure, and dynamic loads. The dynamic loads come from seismic and from hydrodynamic drag loads due to sloshing. The strainers are loaded due to the inertia effect due to the motion of the containment floor during an earthquake. Hydrodynamic loads on the strainers are due to the motion of the water surrounding the strainer during a seismic event. Two weight loads are applicable. This includes the weight of the strainer components themselves and the weight of the debris that accumulates on the strainer. The design weight of the debris per strainer module is taken as 150 lbs. which bounds the calculated weight.

Thermal expansion loads are taken as zero because the strainers are essentially free standing structures that are basically free to expand without restraint due to sufficient gaps built-in to the pin connections that secure the modules to the floor tracks. Thermal expansion loads on the sump pit cover plate and the floor angles are considered negligible because these components have slotted holes or edge clips to allow for substantially unrestrained thermal growth.

The pressure load acting on the strainer is the differential pressure across the strainer perforated plates in the operating condition. This is defined as 5.71 ft. of head.

The load combinations and allowable stresses are based on the requirements of STP design criteria and are provided below.

Enclosure NOC-AE-07002240 Page 51 of 63 Load Condition Combinatioth ' , . Allowabl.e Normal Operating DW + DP + WD 1.0 S Normal Operating (Outage/Lift Load) DW + LL 1.0 S Operating Basis Earthquake DW + DP + WD + OBE 1.0 S Safe Shutdown Earthquake DW + DP + WD + SSE 1.6 S DW = Dead Weight Load LL = Live Load (additional live loads acting on strainer assembly during outages only)

WD = Weight of Debris DP = Differential Pressure OBE = Operating Basis Earthquake SSE = Safe Shutdown Earthquake S = Required section strength based on elastic design methods and the allowable, stress defined in the 7th edition AISC Specification, or other applicable specifications (ASCE 8-00, N-690, etc.)

Content Guide Item k. Sump StructuralAnalysis

• Summarize the structuralqualificationresults and design marginsfor the various components of the sump strainerstructuralassembly

Response

The calculation for seismic design margins for the strainers and their components, shows that the stress Interaction Ratios (calculated stress/allowable stress) are less than one for both Operating Basis Earthquake and Safe Shutdown Earthquake loads.

Content Guide Item 3.k Sump StructuralAnalysis

, Summarize the evaluationsperformedfor dynamic effects such as pipe whip, jet impingement, and missile impacts associated with high-energy line breaks (as applicable).

Response

There are no high energy lines in the area of the emergency sumps except for the High Head Safety Injection lines which are used for accident mitigation and are not assumed to be the accident initiator.

Thus no evaluations were needed for high energy line breaks.

Content Guide Item 3.k Sump StructuralAnalysis

• If a backflushing strategy is credited,provide a summary statement regardingthe sump strainerstructuralanalysisconsideringreverseflow.

Response

The new strainer design does not involve any backflushing.

Content Guide Item 3.1 Upstream Effects The objective of the upstream effects assessment is to evaluate the flowpaths upstream of the containment sump for holdup of inventory which could reduceflow to andpossibly starve the sump.

Provide a summary of the upstream effects evaluation including the information requestedin GL 2004-02 Requested Information Item 2(d)(iv).

Enclosure NOC-AE-07002240 Page 52 of 63 GL 2004-02 Requested Information Item 2(d)(iv)

The basisfor concluding that the water inventory required to ensure adequate ECCS or CSS recirculationwould not be held up or diverted by debris blockage at choke-points in containmentrecirculationsump returnflowpaths.

Summarize the evaluation of the flow pathsfrom the postulated break locations and containment spray washdown to identify potential choke points in the flow field upstream of the sump.

• Summarize measures taken to mitigatepotential choke points.

• Summarize the evaluation of water holdup at installed curbs and/or debris interceptors.

• Describe how potential blockage of reactorcavity and refueling cavity drains has been evaluated, including likelihood of blockage and amount of expected holdup.

Content Guide Item 3.1 Upstream Effects

• Summarize the evaluation oftheflowpathsfrom the postulated break locations and containmentspray washdown to identify potential choke points in the flow field upstream of the sump.

Response

The Upstream Effects Evaluation provides a general description of the containment and sub-compartments as well as an examination of each elevation to identify physical and structural features that affect the flow of debris and water to lower containment. The Upstream Effects Evaluation preceded the Containment Water Level Calculation and served to identify potential flow path choke points and areas of containment where water volumes could potentially be held up from reaching the containment sumps due to the'actual design layout or due to the added effects of debris resulting from high-energy line break accidents. The evaluation was based on a review of STP design documents including the UFSAR, calculations and containment drawings. No containment walkdowns were performed in support of the evaluation; however, containment photographs were reviewed. Plant personnel also provided additional information as needed.

Spray/break inventory and debris originating at upper elevations will eventually flow down to the 19'-0" elevation. The primary flow paths are through significant grated floor areas at upper elevations. See STP Response to Item 3.1 (4th bullet) below for additional information regarding the drainage flow path from the refueling cavity. Once at the 19'-0" elevation, significant concrete flooring routes the flow of water and debris to grated areas inside and outside the secondary shield wall. The primary sources of insulation debris are located above the 19'-0" elevation (e.g., the primary RCS piping and components). Therefore, the majority of insulation debris will be trapped at this elevation unless it can fit through standard floor grating. It is judged that this elevation will not become a choke point for flow because should large debris hold up at area of floor grating, the water has multiple other potential grated flow paths to the lower elevations. In addition, there is open communication between the areas inside and outside the secondary shield wall increasing the grated floor area available to pass flow.

The recirculation pool forms at the (-)11 '-3" elevation. The ECCS emergency sumps are located in the southern quadrants of containment outside the secondary shield wall. The flow path around the outside of the secondary shield wall is generally open providing large flow passages to the ECCS emergency sumps.

See STP Response to Item 3.1 (3rd bullet) for description of flow communication between areas inside and outside the secondary shield wall at the (-)l I '-3" elevation.

Enclosure NOC-AE-07002240 Page 53 of 63 Content Guide Item 3.1 Upstream Effects 0 Summarize measures taken to mitigatepotential choke points.

Response

No measures are necessary to mitigate potential choke points.

Content Guide Item 3.1 Upstream Effects

• Summarize the evaluation of water holdup at installed curbs and/or debris interceptors.

Response

There are only four (4) significant openings through which recirculation water and debris may pass from inside the secondary shield wall to the annular region outside the secondary shield wall at the (-) 11'-3" elevation. These openings are four 30" circular vent holes located-at a centerline elevation of (-)8'-6".

Since these vent holes are above the floor, the secondary shield wall acts as a curb, or debris barrier, in the flow path to the containment sumps. As discussed in the response to Item 3.1 (2nd bullet), only small debris (small enough to fit through standard floor grating) is expected to reach the base floor elevation.

Significant mounding of small debris is not expected to create a dam that would prevent flow through the vent openings. The volume of water below the vent holes is considered lost to the ECCS emergency sump.

No new curbs and/or debris interceptors have been installed.

Content Guide Item 3.1 Upstream Effects

• Describe howpotential blockage of reactorcavity and refueling cavity drains has been evaluated, including likelihood of blockage and amount of expected holdup.

Response

The refueling cavity drains via two (2) horizontal 6" drains with center line elevation located 10.75 inches above the bottom of the lower internals storage area. The two horizontal refueling cavity drains have an inside diameter of 6.065" and are straight pipe segments approximately 7 feet long. Alion Calculation ALION-CAL-STPEGS-2916-006, Rev. 0, "GSI 191 Containment Recirculation Sump Evaluation:

Determination of Fibrous Debris Transport to the Refuel Cavity" and Westinghouse letter LTR-CSA 45 "Refueling Cavity Drain Lines" are the basis for concluding that the refueling cavity drain will not become plugged with debris. Based on debris generation and transport analyses, it was conservatively determined that 71 ft3 of fines (individual fibers) and 177 ft3 of small pieces (< 6") of fibrous insulation are transported to the Refueling Cavity. The STP analyses assume that the drains do not become blocked by debris, thus restricting flow from the cavity. No additional water hold-up are assumed for the refueling cavity except that volume required to induce flow through the cavity drains above the cavity floor.

Debris blown out of the steam generator compartments is expected to be distributed evenly around the operating floor (elevation 68'-0"). The refueling cavity drain lines are located on opposite walls of the lower internals storage area and large concentrations of debris would not be expected to land near both drain lines. There are no drain covers or trash racks for the drains that would allow fibers to build up and block flow. The largest debris transported to the refueling cavity (<6") is smaller than the drain line diameter (6.065"). In addition, fibrous debris is not rigid and will deform to fit through the drain if needed. The flow velocity through the drains has been determined to be greater than the incipient tumbling velocity for 6" pieces of Nukon; however, should debris accumulate in the drain line, the

Enclosure NOC-AE-07002240 Page 54 of 63 buildup of water behind the debris will provide sufficient driving force to push the debris through the straight pipes.

STP RAI #39 is addressed by this evaluation.

Content Guide Item 3.m Downstream effects - Components and Systems The objective of the downstream effects, components and systems section is to evaluate the effects of debris carrieddownstream of the containment sump screen oh thefunction of the ECCS and CSS in terms ofpotential wear of components and blockage offlow streams. Provide the information requested in GL 04-02 Requested Information Item 2(d)(v) and 2(d)(vi) regardingblockage, plugging, and wear at restrictionsand close tolerance locations in the ECCS and CSS downstream of the sump.

GL 2004-02 Requested Information Item 2(d)(v) I The basisfor concluding that inadequate core or containment cooling would not result due to debris blockage atflow restrictionsin the ECCS and CSSflowpaths downstream of the sump screen, (e.g., a HPSI throttle valve, pump bearings and seals,fuel assembly inlet debris screen, or containment spray nozzles). The discussion should consider the adequacy of the sump screen=s mesh spacing and state the basisfor concluding that adverse gaps or breaches are not present on the screen surface.

GL 2004-02 Requested Information Item 2(d)(vi)

Verification that the close-tolerancesubcomponents in pumps, valves and other ECCS and CSS components are not susceptible to plugging or excessive wear due to extended post-accident

-,operationwith debris-ladenfluids.

1

" IfNRC-approved methods were used (e.g., WCAP-16406-P with accompanyingNRC SE),

briefly summarize the applicationof the methods. Indicate where the approved methods were not used or exceptions were taken, and summarize the evaluation of those areas.

" Provide a summary and conclusions of downstream evaluations.

• Provide a summary of design or operationalchanges made as a result of downstream evaluations.

The draft NRC SE for this document was issued to the applicant in November 2007.

Content Guide Item 3.m Downstream effects - Components and Systems

• IfNRC-approved methods were used (e.g., WCAP-1 6406-P with accompanyingNRC SE),

briefly summarize the applicationof the methods. Indicate where the approved methods were not used or exceptions were taken, and summarize the evaluation of those areas.

Response

Methods are discussed below under summary and conclusions. See next response.

Content Guide Item 3.m Downstream effects - Components and Systems

• Provide a summary and conclusions of downstream evaluations.

Enclosure NOC-AE-07002240 Page 55 of 63

Response

The evaluations listed below were developed to address effects of debris carried downstream of the containment sump screen on-the function of the ECCS and containment spray system (CSS) in terms of potential wear of components and blockage of flow streams. Close-tolerance subcomponents in pumps, valves and other ECCS and CSS components were evaluated for potential plugging or excessive wear due to extended post-accident operation with debris-laden fluids. The evaluations were developed in accordance with WCAP-16406-P, ."Evaluation of Downstream Sump Debris Effects in Support of GSI-191" prior to issuance of Revision 1 and the accompanying NRC SER. No exceptions were taken to the WCAP-16406-P methodology. A revised evaluation will be performed using Rev. 1 and the SER and will be described in a later Supplemental response to the GL.

STP RAI #31 is addressed by these evaluations.

The quantity of debris in the recirculating fluid that passes through the sump is characterized in terms of volume concentration. For downstream effects, this debris concentration is defined as the ratio of the solid volume of the debris in the pumped fluid to the total volume of water that is being recirculated by the ECC and CS systems. The resulting volume concentration from the initial debris concentration and total water volume is 0.001021.

The mass of debris in the recirculating fluid that passes through the sump is characterized in terms of parts per million (ppm). For downstream effects, the total initial debris concentration comprised of the individual debris concentrations is defined as the ratio of the solid mass of the debris in the pumped fluid to the total mass of water that is being recirculated by the ECC and CS systems.

Debris Type Concentration Fibrous 14 ppm Particulate 99 ppm Coatings - 1388 ppm Total 1501 ppm It was determined that all of the following ECCS and CSS components evaluated for STP can accommodate sump bypass particles without blockage: throttle valves; pipes, valves, and instrumentation; orifices and eductors; heat exchangers; and nozzles. A review of drawings and documents indicated that none of the ECCS and CS valves are throttled. There are no blockage/plugging issues: for existing piping, valves, and instrumentation lines; for the ECCS and CS flow element orifices, flow restricting orifices or in educator passages; for RHR heat exchangers; and for the CS spray nozzles.

According to the criteria established in WCAP- 16406-P, the wear impact on the valves identified in the STP evaluation was determined not critical and needs no further erosion evaluation.

Pump Wear Evaluation:

For pumps, the effect of debris ingestion through the sump screen were evaluated based on three aspects of operability, including hydraulic performance, mechanical shaft seal assembly performance, and mechanical performance (vibration) of the pumps. The pumps identified for evaluation were the High Head Safety Injection (HHSI), Low Head Safety Injection (LHSI), and Containment Spray (CS) pumps.

According to the methodology established in WCAP-16406-P, because the increased clearance for the pumps is within two times the design clearance, no effect on their hydraulic performance is expected.

Enclosure NOC-AE-07002240 Page 56 of 63 Normal Erosive Abrasive Total Design Increased 2X Design Pump Wear Wear Wear Wear Wear Clearance Clearance (mils) (mils) (mils) (mils) (mils) (mils) (mils)

HHSI 0.0 l.0E-3 19.6766 19.6766 17 36.6776 34 LHSI 0.0 L.OE-3 19.6766 19.6766 23 42.6776 46 CS 0.0 L.0E-3 19.6766 19.6766 23 42.6776 46 For South Texas, the HHSI, LHSI, and CS pumps are multi-stage and must be evaluated for mechanical (vibration) performance. As evaluated in WCAP- 16406-P, the other models of SI pumps will meet operability requirements for wear ring clearances up to 2 times the design clearance. Although the resulting wear ring gap for the HHSI pumps is greater than the 34 mils criteria, the 25% margin in the abrasive wear model (Appendix F.4.4 of WCAP-16406-P) allows for a margin of 34 mils

• 0.25 or 8.5 mils, so there is no expected pump vibration concern due to the containment sump debris for any of the pumps.

The initial results of the pump wear are acceptable; however the STP evaluation will be revised to incorporate the Archard pump wear model from WCAP-16406-P, Revision 1 and the accompanying NRC SER. The results of this evaluation are expected to be completed in 2008 and will be included in the final submittal of the GL 2004-02 Supplemental Responses.

The mechanical shaft seal assembly performance evaluation resulted with the suggested replacement of the Low Head Safety Injection (LHSI), High Head Safety Injection (HHSI) and Containment Spray (CS) pumps' carbon/graphite packing assemblies with a more wear resistant material. However because South Texas .Project has an Engineered Safety Feature (ESF) atmospheric filtration system for the building where the pumps are located, replacement of the carbon/graphite seal bushing is not required.

Heat Exchanger Wear Evaluation:

Tube failure for heat exchangers will occur when the resultant wall thickness after erosion is less than the required wall thickness to retain internal and external pressures. According to methodology established in WCAP- 16406-P, the minimum wall thickness required to retain both internal and external pressures is less than the resultant wall thickness after erosion. Therefore, the heat exchangers are not expected to fail.

Heat Do Required tm tactual teroded Failure Exchangers (in) (in) (in) (in) (yes/no)

RHR 0.75 0.0173 0.049 3.78E-4 no Orifice Wear Evaluation:

If the orifice inside diameter due to erosive wear is changed by less than 3%, the system performance may be considered negligible. This criterion was established in WCAP-16406-P which states that an insignificant amount of wear occurs when they system flow through the orifice is changed by less than 3%. The STP evaluation considers the initial ratio of the diameters before erosive wear and the ratio of the diameters after erosive wear for single plate and multiple plate multiple hole orifices. It was found that the inside diameters of all the orifices change by less than 3% and therefore are not expected to fail.

Spray Nozzle Wear Evaluation:

Failure due to erosive wear for spray nozzles is expected to occur when the flow from the nozzle is increased by 10% due to the increase in the nozzle inner diameter. The STP evaluation considers the

Enclosure NOC-AE-07002240 Page 57 of 63 inner diameter before and after erosive wear begins. This acceptance criterion and methodology was established in WCAP-16406-P. It was found that the flow is changed by less than 4% which is less than the 10% limit; therefore the nozzles do not fail.

Nozzle Velocity Accelerated Wear D, Flow Increase (ftlsec) Rate (inlhr) (in) ,(%)

CSS Spray Headers 44.16 4.538E-6 0.3816 3.6 Instrumentation Blockage Evaluation:

The potential for blockage of the reactor vessel Level Instrumentation System (RVLIS) is not evafuated since South Texas Project has a Westinghouse design RVLIS, for which WCAP-1 6406-P states there is no blockage concern due to the debris ingested through the sump screen during recirculation.

Content Guide Item 3.m Downstream effects - Components and Systems Provide a summary of design or operationalchanges made as a result of downstream evaluations.

Response

No design or operational changes were made as a result of the current downstream evaluations.

Content Guide Item 3.n Downstream Effects - Fuel and Vessel The objective of the downstream effects, fuel and vessel section is to evaluate the effects that debris carrieddownstream of the containment sump screen and into the reactor vessel has on core cooling.

Show that the in-vessel effects evaluation is consistent with, or bounded by, the industry generic 2

guidance (WCAP-1 6793), as modified by NRC staff comments on that document. Briefly summarize the applicationof the methods. Indicate where the WCAP methods were not used or exceptions were taken, and summarize the evaluation of those areas.

2 Because this document is still under NRC review, licensees should be aware of any NRC RAIs on it. The draft NRC SEfor WCAP-16793 is expected to be issued in December 2007. After resolution of any open items from the staff's evaluation of this document, the staff will determine whether additionalinformation is neededfrom licensees. Licensees should not delay their GL responsespending this information.

Content Guide Item 3.n Downstream Effects - Fuel and Vessel

• Show that the in-vessel effects evaluation is consistent with, or bounded by, the industry generic 2

guidance (WCAP-16793) , as modified by NRC staff comments on that document. Briefly summarize the applicationof the methods. Indicate where the WCAP methods were'not used or exceptions were taken, and summarize the evaluation of those areas.

Response

The following evaluations consider the effects that debris carried downstream of the containment sump screen and into the reactor vessel has on core cooling, including fuel and vessel blockage. These evaluations were performed in accordance with WCAP-16406-P and WCAP-16793-NP," Evaluation of Long-Term Cooling Considering Particulate and Chemical Debris in the Recirculating Fluid" with no exceptions taken. The NRC SER is still pending on WCAP-16793-NP.

Enclosure NOC-AE-07002240 Page 58 of 63 STP RAI #31 and 36 are addressed by these evaluations.

It was found that all evaluated dimensions of essential flow paths through the reactor internals are adequate to preclude plugging by sump debris. There is sufficient clearance for debris that may pass the containment sump screen since the limiting dimensions of the essential flow paths in the upper and lower internals are all greater than the maximum particle dimension. The maximum particle dimension is defined as twice the sump screen hole diameter. The sump screen hole diameter evaluated is 0.125 inches. The smallest clearance found in South Texas Project is 1.19 inches. Therefore, any screen size smaller than 0.59 inches will prevent plugging by sump debris in the vessel at South Texas Project. The new strainers have a hole size of 0.095 in. dia.

STPNOC evaluated the potential for fuel blockage from debris carried downstream of the containment sump screen. In the cold-leg break evaluation, the high rate of bypass flow around the core and increased filtering by the containment emergency recirculating sump (CERS) screen is insufficient to preclude the formation of a fiber bed of 0.125 inches from forming on the underside of the bottom nozzles within approximately 10 minutes after initiation of the CERS recirculation flow. At the time of hot-leg injection, 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after accident initiation, an insignificant fraction of the initial fiber concentration remains available in the CERS for deposition on the top of the core. In the hot-leg break evaluation, the thickness of the fibrous bed forming on the underside of the fuel bottom nozzle reaches approximately 0.125 inches immediately after initiation of the CERS recirculation flow. At the time of hot-leg injection, 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after accident initiation, an insignificant fraction of the initial fiber concentration remains available in the CERS for deposition on the top of the core.

The conclusion of this evaluation indicated that the amount of fibrous debris generated by a large break LOCA in STPEGS would produce a fibrous concentration in the CERS volume that would allow fibrous debris on the underside of the fuel bottom nozzle to exceed the acceptance criterion of less than 0.125 inches. STPNOC determined that additional evaluation of fuel blockage potential would be required.

Subsequently, a preliminary refined fuel blockage assessment was performed for STP to demonstrate that blockage from fiber build-up will not compromise fuel cooling. The results of PCI prototype strainer performance testing based on water flow and debris mix conditions expected in South Texas containments following a postulated LOCA was used to determine the potential for STP fuel blockage. The evaluation used fibrous debris bypass test data to determine the fuel blockage potential and was performed in accordance with guidance from WCAP-16406-P, Revision 1 and WCAP-16793-NP (as modified by initial NRC staff comments on that document). The results of this evaluation indicate that the amount of fibrous debris generated by a large break LOCA will not produce a fibrous debris build-up on the underside of the fuel bottom nozzle that exceeds the acceptance criterion of less than 0.125 inches.

Fibrous debris bypass test data from strainer testing in February 2008 will be used in the revised evaluation that will be included in STP's final GL response submittal.

The in-vessel effects evaluation for STP will be performed in accordance with guidance from WCAP-16793-NP as modified by NRC staff comments on that document. The results of this evaluation are expected to be completed in 2008 and will be included in STP's final submittal of GL 2004-02 Supplemental Responses. No design or operational changes have been made as a result of the current fuel blockage evaluation.

3 Content Guide Item 3.o Chemical Effects The objective of the chemical effects section is to evaluate the effect'that chemicalprecipitates have on head loss and core cooling.

Enclosure NOC-AE-07002240 Page 59 of 63

" Provide a summary of evaluation results that show that chemicalprecipitatesformed in the post-LOCA containment environment, either by themselves or combined with debris, do not deposit at the sump screen to the extent that an unacceptablehead loss results, or deposit downstream of the sump screen to the extent that long-term core cooling is unacceptably impeded.

" Content guidancefor chemical effects is provided in Enclosure 3 to a letterfrom the NRC to NEI dated September 27, 2007 (ADAMS Accession No. ML0726007425).

3 The NRC staff expects to issue a draft SE on WCAP-16530, "Evaluationof Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," in November 2007.

Response

The purpose of this analysis is to determine the type and quantity of chemical precipitates which may form post-LOCA. This input is intended to be used for screen performance testing and may be used in the evaluation of chemical effects on downstream equipment. Though the quantities of precipitates expected to form have been calculated, the sump strainer blockage headloss effects will not be known until after testing has been completed in 2008. A later Supplemental response to the GL will describe the chemical effects testing method and results.

STPNOC evaluated the type and expected quantity of chemical products that would be expected to form in the recirculation fluid specifically for STP. Revision 0 of this evaluation used the chemical model/methodology developed in WCAP-16530-NP, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," prior to release of the accompanying NRC SER. No deviations were taken to the WCAP-16530-NP methods.

STP RAI numbers 6, 14 and 20 are addressed by the application of WCAP-16530-NP and the results from this evaluation. STP RAI numbers 2, 3, 4, 5 and 7 are addressed as material and condition inputs to the evaluation.

Input assumptions (and their basis) used to determine chemical effects loading: pH range, temperature profile, duration of containment spray, and materials expected to contribute to chemical effects are described in the chemistry effects evaluation. The spray values from the time of recirculation were assumed to equal the sump pH values. This is conservative because the higher pH of the sump will produce more precipitates. The spray pH curve consists of the initial pH of 4.5 and the calculated values for the sump pH from the time of recirculation. Because the sump temperature data was only provided for 2 days, the final temperature was extended for the 30 day period. Extending the final temperature of 165 'F from 2 days to 30 days will provide more conservative values for precipitate formation since this temperature is higher than the actual temperatures expected due to cooling by the RHR heat exchangers.

Because of the uncertainty of the operator actions which may be taken post-LOCA, the evaluation was performed with spray continuing for both 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 30 day durations for both maximum and minimum recirculation volumes. This resulted in four sensitivity cases. The materials expected to contribute to the formation of chemical precipitates are: CalSil (Marinite) insulation, fiberglass insulation, microtherm, concrete, trisodium phosphate, submerged aluminum, and non-submerged aluminum. The resulting expected chemical precipitates are sodium aluminum silicate (NaAlSi308), aluminum oxyhydroxide (AlOOH), and calcium phosphate (Ca3(P04)2).

The case with the maximum recirculation water volume and 30-day spray duration yields the maximum total amount of precipitates.

Enclosure NOC-AE-07002240 Page 60 of 63 Maximum Recirculation Volume Minimum Recirculation Volume Spray 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 30 days 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 30 days Duration kg ppm kg ppm kg ppm kg ppm NaAlSi308 318.4 128.9 649.5 262.9 295.1 219.6 497.8 370.5 A1OOH 0.0 0.0 35.7 14.5 0.0 0.0 64.9 48.3 Ca3(PO4)2 162.7 65.9 162.7 65.9 132.0 98.2 132.0 98.2 Revision 1 of the STP chemistry effects evaluation used the refined methodology developed in WCAP-16785-NP, "Evaluation of Additional Inputs to the WCAP-16530-NP Chemical Model," to perform additional sensitivity cases. STP will use the base case chemical effects quantities from Revision 0 during the performance of strainer headloss testing with chemical effects surrogates.

Content Guide Item 3 .p Licensing Basis The objective of the licensing basis section is to provide information regardingany changes to the plant licensing basis due to the sump evaluation or plant modifications.

Provide the information requested in GL 04-02 Requested Information Item 2(e) regardingchanges to the plant licensing basis. The effective date for changes to the licensing basis should be specified. This date should correspondto that specified in the 10 CFR 50.59 evaluationfor the change to the licensing basis.

GL 2004-02 Requested Information Item 2(e) A general descriptionof andplanned schedule for dny changes to the plant licensing bases resultingfrom any analysis orplant modifications made to ensure compliance with the regulatoryrequirements listed in the Applicable Regulatory Requirements section of this GL. Any licensing actions or exemption requests needed to support changes to the plant licensing basis should be included.

Response

A license amendment request was submitted that proposed revising the Technical Specification (TS)

Surveillance Requirement (SR) 4.5.2.d for the inspection of the Emergency Core Cooling System (ECCS) sumps for consistency with the new STP sump design.

Enclosure NOC-AE-07002240 Page 61 of 63 Commitments from the Supplemental Response to GL2004-02 Commitment Tracking Action Due Date Content Guide Item 3f Head Loss and Vortexing CR04-12498-15-1 6/30/2008

" Provide a summary of the methodology,. assumptions and results of the vortexing evaluation.Provide basesfor key assumptions.

" Address the ability of the design to accommodate the maximum volume of debris that is predicted to arrive at the screen.

" Address the ability of the screen to resist theformation of a "thin bed" or to accommodatepartialthin bedformation.

" Provide the basisfor the strainerdesign maximum head loss.

" Describesignificant margins and conservatisms used in the head loss and vortexing calculations.

" Provide a summary of the methodology, assumptions, basesfor the assumptions, and resultsfor the clean strainerhead loss calculation.

" Provide a summary of the methodology, assumptions, basesfor the assumptions, and resultsfor the debris head loss analysis.

" State whether near-field settling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used tojustify near-field credit.

" State whether temperature/viscositywas used to scale the results of the head loss tests to actualplant conditions. If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

Content Guide Item 3g. Net Positive Suction Head (NPSH) CR04-12498-15-2 6/30/2008

• Provide the NPSH margin resultsfor pumps taking suction from the sump in recirculationmode.

Content Guide Item 3.h - CoatingsEvaluation CR04-12498-15-3 6/30/2008

" Discuss suction strainer head loss testing performed as it relates to both qualified and unqualified coatings and what surrogate material was used to simulate coatings debris.

• Provide basesfor the choice of surrogates.

Content Guide Item 3.m Downstream effects - Components and Systems CR04-12498-15-4 6/30/2008 e Provide a summary and conclusions of downstream evaluations.

A revised evaluation will be performed using Rev. 1 and the SER and will be described in a later Supplemental response to the GL.

The initial results of the pump wear are acceptable; however the STP evaluation will CR04-12498-15-5 6/30/2008 be revised to incorporate the Archard pump wear model from WCAP- 16406-P, Revision I and the accompanying NRC SER. The results of this evaluation are expected to be completed in 2008 and will be included in the final submittal of the GL 2004-02 Supplemental Responses.

The in-vessel effects evaluation for STP will be performed in accordance with CR04-12498-15-6 6/30/2008 guidance from WCAP-16793-NP as modified by NRC staff comments on that document. The results of this evaluation are expected to -be completed in 2008 and will be included in STP's final submittal of GL 2004-02 Supplemental Responses.

No design or operational changes have been made as a result of the current fuel blockage evaluation.

Enclosure NOC-AE-07002240 Page 62 of 63 Commitment Tracking Action Due Date Content Guide Item 3.o ChemicalEffects3 CR04-12498-15-7 6/30/2008 The objective of the chemical effects section is to evaluate the effect that chemical precipitateshave on head loss and core cooling.

" Provide a summary of evaluation results that show that chemical precipitatesformed in the post-LOCA containment environment, either by themselves or combined with debris, do not deposit at the sump screen to the extent that an unacceptable head loss resulis, or deposit downstream of the sump screen to the extent that long-term core cooling is unacceptably impeded.

" Content guidancefor chemical effects is provided in Enclosure 3 to a letter from the NRC to NEI dated September 27, 2007 (ADAMS Accession No.

3 ML0726007425).

The NRC staff expects to issue a draft SE on WCAP-16530, "Evaluationof Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," in November 2007.

Response

The purpose, of this analysis is to determine the type and quantity of chemical precipitates which may form post-LOCA. This input is intended to be used for screen performance testing and may be used in the evaluation of chemical effects on downstream equipment. Though the quantities of precipitates expected to form have been calculated, the sump strainer blockage headloss effects will not be known until after testing has been completed in 2008. A later Supplemental response to the GL will describe the chemical effects testing method and results.

Text

Attachments 1-5 Not for Public Disclosure per 10CFR2.390 Nuclear Operating Company South Texas Pro/ect Electric GeneratingStation PR. Box 289 Wadsworth, Texas 77483 February 29, 2008 NOC-AE-07002240 10CFR50.54(f) 10CFR2.390 File No. D43.02 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 and 2 Docket Nos. STN 50-498 and STN 50-499 Supplement 3 to the Response to Generic Letter 2004-02 (TAC Nos. MC4719 and MC4720)

References:

1. Letter dated November 21, 2007, from William H. Ruland, NRC, to Anthony Pietrangelo, NEI, "Revised Content Guide for Generic Letter 2004-02 Supplemental Responses"(ML073110269, ML073110278)

2. Letter dated December 13, 2007, from David W. Rencurrel, STPNOC, to NRC Document Control Desk, "Supplement to Request for Extension for Final Response to Generic Letter 2004-02 and Implementation of Revised Design Basis for ECCS Sump (TAC Nos. MC4719 and MC4720)" (ML073580125, NOC-AE-07002249)

3. Letter dated December 19, 2007, from Mohan C. Thadani, NRC, to James J.

Sheppard, STPNOC, "South Texas Project, Units 1 And 2 - Approval Of Extension Request For Corrective Actions Re: Generic Letter 2004-02, "Potential Impact Of Debris Blockage On Emergency Recirculation During Design Basis Accidents At Pressurized Water Reactors," (TAC NOS. MC4719 AND MC4720), (ML073520076)

STP Nuclear Operating Company (STPNOC) submits this supplemental response to Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors." The enclosed response was prepared using the content guidance of Reference 1 with intent of allowing the NRC to close most of the sump debris blockage issues identifiedin GL 2004-02 for STP Units 1 and 2. Final closure is not expected until completion of testing and finalization of the design basis as described in Reference 2. As stated in Reference 2 and approved in Reference 3, STPNOC will submit a letter by June 30, 2008, verifying completion of all GL2004-02 corrective actions and confirming compliance with the regulatory requirements listed in GL2004-02.

The enclosure identifies some responses where supplemental information is to be provided. This information generally depends on the completion of the STP sump strainer testing and integration of the test results into the design. The responses will be updated with the verification letter described above.

The specific items are identified in a list of committed responses in the enclosure.

Povcerr evl-tiII'&

STI 32229932 Attachments 1-5 Not for Public Disclosure per 10CFR2.390 00ma~) (e cuef#.

,'IJ

NOC-AE-07002240 Page 2 of 3 STPNOC requests that Attachments 1 - 5 to the enclosure be withheld from public disclosure in accordance with IOCFR2.390.

If you have any questions concerning the content of this supplemental response, please contact Mr. A. W.

Harrison at (361) 972-7298, or me at (361) 972-7867.

I state under penalty of perjury that the foregoing is true and correct.

Executedon __________

avdyW Ren~curre Vice President, Engineering & Strategic Projects Awh/

Enclosure:

Supplement 3 to the Response to Generic'Letter 2004-02

NOC-AE-07002240 Page 3 of 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 760,11-8064 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Thad Hill Senior Project Manager Eddy Daniels U.S. Nuclear Regulatory Commission Marty Ryan One White Flint North (MS 7 D1) Robert Bailey 11555 Rockville Pike Steve Winn Rockville, MD 20852 NRG South Texas LP Senior Resident Inspector Ed Alarcon U. S. Nuclear Regulatory Commission J. J. Nesrsta P. 0. Box 289, Mail Code: MN1 16 R. K. Temple Wadsworth, TX 77483 Kevin Pollo City Public Service C. M.,Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs Road C. Kirksey Austin, TX 78704 City of Austin Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189

Enclosure NOC-AE-07002240 Enclosure Supplement 3 to the Response to Generic Letter 2004-02 STI 32229932 Attachments 1-5 Not for Public Disclosure per 10CFR2.390

Enclosure NOC-AE-07002240 Page 1 of 63

1. Overall Compliance Upon review of the requirements listed in Generic Letter (GL) 2004-02, STP Nuclear Operating Company (STPNOC) performed an evaluation of the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) recirculation functions. The evaluation demonstrated that modifications were needed to establish the new design basis. STPNOC has implemented these modifications to meet the required schedule as discussed below.

Plant hardware modifications developed in response to issues identified in GL2004-02 are installed in STP Units 1 and 2 and are supporting compliance with the current design and licensing basis regulatory requirements for long term cooling following a design basis loss of coolant accident. Similarly implementation is complete for STPNOC plant administrative procedures and processes needed to support the GL2004-02 hardware modifications and revised operating practices, as well as to support the assumptions, initial conditions and conclusions of GL2004-02 related evaluations, including evaluations of design basis accident debris generation and transport, sump strainer performance, impact of chemical effects and downstream effects of debris. Since hardware, operating procedures and administrative controls required to support actions taken in response to issues identified in GL2004-02 are already implemented at STP, STPNOC has high confidence that if an accident of the type described in GL2004-02 were to occur at STP, plant systems and plant operators would respond in a manner consistent with the intent of the GL2004-02 corrective actions, including conformance with the regulatory requirements listed in GL2004-02.

While STPNOC's confidence in expected operator and plant response to an accident is high, the plant design and licensing basis can not be changed until all regulatory requirements affecting associated change processes are complete. Consequently, STPNOC requested an extension to June 30, 2008 to allow full completion of 10CFR50, Appendix B activities to support completion of chemical effects head loss testing, preparation of the associated test report and changing the plant design and licensing bases to be in compliance with actions taken in response to issues identified in GL2004-02 (Reference 2 to the cover letter). The NRC approved the request in Reference 3 to the cover letter.

2. General Description of and Schedule for Corrective Actions STPNOC will implement sump design modifications to meet the required schedule as discussed below.

The design basis and licensing basis for the plant will be updated to reflect the corresponding changes due to the new regulatory requirements.

For the sump performance evaluation, STPNOC joined with other plants in the Strategic Teaming and Resource Sharing (STARS)/ Utilities Service Alliance (USA) group to engage a contractor team headed by Westinghouse Electric Co. along with Alion Science and Technology and Enercon Services, Inc.

Sump evaluation activities include the following:

• Containment walkdowns

• Debris generation and transport analysis

• Calculation of required and available net positive suction head (NPSH)

• Screen requirements

• Screen structural analyses

• Potential or planned design/operational/procedural modifications

• Downstream effects evaluation 0 Upstream effects evaluation

• Chemical effects evaluation

Enclosure NOC-AE-07002240 Page 2 of 63 STPNOC also joined with other plants in the STARS/USA group to contract with Performance Contracting Inc. (PCI) to provide an advanced design sump strainer for each respective plant. The new sump strainer has replaced the original sump screens for STP. Laboratory testing is being performed by PCI (Alden Research Laboratory and Areva NP are the sub-contractors for this testing) to demonstrate acceptability of the new sump strainer design.

STPNOC will be in full compliance with the regulatory requirements discussed in the applicable regulatory requirements section of GL2004-02 by June 30, 2008, as discussed in Reference 2 to the cover letter.

A three-dimensional computational fluid dynamics (CFD) analysis for debris transport was performed to define the debris loading on the sump strainers and also determine the need to install any debris interceptors. It was determined that debris interceptors were not required.

A revision to the sump water level calculation was prepared to support the CFD analysis and to address the items identified in the upstream effects evaluation that was prepared by Enercon.

A latent debris walkdown inside containment was performed to validate the conservative assumptions used for latent debris in the debris generation analysis.

The design for the new sump strainers will be validated by testing. The test goals are to demonstrate that the thin-bed effect is not a concern and that the head loss due to the STP plant-specific debris loading is acceptable. The testing scheduled for February 2008 is complete and will be discussed later in the response letter due June 30, 2008.

Coatings testing was conducted by Westinghouse to demonstrate that the zone of influence (ZOI) for coatings may be defined using a radius of 5D (5 times the diameter of the break pipe). This result is used to reduce the debris loading on the sump and to demonstrate margin for the new sump strainer design.

The following plant modifications were implemented in Unit 1 during the Fall 2006 refueling outage and in Unit 2 during the Spring 2007 refueling outage:

• Remove existing sump screens from each of the three emergency sumps.

• The vortex breakers will remain in place.

• Install new emergency sump strainer modules by bolting the support frame to the floor.

Modules are bolted to the frame.

3. Specific Information Regarding Methodology for Demonstrating Compliance Content Guide Item 3.a - Break Selection The objective of the break selection process is to identify the break size and location thatpresent the greatest challenge to post-accidentsump performance.

• Describe andprovide the basisfor the break selection criteria used in the evaluation.

• State whether secondary line breaks were considered in the evaluation (e.g., main steam and feedwater lines) and briefly explain why or why not.

• Discuss the basisfor reachingthe conclusion that the break size(s) and locations chosen present the greatest challenge to post-accidentsump performance.

Enclosure NOC-AE-07002240 Page 3 of 63 Content Guide Item 3.a - Break Selection

• Describe andprovide the basisfor the break selection criteria used in the evaluation.

Response

In the debris generation calculation various breaks were evaluated in the Reactor Coolant System (RCS) and connected piping.

Break selection consists of determining the size and location of the high energy line breaks (HELB) that produce debris and potentially challenge the performance of the sump screen. The break selection process evaluated a number of break locations to identify the location that is likely to present the greatest challenge to post-accident sump performance. The debris inventory and the transport path were considered when making this determination.

Regulatory guidance recommends that a sufficient number of breaks bounding variations in debris size, quantity, and type be identified. STP evaluated a number of break locations and piping systems, and considered breaks that rely on recirculation to mitigate the event. The following break locations were considered.

Break Criteria 1 - Breaks in the RCS with the largest potential for debris Break Criteria 2 - Large breaks with two or more different types of debris Break Criteria 3 - Breaks in the most direct path to the sump Break Criteria 4 - Medium and large breaks with the largest potential particulate debris to fibrous insulation ratio by weight Break Criteria 5 - Breaks that generate an amount of fibrous debris that, after transport to the sump screen, could form a uniform thin bed (i.e., usually 1/8" thick) that could subsequently filter sufficient particulate debris to create a relatively high head loss referred to as the "thin-bed effect".

This spectrum of breaks is consistent with that recommended in the NRC's Safety Evaluation Report (SER) for the Nuclear Energy Institute (NEI) Guidance Report (GR), NEI 04-07, "Pressurized Water Reactor Sump Performance Evaluation Methodology." It is also consistent with regulatory position 1.3.2.3 of Regulatory Guide 1.82, "Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident," Revision 3.

Locations were selected for the breaks that produce the maximum amount of debris and also the worst combination of debris mixes with the possibility of being transported to the sump screen. Section 3.3.5.2 of the SER advocates break selection at 5-ft intervals along a pipe in question but clarifies that "the concept of equal increments is only a reminder to be systematic and thorough". It further qualifies that recommendation by noting that a more discrete approach driven by the comparison of debris source term and transport potential can be effective at placing postulated breaks. The key difference between many breaks (especially large breaks) is not the exact location along the pipe, but rather the envelope of containment material targets that is affected.

A small break loss of coolant accident (SBLOCA) inside the secondary shield wall was evaluated for STP. The debris generated by the SBLOCA is less than the debris generated by the large break loss of coolant accident (LBLOCA); however the containment water level at the time of recirculation would be less than the water level caused by the LBLOCA which results in higher average fluid velocities and increases the transportation of debris to the containment sump For SBLOCAs outside the secondary shield wall, SER Section 3.3.5.2 stipulates the need to evaluate breaks in RCS-attached piping beyond isolation points is contingent upon the determination that

Enclosure NOC-AE-07002240 Page 4 of 63 recirculation would not be required should a break occur in these sections. The debris generation analysis for STP considered the failure of a single isolation valve inside the secondary shield wall and includes SBLOCAs outside the secondary shield wall in the spectrum of events evaluated to ensure these would not be limiting Breaks in the RCS with the largest potential for debris (Break Criterion 1)

The break with the largest potential for debris generation is the largest break in an area with the largest concentration of debris source material. For STP, there were seven possible break locations that have the potential to generate the largest concentration of debris:

1. 29" hot leg (LBLOCA) located inside the steam generator compartment inside the secondary shield wall.

2. A hot leg line break in the other compartment was also evaluated since the layout of the STP containment is such that the steam generator compartments each contain two RCS loops.

3. 31" ID RCS cross-over line (LBLOCA), located inside the steam generator compartment inside the secondary shield wall.

4. RCS Nozzle (LBLOCA) in the reactor vessel cavity.

5. 12" residual heat removal (RHR) pump suction line from the RCS hot leg (SBLOCA), located outside the secondary shield wall, but inside the RHR pump/heat exchanger compartment.

6. 8" SI pump discharge line to the RCS hot leg (SBLOCA), located outside the secondary shield wall.

7. 4" chemical and volume control system (CVCS) letdown line (SBLOCA) from the RCS Loop 3 cross-over pipe inside the steam generator (SG) compartment. This break was analyzed because it is the largest pipe break postulated that allows the control room operators time to isolate the safety injection (SI). accumulators before they discharge into the RCS.

Large breaks with two or more different types of debris (Break Criterion 2).

The debris generated by the RCS hot leg line break and the reactor vessel cavity nozzle break discussed in Break Criterion 1 bound the break under criterion 2I The types of insulation debris within the primary shield wall are reflective metal insulation (RMI) and Marinite, and the types of insulation within the secondary shield wall are NUKONTM, Thermal-Wrap and Microtherm.

Breaks with the most direct path to the sump (BreakCriterion 3).

The 12" RHR pump suction lines (A, B and C) from the RCS hot legs have second isolation valves that are located outside the secondary shield wall presenting a potential for direct transport to the sump..

Though these isolation valves are inside the RHR pump/heat exchanger rooms, which are separated from the area where the containment sumps are located and therefore to do not provide a direct path to the sumps, a break in this line was included in the STP analyses. The "A" and ."B" SI system discharge lines to the RCS hot legs also have isolation valves outside the secondary shield wall but are located on the opposite side of containment away from the sump. A break in these lines was also included in the analysis.

Large breaks with the largest potential particulate debris to fibrous insulation ratio by weight (Break Criterion 4).

The types of insulation identified within the containment are RMI, NUKONTM, Thermal-Wrap, Microtherm and Marinite. Since STP has a very limited quantity of particulate type insulation with respect to the fibrous insulation, and this particulate insulation is affected by the LBLOCAs evaluated in

Enclosure NOC-AE-07002240 Page 5 of 63 accordance wvith Break Criterion 1, large breaks with the largest potential particulate debris to fibrous insulation ratio is bounded by Break Criterion 1.

Breaks that generate a "thin bed" - high particulate with 1/8" fiber bed (Break Criterion 5)

Break Criterion 5 postulates a scenario that could generate an amount of fibrous debris that, after its transport to the sump screen, could form a uniform thin bed that could subsequently filter sufficient particulate debris to create a relatively high head loss referred to as "the thin-bed effect" (TBE). The quantity of fiber needed to form a thin bed is the quantity of fiber that would form a 1/8" thick uniform debris bed on the entire surface area of the sump screen.

The STP Debris Accumulation and Head Loss Analysis does consider a thin fibrous bed on the sump screens. The STP containment contains a large quantity of fibrous insulation, which is postulated to become transportable debris due to a LBLOCA. Therefore, the analysis does consider a thin fibrous debris bed as well as the maximum fibrous debris bed.

Content Guide Item 3.a - Break Selection

• State whether secondary line breaks were considered in the evaluation (e.g., main steam and feedwater lines) and briefly explain why or why not.

Response

The large main steam and feedwater line breaks were not evaluated since recirculation is not required under the plant licensing basis for STP.

Content Guide Item 3.a - Break Selection

• Discuss the basisfor reachingthe conclusion that the break size(s) and locationschosen present the greatestchallenge to post-accidentsump performance.

Response

A postulated LBLOCA of the Loop "C" hot leg at the steam generator generates the maximum possible quantity of fibrous debris at STP. This break also produces some Microtherm insulation debris. These LBLOCA debris quantities are significant due to the large zones of influence (ZOI). One other LBLOCA case analyzed is in the RCS hot leg at the reactor vessel nozzle. This break produced Marinite insulation debris and significantly less fibrous insulation debris. This break also produces RMI insulation debris and Microtherm insulation debris. The make up of the total debris generated by these two breaks were different enough to warrant separate transport and head loss analysis to ensure that the head loss at the Containment Sump is thoroughly evaluated.

Content Guide Item 3.b Debris Generation/Zoneof Influence (ZOI) (excluding coatings)

The objective of the debris generation/ZOIprocess is to determine,for each postulated break location:

(1) the zone within which the breakjetforces would be sufficient to damage materialsand create debris; and (2) the amount of debris generatedby the breakjetforces.

• Describe the methodology used to determine the ZOIsfor generatingdebris. Identify which debris analyses used approved methodology default values. For debris with ZOIs not defined in the guidance report/SE, or if using other than default values, discuss method(s) used to determine ZO0 and the basisfor each.

• Provide destruction ZOIs and the basisfor the ZOIsfor each applicabledebris constituent.

Enclosure NOC-AE-07002240 Page 6 of 63 0 Identify if destruction testing was conducted to determine ZOIs. If such testing has not been previously submitted to the NRCfor review or information, describe the test procedure and results with reference to the test report(s).

• Provide the quantiot of each debris type generatedfor each break location evaluated. If more thanfour break locations were evaluated,provide data only for thefour most limiting locations.

0 Provide total surface area of all signs, placards,tags, tape, and similarmiscellaneous

-materialsin containment.

Response

As noted in section 3.4.2.2 of the SER, the debris generation analysis considers the ZOI to be defined based on the material with the lowest destruction pressure. Refinements in the STP analysis include debris-specific (insulation material specific) and non-spherical ZOIs. The debris-specific refinements, as endorsed in SER Section 4.2.2.1.1, provide relief as long as there are two or more district types of insulation within the break location. In the STP containment, there are two or more distinct types of insulation and a debris-sliecific refinement is beneficial in this analysis. The destruction pressures and associated ZOI radii for the insulating materials in the STP containment are listed in Table 1.

Table I - Destruction Pressures and ZOI Radii for Potential Debris Sources Destruction ZOI Radius Insulation Types (Radius/Break Reference/Basis sPressure (psi) Diameter)

Transco RMI 114 2.0 SER Table 3.2 NUKONTM 6 17 SER Table 3.2 Thermal-Wra'p 6 17 Assumed the same as NUKONTM based on GR 3.4.3.3.1 Marinite 114 2.0 See discussion below Microtherm(1) 2.4 28.6 See discussion below Marinite The SER does not recommend a destruction pressure or ZOI for this material and insufficient data exists on its material properties and destruction pressure. However, since this insulation is covered with 3/16" stainless steel plate, the destruction pressure was assumed to be equivalent to that of RMI. This destruction pressure is 114 psig, which corresponds to a ZOI of 2.0D.

Microtherm The material specifications for Microtherm were insufficient to determine an appropriate destruction pressure and ZOI. Therefore, the lowest destruction pressure (Min-K at 2.4 psi) and the greatest ZOI (also Min-K at L/D of 28.6) identified in Table 3-2 of the SER were utilized in the STP analysis.

Robust barriers, i.e., structures and equipment that are impervious to jet impingement, are assumed to prevent further expansion of the break jet. The volume of a spherical ZOI with a radial dimension extending beyond robust barriers such as walls or encompassing a large component such as a tank or

Enclosure NOC-AE-07002240 Page 7 of 63 steam generator is truncated by the barrier. The SER stipulates that deflection/reflection need not be considered but "shadow" surfaces of components should be included in the analysis.

ZOIs were not applied within the primary shield wall due to the relatively small area between the reactor vessel and the primary shield wall. All of the insulation material within the primary shield wall was considered to be destroyed by a LBLOCA within the primary shield wall.

The debris generation analysis identified a LBLOCA break in the Loop C 29" hot leg Line break at the steam generator and the RCS hot leg line break at a nozzle in the reactor cavity as the two limiting breaks in the RCS. The debris quantities for these two breaks as well as Loop A hot leg and the 4" CVCS letdown line are presented in Table 2.

Table 2 - Summary of Debris Generation for Breaks in the RCS Loop "A" hot leg Loop "C" hot leg RCS hot leg Nozzle 4" CVCS Letdown Insulation Type Line Break Line Break Line Break Pipe Break (SBLOCA)

Marinite 0 0 15.2 ft3 0 RMI 0 0 24,493 ft2 0 NUKONTM 838.9 ft 3

908.3 ft 3 424.9 ft 3 212.5 ft 3

Thermal-Wrap 1400.0 ft 3

1400.0 ft 3

85.1 ft3 42.6 ft3 Microtherm 2.6 ft 3 2.3 ft3 0.9 ft3 0 The breaks associated with the potential for direct transport to the sump (Break Criterion 3) resulted in a limiting NUKONTM debris generation of 70.5 ft3 for the 12" RHR suction lines and 31.2 ft3 for the 8" SI pump discharge lines.

Miscellaneous Solid Debris The STP debris generation analysis does recognize the presence of miscellaneous solid object debris sources, such as equipment labels and tags, and plastic signs. As suggested by the GR, this miscellaneous solid object debris source is bounded by 100 ft2 , andincludes an allowance of 14 ft2 for 100 equipment clearance order (ECO) tags (size of 4" x 5") and 2 ft2 for ty-wraps.

Content Guide Item 3c. Debris Characteristics The objective of the debris characteristicsdeterminationprocess is to establish a conservative debris characteristicsprofilefor use in determining the transportabilityof debris and its contributionto head loss.

" Provide the assumed size distributionfor each type of debris.

" Provide bulk densities (i.e., including voids between thefibers/particles)and material densities (i.e., the density of the microscopicfibers/particlesthemselves) forfibrous and particulatedebris.

• Provide assumed specific surface areasforfibrousandparticulatedebris.

• Provide the technical basisfor any debris characterizationassumptions that deviatefrom NRC-approved guidance.

Enclosure NOC-AE-07002240 Page 8 of 63 The debris sources for STP include insulation, coatings, and latent debris. The insulation debris types include RMI, NUKONTM, Thermal-Wrap, Microtherm and Marinite. The RMI is located on the reactor vessel inside the primary shield wall. The NIJKONTM is located on various piping and equipment throughout containment. The Thermal-Wrap is installed on the steam generators. Marinite is installed on the reactor vessel nozzles. The Microtherm is used on some piping in the secondary shield wall penetrations. The characteristics of the insulation debris materials are discussed in this section as the characteristics of the other debris types (e.g., coatings and latent) are included elsewhere Content Guide Item 3c. Debris Characteristics

• Provide the assumed size distributionfor each type of debris.

Response

As recommended by Section 4.2.4 of the SER, a four-size distribution for low density fiberglass (LDFG) insulation material inside the ZOI of a postulated break is used in the STP debris generation analysis. The distribution categorizes destroyed insulation debris as fines, small pieces, large pieces and intact blankets.

Fines are defined as individual fibers, small pieces are smaller than 6" on a side, large pieces are greater than 6" on a side and intact blankets are large pieces that are still protected by the covering, thereby preventing further erosion. Table 3 summarizes the LDFG size distributions.

Table 3 - LDFG Debris Size Distribution Within Each Sub-Zone Size 18.6 psi ZOI 10.0 - 18.6 psi ZOI 6.0 - 10.0 psi ZOI (7.0 L/D) (11.9 - 7.0 L/D) (17.0 - 11.9 L/D)

Fines (Individual Fibers) 20% 13% 8%

Small Pieces (<6" on a Side) 80% 54% 7%

,Large Pieces (>6" on a Side) 0% 16% 41%

Intact (covered) Blankets 0% 17% 44%

Table 4 summarizes the other potential debris sources in the STP containment and the associated debris size distributions from Table 3-3 of the SER. Materials for which debris generation is not known well enough to conservatively estimate debris size distribution will assume maximum destruction as 100%

fines.

Table 4 - Debris Size Distribution Material Percentage Percentage I Small Fines[ Large Pieces Within the ZOI RMI 75 25 Marinite 100 0 Microtherm 100 0 Outside the ZOI Covered Undamaged 0 0 Insulation

Enclosure NOIC-AE-07002240 Page 9 of 63 Content Guide Item 3c. Debris Characteristics

• Provide bulk densities (i.e., including voids between thefibers/particles)and material densities (i.e., the density of the microscopicfibers/particlesthemselves)for fibrous and particulatedebris.

Response

Table 5 and Table 6 provide a summary of the as-fabricated densities, microscopic densities, and dimensions for applicable debris types at STP. Characteristics associated with coatings will be further discussed later in this report.

Table 5 - Fibrous Material Characteristics As-Fabricated Microscopic Characteristic Debris Material Density Density Diameter (lb/ft3 ) (lb/ft3 ) (jim)

NUKON TM 2.4 175 7 jm Thermal-Wrap 2.4 159 5.5 jim Table 6 - Particulate Debris Characteristics As-Fabricated Microscopic Characteristic Debris Material Density Density Diameter (lb/fl3) (lb/ft3) (Gm)

Marinite (1) 14.5 144 5 Microtherm 15 187 2.5 to 20 The material characteristics for Marinite are assumed to be the same as those identified for Calcium Silicate due to their similar appearances.

Content Guide Item 3c. Debris Characteristics

• Provide assumed specific surface areasforfibrousandparticulatedebris.

Response

The specific surface area (Sv) was only used for preliminary analytically determined head loss values across a debris laden sump screen using the correlation given in NUREG/CR-6224. Since the head loss across the installed sump screen is determined via testing, these values are not used in the design basis for STP. Therefore, these values, are not provided as part of this report.

Enclosure NOC-AE-07002240 Page 10 of 63 Content Guide Item 3c. Debris Characteristics

• Provide the technical basisfor any debris characterizationassumptions that deviatefrom NRC-approved guidance.

Response

There are no such assumptions that differ from the guidance.

Content Guide Item 3d. Latent Debris The objective of the latent debris evaluationprocess is to provide a reasonable approximation of the amount and types of latent debris existing within the containment and its potentialimpact on sump screen head loss.

• Provide the methodology used to estimate quantity and composition of latent debris.

0 Provide the basisfor assumptions used in the evaluation.

0 Provide results of the latent debris evaluation, including amount of latent debris types and physical datafor latent debris as requestedfor other debris under c. above.

0 Provide amount of sacrificialstrainersurface areaallotted to miscellaneous latent debris.

Response

The latent debris at STP has been evaluated through containment condition assessments. Containment walkdowns were completedfor Unit 1 and for Unit 2. The conditions were completed in accordance with the guidance of NEI 02-01, "Condition Assessment Guidelines, Debris Sources Inside Containment,"

Revision 1. The quantity and composition of the latent debris was evaluated by extensive sampling for latent debris (dirt/dust and latent fiber) considering the guidance in NEI 04-07, Volume 2.

Samples were taken to determine the latent debris mass distribution per unit area, referred to as latent debris density (e.g. 1bm/1000 ft2) of representative surfaces throughout containment including vertical surfaces such as the liner and walls. These debris densities were then applied to all of the surface areas inside containment to calculate the total amount of latent debris inside containment.

The latent debris density was estimated by weighing sample bags before and after sampling, dividing the net weight increase by the sampled surface area, and converting the result to a density (e.g. lbm/1000 ft2).

Samples were taken for Unit 1. The visual assessments and walkdowns supported that there were no significant differences between the Units that would affect the quantity or types of latent debris.

Therefore, the samples taken are representative of both Units.

The results of the latent debris calculation conservatively determined the debris loading to be less than 160 lbm in each containment. Therefore, it was elected to use a conservative bounding value of 200 lbm for the latent debris source term in containment.

Visual examination of the debris showed very low fiber content. In lieu of analysis of samples, conservative values for debris composition properties were assumed as recommended by NEI 04-07 Volume 2. This results in a very conservative estimate of fiber content. The particulate / fiber mix of the latent debris will be assumed to be 15% fiber. The latent debris source term value incorporated into the STP analysis is presented in Table 7.

Enclosure NOC-AE-07002240 Page 11 of 63 Table 7 - Latent Debris Source Term Latent Debris Type Mass (ibm) Density (lbm/ft3) Characteristic Size (ft)

Dirt and Dust 170 169 5.67E-05 Latent Fiber 30 175 2.3 E-05 The containment condition assessments also included the identification of miscellaneous solid objects such as labels and tags. Qualified tags attached with stainless steel wires were found for much of the equipment. Unqualified items were identified and removed. The total surface area for any remaining debris of this type was determined to be much less than 100 ft2. Therefore, as suggested by NEI 04-07, this miscellaneous solid object debris source is bounded by the 100 ft2 that was implemented in the STP debris generation and transport analyses.

A sacrificial area of 200 ft2 of strainer surface per strainer was designated as a penalty for miscellaneous latent debris including labels and tags. STP has identified tags and labels which are qualified and which have been shown to not transport to the emergency sump strainers (ac ceptable labels).

Content Guide Item 3e. Debris Transport The objective of the debris transportevaluationprocess is to estimate the fraction of debris that would be transportedfrom debris sources within containment to the sump suction strainers.

• Describe the methodology used to analyze debris transportduring the blowdown, washdown, pool-fill-up, and recirculationphases of an accident.

• Provide the technical basisfor assumptions and methods used in the analysis that deviate from the approved guidance.

• Identify any computationalfluiddynamics codes used to compute debris transportfractions during recirculationand summarize the methodology, modeling assumptions, and results.

• Provide a summary of, and supportingbasisfor, any credit taken for debris interceptors.

• State whetherfine debris was assumed to settle andprovide basisfor any settling credited.

" Provide the calculateddebris transportfractions and the total quantitiesof each type of debris transportedto the strainers.

Content Guide Item 3e. Debris Transport

• Describe the methodology used to analyze debris transportduring the blowdown, washdown, pool-fill-up, and recirculationphases of an accident.

Response

The methodology used in the transport analysis is based on the NEI 04-07 guidance report (GR) for refined analyses as modified by the NRC's safety evaluation report (SER), as well as the refined methodologies suggested by the SER in Appendices III, IV, and VI. The specific effect of each of the four modes of transport was analyzed for each type of.debris generated. These modes of transport are:

• Blowdown transport- the vertical and horizontal transport of debris to all areas of containment by the break jet.

" Washdown transport- the vertical (downward) transport of debris by the containment sprays and break flow.

Enclosure NOC-AE-07002240 Page 12 of 63

• Poolfill-up transport- the transport of debris by break and containment spray flows from the refueling water storage tank (RWST) to regions that may be active or inactive during recirculation.

" Recirculation transport- the horizontal transport of debris from the active portions of the recirculation pool to the sump screens by the flow through the emergency core coolant system (ECCS).

The logic tree approach was then applied for each type of debris determined from the debris generation calculation. The logic tree shown in Figure 1 is somewhat different than the baseline logic tree provided in the GR. This departure was made to account for certain non-conservative assumptions identified by the SER including the transport of large pieces, erosion of small and large pieces, the potential for washdown debris to enter the pool after inactive areas have been filled, and the direct transport of debris to the sump screens during pool fill-up. Also, the generic logic tree was expanded to account for a more refined debris size distribution. (Note that some branches of the logic tree may not be required for certain debris types).

Enclosure NOC-AE-07002240 Page 13 of 63 Retained on Structures Remains intact Upper Transport Containment Erodes to Fines Washed Down S d m n Remains intact Transport Sediment Actie Pol Seimen IrErodes to Fines Remains intact Retained onI Structures Remains intact Upper Transport ActivenPool Erodes to Fines Washed Down S d m n Remains intact Transport Sediment Active Pool Erodes to Fines Sediment I Remains intact

Enclosure NOC-AE-07002240 Page 14 of 63 The basic methodology used for the South Texas Project transport analysis is shown below:

1. Based on many of the containment building drawings, a three-dimensional model was built using computer aided design and drafting (CADD) software.

2. A review was made of the drawings and CADD model to determine transport flow paths.

Potential upstream blockage points including screens, fences, grating, drains, etc. that could lead to water holdup were addressed.

3. Debris types and size distributions were gathered from the debris generation calculation for each postulated break location.

4. The fraction of debris blown into upper containment was determined based on the relative volumes of upper and lower containment.

5. The quantity of debris washed down by spray flow was conservatively determined.

6. The quantity of debris transported to inactive areas or directly to the sump screens was calculated based on the volume of the inactive and sump cavities proportional to the water volume at the time these cavities are filled.

7. Using conservative assumptions, the locations of each type/size of debris at the beginning of recirculation was determined.

8. A computerized flow dynamics (CFD) model was developed to simulate the flow patterns that would occur during recirculation.

9. A graphical determination of the transport fraction of each type of debris was made using the.

velocity and turbulent kinetic energy (TKE) profiles from the CFD model output, along with the determined initial distribution of debris.

10. The recirculation transport fractions from the CFD analysis were gathered to input into the logic trees.

11. The effects of erosion on the LOCA generated debris were evaluated to determine the potential significance.

12. The overall transport fraction for each type of debris was determined by combining each of the previous steps in logic trees.

BLOWDOWN TRANSPORT The fraction of blowdown flow to various regions was estimated using the relative volumes of containment. Fine debris would be suspended and carried by the blowdown flow. Small and large piece debris would also be carried by the high velocity blowdown flow in the vicinity of the break. However, in areas farther away from the break that are not directly affected by the blowdown, this debris would likely fall to the floor.

The volumes for the upper containment (including the refueling canal and areas above the operating deck) and for lower containment (including the open area inside the steam generator and pump enclosures, the area inside the secondary shield wall, and the annulus area below the operating deck) were determined from the CADDmodel. Because the debris was assumed to be carried with the blowdown flow, the flow split is then proportional to the containment volumes. This resulted in a transport fraction for the fine debris to upper containment of 69%.

The drywell debris transport study (DDTS) 1 testing provides debris holdup values for blowdown occurring in a wetted and highly congested area. Values associated with grating being present in the D.V. Rao, et al., "Drywell Debris Transport Study: Experimental Work", NUREG/CR-6369, Volume 2, September 1999.

Enclosure NOC-AE-07002240 Page 15 of 63 blowdown flowpath were utilized in the STP blowdown analysis. The DDTS also presents values for holdup when blowdown travels a flow path with 900 turn(s). Although 90' turns might not have to be negotiated by debris blown to upper containment at STP, significant bends would have to be made.

Therefore, it was estimated that 5% (versus the 17% value in the study) of the small fiberglass debris blown upward would be trapped due to changes in flow direction.

Additional guidance was incorporated into the analysis through use of the Boiling Water Reactor (BWR)

Utility Resolution Guide (URG). The guidance from this document indicates that grating would trap approximately 65% of the small RMI debris blown toward it.

Table 8 and Table 9 show the transport fractions for each type/size of debris to upper containment and to the containment pool due to the blowdown forces for breaks inside the steam generator compartments.

Table 10 through Table 13 show the blowdown transport fractions for the break inside the reactor cavity and the small breaks outside the secondary shield wall. Note that debris outside the ZOI is not affected by the blowdown, and therefore the transport fraction for this debris would be 0%.

Table 8 - Blowdown transport fraction of debris to upper containment (Cases 1 and 5)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 69% 460/. 0% 0%

Microtherm TM (Case 1) 69% NA NA NA Qualified Coatings (inside ZOI) 69% NA NA NA

'Unqualified Coatings 0% NA NA NA

"(outside ZOI),

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 9 - Blowdown transport fractions of debris to containment pool (Cases 1 and 5)

Debris Type Fines Small Pieces Unjacketed Jacketed D Large Pieces Large Pieces LDFG 31% 20% 0% 0%

MicrothermTM (Case 1) 31% NA NA NA Qualified Coatings (inside ZOI) 31% NA NA NA Unqualified Coatings. .0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA

Enclosure NOC-AE-07002240 Page 16 of 63 Table 10 - Blowdown transport fractions of debris to upper containment (Case 2)

Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI NA 0% 0% NA LDFG 69% 46% 0% 0%

MariniteTM 0% NA NA NA Qualified Coatings (inside ZOI) 0% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 11 - Blowdown transport fractions of debris to containment pool (Case 2)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces Stainless Steel RMI NA 100% 100% NA LDFG 31% 20% 0% 0%

MariniteiM .100% NA NA NA Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA Table 12 - Blowdown transport fractions of debris to upper containment (Cases 3 and 4)

Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 0% 0% 0% .0%

Qualified Coatings (inside ZOI) 0% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA

Enclosure NOC-AE-07002240 Page 17 of 63 Table 13 - Blowdown transport fractions of debris to containment pool (Cases 3 and 4)

D Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 100% 100% 100% 100%

Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 0% NA NA NA Latent Fiber 0% NA NA NA WASHDOWN TRANSPORT During the washdown phase, debris in upper containment could be washed down by the containment sprays. For STP, some small piece debris as well as all large pieces would be held up by grating.

The debris blown to upper containment was assumed to be scattered around and a reasonable approximation of the washdown locations was made based on the spray flow split in upper containment.

This resulted in the following washdown split of 26% of the containment sprays were estimated to flow directly into the steam generator compartments, 31% were estimated to flow into the steam generator compartments via the refueling canal (28.5%) and cable tray chase (2.7%), and the remaining 43% of the sprays were estimated to flow into the annulus.

Multiple levels of grating are present in the STP Containment. The results of the DDTS testing showed that approximately 40-50% of small fiberglass debris landing on grating would be washed through the grating due to spray flows. (Note that the spray flow at the plant is on the lower end of the 1 to 12 gpm/ft2 spray flow used in the testing). Holdup of small pieces of fiberglass debris was credited at each level of grating that washdown flow passed through. Credit was also taken for holdup of small pieces of RMI on grating based on the BWR URG, which indicates that the retention of small RMI debris on grating is approximately 29%.

The following tables show the fraction of debris in upper containment and the steam generator compartments that would be expected to transport to the pool floor inside and outside the secondary shield wall.

Table 14 - Washdown transport fractions of debris from upper containment to the annulus Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces LDFG 43% 3% 0% 0%

MicrothermTM (Case 1) 43% NA NA NA Qualified Coatings (inside ZOI) 43% NA NA NA Unqualified Coatings NA NA NA NA (outside ZO0)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA

Enclosure NOC-AE-07002240 Page 18 of 63 Table 15 - Washdown transport fractions of debris from upper containment directly to the steam generator compartments Fines Small Pieces Unjacketed Jacketed Debris Type Large Pieces Large Pieces LDFG 26% 7% 0% 0%

MicrothermTM (Case 1) 26% NA NA NA Qualified Coatings (inside ZOI) 26% NA NA NA Unqualified Coatings N NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA Table 16 - Washdown transport fractions of debris from upper containment to the steam generator compartments via the canal drains and cable tray chase Unjacketed Jacketed Fines Small Pieces Large Pieces Large Pieces LDFG 31% 16% 0% 0%

MicrothermTM (Case 1) 31% NA NA NA

,Qualified Coatings (inside ZOI) 31% NA NA NA Unqualified Coatings NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA Table 17- Washdown transport fractions of debris in the steam generator compartments at the end of the blowdown phase Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces LDFG 100% 50% 0% 0%

MicrothermTM (Case 1) 100% NA NA NA Qualified Coatings (inside ZOI) 100% NA NA NA Unqualified Coatings NA NA NA NA (outside ZOI)

Dirt/Dust NA NA NA NA Latent Fiber NA NA NA NA

Enclosure NOC-AE-07002240 Page 19 of 63 POOL FILLUP TRANSPORT During pool fill-up, the flow of water transports insulation debris from the break location to all areas of the recirculation pool. Some of the debris was assumed to transport to inactive areas of the pool and some was assumed to transport directly to the sump screens as the emergency sump cavities are filled. The cavities considered for pool fill up transport include the containment sump, the elevator pit, and the three ECCS sumps. Other potentially inactive areas where debris could be held up including the secondary normal sump were conservatively assumed to be negligible and were not credited.

Assuming that fine debris is uniformly distributed in the pool, and the water entering the pool from the break and sprays is clean (i.e. washdown of debris in upper containment occurs after inactive cavities have been filled), the transport to each of the inactive cavities was calculated for STP. (Note that the assumption that debris washdown occurs after inactive cavities have been filled is consistent with the requirements of the SER Section 3.8.

Table 18 - Pool fill-up transport fractions of debris to the two active sumps Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 8% 0% 0% 0%

MariniteTM (Case 2) 8% NA NA NA MicrothernTM (Case 1) 8% NA NA NA Qualified Coatings (inside ZOI) 8% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 8% NA NA NA Latent Fiber 8% NA NA NA Table 19 - Pool fill-up transport fractions of debris to the inactive sump Debris Type Fines Small Pieces Unjacketed Jacketed Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 4% 0% 0% 0%

MariniterM (Case 2) 4% NA NA NA MicrothermTM (Case 1) 4% NA NA NA Qualified Coatings (inside ZOI) 4% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 4% NA NA NA Latent Fiber 4% NA NA NA

Enclosure NOC-AE-07002240 Page 20 of 63 Table 20 - Pool fill-up transport fractions of debris to the inactive cavities Unjacketed Jacketed Debris Type Fines Small Pieces Large Pieces Large Pieces Stainless Steel RMI (Case 2) NA 0% 0% NA LDFG 13% 0% 0% 0%

MariniteTM (Case 2) 13% NA NA NA MicrothermTM (Case 1) 13% NA NA NA Qualified Coatings (inside ZOI) 13% NA NA NA Unqualified Coatings 0% NA NA NA (outside ZOI)

Dirt/Dust 13% NA NA NA Latent Fiber 13% NA NA NA RECIRCULATION TRANSPORT The recirculation pool debris transport fractions were determined through CFD modeling. To accomplish this, a three-dimensional CADDmodel was imported into the CFD model, flows into and out of the pool were defined, and the CFD simulation was run until steady-state conditions were reached. The result of the CFD analysis is a three-dimensional model showing the turbulence and fluid velocities within the pool. By comparing the direction of pool flow, the magnitude of the turbulence and velocity, the initial location of debris, and the specific debris transport metrics (i.e. the minimum velocity or turbulence required to transport a particular type/size of debris), the recirculation transport of each type/size of debris to the sump screens was determined.

A diagram showing the significant parts of the CFD model is shown below. The sump mass sink, the

.various direct and wash spray regions, and the combined break and spray wash regions are highlighted.

Enclosure NOC-AE-07002240 Page 21 of 63 Modeled Wash Spray

. Regions Combined Case 4b Break Flow with Spray Flow.

Figure 2 - Diagram of significant features modeled Flow-3D Version 9.0 developed by Flow Science Incorporated was used for the CFD modeling. The key CFD modeling attributes/considerations included the following:

ComputationalMesh:

A rectangular mesh was defined in the CFD model that was fine enough to resolve important features, but not so fine that the simulation would take prohibitively long to run. A 6-inch cell length was chosen as the largest cell size that could reasonably resolve the concrete structures that compose the containment floor. For the cells right above the containment floor, the mesh was set to 3 inches tall in order to closely resolve the vicinity of settled debris. To further define specific objects, node planes were placed at the edges of key structures including the top of the sump curb, and the edges of the break and spray mass source obstacles.

Modeling of Containment Spray Flows:

From consideration of various plan and section drawings, as well as the containment building CADDmodel, it was judged that spray water would drain to the pool through numerous pathways. Some of these pathways included: the steam generator compartments through the open area above the steam

Enclosure NOC-AE-07002240 Page 22 of 63 generators, into the refueling canal and through the refueling canal drains, and into the annulus through the various open sections of grating. The sprays were introduced near the surface of the pool.

Modeling of Break Flow.

STP breaks were modeled at the break location which was not directly above the recirculation pool and consideration of the additional free fall energy was not necessary. The break flow falls onto the floor at the associated elevation and then drains through various paths to the recirculation pool. This break flow was combined with the spray flow and introduced to each region where flow occurs near the surface of the pool.

Modeling of the Emergency Sump:

The emergency sumps at STP consist of three sumps. To bound the transport analysis, the worst case scenario (two sumps operating) was modeled. The two outer sumps were chosen as the active sumps since debris would be more likely to transport to the outer sumps. The mass sink used to pull flow from the CFD model was defined within the two sump cavities. A negative flow rate was set for the sump mass sink, which tells the CFD model to draw the specified amount of water from the pool over the entire exposed surface area of the mass sink obstacle.

Turbulence Modeling:

Several different turbulence modeling approaches can be selected for a Flow-3D calculation. The approaches are (ranging from least to most sophisticated):

• Prandtl mixing length

• Turbulent energy model

• Two-equation k-s model

• Renormalized group theory (RNG) model

• Large eddy simulation model The RNG turbulence model was judged to be the most appropriate for this CFD analysis due to the large spectrum of length scales that would likely exist in a containment pool during emergency recirculation.

The RNG approach applies statistical methods in a derivation of the averaged equations for turbulence quantities (such as turbulent kinetic energy and its dissipation rate). RNG-based turbulence schemes rely less on empirical constants while setting a framework for the derivation of a range of models at different scales.

Steady-State Metrics:

The CFD models were started from a stagnant state at a defined pool depth and run long enough for steady-state conditions to develop. A plot of mean kinetic energy was used to determine when steady-state conditions were reached. Checks were also made of the velocity and turbulent energy patterns in the pool to verify that steady-state conditions were reached.

Debris TransportMetrics:

Metrics for predidting debris transport have been adopted or derived from data. The specific metrics are the turbulent kinetic energy (TKE) necessary to keep debris suspended, and the flow velocity necessary to tumble sunken debris along a floor. The metrics utilized in the STP transport analysis originate from the sources below:

1) NUREG/CR-6772 Tables 3.1, 3.2 & 3.5,

2) NUREG/CR-6808 Table 3.2 and Figure 5-2, or

3) Calculated using Stokes' Law using water properties at 1200 F.

Enclosure NOC-AE-07002240 Page 23 of 63 Graphical Determination of Debris Transport Fractions The following steps were taken to determine what percentage of a particular type of debris could be expected to transport through the containment pool to the emergency sump screens.

• Colored contour velocity and TKE maps indicating regions of the pool through which a particular type of debris could be expected to transport were generated from the Flow-3D results in the.

form of bitmap files.

• The bitmap files were overlaid on the initial debris distribution plots and imported into AutoCAD with the appropriate scaling factor to convert the length scale of the color maps to feet.

" For the uniformly distributed debris, closed polylines were drawn around the contiguous areas where velocity or TKE was high enough that debris could be carried in suspension or tumbled along the floor to the sump screens.

• The areas within the closed polylines were determined utilizing an AutoCAD querying feature.

• The combined area within the polylines was compared to the debris distribution area.

• The percentage of a particular debris type that would transport to the sump screens was estimated based on the above comparison.

Plots showing the TKE and the velocity magnitude in the pool were generated for each case to determine areas where specific types of debris would be transported. The limits on the plots were set according to

,the minimum TKE or velocity metrics necessary to move each type of debris. The overlying yellow areas represent regions where the debris would be suspended, and the red areas represent regions where the debris would be tumbled along the floor. The yellow TKE portion of the plots is a three-dimensional representation of the TKE. The velocity portion of the plots represents the velocity magnitude just above the floor level (1.5 inches), where tumbling of sunken debris could occur. Directional flow vectors were also included in the plots to determine whether debris in certain areas would be transported to the sump

screens or transported to quieter regions of the pool where it could settle to the floor.

The following figures and discussion are presented as an example of how the transport analysis was performed for a single debris type - Small Piece Stainless Steel RMI. This same approach was utilized for other debris types analyzed at STP.

Figure 4 and Figure 5 show that the turbulence in the pool is only high enough to suspend small RMI debris in the vicinity of the location where break and spray flow from the steam generator compartments enters the pool.

As shown in Figure 3, the small RMI debris was assumed initially to be uniformly distributed inside the secondary shield wall and in the vicinity of the sump screens. This area was overlaid on top of the plot showing tumbling velocity and flow vectors to determine the recirculation transport fraction. The area where small pieces of RMI would transport'within the initial distribution area is 1,872 ft2 , as shown in Figure 6. Since the initial distribution area was determined to be 5,977 ft2 the recirculation transport fraction for small pieces of RMI is 31%.

Enclosure NOC-AE-07002240 Page 24 of 63 Initial Distribution of Small and Large Piece Debris For mCases 1, 2, and 5 ZO 1 5,977 fl 2 Figure 3 - Distribution of small & large piece debris in lower containment

Enclosure NOC-AE-07002240 Page 25 of 63 Figure 4 - TKE and velocity with limits set at suspension/tumbling of small pieces of stainless steel RMI

Enclosure NOC-AE-07002240 Page 26 of 63 Figure 5 - 3D view of TKE and velocity with limits set at suspension/tumbling of small pieces of stainless steel RMI

Enclosure NOC-AE-07002240 Page 27 of 63 M- Velocity' Ž 0.28 ft/s Floor area where small RMI in lower o ntainm ent would transport to the sumps 1872 ft2 2 2 TKE k 0.21 ft /s Figure 6 - Floor area where small RMI would transport to the sumps This same analysis was applied for each debris type (grouping was performed as applicable) evaluated at STP. Recirculation pool transport fractions were identified for each debris type associated with the location of its original distribution. This includes a transport fraction for debris: 1) not originally blown into upper containment, 2) washed down inside the secondary shield wall, and 3) washed down into the annulus.

Enclosure NOC-AE-07002240 Page 28 of 63 Content Guide Item 3e. Debris Transport

• Provide the technical basisfor assumptions and methods used in the analysis that deviate from the approved guidance.

Response

Debris erosion is the only area where the debris transport analysis deviates from the regulatory guidance.

The guidance specifies that an erosion fraction of 90% should be used for fiberglass debris. However, as described in the justification below, an erosion fraction of 10% was used for fiberglass debris in the recirculation pool.

The only insulation debris with thepotential for erosion at STP is the unjacketed small and large pieces of NukonTM and Thermal-WrapTM fiberglass.

Tests performed as a part of the drywell debris transport study (DDTS) have indicated that the erosion of fibrous debris is significantly different for debris directly impacted by containment sprays versus debris directly impacted by break flow. The erosion of large pieces of fibrous debris by containment sprays was found to be less than 1%, whereas the erosion due to the break flow was much higher. Due to differences in the design of PWR nuclear plants compared to the boiling water reactor (BWR) nuclear plants, the results of the erosion testing in the DDTS are only partially applicable. In a BWR plant, a LOCA accident would generate debris that would be held up below the break location on grating above the suppression pool. In STP, however, the break would generate debris that would either be blown to upper

-containment or blown out away from the break. Most of the debris would not be hung up directly below the break flow where it would undergo the high erosion rates suggested by the DDTS. Any debris blown

.to upper containment that is not washed back down, however, would be subject to erosion by the sprays.

Based on the results of the DDTS testing, a 1%,erosion factor was applied for small and large piece fibrous debris held up in upper containment. This is consistent with the approach taken for the pilot plant

'in the SER (Appendix VI). The erosion mechanism for debris in the pool is somewhat different than what

• wastested in the DDTS. The SER (Appendix III) describes erosion tests that indicated that the erosion

,rate of fibrous debris could be on the order of 0.3 percent of the current debris per hour for a pool with a 16-inch depth (compared to 2 percent per hour for a pool with a 9-inch depth). Using the following equation, this gives a total erosion of 7% after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and 89% after 30 days.

Number fe-oded 1 rate)OJHours where:

feroded = total fraction of debris eroded rate = erosion rate of current debris per hour Number ofHours = Number of hours debris is subject to erosion The SER points out substantial uncertainties associated with the erosion testing including the following:

• The integral debris transport tests lasted 3 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Therefore, the question remains whether the erosion rate tapers off with time. In addition, it is not certain that all of the end-of-test debris accumulation was the result of erosion products.

Enclosure NOC-AE-07002240 Page 29 of 63

• The test results include the usual variances in test data, such as flow and depth control and debris collection.

• Although the test series was designed to approximate the flow and turbulence characteristics of the volunteer-plant sump pool, the tank characteristics may have been significantly different than those at the plant. The difference in the erosion rates between the 9-inch and 16-inch pool depths in the integrated tests clearly illustrates the effect of pool turbulence on fibrous debris erosion.

" The geometry of the volunteer-plant sump pool is larger and more complex than that of the test tank used in the integrated tests.

" The long-term tests did not study large-piece debris.

Since the test data showed in general that the erosion consisted primarily of small, loosely attached pieces of fiber breaking off from larger pieces, it is considered reasonable to assume that erosion would taper off after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. To be conservative, however, the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> erosion was rounded up to 10%. This erosion fraction was applied for both small and unjacketed large fiberglass pieces in the containment pool.

Content Guide Item 3e. Debris Transport

• Identify any computationalfluiddynamics codes used to compute debris transportfractions during recirculationand summarize the methodology, modeling assumptions, and results.

Response

See response in subsection above for first bullet.

Content Guide Item 3e. Debris Transport

• Provide a summary of and supportingbasisfor, any credit takenfor debris interceptors.

Response

Debris interceptors are not integrated into the STP debris transport analysis Content Guide Item 3e. Debris Transport

• State whetherfine debris was assumed to settle andprovide basisfor any settling credited.

Response

Debris settling is not credited for the STP debris transport analyses. The analysis is a model of transport to the sump.

Content Guide Item 3e. Debris Transport

• Provide the calculateddebris transportfractions and the total quantitiesof each type of debris transportedto the strainers.

Enclosure NOC-AE-07002240 Page 30 of 63

Response

Transport logic trees were developed for each size and type of debris generated. These trees were used to determine the total fraction of debris that would reach the sump screen in each of the postulated cases.

The postulated cases include; a break in the Loop C hot leg, a break in reactor cavity, breaks in the RHR and SI pump suction and discharge lines of Loops A and B, a break in the RHR pump suction line of Loop C, and a break in the CVCS letdown line.

Table 21 - Case 1 (Loop C hot leg) debris transport fractions and debris amounts

~Debris DersDebris Debris Debris Type Debris Size Transport Generated AtSubip Fraction Fines 95% 329.2 ft3 312.7 ft3 3

Small Pieces 36% 1238.2 ft 445.8 ft3 LDFG (<6")

Large Pieces LD6" 1% 358.6 ft3 3.6 ft

(>6")

Intact Pieces 0% 382.5 ft Oft3

(>6")

MicrothermTM Total (Fines) 95% 2.3 ft3 2.2 ft3 Qualified Coatings Total (Fines) 95% 586lb 556.7 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb 3278lb (outside ZOI)

Dirt/Dust Total (Fines) 83% '170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb

Enclosure NOC-AE-07002240 Page 31 of 63 Table 22 - Case 2 (Reactor cavity) debris transport fractions Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Small Pieces 31% 18,370 ft2 5694.7 ft2

(<4")

RMI Large Pieces 31% 6,123 ft2 1898 ft2

(>4")

Fines 95% 305.9 ft3 290.6 ft3 Small Pieces 36% NA NA

(<6")

LDFG Large Pieces 1% 204.1 ft 3 2.0 ft3

(>6")

Intact Pieces 0% NA NA

(>6")

Marinite Total (Fines) 83% 15.2 ft3 12.6 ft3 MicrothermTM Total (Fines) 95% 0.9 ft3 0.86 ft3 Qualified Coatings Total (Fines) 83% 586lb 486.4 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278 lb 3278 lb Dirt/Dust Total (Fines) 83% 170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb Table 23 -RHR suction line of Loops A (bounding for suction lines) debris transport amounts Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 42.3 ft3 '42.3 ft3 Small Pieces 76% 0 ft3 0ft3

(<6")

LDFG (NukonTM)

Large Pieces 22% 28.2 ft3 6.20 ft3

(>6")

Intact Pieces 13% 0ft3 0ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI) 586 lb 586_lb Unqualified 100%

Coatings Total (Fines) 3278 lb 3278 lb (outside ZOI)

-Dirt/Dust Total (Fines) 100% 170 lb 170 lb 100% 30 lb 30 lb Latent Fiber Total (Fines)

Enclosure NOC-AE-07002240 Page 32 of 63 Table 24 -SI Discharge line of Loops B (bounding for discharge lines) debris transport amounts Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 18.7 ft3 18.7 ft3 Small Pieces 76% 0 ft3 0 ft3

(<6")

LDFG (NukonTM) Large Pieces 22% 12.5 ft 2.75 ft

(>6")

Intact Pieces 13% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI) Totl_(ins)_00%58 lb_586_lb Unqualified quaifide Coatings COatiTotal (Fines) 100% 3278 lb. 3278 lb (outside ZOI)_________ ________ ___ ______

Dirt/Dust Total (Fines) 100% 170 lb 170 lb Latent Fiber Total (Fines) 100% 30 lb 30 lb Table 25 - RHR pump suction line of Loop C debris transport fractions Debris Debris Debris At Debris Type Debris Size Transport Generated Sump Fraction Fines 100% 41 ft3 41 ft 3 Small Pieces 100% 0 ft3 0 ft3

(<6")

LDFG Large Pieces 100% 27.3 ft3 27.3 ft3

(>6")

Intact Pieces 100% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 100% 586lb 586lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb 3278lb (outside ZOI) Ttl(ns10328b27l Dirt/Dust Total (Fines) 100% 170 lb 170 lb Latent Fiber Total (Fines) 100% 30 lb 30 lb

Enclosure NOC-AE-07002240 Page 33 of 63 Table 26 - CVCS letdown line debris transport fractions Debris Debris Debris Debris Type Debris Size Transport Generated At Sump Fraction Fines 95% 153.1 ft3 145.4 ft3 3

Small Pieces 17% 0 ft 0 ft3

(<6")

LDFG (NukonTM) Large Pieces 1% 102.0 ft3 1.02 ft3

(>6")

Intact Pieces 0% 0 ft3 0 ft3

(>6")

Qualified Coatings Total (Fines) 95% 586lb 556.7 lb (inside ZOI)

Unqualified Coatings Total (Fines) 100% 3278lb' 3278lb (outside ZOI)

Dirt/Dust Total (Fines) 83% 170 lb 141.1 lb Latent Fiber Total (Fines) 83% 30 lb 24.9 lb Content Guide Item 3f Head Loss and Vortexing The objectives of the head loss and vortexing evaluations are to calculate head loss across the sump strainerand to evaluate the susceptibility of the strainerto vortexformation.

" Provide a schematic diagram of the emergency core cooling system (ECCS)and.containment spray systems (CSS).

" Provide the minimum submergence of the strainerunder small-breakloss-of-coolant accident (SBLOCA) and large-breakloss-of-coolant accident (LBLOCA) conditions.

" Provide a summary of the methodology, assumptions and results of the vortexing evaluation.

Provide basesfor key assumptions.

" Provide a summary of the methodology, assumptions, and results ofprototypical head loss testingfor the strainer,including chemical effects. Provide basesfor key assumptions.

• Address the ability of the design to accommodate the maximum volume of debris that is predictedto arrive at the screen.

" Address the ability of the screen to resist the formation of a "thin bed" or to accommodate partialthin bed formation.

" Provide the basisfor the strainerdesign maximum head loss.

• Describe significantmargins and conservatisms used in the head loss and vortexing calculations.

• Provide a summary of the methodology, assumptions,basesfor the assumptions, and results for the clean strainerhead loss calculation.

• Provide a summary of the methodology, assumptions,basesfor the assumptions, and results for the debris head loss analysis.

" State whether the sump is partiallysubmerged or vented (i.e., lacks a complete water seal over its entire surface)forany accident scenarios and describe what failure criteria in addition to loss of net positive suction head (NPSH) margin were applied to addresspotential inability to pass the requiredflow through the strainer.

• State whether near-field settling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used tojustify near-field credit.

• State whether temperature/viscositywas used to scale the results of the head loss tests to

Enclosure NOC-AE-07002240 Page 34 of 63 actualplant conditions.If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

State whether containment accidentpressure was credited in evaluatingwhetherflashing would occur across the strainersurface, and if so, summarize the methodology used to determine the available containmentpressure.

Content Guide Item 3f Head Loss and Vortexing

• Provide a schematic diagram of the emergency core cooling system (ECCS)and containment spray systems (CSS).

Response

See Figure 7 below for schematic with elevation layout.

STP SAFETY, INJECTION AND CONTAINMENT SPRAY TRAIN A LAYOUT EL. _(,25'

-TRAIN A TRAIN B R*AIN C Figure 7 - ECCS Schematic Content Guide Item 3f. Head Loss and Vortexing 0 Provide the minimum submergence of the strainerunder small-break loss-of-coolantaccident (SBLOCA) and large-breakloss-of-coolant accident (LBLOCA) conditions.

Response

For the SBLOCA low water condition, the strainer has /2 in. submergence. For the LBLOCA at the start of recirculation, the minimum water level provides the strainer with 10 in. submergence.

Enclosure NOC-AE-07002240 Page 35 of 63 Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions and results of the vortexing evaluation.

Provide basesfor key assumptions.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions, and results ofprototypical head loss testingfor the strainer,including chemical effects. Provide basesfor key assumptions.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Address the ability of the design to accommodate the maximum volume of debris that is predicted to arrive at the screen.

Response

This information will be provided in a later supplemental response.

'ContentGuide Item 3f Head Loss and Vortexing

• Address the ability of the screen to resist the formation of a "thin bed" or to accommodate partialthin bedformation.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide the basisfor the strainerdesign maximum head loss.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Describe significant margins and conservatisms used in the head loss and vortexing calculations.

Enclosure NOC-AE-07002240 Page 36 of 63

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f.Head Loss and Vortexing

• Provide a summary of the methodology, assumptions,bases for the assumptions, and results for the clean strainerhead loss calculation.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• Provide a summary of the methodology, assumptions, basesfor the assumptions, and results for the debris head loss analysis.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f HeadLoss and Vortexing

• State whether the sump is partiallysubmerged or vented (i.e., lacks a complete'water seal over its entire surface)for any accident scenariosand describe what failure criteriain addition to loss of net positive suction head (NPSH)margin were applied to addresspotential inability to pass the requiredflow through the strainer.

Response

The strainers are fully submerged for SBLOCA and LBLOCA conditions.

Content Guide Item 3f Head Loss and Vortexing

• State whether near-fieldsettling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used to justify near-field credit.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3f Head Loss and Vortexing

• State whether temperature/viscosity was used to scale the results of the head loss tests to actualplant conditions. If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

Response

This information will be providedin a later supplemental response.

Enclosure NOC-AE-07002240 Page 37 of 63 Content Guide Item 3f Head Loss and Vortexing 0 State whether containment accidentpressure was credited in evaluatingwhetherflashing would occur across the strainersurface, and if so, summarize the methodology used to determine the available containmentpressure.

Response

Containment accident pressure is not credited.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

The objective of the NPSH section is to calculate the NPSH marginfor the ECCS and CSS pumps that would exist during a loss-of-coolantaccident (LOCA) consideringa spectrum of break sizes.

" Provide applicablepumpflow rates, the total recirculationsumpflow rate, sump temperature(s),

and minimum containment water level.

" Describe the assumptions used in the calculationsfor the above parametersand the sources/bases of the assumptions.

• Provide the basisfor the requiredNPSH values, e.g., threepercent head drop or other criterion.

• Describe how friction and otherflow losses are accountedfor.

• Describe the system response scenariosfor LBLOCA and SBLOCA 's.

• Describe the operationalstatusfor each ECCS and CSSpump before and after the initiation of recirculation.

• Describe the singlefailure assumptions relevant to pump operationand sump performance.

• Describe how the containment sump water level is determined.

• Provide assumptions that are included in the analysis to ensure a minimum (conservative) water level is used in determiningNPSH margin.

" Describe whether and how the following volumes have been accountedfor in pool level calculations: empty spraypipe, water droplets, condensation and holdup on horizontaland vertical surfaces. If any are not accountedfor, explain why.

" Provide assumptions (and their bases) as to what equipment will displace water resulting in higher pool level.

" Provide assumptions (and their bases) as to what water sourcesprovide pool volume and how much volume is from each source.

• If credit is taken for containment accidentpressure in determining availableNPSH,provide description of the calculationof containment accidentpressure used in determining the available NPSH.

" Provide assumptions made which minimize the containment accidentpressure and maximize the sump water temperature.

" Specify whether the containment accidentpressure is set at the vaporpressurecorrespondingto the sump liquid temperature.

• Provide the NPSH margin resultsforpumps taking suction from the sump in recirculationmode.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide applicablepumpflow rates, the total recirculationsumpflow rate, sump temperature(s),

and minimum containment water level.

Enclosure NOC-AE-07002240 Page 38 of 63

Response

The design flow per sump for LBLOCA is 7,020 gpm. Two of the three sumps are assumed to be operating due to single failure of the diesel for the third train. The flows for the pumps in each operating train are:

LHSI 2,800 gpm HHSI 1,620 gpm CS 2,600 gpm The sump temperature at start of recirculation is 267 degrees F.

The minimum containment water level at start of recirculation is 38 in. off the floor.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the assumptions used in the calculationsfor the above parametersand the sources/bases of the assumptions.

Response

The SI pump flow rates are the maximum values given in the Technical Specifications. The CS pump flow rate is based on calculated maximum flows when two trains are operating. The sump temperature is from the containment LOCA pressure-temperature analysis which maximizes the sump temperature by using the maximum temperatures for cooling water to the heat exchangers and for the water of the ultimate heat sink. The containment water level was determined using conservative input values for the pool contributions and conservatively accounting for items such as holdup in locations in the containment, filling of empty pipe, water in transit, steam holdup, etc.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide the basisfor the requiredNPSH values, e.g., three percent head drop or other criterion.

Response

Westinghouse supplied the LHSI, HHSI, and CS pumps to STP from Pacific Pumps. The required NPSH values are based on input from Westinghouse and are as follows:

LHSI 16.5 ft. HHSI 16.1 ft. CS 16.4 ft.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe howfriction and otherflow losses are accountedfor.

Response

The strainer modification did not change the piping friction losses used in the NPSH calculation. The friction losses are based on the maximum flows of the SI and CS pumps.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the system response scenariosfor LBLOCA and SBLOCA 's.

Enclosure NOC-AE-07002240 Page 39 of 63

Response

For LBLOCA the Safety Injection Pumps and the Containment Spray Pumps start automatically and take suction from the Refueling Water Storage Tank. When the tank is drawn down, the pumps' suction is automatically switched over to the containment sumps for the recirculation mode. The HHSI and CS Pumps may be turned off later in the post-accident mitigation per the emergency operating procedures.

For SBLOCA the HHSI Pump is used to for the core cooling function during the injection and the recirculation phases. The CS pump is also assumed to be in operation due to automatic actuation by reaching the containment pressure set point..

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe the operationalstatusfor each ECCS and CSSpump before and after the initiation of recirculation.

Response

Both before and after the initiation of recirculation, two Trains are operating. Each Train consists of one HHSI, one LHSI, and one CS pump. Each Train has its own containment sump with strainer.

Content Guide Item 3g. Net PositiveSuction Head (NPSH)

• Describe the singlefailure assumptions relevant to pump operationand sump performance.

Response

The STP design has three safety Trains each with its own containment sump. The sump performance analysis is based on a single failure that results in two Trains operating to handle the debris generated.

Content Guide Item 3g. Net PositiveSuction Head (NPSH)

• Describe how the containment sump water level is determined.

Response

The Containment Water Level Calculation analyzed multiple high-energy line break cases including large break and small break LOCA's chosen to encompass a wide range of potential break sizes and locations.

The breaks were analyzed at various times throughout the event including at the start of recirculation, at suspension of containment sprays and at the end of the event. The following methodology was used to.

develop the Containment Water Level Calculation:

1. A correlation was developed for the relationship between containment water level and the containment volume as a function of elevation using information from existing STP calculations. The correlation between containment volume and water level developed in the Water Level Calculation assumes equalization of water level between all areas of containment at the (-) 1 '-3" elevation including internal compartments (e.g., incore instrument room, reactor cavity and elevator shaft). The volume inside the accumulator skirts is only credited as a displacement volume for the small break LOCA case in which the water level does not reach the service way openings preventing this volume from filling. The correlation also includes all volumes below the (-)11 '-3" elevation (e.g., elevator shaft, normal sump, secondary normal sump, emergency sumps, incore instrument room sump and drain lines).

Enclosure NOC-AE-07002240 Page 40 of 63

2. The quantity of water added to containment from the Refueling Water Storage Tank, SI Accumulators, and the Reactor Coolant System was determined for each of the breaks considered.

3. The quantity of water diverted from the containment sump was determined. The following effects were considered:

• Steam holdup in the containment atmosphere

" Additional mass of water that must be added to the RCS due to the increase in the water density at the lower sump water temperature versus the RCS temperature prior to the LOCA

" Water volume required to fill the RCS steam space as condensation occurs

" Condensation on containment surfaces

• Water volume required to fill the Safety Injection and Containment Spray Piping that is empty prior to the LOCA

" Water in transit from the Containment Spray nozzles and the break location to the Containment Sump

" ECCS leakage outside of containment

• Miscellaneous hold-up volumes throughout containment

4. Given the net mass of water added to the containment floor based on items 2 and 3 listed above, the post-LOCA containment water level was then calculated using the correlation developed in item 1.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions that are included in the analysis to ensure a minimum (conservative) water level is used in determiningNPSH margin.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Describe whether and how the following volumes have been accountedfor in pool level calculations:empty spraypipe, water droplets, condensation and holdup on horizontal and vertical surfaces. If any are not accountedfor, explain why.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions (and their bases) as to what equipment will displace water resulting in higherpool level.

Response

See subsection immediately above.

Enclosure NOC-AE-07002240 Page 41 of 63 Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions (and their bases) as to what water sourcesprovidepool volume and how much volume is from each source.

Response

See subsection immediately above.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• If credit is taken for containment accidentpressure in determining availableNPSH,provide description of the calculationof containment accident pressure used in determining the available NPSH.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide assumptions made which minimize the containment accidentpressureand maximize the sump water temperature.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Specify whether the containment accidentpressure is set at the vaporpressurecorrespondingto the sump liquid temperature.

Response

Containment accident pressure is not credited for available NPSH.

Content Guide Item 3g. Net Positive Suction Head (NPSH)

• Provide the NPSH margin resultsfor pumps taking suction from the sump in recirculationmode.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation The objective of the coatings evaluation section is to determine the plant-specific ZOI and debris characteristicsfor coatingsfor use in determining the eventual contribution of coatings to overall head loss at the sump screen.

Enclosure NOC-AE-07002240 Page 42 of 63

• Provide a summary of type(s) of coatingsystems used in containment, e.g., Carboline CZ ))

InorganicZinc primer,Ameron 90 epoxy finish coat.

- Describe andprovide basesfor assumptions made in post-LOCA paint debris transport analysis.

• Discuss suction strainerhead loss testing performed as it relates to both qualified and unqualified coatings and what surrogatematerial was used to simulate coatings debris.

• Provide basesfor the choice of surrogates.

• Describe andprovide basesfor coatings debrisgeneration assumptions. Forexample, describe how the quantity ofpaint debris was determined based on ZOI size for qualified and unqualified coatings.

-Describewhat debris characteristicswere assumed, i.e., chips, particulate,size distributionand provide basesfor the assumptions.

- Describe any ongoing containment coating condition assessmentprogram.

Content Guide Item 3.h - CoatingsEvaluation

• Provide a summary of type(s) of coating systems used in containment, e.g., Carboline CZ 11 InorganicZinc primer,Ameron 90 epoxy finish coat.

Response

The qualified coatings inside the Unit 1 and Unit 2 Reactor Containments are detailed in STP calculations. There are various types of qualified coatings used in the containment including Ethyl Silicate Inorganic Zinc (IOZ), Epoxy System, Phenolic Epoxy, Clear Sealer, Alkyd, Baked Enamel and Epoxy Intumescent.

The unqualified coatings inside the Unit 1 and Unit 2 Reactor Containments are detailed in STP calculations. There are various types of unqualified coatings used in the containment including IOZ, Epoxy System, Phenolic Epoxy, Alkyd and Baked Enamel.

The following is a brief summary of specific equipment and their coatings; the concrete walls are coated with an Epoxy System, the equipment (valves) are coated with IOZ, whip restraints are coated with Epoxy, the equipment supports are coated with IOZ, the pipe supports are coated with both Polyamide Primer (an epoxy coating) and IOZ.

Content Guide Item 3.h - CoatingsEvaluation

• Describe andprovide basesfor assumptions made in post-LOCA paint debris transportanalysis.

Response

The methodology utilized for the STP debris transport analysis is described above in another section. The transport of containment coatings was included in the analyses. In addition to the methodology described above, the following key attributes apply and are intended to describe and provide the bases for assumptions made in post-LOCA paint debris transport analysis.

1. It was assumed that the settling velocity of fine debris (insulation, dirt/dust, and paint particulate) can be calculated using Stokes' Law. This is a reasonable assumption since the particulate debris is generally spherical and would settle slowly (within the applicability of Stokes' Law).

Enclosure NOC-AE-07002240 Page 43 of 63

2. It was assumed that the unqualified coatings would be uniformly distributed in the recirculation pool. This is a reasonable assumption since the unqualified coatings are scattered around containment in small quantities.

3. Both the qualified coatings (inside the ZOI) and the unqualified coatings were conservatively assumed to fail as 10 micron particulate in the debris generation analysis.

The results of debris transport are included in the section above and include the associated values for the transport of coatings debris both within and outside the ZOI. A review of Table 21 through Table 26 identify that for the bounding LOCA analyses, coating debris transports as fines and 83% - 100% are transported to the screen, depending on the case.

Content Guide Item 3.h - Coatings Evaluation

• Discuss suction strainerhead loss testing performedas it relates to both qualified and unqualified coatings and what surrogatematerial was used to simulate coatings debris.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation

• Provide basesfor the choice of surrogates.

Response

This information will be provided in a later supplemental response.

Content Guide Item 3.h - CoatingsEvaluation

- Describe andprovidebasesfor coatings debris generation assumptions.For example, describe how the quantity ofpaint debris was determined based on ZOI size for qualified and unqualified.

coatings.

Response

The methodology utilized for the STPEGS debris generation analyses is described in sections above. The generation of containment coating debris was included in the analyses. In addition to the methodology described in these sections, the following key attributes apply and are intended to describe and provide the bases for coatings debris generation assumptions for STPEGS, and describe how the quantity of paint debris was determined based on ZOI size for qualified and unqualified coatings.

All coatings, qualified and unqualified, within the ZOI are assumed to fail and generate debris in the form of 10ýtm spherical particles, which is equivalent in size to the average zinc particle in inorganic zinc (IOZ) coatings or the pigment used in epoxy coatings.

Qualified Coatings The assumption made for coatings in the zone of influence (ZOI) of the LOCA is based on testing performed on representative coating systems. A spherical ZOI of 5D for qualified coatings was selected based on refined analysis in WCAP-16568-P, "Jet Impingement Testing to Determine the Zone of Influence (ZOI) for DBA Qualified/Acceptable Coatings", Revision 0. This was developed and

Enclosure NOC-AE-07002240 Page 44 of 63 performed in order to identify an appropriate ZOI for DBA-Qualified / Acceptable coating systems less than the 1OD ZOI mandated by the NRC SER on NEI 04-07. The results of this program demonstrate that a ZOI radius of 5D should be used for epoxy and untopcoated inorganic zinc coatings.

Per NEI 04-07, qualified coatings within the ZOI are assumed to fail as a result of impingement and post-accident environmental conditions. Qualified coatings outside the ZOI are assumed to remain intact. In order to determine the amount of qualified coatings that fail, a 3 dimensional model of the containment to calculate the areas of specific surfaces (i.e. floors, walls, equipment, etc.) within the ZOI. Plant documentation identifying coating types and applications were then used to determine the associated volume, weight and density of coatings. The density and weight of each of the various qualified coatings is listed in Table 27.

Unqualified Coatings Per NEI 04-07, all unqualified coatings inside and outside the ZOI are assumed to fail as a result of impingement and post-accident environmental conditions. The amount of unqualified coatings that will fail was determined in a similar manner. However, the weight of the applied coatings are determined based on a theoretical coating spread rates (sq. ft. per gallon @ 1 mil thickness) instead of specific vendor coating spread rates. The density and weight of each of the various unqualified coatings is listed in Table 28.

STP request for additional information (RAI) #26 is addressed by WCAP-16568-P.

Table 27 - Failed Qualified Coating Debris Source Term Type of Coating Density Weight (1b)

(lb/ft_) Weight (lb)

Epoxy 94 23 IOZ 457 553 Polyamide Primer 94 10

Enclosure NOC-AE-07002240 Page 45 of 63 Table 28 - Failed Unqualified Coating Debris Source Term Type of Coating (lb/ft3)

Density Wegt(b Weight (ib)

Epoxy 94 1,815 Alkyd 98 310 IOZ 457 884 Baked Enamel 98 269 Table 29 - Total Failed Qualified and Unqualified Coating Debris Source Term Type of Coating (lb/ft3)Wegt(b Weight (lb)

Density Epoxy 94 1,838 IOZ 457 1,437 Alkyd 98 310 Baked Enamel 98 269 Polyamide Primer 94 10 Content Guide Item 3.h - CoatingsEvaluation

• Describewhat debris characteristicswere assumed, i.e., chips, particulate,size distributionand provide basesfor the assumptions.

Response

See section above.

Content Guide Item 3.h - CoatingsEvaluation Describe any ongoing containment coating condition assessmentprogram.

Enclosure NOC-AE-07002240 Page 46 of 63

Response

STPNOC periodically conducts condition assessments of coatings inside containment. Coating condition assessments are conducted as part of the structures monitoring program. Visual inspection of coatings in containment is intended to characterize the condition of the coating systems. If localized areas of degraded coatings are identified, those areas are evaluated and scheduled for repair/replacement as necessary.

Content Guide'Item 3.i Debris Source Term The objective of the debris source term section is to identify any significant design and operationalmeasures taken to control or reduce the plant debris source term to prevent potential adverse effects on the ECCS and CSS recirculationfunctions.

• Provide the information requested in GL 04-02 Requested Information Item 2.69 regarding programmaticcontrols taken to limit debris sources in containment.

GL 2004-02 Requested Information Item 2(l) A description of the existing or planned programmaticcontrols that will ensure that potential sources of debris introduced into containment (e.g., insulations,signs, coatings, andforeign materials) will be assessedfor potential adverse effects on the ECCS and CSS recirculationfunctions. Addressees may reference their responses to GL 98-04, "Potentialfor Degradationof the Emergency Core CoolingSystem and the Containment Spray System after a Loss-of-Coolant Accident Because of Construction and Protective CoatingDeficiencies and ForeignMaterialin Containment,"to the extent that their

responses address these specificforeign material control issues.

In responding to GL 2004 Requested Information Item 209, provide the following:

• A summary of the containment housekeepingprogrammaticcontrols in place 'to control or reduce the latent debris burden. Specificallyfor RMI/low-fiber plants, provide a description ofprogrammatic controls to maintain the latent debrisfiber source term into the future to ensure assumptions and conclusions regardinginability toform a thin bed offibrous debris remain valid.

" A summary of theforeign material exclusion programmaticcontrols in place to control the introduction offoreign materialinto the containment.

• A description of how permanentplant changes inside containment areprogrammatically controlled so as to not change the analyticalassumptions and numerical inputs of the licensee analyses supportingthe conclusion that the reactorplant remains in compliance with 10 CFR 50.46 and relatedregulatory requirements.

• A descriptionof how maintenance activities includingassociated temporary changes are assessed and managed in accordancewith the Maintenance Rule, 10 CFR 50.65.

If any of the following suggested design and operationalrefinements given in the guidance report (guidancereport, Section 5) and SE (SE, Section 5.1) were used, summarize the applicationof the refinements.

• Recent or planned insulation change-outs in the containment which Will reduce the debris burden at the sump strainers

• Any actions taken to modify existing insulation (e.g., jacketing or banding)to reduce the debris burden at the sump strainers.

• Modifications to equipment or systems conducted to reduce the debris burden at the sump strainers

Enclosure NOC-AE-07002240 Page 47 of 63 Actions taken to modify or improve the containment coatingsprogram Content Guide Item 3.i Debris Source Term

• A summary of the containment housekeeping programmaticcontrols in place to control or reduce the latent debris burden. Specificallyfor RMI/low-fiber plants,provide a description ofprogrammatic controls to maintain the latent debrisfiber source term into the future to ensure assumptions and conclusions regardinginability to form a thin bed offibrous debris remain valid.

Response

During outages, STPNOC maintains containment cleanliness by adherence to the housekeeping procedure. Containment cleanliness is emphasized by the reactor containment building coordinators and the work supervisors. Prior to containment closeout at the end of the outage, the building coordinators oversee the cleanup of the containment work areas to achieve the goal of no loose debris.

Content Guide Item 3.i Debris Source Term

• A summary of the foreign material exclusion programmaticcontrols in place to control the introductionofforeign materialinto the containment.

Response

STPNOC uses a procedure to maintain containment integrity with respect to potential sump debris sources. This procedure provides guidance for a visual inspection of the affected areas inside containment at the completion of each containment entry when containment integrity has been established to verify that no loose debris is present that could be transported to the emergency sump and cause restriction of pump suction during LOCA conditions.

STPNOC has a procedure that governs signs and labels that contains the requirements for labeling inside containment. These requirements are used to minimize potential sump debris items.

Content Guide Item 3.i Debris Source Term

• A description of how permanentplant changes inside containmentare programmatically controlled so as to not change the analyticalassumptions and numerical inputs of the licensee analyses supportingthe conclusion that the reactorplant remains in compliance with 10 CFR 50.46 and relatedregulatoryrequirements

Response

Insulation replacement inside containment is either a like-for-like replacement as a maintenance activity

("rework") or is a modification with a design change that has been approved by STPNOC Engineering.

The STPNOC design change process ensures that new insulation material that differs from the initial design is evaluated.

The STPNOC design change process also calls for evaluations of added metals such as aluminum that could contribute to post-LOCA chemical effects in the sump water. The process looks at coatings that are to be used inside containment. Impacts to post-LOCA recirculation flow paths and recirculation sump debris impact on internals of fluid containing components are part of the design change evaluation process described in the procedure.

Enclosure NOC-AE-07002240 Page 48 of 63 Content Guide Item 3.i Debris Source Term A description of how maintenance activities including associatedtemporary changes are assessed and managed in accordancewith the MaintenanceRule, 10 CFR 50.65.

Response

Maintenance activities inside containment are subject to the cleanliness requirements that are given in the containment integrity surveillance procedure. The temporary change process also calls for an evaluation of items installed inside containment.

Content Guide Item 3.i Debris Source Term

• Recent orplannedinsulation change-outs in the containment which will reduce the debris burden at the sump strainers

• Any actions taken to modify existing insulation (e.g., jacketing or banding) to reduce the debris burden at the sump strainers

" Modifications to equipment or systems conducted to reduce the debris burden at the sump strainers

Response

STPNOC did not perform (and does not plan to perform) any insulation change outs or modifications to insulation banding or jacketing to reduce the potential insulation debris source term. No modifications to components or to systems were made to reduce the debris burden at the sump strainers.

Content Guide Item 3.i Debris Source Term

• Actions taken to modify or improve the containment coatingsprogram

Response

The sump performance evaluation did not result in any changes to the containment coatings program.

Content Guide Item 3.J Screen Modification Package The objective of the screen modificationpackage section is to provide a basic description of the sump screen modification.

• Provide a descriptionof the majorfeatures of the sump screen design modification.

• Provide a list of any modifications, such as reroute ofpiping and other components, relocationof supports, additionof whip restraintsand missile shields, etc., necessitated by the sump strainermodifications.

Content Guide Item 3.J Screen Modification Package

• Provide a descriptionof the majorfeatures of the sump screen design modification

Response

There is no change to the three independent sump pits. The sump screen above the pit has been removed; and now each sump has its own new strainer. There are no shared components between trains.

The new strainer assemblies for each of the 3 emergency sumps consist of two 5-module assemblies, one 4-module assembly, and one 6-module assembly. Each module is made up of eleven strainer disks. The strainer consists of stainless steel perforated plate with 0.095 in. diameter openings. Flow leaving the

Enclosure NOC-AE-07002240 Page 49 of 63 strainer assembly enters a four inlet plenum box (one inlet for each strainer assembly). The plenum box collects the flow from the strainer assemblies and directs it downward directly into the sump pit. An access cover is provided on the plenum box for internal inspection of the sump structures, vortex suppressor, and the strainer assemblies. The sump pit is now covered with a sump cover plate that prevents material from falling directly into the pit without passing through the strainer assemblies.

The new strainers have a surface area of 1,818.5 sq ft per sump. The old screens had a surface area of 155.4 sq ft per sump. For the design flow of 7,020 gpm per sump, the new strainers have a flow velocity of 0.009 ft/sec.

See the attached figures for the old screen design and the new strainer, design.

Content Guide Item 3.J Screen ModificationPackage

• Provide a list of any modifications, such as reroute ofpiping and other components, relocation of supports, addition of whip'restraintsand missile shields, etc., necessitated by the sump strainermodifications.

Response

There are no high energy lines in the area of the emergency sumps except for the High Head Safety Injection lines which are used for accident mitigation and are not assumed to be the accident initiator. No piping reroutes were needed for installation of the new sump strainers. No component relocations or additions were necessitated by the new strainer installation.

Content Guide Item k. Sump StructuralAnalysis The objective of the sump structuralanalysis section is to verify the structuraladequacy of the sump strainerincluding seismic loads and loads due to differentialpressure, missiles, andjet forces.

Provide the information requested in GL 2004-02 Requested Information Item 2(d)(vii).

• GL 2004-02 Requested Information Item 2(d)(vii) Verification that the strength of the trash racks is adequate to protect the debris screensfrom missiles and other large debris. The submittal should also provide verification that the trash racks and sump screens are capable of withstanding the loads imposed by expandingjets, missiles, the accumulation of debris, andpressure differentials caused by post-LOCA blockage underflow conditions

" Summarize the design inputs, design codes, loads, and load combinations utilizedfor the sump strainerstructuralanalysis.

" Summarize the structuralqualificationresults and design marginsfor the various components of the sump strainerstructuralassembly.

" Summarize the evaluationsperformedfor dynamic effects such as pipe whip, jet impingement, and missile impacts associatedwith high-energy line breaks (as applicable).

0 If a backflushingstrategy is credited,provide a summary statement regardingthe sump strainerstructuralanalysis consideringreverseflow.

Content Guide Item k. Sump StructuralAnalysis

• Summarize the design inputs, design codes, loads, and load combinations utilizedfor the sump strainerstructuralanalysis.

Enclosure NOC-AE-07002240 Page 50 of 63

Response

The strainer components are designed in accordance with the AISC "Specification for the Design, Fabrication, and Erection of Structural Steel for Buildings, 7th Edition" with Supplement Numbers 1, 2 and 3; and SEI/ASCE 8-02, "Specification for the Design of Cold-Formed Stainless Steel Structural Members". The acceptance criteria are primarily in accordance with these codes. In circumstances where these specifications do not provide adequate guidance for a particular component, other codes, specifications or standards are used for guidance. For instance, the strainers are made from stainless steel materials. The AISC Specification does not specifically cover stainless steel materials. Therefore, ANSE/AISC N690-1994, "Specification for the Design, Fabrication, and Erection of Steel Safety Related Structures for Nuclear Facilities", is used to supplement the AISC Specification in any areas related specifically to the structural qualification of stainless steel. Note that only the allowable stresses are used from this Specification and load combinations and allowable stress factors for higher service levels are not used.

For the perforated plates, the equations from Appendix A, Article A-8000 of the ASME B&PV Code,Section III, 1998 Edition are used instead of the AISC code. A-8000 is deemed more appropriate because it is written specifically for perforated plates.

The strainer also has several components made from thin gage sheet steel, and cold formed stainless sheet steel. SEI/ASCE 8-02, "Specification of the Design of Cold-Formed Stainless Steel Structural Members", is used for certain components where rules specific to thin gage and cold form stainless steel are applicable. The rules for Allowable Stress Design (ASD) as specified in Appendix D of this specification are used. This is further supplemented by the AISC Specification where the ASCE Specification is lacking specific guidance. Finally, guidance is also taken from AWS D1.6, "Structural Welding Code - Stainless Steel", as it relates to the qualification of stainless steel welds.

The new strainers are designed for loads due to weight, pressure, and dynamic loads. The dynamic loads come from seismic and from hydrodynamic drag loads due to sloshing. The strainers are loaded due to the inertia effect due to the motion of the containment floor during an earthquake. Hydrodynamic loads on the strainers are due to the motion of the water surrounding the strainer during a seismic event. Two weight loads are applicable. This includes the weight of the strainer components themselves and the weight of the debris that accumulates on the strainer. The design weight of the debris per strainer module is taken as 150 lbs. which bounds the calculated weight.

Thermal expansion loads are taken as zero because the strainers are essentially free standing structures that are basically free to expand without restraint due to sufficient gaps built-in to the pin connections that secure the modules to the floor tracks. Thermal expansion loads on the sump pit cover plate and the floor angles are considered negligible because these components have slotted holes or edge clips to allow for substantially unrestrained thermal growth.

The pressure load acting on the strainer is the differential pressure across the strainer perforated plates in the operating condition. This is defined as 5.71 ft. of head.

The load combinations and allowable stresses are based on the requirements of STP design criteria and are provided below.

Enclosure NOC-AE-07002240 Page 51 of 63 Load Condition Combinatioth ' , . Allowabl.e Normal Operating DW + DP + WD 1.0 S Normal Operating (Outage/Lift Load) DW + LL 1.0 S Operating Basis Earthquake DW + DP + WD + OBE 1.0 S Safe Shutdown Earthquake DW + DP + WD + SSE 1.6 S DW = Dead Weight Load LL = Live Load (additional live loads acting on strainer assembly during outages only)

WD = Weight of Debris DP = Differential Pressure OBE = Operating Basis Earthquake SSE = Safe Shutdown Earthquake S = Required section strength based on elastic design methods and the allowable, stress defined in the 7th edition AISC Specification, or other applicable specifications (ASCE 8-00, N-690, etc.)

Content Guide Item k. Sump StructuralAnalysis

• Summarize the structuralqualificationresults and design marginsfor the various components of the sump strainerstructuralassembly

Response

The calculation for seismic design margins for the strainers and their components, shows that the stress Interaction Ratios (calculated stress/allowable stress) are less than one for both Operating Basis Earthquake and Safe Shutdown Earthquake loads.

Content Guide Item 3.k Sump StructuralAnalysis

, Summarize the evaluationsperformedfor dynamic effects such as pipe whip, jet impingement, and missile impacts associated with high-energy line breaks (as applicable).

Response

There are no high energy lines in the area of the emergency sumps except for the High Head Safety Injection lines which are used for accident mitigation and are not assumed to be the accident initiator.

Thus no evaluations were needed for high energy line breaks.

Content Guide Item 3.k Sump StructuralAnalysis

• If a backflushing strategy is credited,provide a summary statement regardingthe sump strainerstructuralanalysisconsideringreverseflow.

Response

The new strainer design does not involve any backflushing.

Content Guide Item 3.1 Upstream Effects The objective of the upstream effects assessment is to evaluate the flowpaths upstream of the containment sump for holdup of inventory which could reduceflow to andpossibly starve the sump.

Provide a summary of the upstream effects evaluation including the information requestedin GL 2004-02 Requested Information Item 2(d)(iv).

Enclosure NOC-AE-07002240 Page 52 of 63 GL 2004-02 Requested Information Item 2(d)(iv)

The basisfor concluding that the water inventory required to ensure adequate ECCS or CSS recirculationwould not be held up or diverted by debris blockage at choke-points in containmentrecirculationsump returnflowpaths.

Summarize the evaluation of the flow pathsfrom the postulated break locations and containment spray washdown to identify potential choke points in the flow field upstream of the sump.

• Summarize measures taken to mitigatepotential choke points.

• Summarize the evaluation of water holdup at installed curbs and/or debris interceptors.

• Describe how potential blockage of reactorcavity and refueling cavity drains has been evaluated, including likelihood of blockage and amount of expected holdup.

Content Guide Item 3.1 Upstream Effects

• Summarize the evaluation oftheflowpathsfrom the postulated break locations and containmentspray washdown to identify potential choke points in the flow field upstream of the sump.

Response

The Upstream Effects Evaluation provides a general description of the containment and sub-compartments as well as an examination of each elevation to identify physical and structural features that affect the flow of debris and water to lower containment. The Upstream Effects Evaluation preceded the Containment Water Level Calculation and served to identify potential flow path choke points and areas of containment where water volumes could potentially be held up from reaching the containment sumps due to the'actual design layout or due to the added effects of debris resulting from high-energy line break accidents. The evaluation was based on a review of STP design documents including the UFSAR, calculations and containment drawings. No containment walkdowns were performed in support of the evaluation; however, containment photographs were reviewed. Plant personnel also provided additional information as needed.

Spray/break inventory and debris originating at upper elevations will eventually flow down to the 19'-0" elevation. The primary flow paths are through significant grated floor areas at upper elevations. See STP Response to Item 3.1 (4th bullet) below for additional information regarding the drainage flow path from the refueling cavity. Once at the 19'-0" elevation, significant concrete flooring routes the flow of water and debris to grated areas inside and outside the secondary shield wall. The primary sources of insulation debris are located above the 19'-0" elevation (e.g., the primary RCS piping and components). Therefore, the majority of insulation debris will be trapped at this elevation unless it can fit through standard floor grating. It is judged that this elevation will not become a choke point for flow because should large debris hold up at area of floor grating, the water has multiple other potential grated flow paths to the lower elevations. In addition, there is open communication between the areas inside and outside the secondary shield wall increasing the grated floor area available to pass flow.

The recirculation pool forms at the (-)11 '-3" elevation. The ECCS emergency sumps are located in the southern quadrants of containment outside the secondary shield wall. The flow path around the outside of the secondary shield wall is generally open providing large flow passages to the ECCS emergency sumps.

See STP Response to Item 3.1 (3rd bullet) for description of flow communication between areas inside and outside the secondary shield wall at the (-)l I '-3" elevation.

Enclosure NOC-AE-07002240 Page 53 of 63 Content Guide Item 3.1 Upstream Effects 0 Summarize measures taken to mitigatepotential choke points.

Response

No measures are necessary to mitigate potential choke points.

Content Guide Item 3.1 Upstream Effects

• Summarize the evaluation of water holdup at installed curbs and/or debris interceptors.

Response

There are only four (4) significant openings through which recirculation water and debris may pass from inside the secondary shield wall to the annular region outside the secondary shield wall at the (-) 11'-3" elevation. These openings are four 30" circular vent holes located-at a centerline elevation of (-)8'-6".

Since these vent holes are above the floor, the secondary shield wall acts as a curb, or debris barrier, in the flow path to the containment sumps. As discussed in the response to Item 3.1 (2nd bullet), only small debris (small enough to fit through standard floor grating) is expected to reach the base floor elevation.

Significant mounding of small debris is not expected to create a dam that would prevent flow through the vent openings. The volume of water below the vent holes is considered lost to the ECCS emergency sump.

No new curbs and/or debris interceptors have been installed.

Content Guide Item 3.1 Upstream Effects

• Describe howpotential blockage of reactorcavity and refueling cavity drains has been evaluated, including likelihood of blockage and amount of expected holdup.

Response

The refueling cavity drains via two (2) horizontal 6" drains with center line elevation located 10.75 inches above the bottom of the lower internals storage area. The two horizontal refueling cavity drains have an inside diameter of 6.065" and are straight pipe segments approximately 7 feet long. Alion Calculation ALION-CAL-STPEGS-2916-006, Rev. 0, "GSI 191 Containment Recirculation Sump Evaluation:

Determination of Fibrous Debris Transport to the Refuel Cavity" and Westinghouse letter LTR-CSA 45 "Refueling Cavity Drain Lines" are the basis for concluding that the refueling cavity drain will not become plugged with debris. Based on debris generation and transport analyses, it was conservatively determined that 71 ft3 of fines (individual fibers) and 177 ft3 of small pieces (< 6") of fibrous insulation are transported to the Refueling Cavity. The STP analyses assume that the drains do not become blocked by debris, thus restricting flow from the cavity. No additional water hold-up are assumed for the refueling cavity except that volume required to induce flow through the cavity drains above the cavity floor.

Debris blown out of the steam generator compartments is expected to be distributed evenly around the operating floor (elevation 68'-0"). The refueling cavity drain lines are located on opposite walls of the lower internals storage area and large concentrations of debris would not be expected to land near both drain lines. There are no drain covers or trash racks for the drains that would allow fibers to build up and block flow. The largest debris transported to the refueling cavity (<6") is smaller than the drain line diameter (6.065"). In addition, fibrous debris is not rigid and will deform to fit through the drain if needed. The flow velocity through the drains has been determined to be greater than the incipient tumbling velocity for 6" pieces of Nukon; however, should debris accumulate in the drain line, the

Enclosure NOC-AE-07002240 Page 54 of 63 buildup of water behind the debris will provide sufficient driving force to push the debris through the straight pipes.

STP RAI #39 is addressed by this evaluation.

Content Guide Item 3.m Downstream effects - Components and Systems The objective of the downstream effects, components and systems section is to evaluate the effects of debris carrieddownstream of the containment sump screen oh thefunction of the ECCS and CSS in terms ofpotential wear of components and blockage offlow streams. Provide the information requested in GL 04-02 Requested Information Item 2(d)(v) and 2(d)(vi) regardingblockage, plugging, and wear at restrictionsand close tolerance locations in the ECCS and CSS downstream of the sump.

GL 2004-02 Requested Information Item 2(d)(v) I The basisfor concluding that inadequate core or containment cooling would not result due to debris blockage atflow restrictionsin the ECCS and CSSflowpaths downstream of the sump screen, (e.g., a HPSI throttle valve, pump bearings and seals,fuel assembly inlet debris screen, or containment spray nozzles). The discussion should consider the adequacy of the sump screen=s mesh spacing and state the basisfor concluding that adverse gaps or breaches are not present on the screen surface.

GL 2004-02 Requested Information Item 2(d)(vi)

Verification that the close-tolerancesubcomponents in pumps, valves and other ECCS and CSS components are not susceptible to plugging or excessive wear due to extended post-accident

-,operationwith debris-ladenfluids.

1

" IfNRC-approved methods were used (e.g., WCAP-16406-P with accompanyingNRC SE),

briefly summarize the applicationof the methods. Indicate where the approved methods were not used or exceptions were taken, and summarize the evaluation of those areas.

" Provide a summary and conclusions of downstream evaluations.

• Provide a summary of design or operationalchanges made as a result of downstream evaluations.

The draft NRC SE for this document was issued to the applicant in November 2007.

Content Guide Item 3.m Downstream effects - Components and Systems

• IfNRC-approved methods were used (e.g., WCAP-1 6406-P with accompanyingNRC SE),

briefly summarize the applicationof the methods. Indicate where the approved methods were not used or exceptions were taken, and summarize the evaluation of those areas.

Response

Methods are discussed below under summary and conclusions. See next response.

Content Guide Item 3.m Downstream effects - Components and Systems

• Provide a summary and conclusions of downstream evaluations.

Enclosure NOC-AE-07002240 Page 55 of 63

Response

The evaluations listed below were developed to address effects of debris carried downstream of the containment sump screen on-the function of the ECCS and containment spray system (CSS) in terms of potential wear of components and blockage of flow streams. Close-tolerance subcomponents in pumps, valves and other ECCS and CSS components were evaluated for potential plugging or excessive wear due to extended post-accident operation with debris-laden fluids. The evaluations were developed in accordance with WCAP-16406-P, ."Evaluation of Downstream Sump Debris Effects in Support of GSI-191" prior to issuance of Revision 1 and the accompanying NRC SER. No exceptions were taken to the WCAP-16406-P methodology. A revised evaluation will be performed using Rev. 1 and the SER and will be described in a later Supplemental response to the GL.

STP RAI #31 is addressed by these evaluations.

The quantity of debris in the recirculating fluid that passes through the sump is characterized in terms of volume concentration. For downstream effects, this debris concentration is defined as the ratio of the solid volume of the debris in the pumped fluid to the total volume of water that is being recirculated by the ECC and CS systems. The resulting volume concentration from the initial debris concentration and total water volume is 0.001021.

The mass of debris in the recirculating fluid that passes through the sump is characterized in terms of parts per million (ppm). For downstream effects, the total initial debris concentration comprised of the individual debris concentrations is defined as the ratio of the solid mass of the debris in the pumped fluid to the total mass of water that is being recirculated by the ECC and CS systems.

Debris Type Concentration Fibrous 14 ppm Particulate 99 ppm Coatings - 1388 ppm Total 1501 ppm It was determined that all of the following ECCS and CSS components evaluated for STP can accommodate sump bypass particles without blockage: throttle valves; pipes, valves, and instrumentation; orifices and eductors; heat exchangers; and nozzles. A review of drawings and documents indicated that none of the ECCS and CS valves are throttled. There are no blockage/plugging issues: for existing piping, valves, and instrumentation lines; for the ECCS and CS flow element orifices, flow restricting orifices or in educator passages; for RHR heat exchangers; and for the CS spray nozzles.

According to the criteria established in WCAP- 16406-P, the wear impact on the valves identified in the STP evaluation was determined not critical and needs no further erosion evaluation.

Pump Wear Evaluation:

For pumps, the effect of debris ingestion through the sump screen were evaluated based on three aspects of operability, including hydraulic performance, mechanical shaft seal assembly performance, and mechanical performance (vibration) of the pumps. The pumps identified for evaluation were the High Head Safety Injection (HHSI), Low Head Safety Injection (LHSI), and Containment Spray (CS) pumps.

According to the methodology established in WCAP-16406-P, because the increased clearance for the pumps is within two times the design clearance, no effect on their hydraulic performance is expected.

Enclosure NOC-AE-07002240 Page 56 of 63 Normal Erosive Abrasive Total Design Increased 2X Design Pump Wear Wear Wear Wear Wear Clearance Clearance (mils) (mils) (mils) (mils) (mils) (mils) (mils)

HHSI 0.0 l.0E-3 19.6766 19.6766 17 36.6776 34 LHSI 0.0 L.OE-3 19.6766 19.6766 23 42.6776 46 CS 0.0 L.0E-3 19.6766 19.6766 23 42.6776 46 For South Texas, the HHSI, LHSI, and CS pumps are multi-stage and must be evaluated for mechanical (vibration) performance. As evaluated in WCAP- 16406-P, the other models of SI pumps will meet operability requirements for wear ring clearances up to 2 times the design clearance. Although the resulting wear ring gap for the HHSI pumps is greater than the 34 mils criteria, the 25% margin in the abrasive wear model (Appendix F.4.4 of WCAP-16406-P) allows for a margin of 34 mils

• 0.25 or 8.5 mils, so there is no expected pump vibration concern due to the containment sump debris for any of the pumps.

The initial results of the pump wear are acceptable; however the STP evaluation will be revised to incorporate the Archard pump wear model from WCAP-16406-P, Revision 1 and the accompanying NRC SER. The results of this evaluation are expected to be completed in 2008 and will be included in the final submittal of the GL 2004-02 Supplemental Responses.

The mechanical shaft seal assembly performance evaluation resulted with the suggested replacement of the Low Head Safety Injection (LHSI), High Head Safety Injection (HHSI) and Containment Spray (CS) pumps' carbon/graphite packing assemblies with a more wear resistant material. However because South Texas .Project has an Engineered Safety Feature (ESF) atmospheric filtration system for the building where the pumps are located, replacement of the carbon/graphite seal bushing is not required.

Heat Exchanger Wear Evaluation:

Tube failure for heat exchangers will occur when the resultant wall thickness after erosion is less than the required wall thickness to retain internal and external pressures. According to methodology established in WCAP- 16406-P, the minimum wall thickness required to retain both internal and external pressures is less than the resultant wall thickness after erosion. Therefore, the heat exchangers are not expected to fail.

Heat Do Required tm tactual teroded Failure Exchangers (in) (in) (in) (in) (yes/no)

RHR 0.75 0.0173 0.049 3.78E-4 no Orifice Wear Evaluation:

If the orifice inside diameter due to erosive wear is changed by less than 3%, the system performance may be considered negligible. This criterion was established in WCAP-16406-P which states that an insignificant amount of wear occurs when they system flow through the orifice is changed by less than 3%. The STP evaluation considers the initial ratio of the diameters before erosive wear and the ratio of the diameters after erosive wear for single plate and multiple plate multiple hole orifices. It was found that the inside diameters of all the orifices change by less than 3% and therefore are not expected to fail.

Spray Nozzle Wear Evaluation:

Failure due to erosive wear for spray nozzles is expected to occur when the flow from the nozzle is increased by 10% due to the increase in the nozzle inner diameter. The STP evaluation considers the

Enclosure NOC-AE-07002240 Page 57 of 63 inner diameter before and after erosive wear begins. This acceptance criterion and methodology was established in WCAP-16406-P. It was found that the flow is changed by less than 4% which is less than the 10% limit; therefore the nozzles do not fail.

Nozzle Velocity Accelerated Wear D, Flow Increase (ftlsec) Rate (inlhr) (in) ,(%)

CSS Spray Headers 44.16 4.538E-6 0.3816 3.6 Instrumentation Blockage Evaluation:

The potential for blockage of the reactor vessel Level Instrumentation System (RVLIS) is not evafuated since South Texas Project has a Westinghouse design RVLIS, for which WCAP-1 6406-P states there is no blockage concern due to the debris ingested through the sump screen during recirculation.

Content Guide Item 3.m Downstream effects - Components and Systems Provide a summary of design or operationalchanges made as a result of downstream evaluations.

Response

No design or operational changes were made as a result of the current downstream evaluations.

Content Guide Item 3.n Downstream Effects - Fuel and Vessel The objective of the downstream effects, fuel and vessel section is to evaluate the effects that debris carrieddownstream of the containment sump screen and into the reactor vessel has on core cooling.

Show that the in-vessel effects evaluation is consistent with, or bounded by, the industry generic 2

guidance (WCAP-1 6793), as modified by NRC staff comments on that document. Briefly summarize the applicationof the methods. Indicate where the WCAP methods were not used or exceptions were taken, and summarize the evaluation of those areas.

2 Because this document is still under NRC review, licensees should be aware of any NRC RAIs on it. The draft NRC SEfor WCAP-16793 is expected to be issued in December 2007. After resolution of any open items from the staff's evaluation of this document, the staff will determine whether additionalinformation is neededfrom licensees. Licensees should not delay their GL responsespending this information.

Content Guide Item 3.n Downstream Effects - Fuel and Vessel

• Show that the in-vessel effects evaluation is consistent with, or bounded by, the industry generic 2

guidance (WCAP-16793) , as modified by NRC staff comments on that document. Briefly summarize the applicationof the methods. Indicate where the WCAP methods were'not used or exceptions were taken, and summarize the evaluation of those areas.

Response

The following evaluations consider the effects that debris carried downstream of the containment sump screen and into the reactor vessel has on core cooling, including fuel and vessel blockage. These evaluations were performed in accordance with WCAP-16406-P and WCAP-16793-NP," Evaluation of Long-Term Cooling Considering Particulate and Chemical Debris in the Recirculating Fluid" with no exceptions taken. The NRC SER is still pending on WCAP-16793-NP.

Enclosure NOC-AE-07002240 Page 58 of 63 STP RAI #31 and 36 are addressed by these evaluations.

It was found that all evaluated dimensions of essential flow paths through the reactor internals are adequate to preclude plugging by sump debris. There is sufficient clearance for debris that may pass the containment sump screen since the limiting dimensions of the essential flow paths in the upper and lower internals are all greater than the maximum particle dimension. The maximum particle dimension is defined as twice the sump screen hole diameter. The sump screen hole diameter evaluated is 0.125 inches. The smallest clearance found in South Texas Project is 1.19 inches. Therefore, any screen size smaller than 0.59 inches will prevent plugging by sump debris in the vessel at South Texas Project. The new strainers have a hole size of 0.095 in. dia.

STPNOC evaluated the potential for fuel blockage from debris carried downstream of the containment sump screen. In the cold-leg break evaluation, the high rate of bypass flow around the core and increased filtering by the containment emergency recirculating sump (CERS) screen is insufficient to preclude the formation of a fiber bed of 0.125 inches from forming on the underside of the bottom nozzles within approximately 10 minutes after initiation of the CERS recirculation flow. At the time of hot-leg injection, 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after accident initiation, an insignificant fraction of the initial fiber concentration remains available in the CERS for deposition on the top of the core. In the hot-leg break evaluation, the thickness of the fibrous bed forming on the underside of the fuel bottom nozzle reaches approximately 0.125 inches immediately after initiation of the CERS recirculation flow. At the time of hot-leg injection, 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> after accident initiation, an insignificant fraction of the initial fiber concentration remains available in the CERS for deposition on the top of the core.

The conclusion of this evaluation indicated that the amount of fibrous debris generated by a large break LOCA in STPEGS would produce a fibrous concentration in the CERS volume that would allow fibrous debris on the underside of the fuel bottom nozzle to exceed the acceptance criterion of less than 0.125 inches. STPNOC determined that additional evaluation of fuel blockage potential would be required.

Subsequently, a preliminary refined fuel blockage assessment was performed for STP to demonstrate that blockage from fiber build-up will not compromise fuel cooling. The results of PCI prototype strainer performance testing based on water flow and debris mix conditions expected in South Texas containments following a postulated LOCA was used to determine the potential for STP fuel blockage. The evaluation used fibrous debris bypass test data to determine the fuel blockage potential and was performed in accordance with guidance from WCAP-16406-P, Revision 1 and WCAP-16793-NP (as modified by initial NRC staff comments on that document). The results of this evaluation indicate that the amount of fibrous debris generated by a large break LOCA will not produce a fibrous debris build-up on the underside of the fuel bottom nozzle that exceeds the acceptance criterion of less than 0.125 inches.

Fibrous debris bypass test data from strainer testing in February 2008 will be used in the revised evaluation that will be included in STP's final GL response submittal.

The in-vessel effects evaluation for STP will be performed in accordance with guidance from WCAP-16793-NP as modified by NRC staff comments on that document. The results of this evaluation are expected to be completed in 2008 and will be included in STP's final submittal of GL 2004-02 Supplemental Responses. No design or operational changes have been made as a result of the current fuel blockage evaluation.

3 Content Guide Item 3.o Chemical Effects The objective of the chemical effects section is to evaluate the effect'that chemicalprecipitates have on head loss and core cooling.

Enclosure NOC-AE-07002240 Page 59 of 63

" Provide a summary of evaluation results that show that chemicalprecipitatesformed in the post-LOCA containment environment, either by themselves or combined with debris, do not deposit at the sump screen to the extent that an unacceptablehead loss results, or deposit downstream of the sump screen to the extent that long-term core cooling is unacceptably impeded.

" Content guidancefor chemical effects is provided in Enclosure 3 to a letterfrom the NRC to NEI dated September 27, 2007 (ADAMS Accession No. ML0726007425).

3 The NRC staff expects to issue a draft SE on WCAP-16530, "Evaluationof Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," in November 2007.

Response

The purpose of this analysis is to determine the type and quantity of chemical precipitates which may form post-LOCA. This input is intended to be used for screen performance testing and may be used in the evaluation of chemical effects on downstream equipment. Though the quantities of precipitates expected to form have been calculated, the sump strainer blockage headloss effects will not be known until after testing has been completed in 2008. A later Supplemental response to the GL will describe the chemical effects testing method and results.

STPNOC evaluated the type and expected quantity of chemical products that would be expected to form in the recirculation fluid specifically for STP. Revision 0 of this evaluation used the chemical model/methodology developed in WCAP-16530-NP, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," prior to release of the accompanying NRC SER. No deviations were taken to the WCAP-16530-NP methods.

STP RAI numbers 6, 14 and 20 are addressed by the application of WCAP-16530-NP and the results from this evaluation. STP RAI numbers 2, 3, 4, 5 and 7 are addressed as material and condition inputs to the evaluation.

Input assumptions (and their basis) used to determine chemical effects loading: pH range, temperature profile, duration of containment spray, and materials expected to contribute to chemical effects are described in the chemistry effects evaluation. The spray values from the time of recirculation were assumed to equal the sump pH values. This is conservative because the higher pH of the sump will produce more precipitates. The spray pH curve consists of the initial pH of 4.5 and the calculated values for the sump pH from the time of recirculation. Because the sump temperature data was only provided for 2 days, the final temperature was extended for the 30 day period. Extending the final temperature of 165 'F from 2 days to 30 days will provide more conservative values for precipitate formation since this temperature is higher than the actual temperatures expected due to cooling by the RHR heat exchangers.

Because of the uncertainty of the operator actions which may be taken post-LOCA, the evaluation was performed with spray continuing for both 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 30 day durations for both maximum and minimum recirculation volumes. This resulted in four sensitivity cases. The materials expected to contribute to the formation of chemical precipitates are: CalSil (Marinite) insulation, fiberglass insulation, microtherm, concrete, trisodium phosphate, submerged aluminum, and non-submerged aluminum. The resulting expected chemical precipitates are sodium aluminum silicate (NaAlSi308), aluminum oxyhydroxide (AlOOH), and calcium phosphate (Ca3(P04)2).

The case with the maximum recirculation water volume and 30-day spray duration yields the maximum total amount of precipitates.

Enclosure NOC-AE-07002240 Page 60 of 63 Maximum Recirculation Volume Minimum Recirculation Volume Spray 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 30 days 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 30 days Duration kg ppm kg ppm kg ppm kg ppm NaAlSi308 318.4 128.9 649.5 262.9 295.1 219.6 497.8 370.5 A1OOH 0.0 0.0 35.7 14.5 0.0 0.0 64.9 48.3 Ca3(PO4)2 162.7 65.9 162.7 65.9 132.0 98.2 132.0 98.2 Revision 1 of the STP chemistry effects evaluation used the refined methodology developed in WCAP-16785-NP, "Evaluation of Additional Inputs to the WCAP-16530-NP Chemical Model," to perform additional sensitivity cases. STP will use the base case chemical effects quantities from Revision 0 during the performance of strainer headloss testing with chemical effects surrogates.

Content Guide Item 3 .p Licensing Basis The objective of the licensing basis section is to provide information regardingany changes to the plant licensing basis due to the sump evaluation or plant modifications.

Provide the information requested in GL 04-02 Requested Information Item 2(e) regardingchanges to the plant licensing basis. The effective date for changes to the licensing basis should be specified. This date should correspondto that specified in the 10 CFR 50.59 evaluationfor the change to the licensing basis.

GL 2004-02 Requested Information Item 2(e) A general descriptionof andplanned schedule for dny changes to the plant licensing bases resultingfrom any analysis orplant modifications made to ensure compliance with the regulatoryrequirements listed in the Applicable Regulatory Requirements section of this GL. Any licensing actions or exemption requests needed to support changes to the plant licensing basis should be included.

Response

A license amendment request was submitted that proposed revising the Technical Specification (TS)

Surveillance Requirement (SR) 4.5.2.d for the inspection of the Emergency Core Cooling System (ECCS) sumps for consistency with the new STP sump design.

Enclosure NOC-AE-07002240 Page 61 of 63 Commitments from the Supplemental Response to GL2004-02 Commitment Tracking Action Due Date Content Guide Item 3f Head Loss and Vortexing CR04-12498-15-1 6/30/2008

" Provide a summary of the methodology,. assumptions and results of the vortexing evaluation.Provide basesfor key assumptions.

" Address the ability of the design to accommodate the maximum volume of debris that is predicted to arrive at the screen.

" Address the ability of the screen to resist theformation of a "thin bed" or to accommodatepartialthin bedformation.

" Provide the basisfor the strainerdesign maximum head loss.

" Describesignificant margins and conservatisms used in the head loss and vortexing calculations.

" Provide a summary of the methodology, assumptions, basesfor the assumptions, and resultsfor the clean strainerhead loss calculation.

" Provide a summary of the methodology, assumptions, basesfor the assumptions, and resultsfor the debris head loss analysis.

" State whether near-field settling was creditedfor the head-loss testing and, if so, provide a description of the scaling analysis used tojustify near-field credit.

" State whether temperature/viscositywas used to scale the results of the head loss tests to actualplant conditions. If scaling was used, provide the basisfor concluding that boreholes or other differential-pressureinduced effects did not affect the morphology of the test debris bed.

Content Guide Item 3g. Net Positive Suction Head (NPSH) CR04-12498-15-2 6/30/2008

• Provide the NPSH margin resultsfor pumps taking suction from the sump in recirculationmode.

Content Guide Item 3.h - CoatingsEvaluation CR04-12498-15-3 6/30/2008

" Discuss suction strainer head loss testing performed as it relates to both qualified and unqualified coatings and what surrogate material was used to simulate coatings debris.

• Provide basesfor the choice of surrogates.

Content Guide Item 3.m Downstream effects - Components and Systems CR04-12498-15-4 6/30/2008 e Provide a summary and conclusions of downstream evaluations.

A revised evaluation will be performed using Rev. 1 and the SER and will be described in a later Supplemental response to the GL.

The initial results of the pump wear are acceptable; however the STP evaluation will CR04-12498-15-5 6/30/2008 be revised to incorporate the Archard pump wear model from WCAP- 16406-P, Revision I and the accompanying NRC SER. The results of this evaluation are expected to be completed in 2008 and will be included in the final submittal of the GL 2004-02 Supplemental Responses.

The in-vessel effects evaluation for STP will be performed in accordance with CR04-12498-15-6 6/30/2008 guidance from WCAP-16793-NP as modified by NRC staff comments on that document. The results of this evaluation are expected to -be completed in 2008 and will be included in STP's final submittal of GL 2004-02 Supplemental Responses.

No design or operational changes have been made as a result of the current fuel blockage evaluation.

Enclosure NOC-AE-07002240 Page 62 of 63 Commitment Tracking Action Due Date Content Guide Item 3.o ChemicalEffects3 CR04-12498-15-7 6/30/2008 The objective of the chemical effects section is to evaluate the effect that chemical precipitateshave on head loss and core cooling.

" Provide a summary of evaluation results that show that chemical precipitatesformed in the post-LOCA containment environment, either by themselves or combined with debris, do not deposit at the sump screen to the extent that an unacceptable head loss resulis, or deposit downstream of the sump screen to the extent that long-term core cooling is unacceptably impeded.

" Content guidancefor chemical effects is provided in Enclosure 3 to a letter from the NRC to NEI dated September 27, 2007 (ADAMS Accession No.

3 ML0726007425).

The NRC staff expects to issue a draft SE on WCAP-16530, "Evaluationof Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," in November 2007.

Response

The purpose, of this analysis is to determine the type and quantity of chemical precipitates which may form post-LOCA. This input is intended to be used for screen performance testing and may be used in the evaluation of chemical effects on downstream equipment. Though the quantities of precipitates expected to form have been calculated, the sump strainer blockage headloss effects will not be known until after testing has been completed in 2008. A later Supplemental response to the GL will describe the chemical effects testing method and results.