ML20317A112

Final Response and Close-out to Generic Letter 2004-02

ML20317A112
Person / Time
Site:	Calvert Cliffs
Issue date:	11/12/2020
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GL 2004-02
Download: ML20317A112 (148)

Text

200 Exelon Way 200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com GL 2004-02 November 12, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Docket Nos. 50-317 and 50-318

Subject:

Calvert Cliffs Nuclear Power Plant, Units 1 and 2 - Final Response and Close-out to Generic Letter 2004-02

References:

1. Letter from James Barstow (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission - "Final Response to Generic Letter 2004-02," dated August 13, 2018 (ML18226A189)

2. Letter from David T. Gudger (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission - "Supplement to Final Response to Generic Letter 2004-02, dated August 13, 2018," dated October 10, 2018 (ML18283A034)

3. Letter from James Barstow (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission - "Revised - Final response to Generic letter 2004-02," dated June 7, 2019 (ML19158A075)

4. Letter from David T. Gudger (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission - "Response to Request for Additional Information Revised - Final Response to Generic Letter 2004-02," dated October 3, 2019 (ML19277D103)

5. Letter from David T. Gudger (Exelon Generation Company, LLC to U.S.

Nuclear Regulatory Commission - Withdrawal of License Amendment Request for Calvert Cliffs Nuclear Power Plant Units 1 and 2 - Final Response to Generic Letter 2004-02, dated October 21, 2019 (ML19294A056)

By letter dated August 13, 2018 (Reference 1), as supplemented by References 2, 3, and 4 above, Exelon Generation Company, LLC (Exelon) submitted a license amendment request (LAR) and Exemption Request for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CCNPP). The proposed amendment and exemption request would have changed the Calvert Cliffs licensing bases, including the affected portions of the Technical Specifications and Updated Final Safety Analysis Report to address Generic Safety Issue -191, "Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance,"

and close out Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" (ML042360586).

CCNPP Final Response and Close-out to Generic Letter 2004-02 November 12, 2020 Page 2 Upon further review, in Reference 5, Exelon had decided to follow a different approach and, accordingly, Exelon withdrew the LAR and Exemption Request documented in Reference 1 and supplemented in References 2, 3, and 4.

This submittal provides the CCNPP Final Response and Close-out to Generic Letter 2004-02. contains the Supplemental Response to Generic Letter 2004-02. contains the Summary of Regulatory Commitments.

There is one regulatory commitment contained in this submittal to revise an emergency procedure EOP-5, Loss of Coolant Accident.

In accordance with 10 CFR 50.91, "Notice for public comment: State consultation," Exelon is transmitting a copy of this letter to the designated State Official.

If you have any questions concerning this submittal, please contact Frank Mascitelli at (610) 765-5512.

Respectfully, David P. Helker Sr. Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC - Supplemental Response to Generic Letter 2004-02 - Summary of Regulatory Commitments cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP Project Manager [CCNPP] USNRC S. Seaman, State of Maryland

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Final Response to NRC Generic Letter 2004-02 Calvert Cliffs Nuclear Power Plant Table of Contents Section Description Page 1 Overall Compliance 1 2 General Description of and Schedule for Corrective Actions 11 3 Information Regarding Methodology Demonstrating Compliance 13 3a Break Selection 13 3b Debris Generation / Zone of influence 16 3c Debris Characteristics 31 3d Latent Debris 35 3e Debris Transport 37 3f Head Loss and Vortexing 40 3g Net Positive Suction Head 82 3h Coating Evaluation 93 3i Debris Source Term 98 3j Screen Modification Package 102 3k Sump Structural Analysis 104 3l Upstream Effects 117 3m Downstream Effects - Components and Systems 119 3n Downstream Effects - Fuel and Vessel 122 3o Chemical Effects 124 3p Licensing Basis 137 4 References 140 Page i

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Attachment 1 to Exelon Letter dated 11/12/20 Updated Final Response to NRC Generic Letter 2004-02 This attachment provides the final response to Generic Letter 2004-02 (Reference 24) for Calvert Cliffs Units 1 & 2. This response uses the Revised Content Guide for Generic Letter 2004-02 Supplemental Responses, November 2007.

OVERALL COMPLIANCE NRC Issue 1:

Provide information requested in GL 2004-02, "Requested Information." Item 2(a) regarding compliance with regulations. That is, provide confirmation that the ECCS and CSS recirculation functions under debris loading conditions are or will be in compliance with the regulatory requirements listed in the Applicable Regulatory Requirements section of this generic letter. This submittal should address the configuration of the plant that will exist once all modifications required for regulatory compliance have been made and this licensing basis has been updated to reflect the results of the analysis described above.

Response to Issue 1:

Calvert Cliffs has completed all necessary testing, analyses, and modifications to be in compliance with the Nuclear Regulatory Commission (NRC) Generic Letter (GL) 2004-02, and 10 CFR 50.46 (Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors).

A Containment Emergency Sump is provided for each unit which serves both trains of the Emergency Core Cooling System (ECCS) and the Containment Spray System (CSS). In response to GL 2004-02, Calvert Cliffs increased the strainer surface area of the Containment Emergency Sump strainer from 150 ft2 to 6,060 ft2. The filtration surface holes were decreased from the previous 0.25 x 0.25 opening to 1/16 diameter openings. The strainer is now entirely submerged under all events requiring containment sump recirculation. The strainer was designed, manufactured and tested by Control Components, Incorporated (CCI) of Winterthur, Switzerland, and the design utilized is not vulnerable to the formation of the thin-bed effect. The sump strainer system ensures the net positive suction head (NPSH) available exceeds the pump requirements following a LOCA, thereby supporting the operability of the ECCS and Containment Spray Systems.

The Containment Emergency Sump strainer was installed in Unit 2 during the Spring 2007 refueling outage (RFO) and in Unit 1 during the Spring 2008 RFO. Structural upgrades were performed on the Unit 2 sump in 2009 and in Unit 1 sump in 2010 to provide additional strength. The system has three strainer module rows utilizing 33 strainer modules connected to a central water duct that discharges directly into the sump pit, which houses the two ECCS/Containment Spray pump suction headers. Each strainer Page 1 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 module has a series of strainer cartridges constructed of perforated stainless-steel plate. Following a LOCA event, all liquid used for recirculation must pass through these strainer cartridge perforations or similar sized strainer system gaps prior to entering the sump. The Containment Emergency Sump strainer has been tested for multiple debris loads.

In addition to strainer and sump modifications, Calvert Cliffs has further reduced the potential impact of chemical effects head loss by replacing the tri-sodium phosphate sump pool buffer with sodium tetraborate to eliminate calcium phosphate precipitates. Aluminum is the remaining primary precipitant for chemical effects at Calvert Cliffs; therefore, a number of actions were taken to reduce the amount of aluminum inside containment. Aluminum scaffolding materiel is no longer stored in containment. The aluminum scissors lift on the polar crane was removed from both units in the 2012 and 2013 RFOs.

Significant amounts of mineral wool insulation were replaced with stainless steel reflective metal insulation (RMI) for both units during the 2013 and 2014 RFOs. The scaffolding material, scissors lift, and mineral wool insulation constituted the majority of aluminum sources inside containment.

Calvert Cliffs has undertaken a significant effort to reduce the fibrous insulation debris source term.

Reducing the amount of fiber decreases strainer head loss and reduces the chemical effects source term. In the 2013/2014 RFOs, multiple sections of insulated piping were re-insulated with RMI. The RMI used at Calvert Cliffs is constructed of stainless steel and does not fail in a manner that contributes to strainer head loss.

Furthermore, during the 2012 and 2013 RFOs, Calvert Cliffs implemented a modification to increase from 1 to 8 the drain flow path from the two refueling pool cavities to the lower level of containment.

This eliminates potential water sequestration in the refueling pool cavities, raises the post-LOCA sump water level, and provides additional margin for ECCS and Containment Spray System pump NPSH and strainer deaeration. A trash rack strainer is installed over each drain entrance to prevent large debris from clogging either of the drains.

Finally, the Calvert Cliffs Technical Specifications (TS) include surveillance requirements for visual inspections of the recirculation strainer to verify inlets are not restricted by debris and that the strainer components show no evidence of structural distress or abnormal corrosion. The Calvert Cliffs Technical Requirements Manual (TRM) includes Technical Normal Condition (TNC) 15.6.2 for cleanliness in accessible areas of the containment to verify no loose debris (rags, trash, clothing, etc.) is present which could be transported to the recirculation sump and cause restriction of the suction strainer during LOCA conditions.

The responses that follow present a number of conservatisms. They are summarized below:

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• The Calvert Cliffs debris generation analysis was performed in accordance with the approved methodology of NEI 04-07 (Pressurized Water Reactor Sump Performance Evaluation Methodology) that includes multiple levels of conservatism:

o A debris generation calculation analyzed break sizes up to and including a double-ended guillotine break (DEGB) of the Main Loop RCS piping. The likelihood of a large rupture in pressurized water reactor coolant piping is less than 3.6x10-6 per year. Estimates for the frequency of a full double-ended rupture of the main coolant piping are on the order of 7.5x10-8 per year. Smaller piping ruptures, while still unlikely, provide a better measure of expected behavior. These smaller breaks would generate significantly less debris and would be far less likely to challenge strainer performance.

o Break opening time and full offset displacement for double-ended guillotine breaks are instantaneous. The non-physical assumption of an instantaneous opening of a fully offset double-ended rupture leads to a significant overestimation of the debris generation potential for a postulated break. Even conservative estimates of minimum break opening times for large bore piping preclude formation of damaging pressure waves. The wide recognition that a large RCS pipe is more likely to leak and be detected by the plants leakage monitoring systems long before cracks grow to unstable sizes is referred to as leak before break and is an accepted part of regulatory compliance with General Design Criterion 4.

o Full destruction of materials within a conservatively determined zone of influence is based upon a conservative extrapolation of limited test data performed under non-prototypical conditions, with limiting configurations. The sparse database on insulation destruction testing has forced the use of bounding results. For example, results based on aluminum jacketed insulation are applied to stainless steel jacketed insulation, and all insulation is presumed to have a worst-case seam orientation relative to the break.

The zone of influence (ZOI) for insulation materials is expected to be significantly smaller than that predicted by the NRC guidance due to real factors including the absence of a damaging pressure wave, greater structural integrity than tested materials, and non-limiting seam orientations.

• The Calvert Cliffs debris transport evaluation was performed in accordance with NEI 04-07, which includes multiple levels of conservatism:

o All debris is assumed to wash down to the sump pool with no holdup on structures.

Although fine debris could be carried by draining containment spray flow, a significant quantity of fines would likely be retained on walls and structures above the containment sump pool due to incomplete spray coverage and hold up on structures. Even in areas that are directly impacted by containment spray flow, some amount of fines would agglomerate together and settle prior to reaching the strainer.

o All fine debris is assumed to transport to the surface of the strainer. Portions of the debris present or generated at the beginning of the event would likely be transported by Page 3 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 break and containment spray flows into quiescent regions in the sump pool, and form debris piles. Once containment sump recirculation began it would take substantially higher flow rates to move these debris piles than to move individual fiber fines. Even if these piles of debris were to move, there are numerous obstacles (e.g. supports, equipment, and curbs) that would prevent debris from reaching the strainer.

o Approved guidance calls for uniform debris transport to and deposition on the strainer surfaces. Testing shows that debris transport to the surface of complex strainers will not be uniform, unless it is artificially induced in the testing. Some settling and uneven debris distribution is prototypical, which results in lowered head loss across the strainers.

• The Calvert Cliffs strainer head loss testing was performed in accordance with the NRC March 2008 guidance [Reference (13)] which includes multiple levels of conservatism:

o During head loss testing, only fiber fines were used to conservatively bound head loss as it was observed that small pieces of fiber dramatically reduced strainer debris bed head loss. The small pieces caused a non-uniform debris bed which could not sustain as high a differential pressure. Should large quantities of debris be generated and transported to the strainer, some transport of small pieces could be expected.

o During head loss testing, fiber fines produced by erosion are assumed to arrive at the strainer at the start of recirculation, instead of hours or days later when strainer performance margin is greater. Fiber fines created by erosion account for approximately 30% of the total fine fiber load and will arrive at the strainer over a period of hours or even days. A significant portion of these fines will arrive after performance margin has increased.

o During head loss testing, a full 30-day chemical precipitate load is assumed to arrive at the strainer at the earliest possible time with no credit for settling or nucleation on containment surfaces. The quantity of precipitate arriving at the strainer is expected to be significantly lower than tested amounts. In addition, the precipitate is expected to arrive or form in the debris bed gradually.

o During head loss testing, all fiber and particulate debris is collected on the strainer prior to addition of chemical precipitates. The chemical precipitate coating on the debris bed observed in head loss testing is not prototypical. In reality it would be less uniform than that achieved during testing since some fiber and particulate debris would arrive along with the precipitates, or the precipitates would form in the debris bed, producing a less uniform deposit. A less uniform deposition of precipitates would yield a lower strainer head loss.

o During head loss testing, the low strainer approach velocity required that non-prototypical agitation be used to get debris that had settled in the immediate vicinity of the strainer to transport onto the strainer. This clearly demonstrated the conservatism of assuming 100% debris transport of fiber fines to the strainer. Much of the debris that Page 4 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 is assumed to transport to the strainer will likely settle prior to reaching the strainer and not become part of the strainer debris bed.

o Head loss test procedures were designed to assure uniform debris distribution on the strainer to maximize debris bed head loss. The design and physical layout of the Calvert Cliffs strainer promotes non-uniform debris distribution.

o During testing, debris materials that were demonstrated to reduce debris bed head loss such as lead shielding blanket fibers and RMI debris were excluded from the tested debris in order to conservatively maximize head loss. The lead shielding blanket fibers and some of the smaller RMI debris would likely transport to the strainer and disrupt formation of a uniform fiber/particulate debris bed. This would result in lower strainer head loss.

o RMI debris that is predicted to enter the sump pool but not reach the strainer is excluded from testing to prevent capture of finer debris before it reaches the strainer.

Any debris that enters the sump pool but does not transport to the strainer would likely capture some of the fine debris before it reaches the strainer.

• The Calvert Cliffs chemical effects head loss analysis was based on testing in accordance with WCAP-16530 [Reference (12)] which includes multiple levels of conservatism:

o One hundred percent of chemical species of interest are assumed to precipitate. When solubility limits are taken into account, the predicted precipitation would be reduced.

o The current models call for chemical precipitate formation in a form readily transported to the sump screen. A significant portion of precipitate formation will occur on large surface areas in containment, and in settled debris, all of which are remote from the strainer, and will not then be readily transported to the strainer.

o The approved testing methodology results in the chemical precipitates being pre-formed and overlaid upon the strainer debris bed as a whole, after debris and particulates are placed into the test. This is conservative.

• No temperature corrections to head loss based on viscosity variations dependent on temperature were credited.

• No containment accident pressure is credited beyond that required to maintain the pressure consistent with the sump fluid temperature at or above saturation conditions of 212°F.

• Assumption of the latent debris quantity based on the larger quantity from the two units.

• Wear analyses were performed in accordance with WCAP-16406-P-A [Reference (8)] using bounding debris quantities and assuming no hold-up of particulate would occur in various locations. These locations include the fiber bed, the reactor vessel, and the refueling canals and reactor cavity.

• The wear analysis also assumed no particulate depletion for the entire 30-day mission time.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• The Calvert Cliffs design incorporates one of the largest strainers in the PWR fleet, along with one of the lowest strainer recirculation flow rates. The resultant low approach velocity will limit the amount of debris transported to the strainer filtration surface.

• Analyses assume that 100% of the unqualified coating debris fail at the time of the accident.

ALTERNATE EVALUATION METHODOLOGY Section 6 of the NEI 04-07 Guidance Report (GR) describes an alternate evaluation methodology for demonstrating acceptable containment sump performance (Reference 1, page 110-127). This alternate evaluation methodology provides separate analysis methods for two distinct break size regions (Ref. 1 pg. 113).

• Region I:

Defined as all breaks up to and including double-ended guillotine breaks (DEGBs) on the largest piping connected to the RCS main loop piping AND breaks on the RCS main loop piping up to a size equivalent to a DEGB of a 14 in sch. 160 pipe (inner diameter = 11.188 in, DEGB flow area =

196.6 in2). Reference 1 refers to this as the Alternate Break Size. Design Basis rules apply to all breaks in this region.

• Region II:

Defined as all breaks larger than the Region I break size up to and including DEGBs on the RCS main loop piping. Mitigative capabilities must be demonstrated, but the fully deterministic design basis rules do not necessarily apply.

The alternate evaluation methodology can be used to demonstrate reasonable assurance of adequate long-term core cooling for the bounding breaks in Region II by allowing the use of more realistic assumptions and methods, credit for mitigative operator action, and use of non-safety-related equipment. Based on various considerations, the NRC Staff determined that the division of the pipe break spectrum proposed for evaluating debris generation is acceptable based on operating experience, application of sound engineering judgement, and consideration of risk-informed principles. Licensees using the methods described in Section 6 of the GR can apply the Alternate Break Size (ABS) for distinguishing between Region I and Region II analyses (Reference 1 pg. 114).

Region I Evaluation The Region I evaluation considers LOCA pipe breaks on piping connected to the RCS main loop piping inside the first isolation valve, which have a maximum nominal pipe diameter of 14 inches, as well as partial pipe breaks equivalent to a 14 Sch. 160 break on the RCS main loop piping. While Reference 1 allows these partial breaks to be modeled with a hemispherical ZOI, for conservatism the Calvert Cliffs Region I analysis applies a spherical ZOI having the same radius as that of the hemispherical ZOI.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The Region I breaks were evaluated in accordance with NRC-approved methods for a deterministic evaluation and were shown to meet all acceptance criteria. The details of this evaluation are described in the Section on Specific Information Regarding Methodology for Demonstrating Compliance. The debris quantities for the bounding Region I break locations are described in the response to Item 3b4.

Region II Evaluation The Region II evaluation considered breaks larger than 14 in Sch. 160 on the RCS Main Loop piping.

These breaks were analyzed using bounding DEGBs on the RCS Main Loop piping at the limiting break locations. The debris quantities for the bounding Region II break locations are described in the response to Item 3b4.

Downstream effects (both in-vessel and ex-vessel) were evaluated for the bounding Region II breaks in accordance with NRC approved methods for a deterministic evaluation and were shown to meet the relevant acceptance criteria. Therefore, the use of the alternate evaluation methodology is limited to strainer head loss concerns and is not utilized for downstream effects.

Analysis of Bounding Region II Breaks.

The head loss test results demonstrate that prior to the formation of chemical precipitates (when sump pool temperatures have dropped to 140°F and below) the strainer head loss is low and there are no challenges to ECCS pump operation either due to inadequate NPSH, or deaeration. Prior to the formation of chemical precipitates, the maximum strainer flow will have been reduced from a maximum value of 5000 gpm to a maximum value of 2365 gpm (see response to item 3g1).

Even after the sump pool temperature drops below 140°F (onset of chemical precipitates) strainer head loss will continue to be acceptable for all Region II breaks at the 2365 gpm maximum strainer flow rate except for the limiting 11 / 21 Hot Leg breaks. At this strainer flow rate the maximum allowable head loss exceeds the limit to avoid deaeration inside the strainer (see the response to 3.f.7).

However, for Hot Leg breaks the EOP criteria to allow all Containment Spray flow to be secured will be reached prior to the onset of Chemical precipitates. The further reduced strainer flow would reduce strainer head losses to acceptable values for the limiting 11 / 21 Hot Leg break cases.

As defense-in-depth, if the remaining Containment Spray pump had not been secured prior to the onset of chemical precipitates, and pump distress were detected for an 11 /21 Hot Leg double-ended guillotine break then either the remaining Containment Spray pump could be secured, or the ECCS could be returned to injection mode taking suction again from the RWT which had been refilled after RAS.

After a second RWT volume has been injected into containment the strainer submergence would be sufficient to prevent deaeration for 11 / 21 Hot Leg Region II breaks even if the strainer flow were returned to its maximum 2365 gpm value.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 As further defense-in-depth it is noted that this evaluation also assumes that only one train of Containment Air Coolers (CACs) is in service. The most likely cause for the loss of a train of CACs is the loss of offsite power combined with failure of a diesel to start. If restoration of offsite power or operation of the EDG was not projected to occur in the short-term the site would align the NSR 0C diesel to the affected bus which would among other things restore the second CAC train to service. Other causes for the loss of a CAC train is the failure of either a Service Water (SRW) or Salt Water (SW) pump causing the loss of a cooling header. In both cases there is a redundant pump that could be started to return the affected header to service. Therefore, for long-term containment response conditions operation with both trains of CACs in service for a significant portion of the operating time is reasonable to assume. Containment response work shows that having both trains of CACs operating significantly reduces the containment pressure and vapor temperature while only slightly reducing sump pool temperature. Therefore, with both trains of CACs operating the containment temperature would be significantly below 120F when the sump temperature reached 140F, and chemical precipitates formed.

These conservatisms are in addition to the conservatisms listed at the beginning of this section (e.g.,

100% transport of fiber fines, no transport of small pieces, etc.) which taken together demonstrate the overall safety of the Calvert Cliffs strainer design.

Risk Evaluation The relaxation of requirements for Region II breaks is based on the low frequency associated with breaks that are greater than the Alternate Break Size. Based on NUREG-1829 Table 7.19, the mean frequency of breaks that are greater than or equal to 14 inches is only 4.8 E-07. In other words if all Region II breaks were to fail due to the effects of debris, the risk associated with these failures (in terms of change in core damage frequency, or CDF) would be less than 1.0E-06 yr-1, which is defined as a very small change in Regulatory Guide (RG) 1.174.

It is noted that Calvert Cliffs is not crediting any relaxation in design requirements to demonstrate that Region II breaks can be successfully mitigated.

Defense-in-Depth Defense-in-depth for Calvert Cliffs Units 1 and 2 is based on plant design, operating procedures, and administrative controls. Operating procedures have actions that prevent and mitigate strainer blockage based on indications available to operators such as instrumentation to monitor sump water levels and containment temperatures. Actions include initiation of core flush (combined cold leg and hot leg injection), which provides an alternate flow path that bypasses core inlet blockage, and refilling the refueling water tank (RWT) which can allow temporary termination of recirculation and a return to injection mode of operation.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The effectiveness of the DID actions is shown to be acceptable when considering the following:

• Calvert Cliffs Emergency Operating Procedures (EOPs) are based on the approved industry standard Emergency Response Guidelines (ERGs). These symptom-based EOPs have generic or site-specific analyses that support them.

• Calvert Cliffs Severe Accident Mitigation Guidelines (SAMGs) are based on approved industry standard guidance.

• The procedures are trained upon and evaluated as part of the classroom training.

• The DID actions are trained upon using the simulator to demonstrate effectiveness.

• The procedures that make the framework for the DID actions are evaluated during the Calvert Cliffs station review and approval process.

Calvert Cliffs Units 1 and 2 have within their EOP framework, specific steps for monitoring for indications of sump strainer blockage and actions to be taken if this condition occurs. These actions are described in the Calvert Cliffs response to NRC Bulletin 2003-01 (ML032270048) and the subsequent responses to the NRC requests for additional information (ML043150282). The actions taken in response to NRC Bulletin 2003-01 are still in effect at Calvert Cliffs Units 1 and 2.

In summary, these actions include (1) reducing flow through the strainer by stopping pumps, (2) monitoring for proper pump operation, core exit thermocouples, and reactor water level indication, (3) refilling the RWT for injection flow, (4) using injection flow from alternate sources, and (5) transferring to combined hot leg/cold leg injection flow paths.

Calvert Cliffs has operational procedures to monitor the High Pressure Safety Injection (HPSI) and Containment Spray (CS) pump flow, discharge pressure, and amperage. By monitoring these operating parameters, control room personnel could properly diagnose the occurrence of cavitation, which would be an indication of sump clogging or significant deaeration. Control room personnel have been trained to evaluate this type of indication and take appropriate action such as reducing strainer flow rate by securing containment spray pumps, or throttling HPSI flow.

Refueling Water Tank Refill and Realignment for Injection Flow - The Calvert Cliffs Emergency Response Plan Implementing Procedures (ERPIPs) provide guidance for refilling the RWT and realigning the SI system for injection flow. The limiting failure mode for the Calvert Cliffs emergency recirculation sump strainer is gas binding due to non-condensable gases released from the fluid due to the pressure drop across the debris bed (deaeration). Refilling the RWT and realigning the SI system for injection flow will increase containment water level which will eliminate the potential for deaeration. Also, terminating recirculation flow temporarily will allow buoyancy forces to eject the non-condensable gases inside the Page 9 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 strainer effectively back-flushing and disrupting the debris bed. The disrupted debris bed would fall to the containment floor as agglomerated large clumps of debris which would not be expected to re-suspend in the flow and transport back to the strainer pockets.

In response to the Nuclear Regulatory Commission (NRC) Order EA-12-049, Mitigation Strategies for Beyond-Design-Basis External Events (BDBEE), Calvert Cliffs developed diverse and flexible coping strategies (FLEX) to maintain RCS inventory control, RCS cooling, and containment integrity. Various modifications have been implemented such that non-emergency equipment can be credited during an event. For example, the FLEX RCS Makeup Pump can be used to inject coolant into the RCS should the emergency recirculation strainer fail.

The leak detection program at Calvert Cliffs is capable of early identification of RCS leakage in accordance with RG 1.45 to provide time for appropriate operator action to identify and address RCS leakage.

The principal design basis for the containment is that it be capable of withstanding the internal pressure resulting from a LOCA with no loss of integrity. The strainer head losses at Calvert Cliffs are negligible down to a sump pool temperature of 140°F. By this time in the accident progression, peak pressure is no longer a concern, and core decay heat reduced to the point that the Containment Air Coolers could limit containment pressure to within the design basis limit. The CACs are designed to operate independently in the post-LOCA environment and are not directly affected by the loss of the recirculation sump or containment spray. This additional and independent capability to reject decay heat from containment ensures that the containment would not fail because of overpressure or overheating. Although core melt could be postulated, containment integrity would be maintained by operation of the CACs and the containment would continue to be maintained as an effective fission product barrier.

In the event that adequate long-term core cooling cannot be established, and core damage occurred, the severe accident management guidelines (SAMGs) would be implemented to effectively mitigate the event and protect plant personnel and the public.

Conclusion Both strainer head loss, downstream effects, and in-vessel effects have been fully addressed using deterministic methods. The evaluation demonstrates that there is reasonable assurance that long-term core cooling can be provided for all LOCA breaks.

Furthermore, a bounding evaluation shows that the risk associated with the loss of long-term core cooling due to the effects of debris in Region II is very small.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 GENERAL DESCRIPTION OF AND SCHEDULE FOR CORRECTIVE ACTIONS NRC Issue 2:

Provide a general description of actions taken or planned, and dates for each. For actions planned beyond December 31, 2007, reference approved extension requests or explain how regulatory requirements will be met as per "Requested Information" Item 2(b). That is provide a general description of and implementation schedule for all corrective actions, including any plant modifications, that you identified while responding to this generic letter. Efforts to implement the identified actions should be initiated no later than the first refueling outage starting after April 1, 2006. All actions should be completed by December 31, 2007. Provide justification for not implementing the identified actions during the first refueling outage starting after April 1, 2006. If all corrective actions will not be completed by December 31, 2007, describe how the regulatory requirements discussed in the Applicable Regulatory Requirements section will be met until the corrective actions are completed.

Response to Issue 2:

In response to GL 2004-02, Calvert Cliffs has completed the following actions for Calvert Cliffs Units 1 and 2.

• Performed walk downs to sample and characterize latent debris, including other debris sources, e.g., labels - Completed September 2010.

• Performed comprehensive debris generation analyses and conservative debris transport assumptions in accordance with approved methods presented in NEI 04 Multiple revisions of these calculations from 2004 to 2020.

• Performed as-built verification walk downs of insulation in Calvert Cliffs Units 1 and 2 Containments - Completed 2012

• Replaced a simple geometry strainer that had a filtering surface area of approximately 150 ft2, and had a gross mesh, with a complex geometry strainer having a filtering surface area of 6,060 ft2 and a finer mesh - Completed Unit 2 during the spring 2007 refueling outage and in Unit 1 during the spring 2008 refueling outage.

• Performed head loss analysis for replacement strainers - Completed May 2009.

• Performed bypass testing for replacement strainers - Completed October 2007.

• Performed vortex testing and analysis - Completed May 2009.

• Performed head loss testing for the replacement strainers (including chemical effects) -

Completed January 2009 and October 2010.

• Completed detailed structural analysis of the new strainers - Completed September 2014.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• Performed High pressure safety injection (HPSI) cyclone separator blockage testing - Completed June 2008.

• Performed HPSI cyclone separator replacement - Completed June 2008.

• Implemented calcium-silicate pipe insulation removal or banding - Completed March 2008.

• Replaced trisodium phosphate containment buffering agent with sodium tetraborate -

Completed March 2009.

• Removed the telescoping aluminum ladder from the polar crane in containment to reduce the aluminum content in containment - Completed March 2013.

• Replaced significant amount of mineral wool insulation with stainless steel RMI to reduce the amount of aluminum inside containment - Completed March 2014.

• Replaced significant amount of fibrous insulation with RMI - Completed March 2014.

• Performed a comprehensive chemical effects head loss experimental and test program -

Completed November 2014.

• Enlarged the reactor refueling cavity drains to reduce post-loss-of-coolant accident water holdup and increase strainer submergence - Completed March 2013.

• Installed blow-out panels in the reactor cavities ventilation ducting to allow early failure of the ventilation duct should it fill with water. This reduced post-loss-of-coolant accident water holdup and increased strainer submergence - Completed March 2011.

• Revised the Emergency Operating Procedures (EOPs) to assure the flow rate through the strainer does not exceed 2,365 gpm prior to the recirculation mode of operation - To be Completed by 1st Quarter 2021. (See Attachment 2 - Summary of Regulatory Commitments)

• Performed plant specific simplified risk-informed analysis. Completed August 2018.

Page 12 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 SPECIFIC INFORMATION REGARDING METHODOLOGY FOR DEMONSTRATING COMPLIANCE NRC Issue 3a:

Break Selection The objective of the break selection process is to identify the break size and location that present the greatest challenge to post-accident sump performance.

1. Describe and provide the basis for the break selection criteria used in the evaluation.

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

3. Discuss the basis for reaching the conclusion that the break size(s) and locations chosen present the greatest challenge to post-accident sump performance.

Response to Issue 3a1:

In accordance with Reference 1 the break selection process was focused on identifying the break size and location which results in debris generation producing the maximum head loss across the sump screen. This included determining both the maximum amount of debris that is transported to the sump screen, and the worst combination of debris mixes transported to the sump screen. Pipe break locations that could generate the maximum amount of fiber fines was the primary criteria used to determine the limiting pipe break locations. This is because head loss testing showed that debris bed strength and in turn debris head loss was primarily a function of the amount of fiber fines in the debris bed.

The particulate load, in addition to having less effect on head loss than fiber fines, did not vary significantly with break location. This is because latent particulate and degraded coatings do not vary with break location, and they account for 90% of the Region I particulate, and 80% of the Region II particulate. In addition, qualified coatings debris, which constituted the majority of the remaining particulate, were computed for each Main Loop piping in toto. In other words, the amount of qualified coatings that could be generated by a break on, for example, 12B Cold Leg, is the combined amount of qualified coating debris that could be generated from a break anywhere along 12B Cold Leg and then summed together. This conservative approach negates the need to evaluate a multitude of break locations in order to determine the limiting break location for qualified particulate debris.

The amount of chemical precipitate (Sodium Aluminum Silicate) generated depends on the amount of aluminum in containment and the fiber debris load. Aluminum in containment is a constant for all break locations. The fiber debris load in the sump pool correlates strongly with the amount of fiber fines generated so that breaks that generate maximum fiber fines in general also generate maximum fiber in the sump pool which in turn generates the most chemical precipitate. Special attention was given to break locations with more Mineral Wool insulation since it has much more of an effect on chemical precipitation than E-Glass. With the insulation replacements done in 2013 and 2014, however, most of the Mineral Wool insulation has been replaced by RMI.

Page 13 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Chemical precipitate, while being the catalyst that greatly magnifies the strainer head loss caused by fiber and particulate, does not generate head loss by itself. The peak head loss the debris bed could sustain was directly proportional to the amount of fiber fines on the debris bed. Therefore, identifying break locations generating maximum fiber fines is the key criteria in identifying limiting break locations for strainer head loss.

Calvert Cliffs Units 1 and 2 are mirror image plants of the same design. However, there are differences in the as-built insulation configuration between the units. The debris generation analysis confirmed that the Unit 1 insulation configuration bounded the Unit 2 configuration with respect to Generic Letter 2004-02 issues.

The debris generation analysis considered the following pipe break criteria prescribed by Reference 1:

1) Breaks in the primary Reactor Coolant System with the largest amount of potential debris within the postulated zone of influence (ZOI).

As discussed above, identifying the break location generating the largest amount of potential fiber fines debris was the preeminent criterion used in the debris generation analysis.

2) Large breaks in the RCS with two or more different types of debris.

The amount of problematic insulation (e.g., Cal-Sil, Marinite) in the ZOI of a large break is very limited. Mineral Wool insulation is also not present in great quantities; however, the break generating the maximum amount of Mineral Wool insulation was identified during the break selection process.

3) Break locations with the most direct path to the recirculation strainer.

As discussed in Section 3e the conservative simplifying assumptions made for debris transport negated the need to evaluate breaks based on whether they had a more direct path for debris to reach the recirculation strainer.

4) Break locations with the largest potential particulate to fiber mass ratio.

As discussed above, the majority of the particulate load is constant for all break locations. See also, response to criteria 5) below.

5) Break locations that could generate an amount of fibrous debris that after transport to the sump could form a uniform thin bed that could subsequently filter sufficient particulate to create a high head loss thin bed effect.

As discussed in response to Item 3f6, head loss testing consistently confirmed that the CCI designed strainer installed at Calvert Cliffs is not susceptible to the thin bed effect.

Page 14 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3a2:

The UFSAR Chapter 14 safety analyses for main steam and feedwater line break accidents do not lead to the recirculation mode of operation, and therefore are not considered in this deterministic evaluation.

Response to Issue 3a3:

For both Region I and Region II a Hot Leg break at the connection to the Steam Generator in both 11 and 12 compartments was evaluated. This location was chosen because of its proximity to the Steam Generator which is the largest single source of fibrous insulation. This location is also in close proximity to other high volume insulation targets including the Hot Leg, both compartment Cold Legs (pump suction side), both compartment RCPs, and the Surge Line (11 Compartment only).

For both Region I and Region II a pipe break was also evaluated on the 11A Cold Leg (pump suction side) at a point where the Steam Generator was still significantly impacted, but also impacted more of the Surge Line, and small-bore Sample Cooler and drain piping located at lower levels. For Region I this break produced 25% less fiber fine debris than the break at the Steam Generator, and for Region II it produced approximately 29% less fine fiber debris than the break at the Steam Generator.

Also, for both Region I and Region II an additional pipe break was also evaluated on the 12B Cold Leg (pump suction side). The Region I break was at a point on 12B Cold Leg where the Steam Generator was still significantly impacted, but also impacted more of the Regen Heat Exchanger, and CVCS piping. This break produced 28% less fiber fine debris than the break at the Steam Generator. The Region II break was at the point where 12B Cold Leg connects to the suction (i.e., underside) of 12B RCP. A double-ended guillotine break at this point was determined to generate the maximum amount of Mineral Wool debris. Although this location generated the most Mineral Wool, the total mass of fiber fines produced was nearly 33% less than that produced by the postulated break at the Steam Generator.

As an independent check on the above, the results from the BADGER debris generation analysis were reviewed to validate that the criteria described in Item 3a1 was sufficient and reliable in determining the limiting break location for strainer head loss. The BADGER software utilizes a three-dimensional computer aided design (CAD) model of the Calvert Cliffs containment building reflecting the as-built insulation configuration. In all over 17,000 break locations/sizes were evaluated. The BADGER results confirmed that a Hot Leg break at the connection to 11 SG generates the debris load most challenging to strainer performance.

Page 15 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3b:

Debris Generation/Zone of Influence (zone of influence) (excluding coatings)

The objective of the debris generation/zone of influence process is to determine, for each postulated break location: (1) the zone within which the break jet forces would be sufficient to damage materials and create debris; and (2) the amount of debris generated by the break jet forces.

1. Describe the methodology used to determine the zone of influences for generating debris. Identify which debris analyses used approved methodology default values. For debris with zone of influences not defined in the guidance report (GR)/safety evaluation (SE), or if using other than default values, discuss method(s) used to determine zone of influence and the basis for each.

2. Provide destruction zone of influences and the basis for the zone of influences for each applicable debris constituent.

3. Identify if destruction testing was conducted to determine zone of influences. If such testing has not been previously submitted to the NRC for review or information, describe the test procedure and results with reference to the test report(s).

4. Provide the quantity of each debris type generated for each break location evaluated. If more than four break locations were evaluated, provide data only for the four most limiting locations.

5. Provide total surface area of all signs, placards, tags, tape, and similar miscellaneous materials in Containment.

Response to Issues 3b1 and 3b2:

The ZOI for generated debris was determined using approved methodologies presented in NEI 04-07 and the associated NRC safety evaluation, Reference (1), for most materials.

Transco RMI The ZOI for Transco reflective metal insulation (RMI) used the approved methodology default value of 2.0 [Reference (1), page 30]. Based on similarity of design and materials of construction this ZOI was applied to the Performance Contracting Inc. (PCI) RMI product.

Marinite Board Fire Barrier The ZOI for Marinite board was based on testing. References (5) and (6) document testing performed in order to determine realistic jet impingement destruction data for Marinite board. Reference (5) documents that of a total of 13 destruction tests performed with Marinite with ZOIs ranging from 13.3D to 3.4D, only three of the tests generated visible debris. The visible debris was generated at ZOIs of 5.5D, 4.5D, and 3.4D. These references establish a final ZOI of 5.6D. Marinite is similar to Cal-Sil, but with higher density. The ZOI for un-banded Cal-Sil is 6.4D. For conservatism a 6.4D ZOI will also be used Page 16 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 for Marinite. With regards to concerns about the nozzle size used in the jet impingement testing it is noted here that Calvert Cliffs does not have any Marinite within 3.4D of any break location.

Nukon and Thermal Wrap Insulation The ZOI for Nukon insulation used the approved methodology default value of 17.0 [Reference (1), page 30]. Based on similarity of design, this ZOI was applied to Thermal Wrap insulation also. The debris size distributions for these insulation materials were modified from that provided on page 38 of Reference 1 as described below.

Using an analysis approach consistent with the methodology of Appendix II of Reference (1), Air Jet Impact Test (AJIT) data was used to compute refined size distributions for low-density fiberglass insulations (i.e., Nukon, Thermal Wrap, generic fiberglass). Table 1 provides the results of this analysis.

Table 1: Nukon & Thermal Wrap Debris Size Distribution Material Size 0-7 L/D 7-11.9 L/D 11.9-17 L/D Fines 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%

All of the insulation within a given sub-ZOI range from the break has the debris size distribution fractions from Table 1 applied to it, and the results from the three sub zones are summed together to compute the total for each debris size category.

Calcium Silicate (Cal-Sil) Insulation The ZOI for banded calcium-silicate insulation uses the approved methodology default value of 5.45 (refer to Reference 1, Volume 2, page 30). Using this ZOI, 100% fines is assumed. There is no calcium silicate insulation within this ZOI for any of the limiting Region I or Region II breaks.

Similar to Table 1, an analysis approach consistent with the methodology of Appendix II of Reference (1),

Air Jet Impact Test (AJIT) data was used to compute refined size distributions for Cal-Sil insulation as shown in Table 2a. While this table is not needed to address any break that could challenge strainer performance it is available for future evaluations.

Page 17 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 2a: Calcium-Silicate Debris Size Distribution Material Size 0-2.7 L/D 2.7-6.4 L/D Fines (particulate) 50% 23%

Small Pieces (1< 3") 50% 15%

Remains on Target 0% 62%

Temp-Mat Insulation The ZOI for Temp-Mat insulation used the approved methodology default value of 11.7 given on page 30 of Reference 1. The debris size distributions for Temp-Mat insulation was modified from that provided on page 38 of Reference 1 as described below.

Using an analysis approach consistent with the methodology of Appendix II of Reference (1), Air Jet Impact Test (AJIT) data was used to compute refined size distributions for Temp-Mat. Table 2b provides the results of this analysis. Again all of the insulation within a given ZOI range from the break has the debris size distribution fractions from Table 2b applied to it, and the results from the two sub-ZOIs are summed together to compute the total for each debris size category (fines, small pieces, large pieces, and intact blankets).

Table 2b: Temp-Mat Debris Size Distribution Material Size 0-3.7 L/D 3.7-11.7 L/D Fines 20% 7%

Small Pieces (< 6" on a side) 80% 27%

Large Pieces (> 6" on a side) 0% 32%

Intact (Covered) Blankets 0% 34%

Mineral Wool Insulation Because mineral wool insulation was found to generate a disproportionately high amount of chemical precipitant most of the mineral wool insulation has been removed, and replaced with RMI. However, a small amount (typically in high dose areas) remains. The mineral wool insulation was provided by Transco Products and is encapsulated in self-contained units of all-stainless steel construction including inner and outer casings and internal reinforcements. The mineral wool cassettes are robustly constructed and are virtually identical to that of the original Transco RMI installed at Calvert Cliffs but with a different filler material ( i.e., mineral wool fibers instead of stainless steel foils).

Page 18 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The Transco stainless steel cassette system includes inner and outer sheaths, slotted end panels, and latch and strike closure buckles similar to the cassettes tested in the air jet impact testing that resulted in the approved ZOI for Transco RMI of 2.0D, Reference (1). The tested cassettes contained metal foil and produced very little or no transportable debris. The contained material contributes no strength to the cassettes. Therefore, the destruction pressure for the Transco mineral wool cassettes and RMI cassettes are considered equal.

However, for conservatism, the ZOI for the mineral wool cassettes will be conservatively doubled from 2.0D to 4.0D.

Generic Fiberglass Insulation Like Nukon and Thermal Wrap, the generic fiberglass insulation at Calvert Cliffs is another low-density fiberglass; therefore a ZOI of 17.0 [Reference (1), page 30] is applied to it as well.

The generic fiberglass at Calvert Cliffs is molded into shape using heavy density resin bonded inorganic glass fibers with 0.010 stainless steel jacketing fitted around it and secured by rivets. This fiberglass has a bulk density generally greater, but no lower than Nukon and Thermal Wrap. Based on insulation density, Calvert Cliffs assumes the same debris size distribution for generic fiberglass that is being used for Nukon and Thermal Wrap. The comparison of debris damage for three insulation types with differing densities shown in Figure II-8 of Reference 1, supports the assumption of less material damage for a higher density material. This assumption was also accepted in Reference (4) by the NRC. As was the case for the plant in Reference 4, there is substantially less generic fiberglass than Nukon and Thermal Wrap at Calvert Cliffs; therefore, the assumed size distribution for generic fiberglass is acceptable.

The generic fiberglass at Calvert Cliffs does not have a cloth jacket that the Nukon and Thermal Wrap insulations have. Therefore, there are no intact pieces of insulation for generic fiberglass, and all insulation that would have been characterized as intact pieces based on Table 1a and 1b will be assumed to be large pieces.

Lead Shielding Blankets The lead shielding blankets potentially exposed to high energy line break jet are both free-hanging blankets hung adjacent to piping and wrapped around piping or components. Typically, there are two lead blankets between the piping and the surrounding area. Blast testing of lead blankets similar to those used at Calvert Cliffs has been performed with both air jets and steam jets. The air jet testing conducted as part of the AJITs [Reference (2)] is included in the Boiling Water Reactor Utility Resolution Guidance for ECCS Suction Strainer Blockage. The steam jet testing was performed by Wyle and is documented in WCAP16727P, [Reference (3)].

Page 19 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The Wyle testing is not used to quantify ZOI information. This testing is used to show that open back (freely hanging) blankets will be torn from their grommets and not generate fine debris when near a break jet and that open back blankets are less likely to generate debris than those installed in a strong back configuration. Furthermore, the inner and outer cover and lead wool on the break side of a lead blanket are sacrificial and provide protection to the inner and outer cover on the opposite side of the blanket.

The AJITs subjected rubberized cloth coated lead shielding blankets to a range of surface pressures up to a maximum pressure of 40 psig. The lead blankets were wrapped around a 12 inch pipe in these tests, not a free hanging, openback configuration. This configuration is similar to the strong back configuration discussed in the Wyle testing, even though the backing in this test was a pipe, not a flat plate.

No debris was generated in any of the AJIT tests. Since these tests were performed with an air jet, the damage pressures are reduced by 40% to account for potentially enhanced debris generation in a two phase jet, consistent with Reference (1). Therefore, a ZOI corresponding to a damage pressure of 24 psig [=(10.4)*40] is applicable to the lead blankets wrapped around piping and components and it is conservative for the free-hanging lead blankets since the blankets at Calvert Cliffs have an openback configuration. This damage pressure corresponds to a PWR ZOI of 5.4 D.

Lead Wool Although lead wool debris may be generated, it will not transport to the strainer due to the high density of lead.

Lead Blanket Covers In the AJITs, no lead blanket debris was generated for surface pressures corresponding to a ZOI of 5.4 D.

In order to determine the size distribution for the lead blanket cover debris which could potentially be generated inside of 5.4 D, other tests performed as part of the AJITs were used.

The cloth cover used on NUKON blankets is similar to the lead blanket Alpha Maritex cover materials, except that the NUKON cover uses a plain weave while the Alpha Maritex 32592SS and 84592SS covers use a 4harness and 8harness satin weave, respectively. The NUKON cover cloth is made of 18 oz/yd2 Eglass. Both Alpha Maritex 32592SS and 84592SS are made with G37 fiberglass yarn, which is also Eglass. The density of Alpha Maritex 32592SS (the inner cover) is 17.5 oz/yd2 while the density of Alpha Maritex 84592SS (the outer cover) is 34 oz/yd2.

The primary difference between the NUKON cover and the Alpha Maritex products is the weave type.

Typically, a plain weave is the least tear resistant since it has a very tight construction which has the Page 20 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 least amount of internal slippage/yarn mobility. In addition, only one yarn bears the load in a plain weave when the fabric is torn. However, satin weaves have fewer yarn interlacings per area (less tight weave) and therefore allow more internal slippage. Furthermore, multiple yarns bear the load in a satin weave when the fabric is torn. This results in satin weaves, used in the Alpha Maritex covers, being much more tear resistant than plain weaves, used in NUKON cloth covers.

Although the materials of construction are similar for the NUKON cloth cover and the Alpha Maritex products, the plain weave utilized in the NUKON cloth cover is less tear resistant than the satin weave utilized in the Alpha Maritex covers. Therefore, the fiberglass cover used for NUKON is less robust than the lead blanket inner and outer covers. Thus, the debris generation properties for the NUKON cover are conservative for Alpha Maritex 32592SS and Alpha Maritex 84592SS.

The AJITs subjected unjacketed NUKON blankets installed on a 12 inch pipe to a range of pressures with the maximum pressure being 190 psig. In all of these tests, the cloth cover and scrim failed in large intact sections and was determined to be nontransportable. Since these tests were performed with an air jet, the damage pressure is reduced by 40% to account for potentially enhanced debris generation in a twophase jet. An air jet damage pressure of 190 psig corresponds to a twophase damage pressure of 114 psig [=(10.4)*190], which corresponds to a ZOI of 2.1 D. Therefore, lead blanket cover debris generated beyond 2.1 D is considered to be large or intact pieces.

Within a ZOI of 2.1 D, the lead blanket covers on the break side of the lead wool in the blankets closest to the break are considered to become 20% fines and 80% small pieces. As the lead blanket covers are more robust than NUKON blanket covers, this approach is conservative.

The lead blanket covers on the opposite side of the lead wool in the blankets closest to the break are considered to form large pieces or remain intact, as are the lead blanket covers on the 2nd outboard set of lead blankets where two blankets are essentially stacked next to each other. These covers are shielded from the break by the innermost lead wool and inner and outer covers. This approach is reasonable since the lead blankets are freely hanging, and therefore would be torn from their grommets and projected away from the pipe in the event that a break occurs.

The size distributions and subzone ZOIs for lead shielding blankets are shown in Table 3.

Page 21 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 3: Lead Shielding Blanket Debris Size Distribution Size Distribution Debris Type Size 2.1D ZOI 2.1D - 5.4D ZOI Lead Blanket Cover Fines 20% 0%

Layers Closest to Pipe Break Small Pieces 80% 0%

(Open Back Configuration) Large/Intact Pieces 0% 100%

Remaining Lead Blanket Fines 0% 0%

Cover Layers Small Pieces 0% 0%

(Open Back Configuration) Large/Intact Pieces 100% 100%

Wrapped Lead Blanket Cover Fines 20% 0%

Layers Small Pieces 80% 0%

(Strong Back Configuration) Large/Intact Pieces 0% 100%

Response to Issue 3b3:

Calvert Cliffs did not conduct destructive testing to determine the zones of influence for materials.

Where destructive test results were used, these tests had been previously reviewed by the NRC.

Response to Issue 3b4:

Table 4a presents the debris generation quantities for the limiting Region II (i.e., LBLOCA) breaks with respect to fine fiber mass and particulate volume. All fiber fines and particulate are assumed to transport to the strainer (i.e., transport fraction = 100%). It is conservatively assumed that small and large pieces of insulation debris do not transport to the strainer (i.e., transport fraction = 0%) because head loss testing demonstrated that small and large pieces of insulation reduced strainer head loss.

An erosion fraction of 10% was used for the small and large pieces of fiberglass debris (Nukon, Thermal Wrap, Temp-Mat, Generic Fiberglass). An erosion fraction of 17% was used for small pieces of Cal-Sil, and small and large pieces of Marinite.

Head loss testing demonstrated that the fibrous debris from Lead Blanket covers was too coarse to assimilate into the fine fiber debris bed, and consequently did not contribute to strainer head loss, or acted to reduce strainer head loss. Similarly, RMI does not contribute to strainer head loss, and is only a consideration in downstream effects. Therefore, only the bounding amount of these two materials is provided.

Page 22 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 4a: Summary of LOCA Generated Debris - Region II Breaks Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11A- Weld 30-RC12B-Type 11 Hot Leg @ SG 12 Hot Leg @ SG 5 11A Cold Leg 7LU 12B Cold Leg Fines 278.11 lbm 158.54 lbm 208.44 lbm 123.89 lbm Small (<6") & Large 1,241.8 lbm 634.20 lbm 991.8 lbm 557.42 lbm Pieces (>6")

Nukon Small & Large Pieces 124.18 lbm 63.42 lbm 99.18 lbm 55.74 lbm Eroded to Fines Intact Pieces (>6") 186.17 lbm 0.0 lbm 256.17 lbm 85.75 lbm Thermal Fines 383.95 lbm 383.45 lbm 261.17 lbm 183.94 lbm Wrap Small (<6") & Large 1805.9 lbm 1803.9 lbm 1227.3 lbm 952.58 lbm Pieces (>6")

Small & Large Pieces 180.59 lbm 180.39 lbm 122.73 lbm 95.26 lbm Eroded to Fines Intact Pieces (>6") 448.63 lbm 448.91 lbm 351.22 lbm 375.64 lbm Generic Fines 204.65 lbm 74.31 lbm 157.47 lbm 54.95 lbm Fiberglass Small (<6") & Large 888.10 lbm 307.4 lbm 933.0 lbm 317.46 lbm Pieces (>6")

Small & Large Pieces 88.81 lbm 30.74 lbm 93.30 lbm 31.75 lbm Eroded to Fines TempMat Fines 16.17 lbm 44.49 lbm 6.18 lbm 15.59 lbm Small (<6") & Large 136.0 lbm 300.5 lbm 52.2 lbm 131.33 lbm Pieces (>6")

Small & Large Pieces 13.60 lbm 30.05 lbm 5.22 lbm 13.13 lbm Eroded to Fines Intact Pieces 78.43 lbm 134.52 lbm 30.05 lbm 75.71 lbm Mineral Fines 80.48 lbm 68.48 lbm 22.88 lbm 114.40 lbm Wool Page 23 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11A- Weld 30-RC12B-Type 11 Hot Leg @ SG 12 Hot Leg @ SG 5 11A Cold Leg 7LU 12B Cold Leg RMI Small Pieces (<4) 1621.21 ft2 (Note 3)

Large Pieces (>4) 540.47 ft2 Cal-Sil Fines 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm (Note 5)

Small Pieces 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Remains on Target 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Marinite Fines (incl erosion) 0.0 ft3 0.0 ft3 0.024 ft3 0.024 ft3 Small Pieces (1/2 0.0 ft3 0.0 ft3 0.006 ft3 0.006 ft3

<2")

Large Pieces (>24) 0.0 ft3 0.0 ft3 0.034 ft3 0.034 ft3 In Sump Pool 0.0 ft3 0.0 ft3 0.057 ft3 0.057 ft3 Lead Cover Fines (Note 4) 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Blankets Lead Wool Fines Note 1 Note 1 Note 1 Note 1 Nuke Tape Fines 0.088 ft3 0.088 ft3 0.088 ft3 0.088 ft3 Particulate (ft3)

Latent Fines 22.50 lbm 22.50 lbm 22.50 lbm 22.50 lbm Fiber (lbm)

Dirt/Dust Particulate 127.50 lbm or 127.50 lbm or 127.50 lbm or 127.50 lbm or (lbm) (ft3) 0.754 ft3 0.754 ft3 0.754 ft3 0.754 ft3 Unqualified Particulate 1.9000 ft3 1.9000 ft3 1.9000 ft3 1.9000 ft3 Alkyds (ft3)

Unqualified Particulate 3.5595 ft3 3.5595 ft3 3.5595 ft3 3.5595 ft3 Epoxy (ft3)

Unqualified Particulate 0.5730 ft3 0.5730 ft3 0.5730 ft3 0.5730 ft3 IOZ (ft3)

Page 24 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11A- Weld 30-RC12B-Type 11 Hot Leg @ SG 12 Hot Leg @ SG 5 11A Cold Leg 7LU 12B Cold Leg Unqualified Particulate 0.1000 ft3 0.1000 ft3 0.1000 ft3 0.1000 ft3 Organic Zinc (ft3)

Degraded Chips 500 ft2 500 ft2 500 ft2 500 ft2 Qualified Epoxy (ft2)

Degraded Particulate 0.6667 ft3 0.6667 ft3 0.6667 ft3 0.6667 ft3 Qualified IOZ (ft3)

Qualified Particulate 1.4405 ft3 1.4405 ft3 1.4405 ft3 1.4405 ft3 Epoxy (ft3)

Qualified Particulate 0.9603 ft3 0.9603 ft3 0.9603 ft3 0.9603 ft3 IOZ (ft3)

Total Fiber Fines 1393.04 lbs 1056.37 lbm 999.07 lbm 711.15 lbm Total Particulate 10.042 ft3 10.042 ft3 10.066 ft3 10.066 ft3 Precipitate 75.3 lbm 67.8 lbm 49.6 lbm 69.0 lbm (NaAlSi 3 O 8 )

Note 1: The quantity of lead wool fines was not explicitly computed as this debris source does not contribute to chemical effects or debris bed head loss.

Note 2: The fiber load for this Cold Leg Break are based on a break on 11A Cold Leg on the Pump Suction side to maximize fiber load. The qualified coating and Marinite load are from 12B Cold Leg which generates the most of these quantities.

Note 3: The RMI result shown is the maximum amount obtained from BADGER and is for a break on 11 Hot Leg. The amount considered in downstream wear evaluations bounds this number with considerable margin. No further documentation of RMI results is required.

Note 4 No Lead Blanket Cover fines are generated for any of the four limiting break locations. In addition, head loss testing showed that fines from Lead Blanket Covers did not contribute to head loss, but instead disrupted the debris bed. Therefore, it is conservative to not include them in the overall debris mix.

Page 25 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Note 5 There is no Calcium-Silicate insulation in any of the limiting Hot Leg or Cold Leg pipe break ZOIs. There is Calcium-Silicate insulation on small-bore piping in the Pressurizer doghouse; however, the RCS piping in this region that could cause a LOCA (Pressurizer RV, Main Spray) have a maximum inside diameter of 3.624 inches. Therefore, the radius of the Calcium-Silicate ZOI for this size pipe is less than 2 feet, and thus only a minimal amount would be generated. Also, the total volume of insulation that might be exposed to a break from this size line would not be enough to cover the strainer with a thin layer of insulation.

Therefore, Calcium-Silicate insulation does not contribute to the debris bed for any significant LOCA break.

Table 4b presents the debris generation quantities for the limiting Region I (i.e., 14 Sch. 160) breaks with respect to fine fiber mass and particulate volume. As with Region II breaks all fine fiber and particulate generated is assumed to transport to the strainer while small and large pieces of insulation are assumed not to transport to the strainer.

For Region I breaks on Hot Leg and Cold Leg piping a hemispherical ZOI is permissible. For conservatism the results below are based on a spherical ZOI having the same radius as the hemisphere. A 14" schedule 160 pipe has an inside diameter of 11.188 inches. Therefore, for example, the ZOI for Nukon is a sphere having a radius of 17 x 11.188 = 190.196 inches = 15.85 feet. Using a spherical ZOI simplified the process of determining the limiting break location as well as providing considerable conservatism to the results.

The RMI generated by Region I breaks is bounded by that of Region II breaks. Since downstream effects are evaluated using the higher Region II debris loads there is no need to evaluate the results of RMI in Region I breaks.

Page 26 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 4b: Summary of LOCA Generated Debris - Region I Breaks Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11-5 Weld 30-RC12-5 Type 11 Hot Leg @ SG 12 Hot Leg @ SG 11A Cold Leg Mid 12B Cold Leg Mid Fines 80.70 lbm 65.59 lbm 69.29 lbm 53.14 lbm Small (<6") & Large 435.0 lbm 360.0 lbm 350.0 lbm 244.0 lbm Pieces (>6")

Nukon Small & Large Pieces 43.50 lbm 36.00 lbm 35.00 lbm 24.40 lbm Eroded to Fines Intact Pieces (>6") 256.38 lbm 234.96 lbm 154.82 lbm 56.34 lbm Thermal Fines 79.51 lbm 79.80 lbm 37.27 lbm 40.54 lbm Wrap Small (<6") & Large 404.0 lbm 405.0 lbm 211.0 lbm 221.0 lbm Pieces (>6")

Small & Large Pieces 40.40 lbm 40.50 lbm 21.10 lbm 22.10 lbm Eroded to Fines Intact Pieces (>6") 168.41 lbm 169.93 lbm 121.43 lbm 115.50 lbm Generic Fines 26.95 lbm 14.58 lbm 27.83 lbm 8.47 lbm Fiberglass Small (<6") & Large 206.7 lbm 120.4 lbm 246.9 lbm 92.0 lbm Pieces (>6")

Small & Large Pieces 20.67 lbm 12.04 lbm 24.69 lbm 9.20 lbm Eroded to Fines TempMat Fines 0.0 lbm 4.96 lbm 0.0 lbm 22.18 lbm Small (<6") & Large 0.0 lbm 42.1 lbm 0.0 lbm 187.0 lbm Pieces (>6")

Small & Large Pieces 0.0 lbm 4.21 lbm 0.0 lbm 18.70 lbm Eroded to Fines Intact Pieces 0.0 lbm 24.27 lbm 0.0 lbm 107.80 lbm Mineral Fines 4.16 lbm 43.20 lbm 11.20 lbm 18.10 lbm Wool Page 27 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11-5 Weld 30-RC12-5 Type 11 Hot Leg @ SG 12 Hot Leg @ SG 11A Cold Leg Mid 12B Cold Leg Mid RMI Small Pieces (<4) NA NA NA NA (Note 3)

Large Pieces (>4) NA NA NA NA Cal-Sil Fines 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Small Pieces 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Remains on Target 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Marinite Fines (incl erosion) 0.0 ft3 0.0 ft3 0.0 ft3 0.0 ft3 Small Pieces (1/2 0.0 ft3 0.0 ft3 0.0 ft3 0.0 ft3

<2")

Large Pieces (>24) 0.0 ft3 0.0 ft3 0.0 ft3 0.0 ft3 In Sump Pool 0.0 ft3 0.0 ft3 0.0 ft3 0.0 ft3 Lead Cover Fines 0.0 lbm 0.0 lbm 0.0 lbm 0.0 lbm Blankets Lead Wool Fines Note 1 Note 1 Note 1 Note 1 Nuke Tape Fines 0.088 ft3 0.088 ft3 0.088 ft3 0.088 ft3 Particulate (ft3)

Latent Fines 22.50 lbm 22.50 lbm 22.50 lbm 22.50 lbm Fiber (lbm)

Dirt/Dust Particulate 127.50 lbm or 127.50 lbm or 127.50 lbm or 127.50 lbm or (lbm) (ft3) 0.754 ft3 0.754 ft3 0.754 ft3 0.754 ft3 Unqualified Particulate 1.9000 ft3 1.9000 ft3 1.9000 ft3 1.9000 ft3 Alkyds (ft3)

Unqualified Particulate 3.5595 ft3 3.5595 ft3 3.5595 ft3 3.5595 ft3 Epoxy (ft3)

Unqualified Particulate 0.5730 ft3 0.5730 ft3 0.5730 ft3 0.5730 ft3 IOZ (ft3)

Page 28 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Debris Generated Debris Generated Debris Generated Debris Generated Debris Debris Size Weld 42-RC-11-4 Weld 42-RC-12-4 2 Weld 30-RC11-5 Weld 30-RC12-5 Type 11 Hot Leg @ SG 12 Hot Leg @ SG 11A Cold Leg Mid 12B Cold Leg Mid Unqualified Particulate 0.1000 ft3 0.1000 ft3 0.1000 ft3 0.1000 ft3 Organic Zinc (ft3)

Degraded Chips 500 ft2 500 ft2 500 ft2 500 ft2 Qualified Epoxy (ft2)

Degraded Particulate 0.6667 ft3 0.6667 ft3 0.6667 ft3 0.6667 ft3 Qualified IOZ (ft3)

Qualified Particulate 0.5375 ft3 0.5375 ft3 0.5375 ft3 0.5375 ft3 Epoxy (ft3)

Qualified Particulate 0.3583 ft3 0.3583 ft3 0.3583 ft3 0.3583 ft3 IOZ (ft3)

Total Fiber Fines 318.39 lbs 323.38 lbm 248.88 lbm 239.33 lbm Total Particulate 8.537 ft3 8.537 ft3 8.537 ft3 8.537 ft3 Total Precipitate(NaAlSi 3 O 8 ) 35.7 lbs 46.6 lbs 33.2 lbs 34.7 lbs Note 1: The quantity of lead wool fines was not explicitly computed as this debris source does not contribute to chemical effects or debris bed head loss.

Note 2: The fiber load for this Cold Leg Break are based on a break on 11A Cold Leg on the Pump Suction side to maximize fiber load. The qualified coating an Marinite load are from 12B Cold Leg which generates the most of these quantities.

Note 3: RMI only impacts downstream effects evaluations. Downstream effects are addressed in a fully deterministic manner. Therefore, Table 4a provides the bounding RMI value.

Page 29 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3b5:

Walkdowns were performed in the Spring 2009 refueling outage to ensure the amount of labels, signs, placards, tape and tags in containment were completely investigated. The total surface area of this type of debris is less than 300 ft2. The strainer design allows for 375 ft2 of sacrificial surface area. After an average mean packing ratio of 0.75 (Reference 1, page 49) is applied to the 375 ft2 the total allowable surface area for this type of debris is 500 ft2.

In addition, valve tag labels are made of materials that will sink intact, and procedures require that all placards be chained so they wont transport to the sump strainer.

Page 30 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3c:

Debris Characteristics The objective of the debris characteristics determination process is to establish a conservative debris characteristics profile for use in determining the transportability of debris and its contribution to head loss.

1. Provide the assumed size distribution for each type of debris.

2. Provide bulk densities (i.e., including voids between the fibers/particles) and material densities (i.e., the density of the microscopic fibers/particles themselves) for fibrous and particulate debris.

3. Provide assumed specific surface areas for fibrous and particulate debris.

4. Provide the technical basis for any debris characterization assumptions that deviate from NRC-approved guidance.

Response to Issue 3c1:

A detailed discussion of the size distribution assumed for Nukon, Thermal Wrap, generic fiberglass, calcium-silicate insulations, Temp-Mat, and lead shielding blankets was provided in the response to Issue 3b1/3b2. Table 5 provides the debris size distribution assumed for the remaining types of debris. Table 5: Debris Size Distribution Material Small Fines Small Pieces Large Pieces Intact Pieces Particulate Chips Mineral Wool 100% 0% 0% 0% 0% 0%

RMI 0% 75% 25% 0% 0% 0%

Marinite 1.3% 0.5% 2.7% 95.5% 0% 0%

Latent Fiber Debris 100% 0% 0% 0% 0% 0%

Latent Dirt/Dust 0% 0% 0% 0% 100% 0%

All Coatings in ZOI 0% 0% 0% 0% 100% 0%

Qualified Coatings 0% 0%

0% 0% 0% 0%

Outside ZOI Degraded Qualified 100% 0%

IOZ Coatings Outside 0% 0% 0% 0%

ZOI Degraded Qualified 0% 100%

Epoxy Coatings 0% 0% 0% 0%

Outside ZOI Never Qualified 100% 0%

0% 0% 0% 0%

Coatings Outside ZOI Page 31 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3c2:

The bulk densities of material and destroyed debris are listed in Table 6 below. These values are obtained from the NRC-approved methodology or vendor specific information (in the case of lead shielding blankets and coatings).

Table 6: Debris Densities Density of Individual Fiber or Density of a Blanket of Product Material Type Particle (lb m /ft3) (lb m /ft3)

Nukon 159 2.4 Transco Thermal Wrap 159 2.4 Generic fiberglass 159 5.5 Temp-Mat 162 11.8 Mineral wool 90 8 Cal-Sil 144 46 Lead Blanket Inner Cover 81 N/A Lead Blanket Outer Cover 76.6 N/A Latent Fiber 94 2.4 Dirt/Dust 169 N/A Marinite1 144 46 Coating Material Material Density (lb m /ft3) Characteristic Size (ft)

Inorganic zinc 300 3.2x10-5 Alkyd coating 98 3.2x10-5 Topcoats Vendor Trade Name Dry Film Density (lb/gal) Dry Film Density (lb/ft3)

Carboline Carboguard 890 14.72 111 Page 32 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Ameron Amercoat 66 14.04 105 Ameron Amercoat 90 14.80 111 Valspar 89 Series 16.60 124 Primers Vendor Trade Name Dry Film Density (lb/gal) Dry Film Density (lb/ft3)

Carboline Carboguard 890 14.7 111 Carboline Starglaze 2011 S 19.4 145 Ameron Dimetcote 6 40.1 300 Ameron Nu-Klad 110AA 20.1 150 Ameron Amercoat 71 16.6 126 Valspar 13-F-12 40.1 300 Shermin Williams Epolon II 16.8 126 Wasser MC-Miozinc 36.1 270 Note 1: Particle density for Cal-Sil applied to Marinite Response to Issue 3c3:

Since the head loss across the ECCS strainers is determined via testing, specific surface areas for fibrous and particulate debris are not used to determine debris head loss. Therefore, these values are not provided as part of this response.

Response to Issue 3c4:

The Calvert Cliffs debris generation, transport, and head loss analyses have used the debris characterization assumptions provided in Reference 1. Specifically, the size of particulates is consistent with 10 microns for coatings particulate. Coatings that were installed as qualified, but have subsequently been classified as unqualified based on inspections are assumed to have failure distribution consistent with that reported in Reference 23. In general, Reference 23 concludes that degraded-qualified epoxy topcoated systems fail as chips when exposed to design basis accident environments, while degraded-qualified inorganic zinc primers fail in pigment size (i.e., 10 microns). For Page 33 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 downstream effect evaluations, the size distribution of unqualified coatings was assumed to be that in the Linear Mass Fraction column of Table I-1 of Reference 8.

Qualified coatings in the ZOI, degraded qualified IOZ coatings, and never-qualified coatings are assumed to fail as particulate.

See Issue 3m for the debris size distribution used in the downstream effect evaluations Page 34 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3d:

Latent Debris The objective of the latent debris evaluation process is to provide a reasonable approximation of the amount and types of latent debris existing within the Containment and its potential impact on sump screen head loss.

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

2. Provide the basis for assumptions used in the evaluation.

3. Provide results of the latent debris evaluation, including amount of latent debris types and physical data for latent debris as requested for other debris under c. above.

4. Provide amount of sacrificial strainer surface area allotted to miscellaneous latent debris.

Response to Issue 3d1:

The Containment was sampled via a walkdown performed to collect latent debris samples from the various surfaces in Containment. The surface types sampled included: 1) containment liner, 2) floor, 3) stair grating, 4) walls, 5) horizontal cable trays, 6) vertical cable trays, 7) horizontal piping, 8) vertical piping, 9) horizontal ducting, 10) vertical ducting, 11) horizontal equipment, and 12) vertical equipment.

A minimum of four samples were taken from each surface type. The area of each sample was recorded along with the weight of latent debris in the sample area. The average and maximum weight per unit surface area were recorded. The averages were then multiplied by the horizontal and vertical surface areas that might have latent debris accumulate on them which resulted in the latent debris loading for Containment. The latent debris load results used the maximum sample for each surface type with the exception of the non-stair grating where it was assumed that the latent debris load was the same as the floor.

Response to Issue 3d2:

Debris was assumed to be normally distributed for a given sample type. This assumption was supported by the walkdown observation that latent debris was uniform for a given surface type. Averaging the latent debris for surface types having multiple samples is consistent with the sampling approach taken to estimate the amount of latent debris inside Containment.

Response to Issue 3d3:

Latent debris includes dirt, dust, lint, fibers, etc., that are present inside the Containment and could be transported to the emergency sump strainer. This debris could be a contributor to head loss across the strainer. In accordance with recommendations in Reference 1, latent debris samples were collected to estimate the actual mass of latent debris inside of Containment. A latent debris load of 150 lbs was Page 35 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 computed. The latent debris was described as dust with no fiber in any sample. However, it is assumed that 15% of the latent debris is fibrous and 85% is particulate.

Response to Issue 3d4:

Latent debris (in the form of dust) is accounted for in test and analysis by including it in the debris mix.

Therefore, no specific sacrificial area needs to be allocated to it. Calvert Cliffs does not provide an amount of sacrificial strainer surface area allotted to miscellaneous latent debris other than that allocated for stick-on labels (see Response to Issue 3b5 above).

Page 36 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3e:

Debris Transport The objective of the debris transport evaluation process is to estimate the fraction of debris that would be transported from debris sources within Containment to the sump suction strainers.

1. Describe the methodology used to analyze debris transport during the blowdown, washdown, pool-fill-up, and recirculation phases of an accident.

2. Provide the technical basis for assumptions and methods used in the analysis that deviate from the approved guidance.

3. Identify any computational fluid dynamics codes used to compute debris transport fractions during recirculation and summarize the methodology, modeling assumptions, and results.

4. Provide a summary of, and supporting basis for, any credit taken for debris interceptors.

5. State whether fine debris was assumed to settle and provide basis for any settling credited.

6. Provide the calculated debris transport fractions and the total quantities of each type of debris transported to the strainers.

Response to Issue 3e1:

Calvert Cliffs conservatively assumed that 100% of the debris that did not remain on the target transported to the containment pool. No debris hold-up on structures, gratings or in quiescent pools was credited.

For the blowdown phase, it was assumed that 100% of the debris was blown into the recirculation pool.

This is a conservative assumption, as it ensures that the entire debris load was available for production of chemical precipitates and transport during recirculation.

The washdown phase of transport was not evaluated, as it was conservatively assumed that all debris was blown directly into the recirculation pool, maximizing the potential for production of chemical precipitates and transport to the strainer.

For the pool-fill phase of transport, the potential for debris to transport to inactive cavities was evaluated and determined to not be significant. Therefore, no credit is taken for debris transport to inactive cavities.

Calvert Cliffs uses the size distribution for fiber and particulates provided in response to Issue 3c1 and assumes that, with the exception of lead wool, all fines, including fines eroded from small and large Page 37 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 pieces of fiberglass insulation, particulate, and precipitate debris transport to the sump strainer during the recirculation phase of transport. Small and large pieces of debris were conservatively assumed to not transport to the strainers as these sizes of debris were demonstrated to reduce strainer head loss in plant-specific strainer head loss testing.

Response to Issue 3e2:

Erosion of low density fiberglass insulation is the only area where the debris transport analysis deviates from the approved guidance. The approved guidance specifies that an erosion fraction of 90% should be used for fiberglass debris.

To quantify the recirculation pool erosion fractions for Calvert Cliffs, 30 day erosion testing was performed. Based on this testing an erosion fraction of 10% was used for fiberglass debris except for that which is contained in an intact blanket/jacket [Reference (11)].

Calvert Cliffs includes debris from permanent lead shielding blankets in the debris source term. The debris from the lead shielding blankets is assumed to not erode in the recirculation pool because the jacket material used on these permanent lead shielding blankets is specifically designed for high temperature with improved resistance to abrasion, flexing, tear and puncture. This assumption is consistent with approved guidance where jacketed pieces of fiberglass insulation are not susceptible to erosion in the recirculation pool.

Response to Issue 3e3:

No computational fluid dynamics codes were used by Calvert Cliffs.

Response to Issue 3e4:

No credit is taken for debris interceptors.

Response to Issue 3e5:

Based on observations from head loss testing where fines from the cover on lead shielding blankets did not transport to the strainer even when using artificial agitation, it is concluded that the cover material of the lead shielding blankets would not transport to the strainer during sump recirculation. Head loss testing also showed that even when these fines were dropped right onto the debris bed they were too course to assimilate into the fiber fine debris bed. Calvert Cliffs did not credit the settling of any other fine debris in the transport calculations.

Page 38 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3e6:

As mentioned under Item 3e1 Calvert Cliffs simplifies its debris transport analysis by assuming 100% of debris coming off the target transports to the sump pool. As mentioned under Item 3b4 Calvert Cliffs conservatively assumes 100% pool transport of fiber fines and particulate, and 0% pool transport of small and large pieces of debris. Debris size distributions are provided under the response to Item 3b1/3b2 and in Table 5 provided under Issue 3c1. Erosion factors are given under Item Section 3b4.

Debris Transport assumptions are summarized in Table 7.

Under Item 3b4, Tables 4a and 4b provide the quantity and type of debris for each debris component for the limiting Region II and Region I breaks respectively. The total fiber fines and particulate quantity for each break are summed at the bottom of Tables 4a and 4b.

Table 7: Summary of Debris Transport Assumptions.

Debris Type Transport Fraction Fraction of Debris Generated that 1.00 Enters Sump Pool Fraction of Insulation Fines that 1.00 Transport to Sump Screen Fraction of Insulation Small and Large 0.00 Pieces that Transport to Sump Screen Fraction of Particulate that Transports 1.00 to Sump Screen Fraction of Lead Shield Blanket Cover 0.00 Material that Transports to Sump Screen Page 39 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3f:

Head Loss and Vortexing The objectives of the head loss and vortexing evaluations are to calculate head loss across the sump strainer and to evaluate the susceptibility of the strainer to vortex formation.

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

2. Provide the minimum submergence of the strainer under small-break loss-of-coolant accident (SBLOCA) and large-break loss-of-coolant accident (LBLOCA) conditions.

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

Provide bases for key assumptions.

4. Provide a summary of the methodology, assumptions, and results of prototypical head loss testing for the strainer, including chemical effects. Provide bases for key assumptions.

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

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

7. Provide the basis for the strainer design maximum head loss.

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

9. Provide a summary of the methodology, assumptions, bases for the assumptions, and results for the clean strainer head loss calculation.

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

11. State whether the sump is partially submerged or vented (i.e., lacks a complete water seal over its entire surface) for any accident scenarios and describe what failure criteria in addition to loss of net positive suction head (NPSH) margin were applied to address potential inability to pass the required flow through the strainer.

12. State whether near-field settling was credited for the head-loss testing and, if so, provide a description of the scaling analysis used to justify near-field credit.

13. State whether temperature/viscosity was used to scale the results of the head loss tests to actual plant conditions. If scaling was used, provide the basis for concluding that boreholes or other differential-pressure induced effects did not affect the morphology of the test debris bed.

14. State whether containment accident pressure was credited in evaluating whether flashing would occur across the strainer surface, and if so, summarize the methodology used to determine the available containment pressure.

Page 40 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3f1:

Diagrams of the Calvert Cliffs ECCS and CS system for Units 1 and 2 are provided in Enclosure (1-2.1) to the submittal.

Response to Issue 3f2:

Calculations for minimum containment flood level have demonstrated that, for a small break LOCA (SBLOCA) and large break LOCAs (LBLOCA), the emergency sump strainer will be completely submerged at the time of switchover to containment sump recirculation. Minimum sump pool water level heights above the containment floor are provided in Table 13 in Issue 3g8. The minimum strainer submergence is the difference between the minimum sump pool water level, and the top of the highest strainer pocket (35.5" above floor) occurring after the initiation of recirculation. Table 8 below provides the strainer submergences when the 35.5" strainer height is subtracted from the minimum sump pool water level heights given in Table 13. Similarly, the minimum submergence over the mid-point of the strainer (19.525" above floor) is provided in Table 8 below as it establishes the maximum allowable head loss for deaeration (see Issue 3f7 and Table 11a).

Table 8: Emergency Recirculation Sump Strainer Submergence Sump Water Strainer Strainer Submergence Break Size Temperature (°F) Submergence at at Mid-Point of Top of Strainer (feet) Strainer (feet)

T sump 140 1.89 3.227

> 0.08 ft2 140 < T sump < 220 1.77 3.103 T sump 140 1.48 2.812 0.08 ft2 140 < T sump 220 1.35 2.689 Response to Issue 3f3:

Calvert Cliffs has completed vortex testing and analysis. CCI performed generic vortex testing for their strainer design in March 2005. The test results from those tests are used in the analysis which shows that vortexing is not possible at the design flows for the Calvert Cliffs strainers.

A Clean Strainer vortex analysis computed a Froude number for the Calvert Cliffs strainers of 0.0025 (Fr = flow speed squared divided by the product of gravitational constant times the submergence depth) which is well below the allowed Froude number of approximately 0.2 at these conditions. Key conservatisms in this analysis include:

i. A submergence level of 1.17 inches (29.8 mm) is assumed while the minimum strainer submergence is 16.2 inches (1.35 feet, see Table 8).

Page 41 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 ii. The vortexing limit was derived from test data based on results with substantially less than 1% air intake while 2% air intake is generally considered acceptable.

Vortex development may arise due to borehole flow disturbances. Borehole formation most likely is due to stochastic structural anomalies in the debris accumulated in and around the strainer pocket which has the borehole. The resulting flow disturbances due to the altered flow field around the borehole can lead to vortexing. Once the bore hole forms, the strainer differential pressure causes a large increase in flow speed through the newly formed borehole. This flow speed change itself is a perturbation of the flow field (a change from before the borehole formed to as it forms to after formation). CCI testing for this phenomenon includes local vortex formation. Based on CCI test results including tests specific for Calvert Cliffs, the critical Froude number for borehole induced vortexing at Calvert Cliffs is 384.1. The Froude number is defined as follows: Fr = 2 x measured head loss ÷ submergence depth. Based on the maximum head loss from testing in Table 10a and Table 10b (Test No. 3) and the minimum submergence from Table 8, the plant Froude number is:

2 x 3.155 ÷ 1.35 = 4.7 Region I Breaks 2 x 6.485 ÷ 1.77 = 7.3 Region II Breaks The actual Froude number is significantly less than the critical Froude number for borehole induced vortexing from the CCI test. A key conservatism in this analysis is that a strainer submergence of 6.1 inches is assumed in determining the 384.1 critical Froude number. Using the actual minimum strainer submergence of 1.35 feet would increase the critical Froude number to over 1000. Therefore, the strainer will not ingest air via vortices caused by boreholes.

Additionally, observations during the head loss testing flow sweeps did not detect vortex formation in any head loss test even at flows of 250% of the design flow rate.

Additional information on vortexing was provided in response to Request for Additional Information (RAI) 17 [Reference(20)].

Response to Issue 3f4:

Calvert Cliffs used the strainer vendor, CCI, to perform plant specific strainer head loss testing. Four different test programs were performed; however, only the results from the last two test programs are credited in this response. Calvert Cliffs redesigned the strainer head loss test program based on experience gained in the first two test programs and NRC guidance [Reference (13)]. The third set of tests was conducted in late-2008, and used larger quantities of debris. These tests are used to evaluate some of the limiting breaks from Region II. The fourth and final set of tests was conducted in the Page 42 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 summer of 2010. These tests are used to evaluate the limiting breaks from Region I and some of the Region II breaks.

In each test one or more full-size strainer cartridges were placed in CCIs Multi Functional Test Loop (MFTL) in Winterthur, Switzerland, and are subsequently loaded with the amount of debris computed to transport to this portion of the overall strainer.

The CCI MFTL is a closed recirculation loop as shown in Figure 1. The volume of water in the test loop is approximately 2400 liters. The water recirculation in the loop occurs by means of a centrifugal pump with a flow rate capacity up to 125 m3/h. The flow rate is adjustable by controlling the speed of the pump motor via a frequency based variable speed controller. Additionally, the flow rate can be pre-adjusted by means of a valve in the downstream line. The water flow rate is measured using a KROHNE magnetic inductive flow meter with a capacity of 200 m3/h. The temperature of the water is measured using a Ni-CrNi Thermocouple Type K.

Figure 1: Outline of MFTL for Calvert Cliffs Testing (3 Modules Shown)

Two CCI strainer cartridges containing 36 representative pockets was placed in the Plexiglas channel.

The strainer cartridges tested were identical to those installed in the Plant. This scaling factor between the Plant and Test configurations is 282.25. The test module is shown in Figure 2. The 36 pocket prototype had a vertical orientation while the water flow was horizontal into the pockets. The prototype was 9 pockets high (90 mm height per pocket) by 4 pockets wide (84 mm per pocket) and the pockets were 200 mm deep. The distance of the test pockets above the floor was approximately 5 cm.

Side plates (200 mm long), top and bottom sealing plates were made from solid, non-perforated steel Page 43 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 plate. The hole diameter in the perforated strainer pockets was 1.6 mm (1/16") and the test cartridge plate thickness was 1.25 mm.

Figure 2: Strainer Test Module After preparation and addition of the fiber, particulate and chemical precipitate test debris mixtures into the test loop, the head loss was monitored until it reached a satisfactory stabilization point. Head loss, temperature and flow rate measurements were taken throughout the test.

For both sets of tests being credited the fibrous insulation debris used in the test were provided to CCI by Calvert Cliffs from materials identical to plant insulation. Cal-Sil was not included in the test debris mix due to the insignificant quantity of Cal-Sil generated by large break LOCAs. As shown in Tables 4a and 4b, the bounding breaks did not generate any Cal-Sil debris.

The differences between the two test programs being credited are principally the surrogate used for particulate, and the test flowrate.

Particulate Surrogate The late-2008 testing used stone flour (mean particle size = 7.7 m) as a surrogate for particulate in addition to some actual epoxy particulate that was used.

The summer-2010 testing used Silicon Carbide (mean particle size = 9.7 m)as a surrogate for particulate debris except for degraded epoxy coatings where epoxy coatings chip debris was produced from the same epoxy coating used in containment at Calvert Cliffs, and for marinite where actual marinite debris Page 44 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 was used.

In both cases the average surrogate size was less than the particle sizing requirement of 10 m, and are therefore acceptable.

Strainer Flowrate The summer-2010 testing scaled the volumetric flow rate so that the average velocity through the test strainer cartridges corresponded to the expected average flow speed through the strainer installed in the plant at the strainer design flow of 5000 gpm. In addition, the test flow was reduced to 2400 gpm prior to the introduction of chemical precipitates to reflect emergency operating procedure changes to have one Containment Spray pump secured prior to the onset of chemical precipitates. The recorded head loss at 2400 gpm is scaled to 2365 gpm to reflect the maximum actual strainer flow. See response to Issue 3g1.

The late-2008 testing utilized flow rates that resulted in average velocities higher than the average velocity through the plant strainer. The bulk of the non-chemical debris was introduced at a flow rate corresponding to 2.7 times the strainer design flow of 5000 gpm. Once the non-chemical debris addition was complete the flow was reduced to 5000 gpm, and the head loss was recorded. Chemical debris was introduced at the expected average flow speed through the strainer corresponding to the strainer design flow of 5000 gpm. The recorded head loss is scaled from 5000 gpm to 2365 gpm.

Debris Preparation and Addition Methods The debris preparation and addition methods used by CCI for both sets of tests being credited for Calvert Cliffs are identical to each other, and to those witnessed by the NRC in Spring 2008 at CCI's laboratory in Switzerland.

Fibrous debris for use in tests was prepared by the following method:

Fiber Fines

• The fibers from all fibrous insulation were freed from the jacketing (if jacketed). Then the fibers were baked by placing them in an oven with a regulated temperature of 250°C (480°F) for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to testing. Generic fiberglass insulation was not baked for the tests since it is used at Calvert Cliffs on relatively cool pipes.

• The fibers were hand cut in pieces of approx. 50 x 50 mm (2 in. x 2 in.).

• The dry material was weighed

• The fibers were split in batches of 3 to 4 dm3 (0.1 to 0.14 ft3)

• Each batch was soaked in 2 liter (1/2 gal) of water until they appeared saturated Page 45 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• Each batch of debris was then pressure washed by applying a high pressure water jet with a capacity of 100 bar (1450 psig) at a distance of +/- 0.05 m (2 in.) to the water surface for approximately 4 minutes.

• It was ensured by visual means that the insulation was decomposed in the water in fine pieces with no clumps of fibers remaining and individual fiber pieces were smaller than 8 mm (0.3 in.).

Fiber Small Pieces

• The fibers were freed from the blanket/jacketing (if jacketed). Then the fibers were baked by placing them in an oven with a regulated temperature of 250°C (480°F) for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to testing. Generic fiberglass insulation was not baked for the tests since it is used at Calvert Cliffs on relatively cool pipes.

• The fibers were hand cut in pieces of approx. 50 x 50 mm (2 in. x 2 in.).

• The dry material was weighed

• The fibers were split in batches of 3 to 4 dm3 (0.1 to 0.14 ft3)

• The fiber material was run through an electric leaf shredder one time

• Each batch was soaked in several liters of water (preferably using water from the test loop) at no more than a 100 - 200g (3.5 - 7 oz.) fiber smalls per preparation bucket.

• Prior to addition to the loop the fiber smalls were mixed briefly using either the propeller drill bit, hand agitation or some other means to prevent agglomeration. Caution was used to prevent breaking the small pieces into fines.

• The fiber small pieces were used in their respective sizes once saturated Marinite Marinite was pulverized using mechanical means to a powder form. The Marinite was combined with the Silicon Carbide particulate debris bucket.

Degraded Qualified Epoxy Coatings Outside ZOI

• Epoxy coating was applied to a plastic sheet and allowed to cure.

• The cured epoxy coating was removed from the plastic sheet and disintegrated into large chips which were placed in a bucket.

Page 46 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• The large chips were further disintegrated into smaller chips using a drill machine with an agitating propeller.

• The small chips were then sieved to obtain the proper size.

Particulate and fibrous materials were prepared and maintained separately. Neither type was mixed together; there were no mixed mode suspensions during preparation and addition. Both debris types were further diluted during the addition process. The normal test sequence was to alternate particulate and fibrous insulation additions during a single batch add. That is, one batch might consist of several containers of particulate debris and several of fibrous debris; additions of each type would be alternated until the entire batch was added. Particulate was added before fiber as CCI experience showed that this resulted in higher head loss. Paint chips were added after all particulate and fibrous debris was added.

The particulate and fibrous debris was added to the flume approximately midway between the return pipe opening and the strainer face, approximately 1.5 meters (5 ft.) from the strainer face. The coatings chips were added immediately upstream of the strainer face as the chips would not transport along the flume. Care was taken to assure uniform distribution of debris across the strainer face. Care was also taken to add the debris slowly, avoiding disturbance of the debris bed.

Mechanical agitation was used to suspend debris that settled in the flume (see response to 3f12).

Debris at the base of the strainer was allowed as long as this debris appeared as a natural slope with no visible humps away from the slope. Agitation was performed provided particulate and fibrous debris was free in the flume or had settled to the flume floor greater than approximately 50 cm (20 in.) away from the upstream strainer face. Guidance was provided to not force debris onto the strainer face through this agitation.

After all non-chemical debris was added to the flume, head loss was allowed to stabilize. The head loss stabilization criterion was less than a 1% increase per hour for head loss values >60 mbar (2 ft-water) or 0.6 mbar (0.25 in.-water) increase per hour for head loss values 60 mbar (2 ft-water).

Chemical precipitate formation does not need to be considered until the containment pool cools to 140°F (see response to Issue 3o2.8). Multiple containment response analyses show that when the containment pool cools to 140°F the containment pressure is less than 2.2 psig. The Calvert Cliffs Emergency Operating Procedure for LOCA directs the operators to secure one containment spray pump when containment pressure drops below 4.0 psig. This action is credited in reducing strainer flowrate prior to the formation of chemical precipitates.

Page 47 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Calvert Cliffs prepared a special GOTHIC containment response calculation to verify that sufficient time was available to assure one containment spray pump could be secured and strainer flow rate reduced before the containment pool temperature reduces to 140°F. This GOTHIC analysis used assumptions and inputs that very conservatively maximized containment cooldown rates and considered maximum instrument uncertainty to delay operator action. The results of these calculations showed that for maximum cooldown conditions, containment pressure reduces to 3.68 psig (4 psig indicated) about 30 minutes into the event and the containment sump temperature reduces to 140°F more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> later. See Figure 3.

Cold Leg Break Max Cooldown 280 10 260 9 240 24.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> 8 220 7 Temperature (F) Pressure (psig) 200 6 Sump Water 180 5 Vapor Temp Pressure 160 4 CS Pump Trip 140 3 Sump @ 140F 120 2 100 1 80 0 100 1000 10000 100000 1000000 Time (sec)

Figure 3: Time from Securing CS pump to Pool Reaching 140°F For the summer 2010 testing, prior to adding chemical precipitates to the test loop, the test flow was reduced to 2400 gpm to account for securing one containment spray pump, and one HPSI pump going to Core Flush mode. The strainer head losses obtained at this reduced flow rate were then linearly scaled to a flow of 2365 gpm to account for some over-conservatisms in the 2400 gpm flow rate.

For the late-2008 testing the chemical precipitate debris was added at the 5000 gpm nominal strainer flow rate. The strainer head loss test results are then linearly scaled to 2365 gpm which is the Page 48 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 equivalent strainer flow rate of one HPSI pump in Cold Leg Injection mode, one HPSI pump in Core Flush mode, and one containment spray pump in operation.

Chemical addition was performed in a continuous fashion by a peristaltic metering pump and was introduced immediately below the return via a hollow tube. This configuration provided the best chance for the chemical precipitate surrogates to fully mix in the flume flow prior to arrival at the strainer and debris bed.

Agglomeration was not observed. All debris was transported to the strainer module either directly or via resuspension in the flume flow through the action of agitation methods. Calvert Cliffs test methods are conservative in the delivery of material to the strainer.

The abbreviated procedure for performance of the tests is provided below.

1) Prepare fibrous insulation debris.

2) Prepare particulate debris.

3) Prepare chemical precipitate surrogate.

4) Perform clean head loss test from 12% to 200% design flow rate.

5) Fiber / Particulate debris introduction:

a) Ensure appropriate flow rate and water temperature per test plan.

b) Starting with particulate, alternate additions of fiber fines, fiber smalls and particulate.

c) Ensure transport to the strainer by appropriate agitation. Ensure appropriate distribution of debris across the strainer without center weighting.

d) Add debris for thin bed investigation or for normal bed investigations as required in the test plan.

e) Maintain water level, flow rate, and temperature within tolerance.

f) Allow head loss to stabilize in accordance with criteria in test plan.

6) Chemical precipitate introduction.

a) Adjust flow rate per test plan.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 b) Add sodium aluminum silicate precipitate immediately below the sparger (return of flow from the heater to the test flume) per test plan using a peristaltic pump.

c) Addition rate is specified in the test plan.

d) Ensure transport of the debris by appropriate agitation.

e) Maintain water level, flow rate, and temperature within tolerance.

f) Allow head loss to stabilize in accordance with criteria in test plan.

7) Perform optional flow sweep at the end of the test to demonstrate bed stability:

a) Reduce flow rate to 80% design.

b) Increase flow rate in increments to at least 120% of design. A few tests investigated flow rates as high as 250% of design.

The MFTL was heated to between 45-50°C (115 - 125°F) for the Calvert Cliffs tests. The submergence was about 10 cm (~4 in.). The strainer test modules were elevated above the flume floor about 5 cm (~

2 in.) consistent with the plant installation.

Summer 2010 Test Summary (used to Qualify Region I Breaks and Most Region II Breaks).

Seven head loss tests were performed in the summer of 2010. These tests included head loss for fibrous and particulate debris (conventional debris) as well as head loss with chemical precipitates. This was a test for success program based on multiple insulation replacement schemes. Test debris quantities at the test scale and at the plant scale are presented in Tables 9a-1 and 9a-2 below, respectively.

Table 9a-1: Test Debris Quantities (kg) of Summer 2010 Head Loss Testing at Test Scale Transco Temp Generic Paint Silicon Precipitate Nukon Marinite Fiber Mat Fiber Chips Carbide (SAS)

Test 1 1.516 2.681 0.069 0.173 0.254 0.015 2.844 0.088 Test 2 0.336 0 0.070 0.242 0 0.015 3.581 0.096 Test 3 0.644 0.594 0.069 0.394 0.254 0.015 3.581 0.096 Test 4 0.138 0.873 0.069 0.036 0.254 0 2.908 0.077 Test 5 0.339 0.873 0.069 0.046 0.331 0 3.645 0.087 Test 6 0.339 0.873 0.069 0.046 0.331 0 3.645 0.087 Test 7 0.237 0.873 0.069 0 0.254 0.015 2.844 0.091 Page 50 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 9a-2: Test Debris Quantities of Summer 2010 Head Loss Testing at Plant Scale Transco Temp Generic Paint Silicon Nukon Marinite Precipitate Fiber Mat Fiber Chips Carbide (lbm) (ft3) 2 (SAS) (lbm)

(lbm) (lbm) (lbm) (ft2) 1 (ft3) 3 Test 1 943.2 1668.0 42.6 107.5 2871.0 0.2 8.875 55.00 Test 2 209.07 0 43.56 150.58 0 0.2 11.175 59.48 Test 3 400.8 369.6 42.6 245.0 2871.0 0.2 11.175 59.48 Test 4 86.17 543.28 42.6 22.5 2871.0 0 9.075 47.70 Test 5 211.212 543.28 42.6 28.62 3750.0 0 11.375 54.10 Test 6 211.212 543.28 42.6 28.62 3750.0 0 11.375 54.10 Test 7 147.54 543.28 42.6 0 2871.0 0.2 8.875 56.80 Note 1. Chip thickness is 0.006 inches (0.1524 mm). Density is 110 lbs/ft .

3

2. Density of Marinite is 46 lbm/ft3.

3. Density of Silicon Carbide is 199.4 lbs/ft3.

The head loss results from these tests are presented in Table 10a below. Adding the clean strainer head loss to the Conventional and Chemical Debris Head Loss at 2365 gpm yields the maximum strainer head loss for each test except for Tests 1 and 2 where head loss at 5000 gpm was limiting.

Page 51 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 10a: Maximum Strainer Head Losses (ft-water) based on Summer 2010 Head Loss Testing Test 1* Test 2 Test 3 Test 4 Test 5 Test 6** Test 7 Conventional Debris 0.105 0.034 0.085 0.051 0.058 0.061 0.047 Only @ 5000 gpm Clean Strainer Head 0.288 0.288 0.288 0.288 0.288 0.288 0.288 Loss @ 5000 gpm Total Strainer Head 0.393 0.322 0.373 0.339 0.346 0.349 0.335 Loss @ 5000 gpm no Chemical Debris Conventional and 0.149 0.051 3.202 0.606 1.225 3.310 0.663 Chemical Debris @

2400 gpm Conventional and 0.147 0.050 3.155 0.597 1.207 3.262 0.653 Chemical Debris @

2365 gpm Clean Strainer Head 0.064 0.064 0.064 0.064 0.064 0.064 0.064 Loss @

2365 gpm Total Strainer Head 0.211 0.114 3.219 0.661 1.271 3.326 0.717 Loss @ 2365 gpm w/ Chemical Debris Maximum Strainer 0.393 0.322 3.219 0.661 1.271 3.326 0.717 Head Loss

• Test rejected due to non-conservative inclusion of small fiber pieces.

• • Test rejected due to improper flume agitation impacting the debris bed in non-prototypical manner.

The conventional debris head loss results were obtained at a strainer flow of 5000 gpm. The combined conventional and chemical debris head loss results were obtained at a strainer flow of 2400 gpm. The head loss test results obtained at 2400 gpm were then linearly scaled to a flow of 2365 gpm to bound the maximum strainer flow with one containment spray pump operating, one HPSI pump providing Cold Leg Injection, and one HPSI pump providing Core Flush flow. Using linear scaling going from a higher flow to a lower flow is quite conservative based on data taken during head loss testing. For the Clean Strainer Head Loss, at 2365 gpm the internal flow velocities are still well within the turbulent range; therefore, the Clean Strainer Head Loss, which was computed using hydraulic resistance data at a flowrate of 5000 gpm, was scaled to 2365 gpm by the square of the flows in accordance with the affinity laws.

All head loss tests conducted for the Calvert Cliffs strainer utilized sufficient chemical precipitate to cause a break-through in the debris bed, which consistently reduced the measured head loss. However, Page 52 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 no credit is taken for the lower head losses observed after the break-through. The maximum head loss recorded for each test applies to each break case having a fiber fines and particulate load less than or equal to the amount tested. If the break has a chemical precipitate load less than the amount tested it was conservatively assumed that the head loss still reached the peak value observed during testing. If the break has a chemical precipitate load equal to, or greater than that tested it was conservatively assumed that the excess precipitate did not reach the strainer to cause a break-through and therefore the peak head loss recorded during testing was used.

Page 53 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 1 The first test in the summer 2010 series used fine and small piece fibrous debris along with particulate.

The debris load consisted of an equivalent quantity of 313 ft3 (846.1 lbm) of fine fibers and 798 ft3 (1915.2 lbm) of small pieces of fiber. The fiber and particulate debris were introduced in five equal batches in the order of particulate, fines, then small pieces. A photograph of the debris loaded strainer after introduction of the chemical precipitates is shown in Figure 4. The maximum debris bed head loss in this test was less than 4.4 mBar (1.787 inches of water, 0.06 psid) as shown in Figure 5. Note that data were not provided between 42.2 and 48.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> into the test; however, the incremental rise in head loss shown in Figure 5 can be confirmed by examining the test data recorded in the test report.

The maximum head loss was low, less than 2 inches of water, and the debris bed was non-uniform as shown in Figure 4.

Figure 4: Test 1 Non-Uniform Debris Deposition When Small Fiber Pieces Included Page 54 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 5: Test 1 Head Loss Data Two key conclusions were drawn from Test 1:

1) Debris deposition on the strainer for large break LOCA at Calvert Cliffs is non-uniform.

2) Testing with small-pieces of fibrous insulation is potentially non-conservative due to the very low head loss observed.

The decision was made to exclude small pieces of fibrous debris from further head loss testing. Test 5 included a comparable quantity of fine fibers to that of Test 1 and resulted in significantly higher head loss.

Page 55 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 2 Test 2 was a thin-bed test. The test alternated the addition of fiber fines and particulate to the loop, starting with particulate. This sequence was chosen due to previous CCI experience which showed this methodology resulted in higher head loss than initially adding all particulate to the loop followed by batching in fiber. This test resulted in debris bed head losses approximately 1.5 mBar (0.609 inch or 0.051 feet of water). A photograph of the debris loaded strainer after introduction of the chemical precipitates is shown in Figure 6. A plot of the head loss data is shown in Figure 7.

Consistent with earlier thin-bed testing attempt, no thin-bed formation was observed. The head loss results were very low. The Calvert Cliffs emergency recirculation strainer is not susceptible to the thin-bed effect.

Figure 6: Debris Deposition in Thin-Bed Test Page 56 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 7: Test 2 Head Loss Data Page 57 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 3 The third test in the series was a test with the equivalent of 369 ft3 (1058 lbm) of fine fibrous debris.

The maximum debris bed head loss from conventional debris only was 2.5 mBar (1.02 inch or 0.085 ft of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 94.6 mBar (38.42 inches or 3.202 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to approximately 33.0 mBar (13.4 inches of water) before leveling off at 35.2 mBar (14.3 inches of water). Photographs of the Test 3 debris bed are shown in Figure 8. A plot of the head loss data is shown in Figure 9.

The debris bed bore hole from Test 3 is shown in Figure 10. This is typical of the remaining tests in this series. Each of tests 3 through 7 experienced at least one debris bed break-through after introduction of the chemical precipitate debris. The low strainer approach velocity at Calvert Cliffs results in the strainer pockets filling with loosely packed fiber followed by the fibrous debris building a debris bed across the face of the strainer. When the chemical precipitates cover the debris bed, the soft bed compresses and eventually ruptures into one pocket which relieves the differential pressure.

Figure 8: Test 3 Debris Bed Before and After Chemical Precipitates Page 58 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 9:Test 3 Head Loss Data Figure 10: Test 3 Debris Bed Bore Hole Page 59 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 4 The fourth test in the series was a test with the equivalent of 270 ft3 (694.55 lbm) of fine fibrous debris.

The maximum debris bed head loss from conventional debris only approximately 1.5 mBar (0.609 inch or 0.051 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 15.1 mBar (6.13 inches of water) at which time a bore hole formed in the debris bed. The last of the precipitate was added to the loop and the head loss slowly returned to 17.9 mBar (7.27 inches or 0.606 feet of water) at which time another bore hole formed in the debris bed. The head loss leveled off to approximately 10.3 mBar (4.18 inches of water) at the end of the test. The head loss data from Test 4 is shown in Figure 11.

Figure 11: Test 4 Head Loss Data Page 60 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 5 The fifth test in the series was a test with the equivalent of 323 ft3 (825.7 lbm) of fine fibrous debris.

The maximum debris bed head loss from conventional debris only was 1.7 mBar (0.69 inch or 0.058 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to approximately 36.2 mBar (14.70 inches or 1.225 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to approximately 10.6 mBar (4.30 inches of water). The head loss leveled off at test end to 19.4 mBar (7.88 inches of water). The head loss data from Test 5 is shown in Figure 12.

Figure 12: Test 5 Head Loss Data Page 61 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 6 The sixth test in the series was a test using the same debris load as Test 5 with the addition of lead shielding blanket cover broken down as fine as possible. The maximum debris bed head loss from conventional debris only was approximately 1.8 mBar (0.73 inch or 0.061 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 97.8 mBar (39.718 inches or 3.310 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to 31.7 mBar (1.073 feet of water). The head loss leveled off at test end to approximately 58.7 mbar (1.987 feet of water). The head loss data from Test 6 is shown in Figure 13.

Figure 13: Test 6 Head Loss Data Test 6 was rejected due to improper agitation of debris in the test flume. The Calvert Cliffs test engineer on duty witnessed agitation where an electric drill driven propeller disturbed the debris on the face of the strainer. The use of the hand-held drill was observed lifting the debris within the debris bed and creating a non-prototypical debris profile that was considered not to be consistent with previous testing.

Test 6 was rejected and additional guidance on agitation was provided before proceeding with additional testing.

Page 62 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 7 The final test in the series was a test with the equivalent of 291 ft3 (733.4 lbm) of fine fibrous debris.

The maximum debris bed head loss from conventional debris only was 1.4 mBar (0.57 inch or 0.047 feet of water). After introduction of the chemical precipitates, the highest debris bed head loss was 19.6 mBar (7.96 inches or 0.663 feet of water) before an interruption formed in the debris bed. The head loss leveled off at test end, prior to flow sweeps, at around 17.9 mBar (0.606 feet of water) after multiple debris bed interruptions. The head loss data from Test 7 is shown in Figure 14.

Figure 14: Test 7 Head Loss Data Page 63 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Late-2008 Test Summary (used to Qualify Certain Region II Breaks).

Head loss testing was performed in late-2008. These tests included head loss for fibrous and particulate debris (conventional debris) as well as head loss with chemical precipitates. Varying debris loads were considered, but in all cases the debris loads were significantly higher than those used in the summer-2010 testing discussed above.

The first two tests were run successfully during the conventional debris portion of the test, but test anomalies invalidated the chemical debris portion of the test. These anomalies were addressed for the remainder of the tests. In Test 5 flowrate was not controlled as required, and consequently the results are not valid. Test 4 and 9 included the chemical precipitate calcium phosphate which only applies to the previous Tri-Sodium Phosphate buffer. Tests 3, 6, and 7 used the current Sodium Tetraborate buffer and were successful; however Test 6 and 7 used fiber quantities approximately 21/2 times greater than what is in the plant now, and thus the results are not reflective of the current plant condition.

Therefore, Test 3 is used to augment the Summer 2010 Testing for evaluating the Region II breaks.

Test debris quantities at the test scale and plant scale are presented in Table 9b-1 and Table 9b-2, respectively. The head loss results based on these tests are shown in Table 10b.

Table 9b-1: Test Debris Quantities (kg) of Late 2008 Head Loss Testing at Test Scale Transco Temp Generic Mineral Epoxy Stone Precipitate Nukon Fiber Mat Fiber Wool Dust Flour (SAS)

Test 3 0.868 1.065 0.247 0.415 0.112 0.265 1.991 0.172 Test 6 0.889 1.065 0.455 0.530 0.771 0.382 2.042 0.339 Test 7 0.926 1.111 0.341 1.149 1.928 0.382 2.042 0.418 Table 9b-2: Test Debris Quantities of Late 2008 Head Loss Testing at Plant Scale Transco Temp Generic Mineral Epoxy Stone Precipitate Nukon Fiber Mat Fiber Wool Dust Flour (SAS)

(lbm)

(lbm) (lbm) (lbm) (lbm) (ft3)1 (ft3)2 (lbm)

Test 3 540.0 662.4 153.4 258.5 69.6 1.0 7.4 107.20 Test 6 552.96 662.4 283.2 330.0 480.0 1.44 7.59 211.10 Test 7 576.0 691.2 212.4 715.0 1200.0 1.44 7.59 259.80

1. Density of Epoxy Dust is 165.0 lbs/ft .

3

2. Density of Stone Flour is 167.4 lbs/ft3.

Page 64 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The conventional debris head loss results were obtained at a strainer flow of 5000 gpm as was the combined conventional and chemical debris head loss results. The conventional and chemical head loss test results were then linearly scaled to a flow of 2365 gpm to bound the maximum strainer flow with one containment spray pump operating, one HPSI pump providing Cold Leg Injection, and one HPSI pump providing Core Flush flow. Using linear scaling in this circumstance was found to be quite conservative based on data taken during head loss testing. As discussed earlier, the Clean Strainer Head Loss which was computed using hydraulic resistance data at a flow rate of 5000 gpm was scaled to a flowrate of 2365 gpm by the square of the flows in accordance with the Affinity Laws. The head loss results are summarized in Table 10b below.

Table 10b: Maximum Strainer Head Losses based on Late 2008 Testing Results (ft-water)

Test 3 Test 6 Test 7 Conventional Debris Only @ 5000 0.156 0.244 0.278 gpm Clean Strainer Head Loss 0.288 0.288 0.288

@ 5000 gpm Total Strainer Head Loss @ 5000 gpm 0.444 0.532 0.566 w/o Chemical Debris Conventional and Chemical Debris 13.710 23.491 22.777

@ 5000 gpm test flow Conventional and Chemical Debris 6.485 11.111 10.774 linearly scaled to 2365 gpm Clean Strainer Head Loss 0.064 0.064 0.064

@ 2365 gpm Total Strainer Head Loss @ 2365 gpm 6.549 11.175 10.838 with Chemical Debris Maximum Total Strainer Head Loss 6.549 11.175 10.838 Page 65 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 3 (late-2008 Testing).

The third test from the late-2008 testing was a test with the equivalent of 1681 lbs of fine fibrous debris of all insulation types. The maximum debris head loss from conventional debris only was 4.6 mBar (1.868 inches or 0.156 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 405.1 mBar (13.710 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to approximately 50.5 mBar (1.71 feet of water). After experiencing a couple debris bed bore holes at smaller peaks the head loss leveled off to approximately 135 mBar (4.57 feet). A plot of the head loss data is shown in the figure below.

Page 66 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 6 (late 2008 Testing)

The sixth test from the late-2008 testing was a test with the equivalent of 2304 lbs of fine fibrous debris.

The maximum debris head loss from conventional debris only was 7.2 mBar (2.924 inches or 0.244 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 694.1 mBar (23.491 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to approximately 80 mBar (2.71 feet of water). The head loss leveled off to approximately 400 mBar (13.54 feet of water). A plot of the head loss data is shown in the figure below Page 67 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Test 7 (late 2008 Testing)

The seventh test from the late-2008 testing was a test with the equivalent of 3387 lbs of fine fibrous debris. The maximum debris head loss from conventional debris only was 8.2 mBar (3.33 inches or 0.278 feet of water). After introduction of the chemical precipitates, the debris bed head loss climbed to 673 mBar (22.777 feet of water) at which time a bore hole formed in the debris bed and the head loss dropped to approximately 78.7 mBar (2.663 feet of water). The head loss leveled off to approximately 270 mBar (9.138 feet of water). A plot of the head loss data is shown in the figure below Response to Issue 3f5:

The pockets in CCIs strainer cassettes are designed to fill with debris with additional debris depositing on the outside of the strainer. The distributed layout of the strainer module rows allows sufficient space for the debris to accumulate and completely envelop the strainer. The low flow velocity into the strainer prevents the strainer pockets from becoming tightly packed with debris. Therefore, complete envelopment of strainer, as demonstrated in strainer head loss testing, is acceptable.

Page 68 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3f6:

The strainer installed at Calvert Cliffs is CCIs pocket cassette type strainer. Figure 15 shows a representative pocket cassette strainer. During the April/May 2008 testing, the late 2008 testing, and the summer 2010 testing at CCIs MFTL, several attempts were made to generate a thin bed using Calvert Cliffs-specific debris. The geometry of the pocket filtration surface is such that it was not possible to have a uniform fiber bed on the filtration surface.

Figure 15: Pocket Cassette Strainer The April-May 2008 tests used the following thin bed test methodology:

• Add 50% of the particulate and 10% of the fibrous debris (expected bed thickness 0.1 inch).

Measure head loss.

• Add 50% of the particulate and 10% of the fibrous debris (expected total bed thickness 0.2 inches). Measure head loss.

The late 2008 tests used the following thin bed test methodology:

• Add 50% of the particulate and 10% of the fibrous debris (expected bed thickness 0.1 inch).

Measure head loss.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• Add 50% of the particulate and 5% of the fibrous debris (expected total bed thickness 0.15 inches). Measure head loss.

• Add 5% of the fibrous debris (expected total bed thickness 0.2 inches). Measure head loss.

• Add 10% of the fibrous debris (expected total bed thickness 0.3 inches). Measure head loss.

• Add 10% of the fibrous debris (expected total bed thickness 0.4 inches). Measure head loss.

• Add 20% of the fibrous debris (expected total bed thickness 0.6 inches). Measure head loss.

• Repeat the previous step twice more. Final expected total bed thickness 1.0 inch.

The summer 2010 tests used the following thin bed test methodology:

• Add particulate debris, 100% of the Marinite and 20% of the Silicon Carbide, and 20% of the fibrous debris (expected bed thickness 0.125 inch). Observe strainer coverage and measure head loss.

• Add 60% of the Silicon Carbide particulate and 20% of the fibrous debris (expected total bed thickness 0.25 inches). Observe strainer coverage and measure head loss.

• Add remaining 20% of the Silicon Carbide particulate debris (full screen coverage verified).

Measure head loss.

• Add chemical precipitate surrogates. Measure head loss.

Calvert Cliffs thin bed testing included beds as thin as 1/16 inch up to a nominal full load of debris and included a wide range of simultaneous particulate loading. This ensures that the maximum head loss condition for the CCI strainers and for the Calvert Cliffs debris loads is identified. Maximum head loss occurs with maximum debris. No significant increase in head loss was seen in any thin-bed test. The Calvert Cliffs strainer exhibits no thin bed effect.

Response to Issue 3f7:

The Calvert Cliffs response to Generic Letter 2004-02 considered the following debris-related strainer failure modes:

a. Loss of pump NPSH margin due to excessive strainer head loss.

b. Structural failure of strainer due to excessive strainer head loss.

c. Release of dissolved gases (i.e., deaeration) inside strainer due to excessive strainer head loss.

d. Vortexing.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 As discussed under Issue 3f3, vortexing is not an issue for the Calvert Cliffs strainer. Adequate NPSH was found to be the limiting strainer failure mode at elevated sump pool temperatures. Deaeration was found to be the limiting strainer failure mode at sump pool temperatures of 140°F and below. Incipient deaeration occurs at the downstream side of the debris bed when debris bed head loss exceeds submergence to the strainer mid-point (see Issue 3f2). Strainer submergence is dependent on LOCA size and break location. Smaller LOCAs have less water injected because the Safety Injection Tanks do not inject. The maximum allowable head loss for three different strainer failure modes and two LOCA sizes is presented in Table 11a Table 11a Maximum Allowable Head Loss Maximum Strainer Failure Sump Water Break Size Allowable Head Mode Temperature (°F)

Loss (feet)

Structural All T sump 220 23.461 Overload T sump 140 27.552 Insufficient All NPSH a 140 < T sump 219 2.073 Deaeration 120 T sump 140 3.227 Break Sizes > 0.08 ft2 140 < T sump < 220 3.103 120 T sump 140 2.812 Break Sizes 0.08 ft2 140 < T sump 220 2.689

1. From Section 3k1 the strainer is structurally qualified for a differential pressure of 700 mBar at 70°F (equates to 23.46 feet).

2. NPSH available consists of the static head between the sump pool surface and the pump suction, and the sub-cooled margin at a fluid temperature of 140°F. It is reduced by the strainer head loss and hydraulic friction losses between the strainer and the pump suction. A strainer head loss of 27.55 feet is the maximum allowable head loss to maintain NPSHa > NPSHr.

3. NPSH available consists of the static head between the sump pool surface and the pump suction (no sub-cooled margin). It is reduced by the strainer head loss and hydraulic friction losses between the strainer and the pump suction. A strainer head loss of 2.07 feet is the maximum allowable head loss to maintain NPSHa > NPSHr.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Demonstration that Strainer Head Losses Will be Below Maximum Allowable Limits.

The discussion in Sub-Sections A through D below demonstrate that the Calvert Cliffs containment sump strainer head losses will be below the maximum allowable values given in Table 11a. The debris loads for each of the limiting breaks is compared to the debris loads used in the head loss tests to identify which head loss tests can be considered to bound that break. The head loss from these bounding tests are then compared to the maximum allowable head loss values of Table 11a. Those tests having a lower head loss than the Table 11a limits can be used to qualify that break case.

This evaluation is done for each of the limiting Region I and Region II breaks as well as for breaks smaller than 0.08 ft2, and also for sump pool temperatures greater than 140°F, and sump pool temperatures less than or equal to 140°F. The following table summarizes which section addresses which break case.

Sump Pool Temperature Break Size Sub-Section 140°F All A 140°F Region I ( 0.08 ft2 ) B Region I ( > 0.08 ft2 ) C Region II D A. Qualification of All Breaks When T Sump > 140°F As seen in Tables 10a and 10b the strainer head loss for conventional debris only (i.e., sump pool temperatures greater than 140°F) is very small. The highest head loss for any test being credited is 0.444 feet. This is well below the limiting allowable head loss of 2.07 feet given in Table 11a. At sump pool temperatures where chemical precipitates do not exist there are no head loss concerns for the Calvert Cliffs strainer.

B. Qualification of Breaks 0.08 ft2 at T Sump 140°F The debris loads for the Region I Breaks less than 0.08 ft2 are bounded by the thin-bed test debris loads.

Test No. 2 from Table 10a is the thin-bed test from the Summer 2010 Head Loss testing. The maximum head loss is 0.322 feet which is well below the limiting allowable head loss limit of 2.812 feet given in Table 11a for break sizes 0.08 ft2, and sump pool temperatures 140°F. Therefore, these breaks will not challenge strainer performance.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 C. Qualification of Region I Breaks > 0.08 ft2 at T Sump 140°F.

Table 4b from Issue 3b4 provides the debris load of the four limiting Region I breaks. The loads are repeated and summarized in Table 11b-I below.

Table 11b-I Region I Debris Load Summaries Debris Type 11 Hot Leg @ 12 Hot Leg @ 11A Cold Leg 12B Cold Leg SG SG Fiber Fines (lbs) 318.39 323.38 248.88 239.33 Particulate (ft3) 8.537 8.537 8.537 8.537 Precipitate (lbs) 35.7 46.6 33.2 34.7 The Summer 2010 Head Loss Tests results are used to qualify the Region I breaks. Table 9a-2 from Issue 3f4 provides the debris loads used in the Summer 2010 Head Loss Testing. Table 10a from Issue 3f4 provides the maximum strainer head losses recorded for each of these debris loads with the clean strainer head loss also accounted for. The debris loads and resulting strainer head losses for the relevant tests are repeated and summarized in Table 11c-I below.

Table 11c-I Summer 2010 Debris Load Summaries Debris Type Test 2 Test 3 Test 4 Test 5 Test 7 Fiber Fines (lbs) 403.21 1058.00 694.55 825.71 733.40 Particulate (ft3) 11.375 11.375 9.275 11.575 11.575 Precipitate (lbs) 59.48 59.48 47.70 54.10 56.80 Maximum 0.322 3.219 0.661 1.271 0.717 Strainer Head Loss (ft)

Comparing the Summer 2010 test debris loads from Table 11c-I to the limiting Region I debris loads of Table 11b-I shows that each debris component of each of the four limiting Region I breaks is bounded by each of the five Summer 2010 Head Loss tests. Therefore, the head loss from any of the tests listed in Table 11c-I can be compared to the allowable strainer head loss from Table 11a. Comparing the head losses from the Summer 2010 Tests shown in Table 11c-I to the maximum allowable strainer head loss from Table 11a shows that all the Summer 2010 Head tests have a lower head loss than the maximum Page 73 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 allowable head loss. Therefore, any of the Table 11c-I tests can be used to qualify a Region I break greater than 0.08 ft2 at sump pool temperatures less than or equal to 140°F.

D. Qualification of Region II Breaks at T Sump 140°F.

Table 4a from Issue 3b4 provides the debris load summaries of the four limiting Region II break cases.

The loads are repeated and summarized in Table 11b-II below.

Table 11b-II Region II Debris Load Summaries Debris Type 11 Hot Leg @ 12 Hot Leg @ 11A Cold Leg 12B Cold Leg SG SG Fiber Fines (lbs) 1393.04 1056.37 999.07 711.15 Particulate (ft3) 10.042 10.042 10.066 10.066 Precipitate (lbs) 75.3 67.8 49.6 69.0 The Summer 2010 and Late-2008 Head Loss tests results are used to qualify the Region II breaks. The debris loads and resulting strainer head losses from the Summer 2010 Head Loss testing are given above in Table 11c-I. Table 9b-2 from Issue 3f4 provides the debris loads used in the Late 2008 Head Loss Testing. Table 10b from Issue 3f4 provides the maximum strainer head losses recorded for each of these debris loads with the clean strainer head loss also accounted for. The debris loads and resulting strainer head losses for three tests from the Late 2008 head Loss testing are repeated and summarized in Table 11c-II below.

Table 11c-II Late 2008 Debris Load Summaries Debris Type Test 3 Test 6 Test 7 Fiber Fines (lbs) 1683.90 2308.56 3394.60 Particulate (ft3) 8.40 9.03 9.03 Precipitate (lbs) 107.20 211.10 259.80 Maximum 6.549 11.175 10.838 Strainer Head Loss (ft)

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

1. Qualification of 11A Cold Leg Break.

The fiber fines, particulate, and chemical precipitate loads used in Test No. 3 of the Summer 2010 tests each bound the predicted values for the 11A Cold Leg Case. From Table 10a and Table 11c-I, the head loss from this test is 3.219 feet. This is below the limiting allowable head loss of 3.227 feet shown in Table 11a for breaks > 0.08 ft2 and T Sump 140°F. Therefore, the head loss from this break location is acceptable.

2. Qualification of 12B Cold Leg Break.

The fiber fines, and particulate used in Test Nos. 5 and 7 of the Summer 2010 tests bound the predicted values for the 12B Cold Leg Case. Although the precipitate mass used in these two tests does not bound the precipitate mass predicted for the 12B Cold Leg Case these two tests can still be considered bounding.

First the head loss plots for each test showed that a debris bed break-through occurred during the addition of chemical precipitates. In both cases the chemical precipitate caused a head loss greater than that which the fiber bed could support. Therefore, additional precipitate would not have resulted in increased strainer head loss.

Second particulate and precipitate debris has a similar effect on head loss by filling in the voids in the fiber bed. Therefore, the underage in chemical precipitate debris is offset by the overage in particulate debris used in Test No. 5 and 7.

From Table 10a and Table 11c-I, the head loss from these tests are 1.271 feet and 0.717 feet respectively. This is below the limiting allowable head loss of 3.227 feet shown in Table 11a for breaks >

0.08 ft2 and T Sump 140°F. Therefore, the head loss from this break location is acceptable.

3. Qualification of 12 Hot Leg Break.

The fiber fines, and particulate used in Test No. 3 of the Summer 2010 tests bound the predicted values for the 12 Hot Leg Case. Although the precipitate mass used in this test does not bound the precipitate mass predicted for the 12 Hot Leg Case this test can still be considered bounding.

The head loss plot for Test No. 3 shows that a debris bed break-through occurred during the addition of chemical precipitates. Since the chemical precipitate caused a head loss greater than that which the fiber bed could support additional precipitate would not have resulted in increased strainer head loss.

And again, particulate and precipitate debris has a similar effect on head loss by filling in the voids in the fiber bed. Therefore, the underage in chemical precipitate debris is offset by the overage in particulate used in Test No. 3.

From Table 10a and Table 11c-I, the head loss from this test is 3.219 feet. This is below the limiting allowable head loss of 3.227 feet shown in Table 11a for breaks > 0.08 ft2 and T Sump 140°F. Therefore, the head loss from this break location is acceptable.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

4. Qualification of 11 Hot Leg Break.

The fiber fines, and chemical precipitate used in Test No. 3 of the Late 2008 testing bound the predicted values for the 11 Hot Leg Case. Although the particulate volume used in this test does not bound the particulate volume predicted for the 11 Hot Leg Case this test can still be considered bounding.

As discussed above, particulate and chemical precipitate debris have a similar effect on head loss by filling in the voids in the fiber bed. Therefore, the underage in particulate is offset by the overage in chemical precipitate. Moreover, a debris bed breakthrough occurred signifying that the maximum differential pressure the fiber bed could sustain was exceeded, and that further particulate/precipitate would not have increased strainer head loss. Furthermore, Test No. 3 from the late 2008 testing also used a fiber load 20% greater than the fiber load predicted for the 11 Hot Leg Break case. As shown in Table 11c-I and Table 11c-II, the strainer head loss increases as the tested fiber load increases, indicating that, for Calvert Cliffs, fiber debris quantity is the foremost factor affecting strainer head loss.

Therefore, it is concluded that the debris loads used in Test No. 3 from the late 2008 testing bound the debris loads predicted for the 11 Hot Leg break case.

From Table 10b and Table 11c-II, the head loss from this test is 6.549 feet at a strainer flow of 2365 gpm.

While this is above the limiting allowable head loss of 3.227 feet shown in Table 11a, in the case of a Hot Leg break, Containment Response analyses show that by the time the sump pool temperature drops to 140°F and below the containment vapor temperature will have dropped well below the point where all Containment Spray flow can be secured, and containment cooling can continue with the Containment Air Coolers alone. Without Containment Spray flow the total strainer flow will drop to approximately 600 gpm. If the measured head loss from Test No. 3 of the late 2008 testing is scaled down to 1150 gpm it will be below all applicable head loss limits in Table 11a. Operators are trained to secure all unnecessary flow in the event pump distress is detected. Therefore, for the break scenario concerned here, even if the Containment Spray flow had not been terminated based on low containment vapor temperature Operator Action would have terminated Containment Spray flow if pump distress was detected, and acceptable operation of the remaining pumps would be ensured.

Additional defense-in-depth measures are available to mitigate this condition. It is noted that in accordance with Bulletin 2003-01 there are existing procedures and training for refilling the RWT after RAS has occurred, and further that there are multiple in-plant and Flex strategies to accomplish refilling the RWT. With a refilled RWT available the plant can return to injection mode when ECCS pump distress is detected. Once a second RWT inventory has been injected there would be sufficient water height to prevent pump distress even if a Containment Spray pump were left operating. While refilling the RWT utilizes NSR equipment, based on the above, there is high confidence that refilling the RWT will be accomplished. Therefore, this provides defense-in-depth for mitigating the limiting Region II breaks.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3f8:

The margins and conservatisms associated with the vortex analysis are discussed in the response to Issue 3f3.

For strainer head loss, as described in response to Issue 1, the Calvert Cliffs debris generation and debris transport calculations include multiple levels of conservatism that maximize debris on the strainer.

During head loss testing, only fiber fines were used to conservatively bound head loss as it was observed that small pieces of fiber reduced debris bed head loss (Summer 2010 Test 1). In reality, should there be large quantities of LOCA-generated debris then small pieces discharged in the vicinity of the strainer might transport to the screen, and act to form the irregular debris bed that was shown during head loss testing to have a lower maximum head loss than a pure fiber fine debris bed. Also, fiber fines produced by erosion are assumed to arrive at the strainer at time t = 0, instead of hours or days later when flow margin is greater.

Another key conservatism is the assumption that all fines transport to the sump strainer. Strainer head loss testing conducted at approach flow velocities representative of the Calvert Cliffs sump pool recirculation flow rates demonstrated that the majority of the fines settled rather than transported to the sump screen even when the debris was deposited only a few feet from the test screen. The fact that the strainer approach velocity is so small that fines tend to settle, even at the inlet to the strainer, indicates a conservative overall design. Only by use of artificial agitation of the test pool water were fines made to transport to the strainer test screen. By use of this artificial pool agitation fine debris was made to transport into the pockets of the test strainer, and once these filled to collect on the face of the test strainer.

Head loss test procedures were designed to ensure uniform debris distribution on the strainer to maximize debris bed head loss; however, the design and physical layout of the Calvert Cliffs strainer promotes non-uniform debris distribution which is conducive to lower head loss.

Debris materials that had been demonstrated to reduce strainer head loss, such as lead shielding cover blanket and metal reflective insulation, were excluded from strainer head loss testing in order to maximize strainer head loss. Though it is unlikely that lead shielding cover blanket and metal reflective insulation debris will transport to the strainer in measurable quantities, it is possible that random pieces of this debris might be at the strainer where it could disrupt the formation of a high-head-loss uniform fiber/particulate debris bed. Also, metal reflective insulation debris is excluded from testing to prevent capture of finer debris before it reaches the strainer; however, in actuality metal reflective insulation in the sump pool would likely capture some of the fine debris before it reaches the strainer.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The chemical precipitates used in the strainer head loss testing was prepared and introduced in accordance with WCAP-16530 that includes multiple levels of conservatism. The full 30 day chemical precipitate load was assumed to arrive at the strainer at the earliest possible time with no credit for settling or nucleation on containment surfaces. Also, the quantity of precipitate arriving at the strainer is expected to be significantly lower than tested amounts. In addition, the precipitate is expected to arrive at the debris bed gradually and the resultant head loss would be lower initially and increase gradually with time. This effect would be offset by reduced strainer recirculation flow later in the accident.

Response to Issue 3f9:

The clean strainer head loss across the filtration surface of the prototypical strainer module as measured in CCIs Large Scale Test Loop Facility was approximately zero. This head loss was confirmed in the demonstration testing performed in the MFTL.

The head loss in the axial flow channel between cartridge modules and in the radial duct is computed using formulas in Reference (14). Flow formulas applicable to turbulent flow are used because the flow velocity in the strainer internals is well within the turbulent range.

Influx flow from the side (i.e., through the cartridges) into the axial flow channel is considered. The friction drag coefficient is developed from the well-known Moody friction curves. A friction factor of 0.025 is used which is conservative for high Reynolds numbers. A relative roughness of 0.001 is used for the smooth stainless steel.

Head loss due to flow obstructions (i.e., seven stabilizer plates within the strainer assembly) and enlargements in the flow stream are considered using equations from Reference (14). The computed analytical head loss for the strainer interior for the design flow rate of 5000 gpm is approximately 0.288 WC (8.6 millibar). A clean strainer head loss of 0.064 at a strainer flow of 2365 gpm is obtained by scaling head loss with the square of flow based on the Affinity Laws.

Additional information on clean strainer head loss was provided in response to RAI 16 [Reference (20)].

Response to Issue 3f10:

The overall strainer head loss consists of a clean strainer head loss (i.e., head loss due to flow through the strainer internals), a head loss due to conventional debris (e.g., fiber and particulate debris), and a head loss due to chemical precipitates. The debris head loss results were obtained by test. The methodology, assumptions and results are provided in Section 3f4. The clean strainer head loss was determined by analysis with methodology and results provided in Section 3f9. A summary of the results used to answer Generic Letter 2004-02 are provided in Tables 10a and 10b under Issue 3f4.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3f11:

The emergency sump strainer is fully submerged under all accident scenarios that include recirculation.

There is no vent above the water level. For additional information refer to the response to Issue 3f2.

Response to Issue 3f12:

The head loss testing used in this submittal did not credit near-field debris settling. Settling distant from the test strainer was prevented by careful debris addition and agitation in the test loop. All debris added to the test reached the strainer. However, not all debris entered the strainer pockets. The large quantity of fibrous debris exceeded the volume of the strainer pockets. The debris that did not enter the strainer pockets attached to the front face of the strainer outside of the pockets, and some debris settled at the base of the strainer, within about 30 centimeters of the strainer face. Figure 16 below shows a relatively uniform debris mass protruding from the entrance to the strainer pockets. The lower portion of that mass forms a ramp of debris supported by the test flume floor immediately at the base of the test strainer. The portion that is partially supported by the flume floor is generally about 10% of the total. The balance is in the pockets or attached to the face of the strainer (about 85%), or has settled on top of the strainer test module (about 5% of the total).

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 16: Typical Debris Bed from Testing at CCI Agitation was used to ensure transport of all forms of debris to the entrance of the strainer. Because of the extensive artificial agitation used to effect debris transport to the strainer during head loss testing Page 80 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 the actual amount which might transport during an accident is bounded by that in the head loss testing.

In addition, the artificial agitation in the test facility was conducted with great care to prevent debris bed disturbances. Photographic and video records show that the test debris beds remain undisturbed during agitation.

Response to Issue 3f13:

No scaling via temperature dependent dynamic viscosity was used.

Response to Issue 3f14:

Containment accident pressure is not credited in evaluating whether flashing occurs across the strainer surface. High strainer head losses are not encountered until the sump pool temperature falls to 140°F and below. At 140°F the vapor pressure is only 2.889 psi, thus providing 11.8 psi (>27 ft) of sub-cooled margin which is more than adequate to prevent flashing.

Containment accident pressure is also not credited in evaluating whether deaeration occurs in the strainer. If the strainer submergence at the mid-height of the strainer is greater than the strainer head loss deaeration would not occur. Conservatively, a zero deaeration acceptance limit is used instead of the 2% limit allowed by Reg Guide 1.82.

Page 81 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3g:

Net Positive Suction Head (NPSH)

The objective of the NPSH section is to calculate the NPSH margin for the ECCS and CSS pumps that would exist during a loss-of-coolant accident (LOCA) considering a spectrum of break sizes.

1. Provide applicable pump flow rates, the total recirculation sump flow rate, sump temperature(s),

and minimum containment water level.

2. Describe the assumptions used in the calculations for the above parameters and the sources/bases of the assumptions.

3. Provide the basis for the required NPSH values, e.g., three percent head drop or other criterion.

4. Describe how friction and other flow losses are accounted for.

5. Describe the system response scenarios for LBLOCA and SBLOCAs.

6. Describe the operational status for each ECCS and CSS pump before and after the initiation of recirculation.

7. Describe the single failure assumptions relevant to pump operation and sump performance.

8. Describe how the containment sump water level is determined.

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

10. Describe whether and how the following volumes have been accounted for in pool level calculations: empty spray pipe, water droplets, condensation and holdup on horizontal and vertical surfaces. If any are not accounted for, explain why.

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

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

13. If credit is taken for containment accident pressure in determining available NPSH, provide description of the calculation of containment accident pressure used in determining the available NPSH.

14. Provide assumptions made which minimize the containment accident pressure and maximize the sump water temperature.

15. Specify whether the containment accident pressure is set at the vapor pressure corresponding to the sump liquid temperature.

16. Provide the NPSH margin results for pumps taking suction from the sump in recirculation mode.

Page 82 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3g1:

A single Emergency Containment Sump supplies inventory to both trains of the Safety Injection and Containment Spray systems. During sump recirculation operation each train consists of a HPSI pump and a Containment Spray pump.

Maximum HPSI pump flow rate = 1045 gpm (two pumps operating)

Maximum CS pump flow rate = 3450 gpm (two pumps operating)

Maximum Total Strainer Flowrate = 1045 gpm + 3450 gpm = 4495 gpm Strainer design flow = 5000 gpm The condition of a LPSI pump failure to stop at recirculation actuation signal (RAS) may result in a LPSI pump operating post-RAS. Procedure changes are being implemented to assure that post-RAS LPSI flow is throttled to 600 gpm indicated, which could be as high as 800 gpm maximum, and that one HPSI pump is secured if two HPSI pumps are operating. The flow from the HPSI pump would be throttled per procedure to 600 gpm indicated which ensures decay heat removal requirements are met. Maximum HPSI flow is taken as 645 gpm; therefore, for the Failure of a LPSI Pump to Stop scenario the Maximum Total Strainer Flowrate is:

Maximum Total Strainer Flowrate = 645 gpm + 3450 gpm + 800 = 4895 gpm This flow is still less than the Strainer design flow of 5000 gpm.

Prior to reaching sump pool temperatures of 140°F and below, only one containment spray pump will be operating (1759 gpm maximum), and one HPSI pump will transition to Core Flush flow(173 gpm maximum), and one HPSI pump will be providing cold leg injection (430 gpm maximum)

Maximum Total Strainer Flowrate @ 140°F and below = 430 gpm + 1759 gpm + 173 gpm = 2362 gpm This flow is rounded to 2365 gpm. This total flow rate contains inherent conservatism. The 430 gpm Cold Leg Injection flow is at a time when the required flow is only 130 gpm. The Containment Spray flow rate of 1759 gpm assumes a pump operating 10% above its pump curve. A more realistic flow would be 1600 gpm.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The maximum post-RAS sump temperature is less than 212°F. The following post-RAS sump temperature values are from the current containment response calculation:

= 205.0°F for cold leg break LBLOCA with two safety trains operating

= 193.2°F for cold leg break LBLOCA with one safety train operating

= 198.3°F for hot leg break LBLOCA with two safety train operating

= 201.2°F for hot leg break LBLOCA with one safety train operating Should the post-RAS sump water temperature exceed 212°F, the containment pressure would be assumed to be the saturation pressure at that the sump pool temperature. This is a reasonable approach which does not credit containment accident pressure in the NPSH available computation. This approach is similar to that found in Reference (16), Section 1.3.1.1.

The minimum sump pool water levels for the various break sizes are provided under Item 3g8, and are converted to strainer submergences in Item 3f2 (see Table 8).

Response to Issue 3g2:

The assumptions used for the above analysis are:

• HPSI flow rate is throttled as directed by procedure to ensure decay heat removal and NPSH requirements are met.

• CS flow rate is that predicted by a hydraulic flow model where the containment spray flow rate is upgraded 10% above the vendor pump curve which bounds the tested performance of the pumps.

• To increase NPSH requirements the diesel generator is assumed to be at 2% over-frequency which bounds the performance of the emergency diesel generator.

Response to Issue 3g3:

The NPSH required values are provided on the vendor pump curve as a function of flow rate.

Page 84 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 The original test data for the CS pumps was used to determine the NPSH required. The CS pump was tested at decreasing NPSH available values at a given flow rate. The last data point taken during testing was that NPSH available value where a decrease in total developed head was observed. The NPSH required value was then established as the second to last tested NPSH available value (i.e., the lowest one for which no decrease in total developed head was detected).

Similar data for Calvert Cliffs HPSI pumps could not be recovered from plant history records. However, correspondence with the HPSI pump vendor (Sulzer) regarding testing they did for another client having an identical pump indicates that the NPSH required values on the pump curve are based on a 3%

degradation in the pump total developed head. The 3% degradation point is a pump industry standard for reporting NPSH required.

Response to Issue 3g4:

As described in the response to Issue 3f4, hydraulic friction losses across the strainer debris bed are determined by head loss testing. As described in the response to Issue 3f9, hydraulic friction losses in the strainer flow channels are computed analytically. Hydraulic friction flow losses in the ECCS recirculation pump suction piping are computed using a hydraulic model of the ECCS piping. The NPSH available to the HPSI and Containment Spray pumps is obtained by subtracting these hydraulic friction losses from the static head differential between the containment water height and the pump suction elevation and the sub-cooled margin available at the limiting fluid temperature.

Response to Issue 3g5:

The ECCS consists of three HPSI pumps, two LPSI pumps, and four safety injection tanks (SITs). After a Safety Injection Actuation Signal (SIAS) is received (generated by either a low pressurizer pressure (1725 psia) or a high containment pressure signal (4.75 psig)) a start signal is given to two HPSI pumps and both LPSI pumps. Each HPSI pump has its own injection header (Main and Auxiliary) which branches into four separate lines. The four branch lines from each header join prior to injecting into each of the four Cold legs. The LPSI pumps inject into a low-pressure injection header that joins the HPSI combined HPSI header prior to injecting into each of the four cold legs. Each SIT injects into a single cold leg. The SITs automatically discharge when the RCS pressure decreases below the SIT pressure.

LBLOCA Two HPSI and both LPSI pumps are automatically given a start signal when the pressurizer pressure is 1725 psia, or containment pressure is 4.75 psig. The third HPSI pump could be manually started if one of the other two HPSI pumps did not start. Actual HPSI pump flow to the core will not begin until the Page 85 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 pressurizer pressure is approximately 1280 psia, and actual LPSI pump flow to the core will not begin until the pressurizer pressure is approximately 185 psia.

The Containment Spray pumps automatically start on safety injection actuation signal setpoint, low pressurizer pressure. Afterward, flow to the containment environment is delayed only by the time required to fill the empty Containment Spray headers as soon as the spray control valve begins to open at a containment pressure of 4.75 psig. Containment Air Coolers will also start at a containment pressure of 4.75 psig with their associated delay for heat removal from Containment.

The SITs automatically discharge to the RCS when the RCS pressure drops to about 200 - 250 psig.

Initially, the Safety Injection and Containment Spray pumps take suction from the RWT. When the RWT level reaches the low-low level signal setpoint level, a RAS is generated, and HPSI and Containment Spray pumps suction switches from the RWT to the containment emergency sump. The LPSI pumps are automatically stopped when the RAS is generated.

The HPSI flow is throttled post-RAS to a constant value. Additional throttling of the HPSI flow rate may be implemented to match the decreasing rate of heat addition to the RCS by the decay heat.

Containment Spray flow continues until the containment pressure decreases to 4.0 psig or less at which point one Containment Spray pump is turned off.

SBLOCA The same automatic actuations exist for a SBLOCA. However, for a SBLOCA where the pressurizer pressure remains high for an extended period of time, the Operators may take actions to secure the LPSI pumps to avoid running on mini-flow recirculation for an extended period of time. Also, for SBLOCAs the SITs may be isolated prior to these tanks injecting into the RCS.

Page 86 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3g6:

The following table describes the operational status of the ECCS and CS pumps before and after the start of recirculation.

Pump Injection Phase Recirculation Phase HPSI (maximum 2 of 3) On On/Throttled LPSI On Off CS On On Response to Issue 3g7:

Three design basis cases are used to establish the design limits for pump operation and sump performance. Both a hot leg break and a cold leg break are analyzed assuming the failure of a diesel generator (and therefore, the failure of a safety train) as a single failure case. Another single failure case is the loss of a train of the Service Water System which removes a train of Containment Air Coolers from service resulting in reduced containment cooling .

For GL 200-4-02 an additional single failure case was identified. This is the failure of one LPSI pump to turn off upon initiation of recirculation. This single failure would cause additional flow through the strainer, the accumulating debris bed, and the suction piping from the strainer to the pumps. As described in response to Issue 3g1, procedure changes are being implemented to assure the LPSI pumps are either secured prior to RAS, or LPSI flow is throttled to 600 gpm indicated, which could be as high as 800 gpm, and a HPSI pump secured (if two operating).

Response to Issue 3g8:

The water level above the containment floor is defined as a function of pool volume. The volume of water in the sump pool is determined by summing all the sources that contribute to the pool inventory, and subtracting the volume of water in the hold-up volumes.

There are three sources of water that contribute to the containment sump pool inventory: RWT, SITs, and RCS.

1) The total quantity of water delivered from the RWT is the difference between the initial and final tank levels. The initial level is based on the minimum Tech Spec required RWT level, and the final level is based on the maximum RWT level at which a Recirculation Actuation Signal (RAS) occurs.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

2) There are four SITs that provide rapid cooling, and the mass contributed is the sum of all four SITs. SIT inventory is not credited for break sizes 0.08 ft2.

3) The contribution of RCS inventory into the sump pool depends on break size and elevation. For conservatism this source is not included in the computation of sump water level height.

Note: No chemical control fluid storage volumes are credited because the charging pumps are not safety-related.

The sump pool inventory is reduced by considering the following hold-up volumes:

1) Water used to fill the containment spray and other piping.

2) Water used to fill the containment sump trench.

3) Water beading on surfaces., condensation, and moisture in containment atmosphere.

4) Water volume lost by spray flow that beads on horizontal surfaces

5) Water condensing on surfaces inside containment

6) Water sequestered in the refueling pool transfer tube and upper guide structure compartments

7) Water sequestered in the Reactor Cavity Compartment.

8) Water in the Cavity Cooling Ventilation System

9) Piping and sump trench volumes

10) Water required to fill the sloped section of the containment floor between elevation 9-9 and elevation 10-0 Water level values based on break size are presented in Table 13 below.

Table 13: Water Level Heights Case Break Size Sump Pool Water (inches)(ft2) Temperature Height RWT and SIT Inventory >3.8 (0.08 ft2) T Sump 140°F 4 -10.25 RWT and SIT Inventory >3.8 (0.08 ft2) T Sump >140°F 4 -8.77 RWT Inventory Only 3.8 (0.08 ft2) T Sump 140°F 4-5.27 RWT Inventory Only 3.8 (0.08 ft2) T Sump >140°F 4-3.80 Page 88 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3g9:

The conservatism of the minimum containment water level is maintained by minimizing the sources of water and by maximizing the volume of water entrapment. Some of the specific examples of water sources that are minimized are given below:

• Minimum RWT inventory

- minimum initial RWT volume allowed by Technical Specifications

- RAS occurs at earliest point in setpoint band

- no water transfer from RWT post-RAS even though it is the preferred source for an additional minute due to valve operation times

• RCS inventory assumed to remain in RCS for all break sizes.

• The sump piping assumed empty up to sump valves.

Response to Issue 3g10:

Assumptions are made to conservatively maximize the amount of water in the atmosphere (i.e.,

minimize the containment sump water level). These are:

• The maximum containment free volume is used.

• The initial humidity in containment is 0%.

• Post accident, the containment atmosphere is assumed to be fully saturated (i.e., 100%

humidity).

• Bounding temperatures are used.

o Warmer air can hold more moisture.

o Maximum post-RAS temperature (approximately 200°F) used for all temperatures The containment spray pipe and other selected pipes are assumed to be empty for the water level calculation.

The hold up of water on horizontal surfaces was investigated and it was found that a 1/16" film would account for approximately 450 gallons. This value was doubled to account for the fact that water might Page 89 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 bead on a horizontal surface below the initial surface it beaded on for a total held-up volume of approximately 900 gallons.

The outer wall of Containment is not close enough to the spray nozzles for the containment spray to effectively reach them. The surface areas of the other vertical surfaces that could be sprayed are not sufficient to affect the water level calculation.

Condensation of water vapor released from the RCS and subsequently condensed onto surfaces is estimated to hold-up approximately 1,370 gallons.

The water volume equivalent to the mass of water in the atmosphere is calculated by multiplying the containment free volume by the ratio of the specific volume of saturated liquid to the specific volume of saturated vapor at the temperature of interest. Spray droplets in motion from the spray nozzles to any intersecting surface were not specifically considered in the minimum pool depth analysis. Moisture contained in the containment atmosphere is estimated to be approximately 7,500 gallons.

Calvert Cliffs implemented a modification to increase the size of the line from each refueling cavity drain line to general area of containment from 1 to 8. Increasing this line to 8 eliminates potential water sequestration in the refueling cavities, raises the post-LOCA sump water level, and provides additional margin for ECCS and CSS pump net positive suction head (NPSH) and strainer deaeration. A trash rack strainer is installed over the drain entrance to prevent large debris from clogging the drain. This trash rack is approximately 31/2 ft long, 11/2 ft wide, and 21/2 ft high. The trash rack has approximately 420 equally spaced square openings measuring 2-1/8 on each side.

Response to Issue 3g11:

In the sump water level calculation, the volume occupied by concrete pillars is considered in the displacement of water. Additionally, some miscellaneous structures and components in the sump pool are assumed to displace water.

Page 90 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3g12:

The following water sources are considered as contributors to the containment post-accident pool volume:

• RWT - It is assumed that the RWT provides 49,945.16 ft3 of water that empties to the lower level of Containment. This assumes the RWT is at the minimum water level allowed by the low-level alarm setpoint (including uncertainty) at the start of the accident. It also assumes that RAS occurs at the highest value in the setpoint band, and furthermore that no water transfers from the RWT after a RAS is reached even though the RWT will be discharging inventory to the RCS for over a minute after that time.

• Safety Injection Tanks - For LOCAs greater than 0.08 ft2 in size it is assumed that the inventory from four SITs inject into the RCS. The minimum volume of 1113 ft3 per SIT (Technical Specification 3.5.1) is assumed to inject into the core. Since only passive components separate the SITs from the RCS at the start of an accident the inventory from all four SITs is assumed to empty to the RCS.

Response to Issue 3g13:

Credit is not taken for containment accident pressure in determining the available NPSH.

Response to Issue 3g14:

Containment pressurization is not credited in our pump NPSH calculations. All LOCA cases have sump water temperature above 212°F at some point but none of them have sump water temperature above 212°F at the start of or after recirculation.

The sump pool temperature calculation assumes a single failure of one emergency diesel generator resulting in a loss of one ECCS train (including HPSI and CS pumps and containment air cooler), or the loss of one containment air cooler train and loss of one decay heat removal heat exchanger. There is no sump cooling since heat transfer to the containment basemat is not credited in the analysis. The sump pool temperature analysis also neglects any cooling from the sump pool by means of evaporation.

Finally, a containment pressure of 14.7 psia (as compared to 16.5 psia) is assumed along with 100%

humidity. All of these factors result in a conservatively high prediction of sump pool temperature.

Page 91 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3g15:

The containment accident pressure is set at the vapor pressure corresponding to the sump liquid temperature for sump liquid temperatures greater than 212°F. For the NPSH calculation 1 psi below atmospheric pressure is used (i.e., 13.696 psia) as the containment pressure during a LOCA. This corresponds to the minimum containment pressure that might exist at the start of an accident per Technical Specification.

Response to Issue 3g16:

The maximum sump fluid temperature at which the NPSH margin analysis is performed is 212°F. At this temperature there is no sub-cooled margin, and NPSH available comes only from the static head of water. The NPSH margin is also considered at 140°F because this is the temperature at which chemical precipitates are assumed to form. However, a sub-cooled margin of 27.235 feet also exists at 140°F.

The increased NPSH margin at 140°F due to the 27.235 feet of sub-cooled margin is much greater than the increased head loss due to the effect of chemical precipitates as presented in Table 10b under Issue 3f4 (maximum head loss for valid test being used is 8.160 ft). Therefore, for NPSH margin the limiting condition is at maximum sump pool temperatures as shown in Table 14 below.

Table 14: NPSH Margin at Limiting Sump Temperature Pump Sump Temp NPSH R NPSH A NPSH Margin HPSI 212°F 19.5 22.483 2.983 LPSI 120°F 12.5 42.657 30.157 CS 212°F 23.5 25.130 1.630 Page 92 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3h:

Evaluation The objective of the coatings evaluation section is to determine the plant-specific zone of influence and debris characteristics for coatings for use in determining the eventual contribution of coatings to overall head loss at the sump screen.

1. Provide a summary of type(s) of coating systems used in Containment, e.g., Carboline CZ 11 Inorganic Zinc primer, Ameron 90 epoxy finish coat.

2. Describe and provide bases for assumptions made in post-LOCA paint debris transport analysis.

3. 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.

4. Provide bases for the choice of surrogates.

5. Describe and provide bases for coatings debris generation assumptions. For example, describe how the quantity of paint debris was determined based on zone of influence size for qualified and unqualified coatings.

6. Describe what debris characteristics were assumed, i.e., chips, particulate, size distribution and provide bases for the assumptions.

7. Describe any ongoing containment coating condition assessment program.

Response to Issue 3h1:

A Bechtel construction specification was used to specify the coatings used during plant construction. It identifies the original primers used in Containment as Dimetcote No. 6 (also known as D6) and Mobilzinc

7. The original topcoats were Amercoat 66 and Mobil 89 Series.

Coatings that have been used at Calvert Cliffs since construction are identified in internal plant documents. These documents identify the primer, topcoat, and application standard to be used on the various surfaces inside Containment. A primer of Ameron D6 and a topcoat of Ameron 66 are the primary coatings referenced; however, Valspar 13F12 is used as a primer on some surfaces and Valspar 89 is used as the corresponding topcoat. Valspar 13F12 is the same as Mobilzinc 7 and Valspar 89 is the same as Mobil 89 Series.

The current service level 1 coatings allowed to be used in containment at Calvert Cliffs are Carboline Carboguard 890 metal primer, Carboline Starglaze 2011S concrete primer, and Carboline Carboguard 890 topcoat.

Page 93 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Also in containment are multiple coatings of unknown pedigree. Most of these coatings were applied to equipment and small components by the original equipment vendor. These unqualified coatings are tracked in a calculation.

Response to Issue 3h2:

All coatings in the zone of influence, and all coatings of unknown pedigree (i.e., no proof it was ever qualified) are assumed to fail as 10 m particles and transport to the strainer. Degraded qualified inorganic zinc (IOZ) coatings are also assumed to fail as 10 m particles and transport to the strainer.

As discussed in Response to Issue 3c4 , for epoxy coatings that were installed as qualified, but subsequently found to be degraded per site inspection procedures, fail as chips. During head loss testing these chips were shown not to be drawn to the debris bed even when dropped in front of the strainer, and normal test loop agitation was in process. This confirmed the Reference (17) study which demonstrated that paint chips will not transport in sump pool velocities less than 0.2 ft/sec.

Degraded qualified coatings systems used at Calvert Cliffs are of a comparable nuclear grade to those tested by Keeler and Long. Calvert Cliffs verified that the coatings applied were of a nuclear grade comparable to those in the K&L report [Reference (7)]. However, the inorganic zinc primers will fail as particulates and the epoxy top coats will fail as chips (greater than 1/32").

Additional testing was performed to investigate the transportability of coatings chips. The test of transportability of coatings chips used coating chips size distribution of 1-4 mm. Results of transport test for these coating chips are provided in Figure 17 below. These results show that at high flow rates, 8 times nominal, average transport is well under 1 meter (40 inches) from the introduction point for settlement equal to the entire depth of the containment pool. The test flow rates were much greater than expected in the plant post-LOCA. Transport distances are negligible for the size of the Containment at Calvert Cliffs.

Page 94 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 17: Coating Transport Test Results Response to Issue 3h3:

The head loss testing used scaled quantities of coatings as part of the strainer debris load. For the Summer 2010 head loss testing Silicon Carbide was used as a surrogate material for coatings. For the late Fall 2008 head loss testing Stone Flour was used as a surrogate material for coatings.

These surrogate materials were used for coatings assumed to fail as 10 m particles. Actual paint chips made of Carboline Carboguard 890 were used to simulate qualified, but degraded epoxy coatings. The size distribution of the paint chips was controlled by sieving.

Response to Issue 3h4:

Silicon Carbide particles have a median sphere diameter of 9.3 +/- 1 m, and Stone Flour has a medium sphere diameter of 7.7 m. Coatings that fail as particulate are assumed to fail at a conservatively small size of 10 m particles (page 21-22 of Ref. 1). Since an equivalent volume of surrogate was used in head loss testing, and the surrogate has a smaller particle size in order to obtain an equivalent volume a larger number of particles were used. Since it is the effect of individual particulate filling interstitial voids in the fiber bed that increases flow resistance and head loss the use of these surrogates for coatings is conservative.

Page 95 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3h5:

Calvert Cliffs has followed the guidance from Reference (1) for determining the quantity of coating debris. Per Reference (1), Section 3.4.2.1:

• All coating (qualified and unqualified) in the zone of influence will fail,

• All qualified (design basis accident-qualified or acceptable) coating outside the zone of influence will remain intact,

• 100% of the unqualified coatings outside the zone of influence will fail. Degraded-qualified inorganic zinc coatings will fail as particulate, Degraded-qualified epoxy coatings will fail as chips, and Never-qualified coatings will fail as particulate.

A zone of influence of 4.0 L/D was used for epoxy-based coatings, and a zone of influence of 10.0 L/D was used for un-topcoated inorganic zinc primer. All unqualified coatings (including degraded qualified coatings) were assumed to fail, as noted above.

The volume of coatings debris was determined by multiplying the surface area of affected coating by a measured or conservatively assumed dry film thickness (DFT). The DFT of degraded-qualified coatings was assumed to be 12 mils. This is the maximum thickness permitted for replacement Service Level 1 coatings on steel substrate [Reference (7)]. All degraded-qualified coatings are conservatively assumed to consist of an 8 mils epoxy topcoat and a 4 mils IOZ primer. All qualified coatings are conservatively assumed to consist of 4 mils IOZ primer and 6 mils epoxy topcoat which are the maximum thicknesses allowed during construction.

The DFT of never-qualified coatings is variable and obtained from the containment assessments done during the 2003 and 2004 refueling outages. The purposes of these surveys was to locate, identify, and determine the extent of never-qualified coatings within containment. The coating thicknesses were obtained using a digital coating thickness gauge. The majority of these items have a DFT of 1 to 3 mils.

For conservatism a 15% margin was applied to the Alkyd-based never-qualified coating quantities.

Response to Issue 3h6:

See the Response to Issue 3h2 above.

Response to Issue 3h7:

Calvert Cliffs conducts condition assessments of Service Level I coatings inside the Containment once each refueling cycle at a minimum. Generally, all of the accessible areas within the Containment are Page 96 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 visually inspected. As localized areas of degraded coatings are identified, those areas are evaluated and scheduled for repair or replacement, as necessary. The periodic condition assessments, and the resulting repair/replacement activities, assure that the amount of Service Level I coatings that may be susceptible to detachment from the substrate during a LOCA event is minimized and is identified and tracked by the plant coatings condition assessment program.

Page 97 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3i:

Debris Source Term The objective of the debris source term section is to identify any significant design and operational measures taken to control or reduce the plant debris source term to prevent potential adverse effects on the ECCS and CSS recirculation functions.

1. Provide the information requested in GL 04-02 Requested Information Item 2(f) regarding programmatic controls taken to limit debris sources in Containment.

GL 2004-02 Requested Information Item 2(f)

A description of the existing or planned programmatic controls that will ensure that potential sources of debris introduced into Containment (e.g., insulations, signs, coatings, and foreign materials) will be assessed for potential adverse effects on the ECCS and CSS recirculation functions. Addressees may reference their responses to GL 98-04, "A Potential for Degradation of the Emergency Core Cooling System and the Containment Spray System after a Loss-of- Coolant Accident Because of Construction and Protective Coating Deficiencies and Foreign Material in Containment," to the extent that their responses address these specific foreign material control issues. In responding to GL 2004 Requested Information Item 2(f), provide the following:

2. A summary of the containment housekeeping programmatic controls in place to control or reduce the latent debris burden. Specifically for RMI/low-fiber plants, provide a description of programmatic controls to maintain the latent debris fiber source term into the future to ensure assumptions and conclusions regarding inability to form a thin bed of fibrous debris remain valid.

3. A summary of the foreign material exclusion programmatic controls in place to control the introduction of foreign material into the Containment.

4. A description of how permanent plant changes inside Containment are programmatically controlled so as to not change the analytical assumptions and numerical inputs of the licensee analyses supporting the conclusion that the reactor plant remains in compliance with 10 CFR 50.46 and related regulatory requirements.

5. A description of how maintenance activities including associated temporary changes are assessed and managed in accordance with the Maintenance Rule, 10 CFR 50.65.

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

6. Recent or planned insulation change-outs in the Containment which will reduce the debris burden at the sump strainers Page 98 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

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

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

9. Actions taken to modify or improve the containment coatings program Response to Issues 3i1:

Coatings installed inside containment are controlled per procedure which requires involvement of the coatings engineer who maintains the GSI-191 coatings calculations. This ensures only qualified coatings are installed by Maintenance. Maintenance refers to an Engineering Standard on acceptable insulation for use inside containment. Operations procedures ensure tags and signage to be installed in containment is non-floatable.

Several Calvert Cliffs procedures and practices are in place to ensure containment cleanliness is maintained and that debris inside Containment is identified and minimized prior to power operations.

Site procedures require that specific inspections be performed and documented for loose debris prior to containment closeout and an intense search be made of Containment prior to entering Mode 4 for sources of loose debris and corrective actions taken. Another procedure assigns specific ownership responsibilities for plant areas including Containment when accessible, and requires weekly cleanliness inspections and prompt actions to remediate.

Response to Issues 3i2:

As discussed in Item 3i1 Calvert Cliffs has implemented several containment housekeeping actions.

Calvert Cliffs is not a low fiber plant, nor is the Calvert Cliffs strainer susceptible to the thin bed effect; therefore, no specific controls exist to maintain latent debris within analyzed limits. However, latent debris is maintained at a more or less constant value due to normal containment cleanliness initiatives.

Response to Issue 3i3:

An Exelon fleet procedure contains guidance specifically addressing foreign material exclusion (FME) concerns in areas like the Containment and the containment emergency sumps. It classifies the containment emergency sumps as a Special Foreign Materials Exclusion Area (FME Zone-1), and requires an FME project plan for any entry into the sumps. Foreign material exclusion project plans are prepared, reviewed, and approved. The requirements of this procedure are stringent with regard to standards but allow flexibility for adapting an FME project plan for any kind of maintenance evolution.

This procedure also requires FME training for all personnel working in Containment.

Page 99 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 An Engineering Standard is being prepared that will include guidance and restrictions on materials installed or left in containment. An Exelon fleet procedure contains requirements for verifying containment cleanliness through closeout inspections after containment entries.

Response to Issue 3i4:

The Design Attribute Review for the Common Design Process contains a list of topics for which plant changes must be screened against to ensure all potential impacts of the change are properly assessed.

The list of topics specifically identifies the introduction of materials into containment that could affect sump performance. In addition, the introduction of aluminum into containment as well as coated systems in containment are other specific topics to be evaluated. This ensures that future plant changes are properly evaluated for impact on GSI-191 analyses.

Another site procedure controls the requirements for research on the part of maintenance planners for maintenance which could introduce new debris sources into Containment. The procedure has been revised to require that for any maintenance activity that will install any materials in either Unit 1 or Unit 2 Containments expected to remain there during Mode 4 or higher operations, engineering reviews the installation details for impact on the containment emergency sump strainer analyses and must approve the usage of these new materials.

Response to Issue 3i5:

A Calvert Cliffs site procedure establishes requirements for effective implementation of the Maintenance Rule program at the site. It describes approved methods to monitor, trend, establish and modify goals for system, structures and components. Additional site procedures for integrated work management and integrated risk management provide specific guidance on risk assessment and scheduling of maintenance and temporary changes.

Response to Issue 3i6 Calvert Cliffs has undertaken a significant effort to reduce the fibrous insulation debris source term in the design basis LOCA break ZOI. Reducing the amount of fiber decreases strainer head loss and reduces the chemical effects source term. Starting during the 2012 RFO, multiple sections of insulated piping were re-insulated with RMI. The RMI used at Calvert Cliffs is constructed of stainless steel, and does not fail in a manner that contributes to strainer head loss.

Page 100 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3i7:

For Units 1 and 2, calcium-silicate pipe insulation within 17 L/D of the RCS piping was banded on 2 3/4 centers. Calcium-silicate pipe insulation outside of 17 L/D was banded at 6 centers. Any calcium-silicate insulation within 3 L/D of the RCS piping was replaced on Units 1 and 2 with fiberglass insulation.

For margin improvement, two pipes in Unit 1 had insulation removed during the 2010 RFO. The pipes are the shutdown cooling line which was insulated with mineral wool insulation and the pressurizer relief valve line outside of the pressurizer compartment which was insulated with generic fiberglass insulation. The corresponding pipes in Unit 2 are uninsulated.

During the Unit 1 2012 RFO and the Unit 2 2013 RFO the telescoping aluminum ladder from the polar crane was removed to reduce the aluminum content in containment, significant amounts of mineral wool and fibrous insulation were replaced with stainless steel RMI to reduce the debris burden on the strainers.

Response to Issue 3i8:

Valve equipment tags are now made of materials that would sink in water and not transport to the containment emergency sump. In addition, the tags will not delaminate in a post-accident environment.

Calvert Cliffs investigated re-coating the reactor coolant pump motors with qualified coatings to reduce the unqualified coating debris load (approximate surface area is 2000 ft2 per Unit). The reactor coolant pump motor coating was verified to be qualified and no further action is required.

Response to Issue 3i9:

Calvert Cliffs has an existing coatings program that monitors and controls the quantities and types of coatings installed inside Containment. As noted in Reference (18), Calvert Cliffs has implemented controls for procurement, application, and maintenance of qualified coatings used inside Containment that are consistent with the licensing basis and regulatory requirements. This program conducts periodic condition assessments, typically each outage, to verify the adequacy of existing coatings and direct repair/replacement, as necessary. The quantity of unqualified coatings that are added inside Containment is tracked. This program is adequate in its current form to ensure coatings are properly controlled, and that future installations of unqualified coatings are quantified.

Page 101 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3j:

Screen Modification Package The objective of the screen modification package section is to provide a basic description of the sump screen modification.

1. Provide a description of the major features of the sump screen design modification.

2. Provide a list of any modifications, such as reroute of piping and other components, relocation of supports, addition of whip restraints and missile shields, etc., necessitated by the sump strainer modifications.

Response to Issue 3j1:

In Calvert Cliffs Units 1 and 2, a strainer of 6,060 ft2 filtration surface area (nominal) has been installed.

The strainer is CCIs cassette pocket strainer design. The hole size through the filtration surface is 1.6 mm (1/16") with no more than 3% larger holes and no holes larger than 2 mm (0.08"). There are 33 strainer modules divided among three strainer rows. These modules are approximately 3' high. There are 324 pockets in 29 of the strainer modules, and 252 pockets in four of the strainer modules. The pocket dimensions are 84 mm x 90 mm in cross-section, and 200 mm deep. The strainer rows tie into a common duct which directs the flow to the existing containment emergency sump, sometimes referred to as the sump pit. The containment emergency sump is a concrete curb with a steel roof, and contains the inlets to both recirculation headers. See Figure 18.

Figure 18: Strainer Arrangement Page 102 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3j2:

A 16" feedwater pipe support was modified on Unit 2 to allow clearance for one of the strainer rows. A cable tray support was also modified on Unit 2 to allow clearance for the radial duct. These modifications were not required on Unit 1. In addition, the 6" curb around the emergency recirculation sump was notched to allow for installation of the common duct to the sump.

Page 103 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3k:

Sump Structural Analysis The objective of the sump structural analysis section is to verify the structural adequacy of the sump strainer including seismic loads and loads due to differential pressure, missiles, and jet forces. Provide the information requested in GL 2004-02, "Requested Information," Item 2(d)(vii), that is, provide verification that the strength of the trash racks is adequate to protect the debris screens from 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 expanding jets, missiles, the accumulation of debris, and pressure differentials caused by post-LOCA blockage under flow conditions.

1. Summarize the design inputs, design codes, loads, and load combinations utilized for the sump strainer structural analysis.

2. Summarize the structural qualification results and design margins for the various components of the sump strainer structural assembly.

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

4. If a backflushing strategy is credited, provide a summary statement regarding the sump strainer structural analysis considering reverse flow.

Response to Issue 3k1:

Classical and finite-element (ANSYS or ME035) methods were used to analyze the following parts of the strainer:

- Standard cartridges (cartridge depth 200 mm)

- Support structure and duct of a standard module

- Radial Duct

- Sump Cover

- Sump Back Plate Note that the Response to Issue 3k2 below provides descriptions of these strainer parts.

The strainers and their supports were analyzed according to the rules of ASME Section III, 2004 Edition, 2005 Addenda, Subsection NF, "Supports" for Class 2 components [Reference (21)]. These rules were Page 104 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 chosen to provide a recognized standard for structural analyses, however, the strainer components are non-ASME code items, Seismic Category 1.

The standard module analysis assumes an 18 cartridge design which envelopes the smaller 14 cartridge design.

Design Inputs Total weight of modules (2 support structures, duct, cover plate, and cartridges) 18 Cartridge Module 941.73 lbm (427.16 kg) 14 Cartridge Module 802.68 lbm (364.09 kg)

Total debris mass transported to sump = 10,783 lbm (4,891 kg)

(Note: this is an enveloping value used for structural analyses only)

Based on conservative head loss testing conducted in 2008 completed with sodium tetraborate decahydrate (STB) buffer, the differential pressure determined by WCAP-16530-NP based tests was 10.15 psi (700 millibar) at 70°F (21°C). As described in Issue 3o2.10, Calvert Cliffs assumes that aluminum will precipitate out as sodium aluminum silicate and affect head loss at a temperature below 140°F.

Newer head loss tests conducted in 2010 as well as new chemical effects head loss methodology discussed in the response to Issue 3f4 determine the differential pressure due to chemical effects to be much less than 700 millibar. Nevertheless, the strainer is conservatively structurally qualified to a Differential Pressure of 700 millibar.

For both Units:

Operating Basis Earthquake Maximum Horizontal Acceleration 1.96 g at 3 Hz Maximum Vertical Acceleration 0.59 g at 10 Hz Page 105 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Safe-Shutdown Earthquake Maximum Horizontal Acceleration 2.75 g at 3 Hz Maximum Vertical Acceleration 1.11 g at 10 Hz Additional load from shielding blankets = 885.91 lbf (3940.76 N)

Summary of Design Load Combinations The load combinations are summarized in Table 15 below. It was determined in the strainer structural analysis that load combinations 1, 7, and 8 enveloped the other load combinations. Therefore, only load combinations 1, 7, and 8 were analyzed.

Table 15: Load Combinations Used in Emergency Sump Strainer Verification

1. Load Combination Type Temperature (°F) Temperature (°C) 1 W(pool dry) 280 137.8 2 W+OBE(pool dry) 280 137.8 3 W+SSE(pool dry) 280 137.8 4 W+OBE(pool filled) 280 137.8 5 W+SSE(pool filled) 280 137.8 6 W+WD+OBE(pool filled)+PD 70(220) 21(104.4) 7 W+WD+SSE(pool filled)+PD 70(220) 21(104.4) 8 W+AddL 70 21 Variables:

W weight of strainers & supporting structures WD weight of debris PD pressure differential OBE operating basis earthquake Page 106 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 SSE safe-shutdown earthquake AddL additional load caused by radiation shielding blankets For the OBE and SSE cases, a sloshing load also was computed to account for the impact of water sloshing in the sump pool.

Response to Issue 3k2:

The emergency recirculation sump strainer structure consists of two separate structures: the floor structures, and the sump pit structures.

The floor structures consist of the strainer modules themselves which provide the filtration surface area, and a radial duct which channels the flow from the three rows of strainer modules to the sump pit. The radial duct consists of six segments each approximately 4' long. There are 29 strainer modules that are approximately 5' long, and four strainer modules that are approximately 4' long. Each of these strainer modules/radial duct segments are anchored to the concrete floor via an anchor plate at each end.

There are four anchor bolts (1/2" Hilti bolts at 31/2" minimum embedment torqued to 40 ft-lbs) on each anchor plate. A retaining structure is mounted on top of each anchor plate. This retaining structure provides the mounting frame for the radial duct segments and the interior duct of the strainer modules.

The various connections are made using M8, M12, M16, and M20 bolting hardware. The retaining structures are attached to the anchor plates using two M30 bolts. The strainer cassettes (filter surface) attach to the strainer interior duct, and are covered with a deck plate.

The sump pit structure consists of cover plates which cover the sump pit and support beams fixed on and about a concrete curb and additionally supported by short columns that bear directly on the sump floor. Two pairs of mounting brackets are anchored to the concrete curb using four anchor bolts (1/2" Hilti bolts at 31/2" minimum embedment torqued to 40 ft-lbs) on each bracket.

Brackets are used to locate the two side beams. A pair of posts support each side beam and are anchored in a similar fashion as above. Three posts, one at each end and one in the center support the middle beam.

The beams noted above are 140 mm x 140 mm I-beam and are fastened to these mounting brackets/mounting posts.

Page 107 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Ratios of design stress and corresponding allowable stress for various components of the emergency recirculation sump strainer structural assembly are given below. The figures illustrate the component analyzed.

Figure 19: Cartridges Table 16: Cartridges Allowable Calculated Ratio MPa Stress Location and Type MPa (Level C) 1.337 306.9 410.6 Sidewall global + local bending stress 0.8% Strain intensity for collapse load evaluations 0.116 122.8 14.3 Sidewall connection to coverplate shear stress 0.015 204.6 3.12 Sidewall connection to coverplate tension 0.609 252.8 154.0 Upper cover plate bearing stress 0.557 122.8 68.4 Upper cover plate shear stress 0.429 306.9 131.6 Upper cover plate bending stress Page 108 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 0.609 252.8 154.0 Lower cover plate bearing stress 1.56 306.9 479.7 Cartridge pocket bending stress 1.6% Strain intensity for collapse load evaluations 0.035 204.6 7.2 Cartridge pocket tension stress 0.033 122.8 4.07 Cartridge pocket support clip shear stress Figure 20: Standard Strainer Module Page 109 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 17 Standard Module Support Structure Allowable Calculated Ratio Stress Location and Type MPa MPa 0.556 115.1 64 Maximum principle stress intensity - Load 1 (Level A) 0.759 259 196.6 Maximum principle stress intensity - Load 7 (Level C) 0.913 172.65 157.56 Maximum principle stress intensity - Load 8 (Level A) 0.116 259 30 Welded joints (Level C) 0.023 279.77 6.56 M16 leveling screws compression stress 0.045 282.98 12.65 M20 leveling screws compression stress 0.426 239.04 101.9 M16 bolt membrane & bending stress (Level C) 0.058 89.82 5.24 M16 bolt shear stress (Level C) 0.013 92.68 1.21 M20 screws shear stress (Level C) 0.005 246.64 1.2 M12 head screws normal stress - Load 7 (Level C) 0.005 92.68 0.48 M12 head screws shear stress - Load 7 (Level C) 0.449 122.9 55.2 Pin Ø 12/M8 screws shear stress (Level C) 0.181 259.0 46.86 Closure plate of the duct bending 0.042 1515 lb f 64.2 lb f Loads on anchorage - normal 0.030 3040 lb f 92.55 lb f Loads on anchorage - shear The bulk of the support structure is not loaded by the pressure differential created due to debris and chemical effects. However, the cartridge to duct cover and bottom are addressed in the cartridge section above. The module components are loaded by seismic effects including sloshing.

Page 110 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 21: Radial Duct Page 111 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 18: Radial Duct (nominal for all segments)

Allowable Calculated Ratio Stress Location and Type MPa MPa 0.002 82.74 0.18 Global bending of duct shear stress - Load 8 (Level A) 0.003 206.85 0.7 Global & local bending of cover plate - Load 8 (Level A) 0.007 61.03 0.439 Sidewalls compression stress - Load 8 (Level A) 0.002 122.76 0.21 Global bending of duct shear stress - Load 7 (Level C)

Loads in horizontal directions shear stress - Load 7 (Level 0.003 124.11 0.43 C)

Global bending due to Weight & Earthquakes - Load 7 0.002 306.9 0.67 (Level C) 0.109 306.9 33.3 Local & global bending of cover plate - Load 7 (Level C) 0.074 63.5 4.72 Membrane stress in compression - Load 7 (Level C) 0.053 71.9 3.81 Axial compression of the sidewalls - Load 7 (Level C) 340.3 Global & local bending sidewalls - Load 7 (Level C) 1.11 306.9 1.2% Strain intensity for collapse load evaluation 0.375 17.45 6.55 Inner duct walls - Load 7 (Level C)

The bending stress for the radial duct is above the Level C allowable stress. Plastic-elastic analysis demonstrates that the strain intensity is well below 2/3 of the collapse load and the permanent distortion of the side walls do not lead to loss of function of the duct segment.

Table 19: Analysis of Retaining Structure of Radial Duct Segment 4 Allowable Calculated Ratio Stress Location and Type MPa MPa 0.002 239.04 0.7 Support plate w/anchorage M30/M16 tension (Level C) 0.185 89.82 16.6 Support plate w/anchorage M30/M16 shear stress (Level C) 0.019 92.7 1.8 Connection duct to retaining structure shear stress Page 112 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 0.012 246.64 3.0 Cylinder head screw M12 normal stress - Load 7 0.024 92.68 2.2 Cylinder head screw M12 shear stress - Load 7 0.360 259 93.14 Support legs membrane bending stress (Level C) 0.018 103.6 1.83 Support legs shear stress (Level C) 0.124 259 32.2 Closure plate of the duct bending stress (Level C) 0.008 1515 lb f 12.5 lb f Anchor plate w/4 Hilti Kwik Bolts 111 tension 0.096 3040 lb f 292.5 lb f Anchor plate w/4 Hilti Kwik Bolts 111 shear Table 20: Analysis of the Duct Structure of Radial Duct Segment 1 Allowable Calculated Ratio Stress Location and Type MPa MPa 0.002 82.74 0.18 Global bending of duct shear stress 0.002 206.85 0.35 Global & local bending of cover plate 0.006 82.3 0.51 Sidewalls compression stress 0.001 122.76 0.17 Global bending of duct shear stress (Level C) 0.001 122.76 0.13 Loads in horizontal directions shear stress (Level C) 0.001 306.9 0.4 Global bending due to Weight & Earthquakes (Level C) 0.389 306.9 119.4 Global and local bending of cover plate (Level C) 0.082 23.67 1.94 Membrane stress in compression (Level C) 0.089 100.6 9.0 Axial compression of the sidewalls (Level C) 0.187 306.9 57.5 Global & local bending sidewalls (Level C) 1.50 24.8 37.3 Inner duct walls (Level C) 0.67 15.3 psi 10.2 psi Level C Allowable Differential Pressure (NB-3228.3 of Reference (22))

The inner duct walls exhibit greater stress than that allowed for a Level C evaluation. However, an elastic-plastic analysis was performed. The actual differential pressure is below 2/3 of the collapse Page 113 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 differential pressure. Therefore, Segment 1 of the radial duct will not collapse and the radial duct will perform its function.

Table 21: Analysis of Retaining Structure of Radial Duct Segment 1 Ratio Allowable MPa Calculated MPa Stress Location and Type 0.138 89.82 12.4 Support plate w/anchorage M30/M16 shear (Level C) 0.014 92.68 1.32 Connection duct to retaining structure shear 0.012 246.64 2.95 Cylinder screw M12 normal stress - Load 7 0.023 92.68 2.16 Cylinder screw M12 shear stress - Load 7 0.116 259 30.0 Support legs membrane bending stress (Level C) 0.013 103.6 1.37 Support legs shear stress (Level C) 0.072 3040 lb f 218.8 lb f Anchor plate w/4 Hilti Kwik Bolts III shear stress Page 114 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 22: Sump Cover Page 115 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Table 22: Sump Cover (700 millibar differential pressure)

Ratio Allowable Calculated Stress Location and Type 0.121 296.6 MPa 35.8 MPa Cover plate bending stress (Level C) 0.166 155.8 MPa 25.8 MPa Stresses in support beam IPB 140 (lateral beams)

(Level C) 0.141 155.8 MPa 21.9 MPa Stresses in support beam IPB 140 (middle beam)

(Level C) 0.205 336.6 MPa 68.9 MPa Adjusting Bolts (bending) (Level C) 0.33 N/A N/A Adjusting Bolts (combined compression, and bending stress ratios) 0.032 177.1 MPa 5.71 MPa Support columns bending stress 0.018 177.1 MPa 3.27 MPa Support columns compression stress 0.58 N/A N/A Anchor Bolts (combined compression/tension, shear, and bending stress ratios)

Response to Issue 3k3:

Calvert Cliffs has approval to use leak-before-break methodology so that the dynamic effects of a LOCA do not need to be considered in the design of structures and components. Emergency Core Cooling System sump recirculation is not required for breaks in other piping systems.

Response to Issue 3k4:

The Calvert Cliffs emergency recirculation sump strainer design does not incorporate a backflushing strategy.

Page 116 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3l:

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 reduce flow to and possibly starve the sump.

Therefore, provide a summary of the upstream effects evaluation including the information requested in GL 2004-02, "Requested Information," Item 2(d)(iv) including the basis for concluding that the water inventory required to ensure adequate ECCS or CSS recirculation would not be held up or diverted by debris blockage at choke-points in containment recirculation sump return flowpaths.

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

2. Summarize measures taken to mitigate potential choke points.

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

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

Response to Issue 3l1:

The lower level of Containment is open and contains no compartment or choke point which could prevent water from flowing to the sump.

The flow path of water from the Containment Spray System is from the containment dome area and falls into the refueling pool cavities and directly into lower containment. The refueling pool cavities drain to the sump through the enlarged drain lines with trash racks to prevent blockage by large pieces of debris.

Response to Issue 3l2:

The drain flow path from the refueling pool cavities to the lower level of containment was modified to increase the diameter of the line to 8 for the entire distance. A trash rack was installed over the drain opening in the refueling pool cavities to eliminate potential water sequestration in the refueling pool cavities.

Response to Issue 3l3:

There are no curbs of sufficient dimension to impact water flow to the sump.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3l4:

Potential blockage of the refueling pool cavity drains was discussed in Issue 3I1 and 3I2 above. The reactor cavity drains were inspected via camera and found to be functional. For breaks that originate in the cavity it must be assumed that debris blocks the drain. The door to the reactor cavity is not water-tight; therefore, it is assumed that the cavity water-level is the same as that in the rest of the lower-level of containment.

Page 118 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3m:

Downstream effects - Components and Systems The objective of the downstream effects, components and systems section is to evaluate the effects of debris carried downstream of the containment sump screen on the function of the ECCS and CSS in terms of potential wear of components and blockage of flow streams. Provide the information requested in GL 04-02, "Requested Information," Item 2(d)(v) and 2(d)(vi) regarding blockage, plugging, and wear at restrictions and close tolerance locations in the ECCS and CSS downstream of the sump. If approved methods were used (e.g., WCAP-16406-P), briefly summarize the application of the methods. The objective of the downstream effects, components and systems section is to evaluate the effects of debris carried downstream of the ECCS Sump screen on the function of the ECCS and CSS in terms of potential wear of components and blockage of flow streams. Provide the information requested in GL 04-02 Requested Information Item 2(d)(v) and 2(d)(vi) regarding blockage, plugging, and wear at restrictions and close tolerance locations in the ECCS and CSS downstream of the ECCS Sump.

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

The basis for concluding that inadequate core or containment cooling would not result due to debris blockage at flow restrictions in the ECCS and CSS flowpaths downstream of the ECCS 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 ECCS Sump screen's mesh spacing and state the basis for 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-tolerance subcomponents in pumps, valves and other ECCS and CSS components are not susceptible to plugging or excessive wear due to extended post-accident operation with debris-laden fluids.

3m1. If NRC-approved methods were used (e.g., WCAP-16406-P with accompanying NRC SE) briefly summarize the application of the methods. Indicate where the approved methods were not used or exceptions were taken, and summarize the evaluation of those areas.

3m2. Provide a summary and conclusions of downstream evaluations.

3m3. Provide a summary of design or operational changes made as a result of downstream evaluations.

Response to Issue 3m1:

Reference (8) is used to evaluate the downstream components for the effects of plugging/wear with no exceptions. A bounding debris source term was used in this evaluation addressing all potential LOCA scenarios. All particulate debris is assumed to transport through the system, and not deplete over 30 Page 119 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 days. A conservative wear equation which does not use any debris size distribution was used in the wear analysis of downstream components excluding pumps.

In the evaluation of pump wear, the size distribution from Table I-1 of WCAP-16406 was used for unqualified coatings to determine the amount that passes through the strainer. The pump wear evaluation also does not model any depletion over time for unqualified coatings.

The use of Table I-1 of WCAP-16406 for unqualified coatings is conservative when compared to using a uniform 10 m distribution. Based on Section F8 of WCAP-16406-P-A, 10 m debris particles cause erosive wear of pump clearances. Per Equation F6-1 of WCAP-16406-P-A, the erosive wear rate caused by particles less than 100 m is reduced by multiplying the mass of the particles by the square of the ratio of the debris size to 100 m. Therefore, the mass of debris with a size equal to 10 m is reduced to (10 m/ 100 m)2 = 0.01 = 1% of the original quantity. Thus, if the unqualified coating at Calvert Cliffs were modeled using 100% 10 m particles, effectively 1% of the total amount of unqualified coatings would contribute to wear in the pumps. The pump wear evaluation size distribution based on Table I-1 of WCAP-16406 resulted in 26.9% of the total amount of the unqualified coatings going downstream of the sump screen and never getting depleted. It did not credit size distribution for reducing the effective concentration of unqualified coatings. Thus, 26.9% of the total amount of unqualified coating conservatively contributes to wear in the pumps as compared to 1% that would result from using a 10 m uniform distribution.

The downstream effects calculations used fine fiber debris load masses from 2,930 lb m to 4,400 lb m which is two to three times greater than the maximum fine fibrous debris load predicted on the strainer for a double-ended guillotine break of the RCS Hot Legs and Cold Legs.

Response to Issue 3m2:

Testing of a replacement HPSI pump cyclone separator was performed by Wyle Labs in May and June 2008. The testing demonstrated that the selected replacement cyclone separator would not plug and would not erode sufficiently to defeat its function. Replacement of all HPSI pump cyclone separators with the tested unit was completed by June 30, 2008.

Evaluation of the HPSI and Containment Spray pump mechanical seals determined that testing was not needed.

Debris loads for the downstream analytical evaluations are based on bypass testing of the CCI strainer.

The sump strainer opening consists of 1.6 mm (1/16") diameter holes. A post-installation examination Page 120 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 inspects for gaps at all strainer interfaces/joints. The acceptance criterion is no gap greater than 1/32" can remain. These small openings will ensure no large particles enter the downstream recirculation piping.

Impeller / casing wear of the HPSI, LPSI, and Containment Spray pumps was performed using bounding debris bypass quantities. All static piping components and valves were evaluated according to methods of Reference (8) as noted in Response to Issue 3m1 above. Most piping components pass the evaluation criteria for plugging and wear. Those that did not pass the evaluation criteria were shown to have no adverse effect on component function.

Response to Issue 3m3:

Replacement of the HPSI pump cyclone separators was the only design modification change required as a result of Calvert Cliffs downstream effects evaluations. The only operational change was to revise the Emergency Operating procedures to ensure that when the HPSI MOVs are throttled they are still at least 30% open to avoid excessive wear.

Page 121 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3n:

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

1. Show that the in-vessel effects evaluation is consistent with, or bounded by, the industry generic guidance (WCAP-16793), as modified by NRC staff comments on that document. Briefly summarize the application of the methods. Indicate where the WCAP methods were not used or exceptions were taken, and summarize the evaluation of those areas.

Response to Issue 3n1:

The methods described in WCAP-16793-NP-A [Reference (19)] as modified and approved by the NRC (refer to ADAMS accession No. ML15096A012) were used to evaluate downstream effects on the fuel and in the reactor vessel. A bounding debris source term was used in this evaluation addressing all potential LOCA scenarios. The 14 limitations and conditions presented in the Safety Evaluation on WCAP-16793 were addressed in the evaluation.

The fuel used at Calvert Cliffs is Framatome (formerly AREVA) Advanced CE-14 HTP/HMP Fuel with FUELGUARD lower end fitting. For this hardware, WCAP-16793 establishes a 15 g/FA fiber limit to assure long-term core cooling provided the flow per fuel assembly (FA) does not exceed 44 gpm. The maximum flowrate per fuel assembly at Calvert Cliffs is 6.9 gpm which assumes a LPSI pump failed to trip and is operating at 800 gpm, and a HPSI pump is at a conservatively high flow of 700 gpm. Calvert Cliffs has demonstrated an in-vessel fiber loading ranging from 7.6 to 14.4 grams of fiber per fuel assembly (7.6 g/FA to 14.4 g/FA) depending upon whether containment spray flow split is credited for debris diversion from the core region. Both fiber bypass quantities (7.6 g/FA and 14.4 g/FA) are based on a hot leg break with cold leg recirculation. The grams of fiber per fuel assembly would be less for a cold leg break since some fiber will spill out the break before reaching the core.

WCAP-16793 also presents a method for evaluating debris deposition on the fuel rods (LOCADM). The Calvert Cliffs LOCADM evaluation demonstrated acceptable deposition thickness and acceptable long-term core cooling. The maximum cladding temperature was 365.2°F resulting in a margin of 434.8°F based on the allowable maximum cladding temperature of 800°F. The maximum total LOCA generated debris deposition thickness was 872.2 microns or 34.3 mils as compared to the allowable of 50 mils.

The amount of fiber that transports to the reactor core was determined by the strainer vendor performing scaled fiber bypass testing using a prototypical fiber debris mix and a nominal strainer flow rate. Two bypass tests were performed, and the results from the test having the higher amount of fiber bypass were used in subsequent calculations.

Page 122 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 A similar bypass test was performed by the same vendor for the Salem Nuclear Generating Station.

Following an extensive review of the Salem test work, the NRC accepted the Salem response to fiber bypass to the core, which included an adjustment factor to be applied to the original fiber bypass test results.

Calvert Cliffs used the same evaluation approach as approved by the NRC for the Salem Station, and following discussions on July 2, 2014, Calvert Cliffs submitted their fiber bypass calculation for NRC review (ADAMS Accession No. ML15096A012).

In 2018 the Calvert Cliffs fiber bypass calculation was updated to reflect the latest input data. The calculation methodology itself is nearly the same as that used in the original version. The only notable difference is that during the computation of the fiber quantity predicted to bypass the test loop fiber bypass capture screen, it is assumed that all fibers shorter than or equal to the largest capture screen dimension (0.44 mm) penetrate through the capture screen. This is different from the original version, which assumed all fibers shorter than or equal to 0.50 mm penetrate through the capture screen. While it is possible that some fibers longer than 0.44 mm may have passed through the fiber bypass capture screen this is offset by the fact that some fibers less than 0.44 mm will be filtered out on the fiber bypass capture screen.

After the strainer bypass test results are adjusted using the Salem methodology the resultant fiber bypass quantity is 14.4 grams per fuel assembly. The adjustment factor was also updated to be correlated to the total captured mass in the fiber bypass test.

This result conservatively assumes that all fiber which passes through the sump strainer transports to the reactor fuel assemblies; i.e., no credit is taken for containment spray flow split reduction.

Page 123 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3o:

Chemical Effects The objective of the chemical effects section is to evaluate the effect that chemical precipitates have on head loss and core cooling.

1. Provide a summary of evaluation results that show that chemical precipitates formed 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 results, or deposit downstream of the sump screen to the extent that long-term core cooling is unacceptably impeded.

2. Content guidance for chemical effects is provided in Enclosure 3 to a letter from the NRC to NEI dated September 27, 2007 (ADAMS Accession No. ML072600372).

2.1 Sufficient Clean Strainer Area: Those licensees performing a simplified chemical effects analysis should justify the use of this simplified approach by providing the amount of debris determined to reach the strainer, the amount of bare strainer area and how it was determined, and any additional information that is needed to show why a more detailed chemical effects analysis is not needed.

2.2 Debris Bed Formation: Licensees should discuss why the debris from the break location selected for plant-specific head loss testing with chemical precipitate yields the maximum head loss. For example, plant X has break location 1 that would produce maximum head loss without consideration of chemical effects. However, break location 2, with chemical effects considered, produces greater head loss than break location 1. Therefore, the debris for head loss testing with chemical effects was based on break location 2.

2.3 Plant Specific Materials and Buffers: Licensees should provide their assumptions (and basis for the assumptions) used to determine chemical effects loading: pH range, temperature profile, duration of containment spray, and materials expected to contribute to chemical effects.

2.4 Approach to Determine Chemical Source Term (Decision Point): Licensees should identify the vendor who performed plant-specific chemical effects testing.

2.5 Separate Effects Decision (Decision Point): State which method of addressing plant-specific chemical effects is used.

2.6.i AECL Model: Since the NRC USNRC is not currently aware of the testing approach, the NRC USNRC expects licensees using it to provide a detailed discussion of the chemical effects evaluation process along with head loss test results.

2.6.ii AECL Model: Licensees should provide the chemical identities and amounts of predicted plant-specific precipitates.

2.7.i WCAP Base Model: For licensees proceeding from block 7 to diamond 10 in the Figure 1 flow chart [in Enclosure 3 to a letter from the NRC to NEI dated September 27, 2007 (ADAMS Accession No. ML0726007425)], justify any deviations from the WCAP base model spreadsheet (i.e., any plant specific refinements) and describe how any exceptions to the base model spreadsheet affected the amount of chemical precipitate predicted.

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ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 2.7.ii WCAP Base Model: List the type (e.g., AlOOH) and amount of predicted plant-specific precipitates.

2.8 WCAP Refinements: State whether refinements to WCAP-16530-NP were utilized in the chemical effects analysis.

2.9.i Solubility of Phosphates, Silicates and Al Alloys: Licensees should clearly identify any refinements (plant-specific inputs) to the base WCAP-16530 model and justify why the plant-specific refinement is valid.

2.9.ii Solubility of Phosphates, Silicates and Al Alloys: For crediting inhibition of aluminum that is not submerged, licensees should provide the substantiation for the following: (1) the threshold concentration of silica or phosphate needed to passivate aluminum, (2) the time needed to reach a phosphate or silicate level in the pool that would result in aluminum passivation, and (3) the amount of containment spray time (following the achieved threshold of chemicals) before aluminum that is sprayed is assumed to be passivated.

2.9.iii Solubility of Phosphates, Silicates and Al Alloys: For any attempts to credit solubility (including performing integrated testing), licensees should provide the technical basis that supports extrapolating solubility test data to plant-specific conditions. In addition, licensees should indicate why the overall chemical effects evaluation remains conservative when crediting solubility given that small amount of chemical precipitate can produce significant increases in head loss.

2.9.iv Solubility of Phosphates, Silicates and Al Alloys: Licensees should list the type (e.g., AlOOH) and amount of predicted plant specific precipitates.

2.10 Precipitate Generation (Decision Point): State whether precipitates are formed by chemical injection into a flowing test loop or whether the precipitates are formed in a separate mixing tank.

2.11.i Chemical Injection into the Loop: Licensees should provide the one-hour settled volume (e.g., 80 ml of 100 ml solution remained cloudy) for precipitate prepared with the same sequence as with the plant-specific, in-situ chemical injection.

2.11.ii Chemical Injection into the Loop: For plant-specific testing, the licensee should provide the amount of injected chemicals (e.g., aluminum), the percentage that precipitates, and the percentage that remains dissolved during testing.

2.11.iii Chemical Injection into the Loop: Licensees should indicate the amount of precipitate that was added to the test for the head loss of record (i.e., 100%, 140%).

2.12 Pre-Mix in Tank: Licensees should discuss any exceptions taken to the procedure recommended for surrogate precipitate formation in WCAP-16530.

2.13 Technical Approach to Debris Transport (Decision Point): State whether near field settlement is credited or not.

2.14.i Integrated Head Loss Test with Near-Field Settlement Credit: Licensees should provide the one-hour or two-hour precipitate settlement values measured within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of head loss testing.

Page 125 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 2.14.ii Integrated Head Loss Test with Near-Field Settlement Credit: Licensees should provide a best estimate of the amount of surrogate chemical debris that settles away from the strainer during the test.

2.15.i Head Loss Testing Without Near Field Settlement Credit: Licensees should provide an estimate of the amount of debris and precipitate that remains on the tank/flume floor at the conclusion of the test and justify why the settlement is acceptable.

2.15.ii Head Loss Testing Without Near Field Settlement Credit: Licensees should provide the one-hour or two-hour precipitate settlement values measured and the timing of the measurement relative to the start of head loss testing (e.g., within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).

2.16 Test Termination Criteria: Provide the test termination criteria.

2.17.i Data Analysis: Licensees should provide a copy of the pressure drop curve(s) as a function of time for the testing of record.

2.17.ii Data Analysis: Licensees should explain any extrapolation methods used for data analysis.

2.18 Integral Generation (Alion): Licenses should discuss why the test parameters (e.g.,

temperature, pH) provide for a conservative chemical effects test.

2.19.i Tank Scaling / Bed Formation: Explain how scaling factors for the test facilities are representative or conservative relative to plant-specific values.

2.19.ii Tank Scaling / Bed Formation: Explain how bed formation is representative of that expected for the size of materials and debris that is formed in the plant specific evaluation.

2.20 Tank Transport: Explain how the transport of chemicals and debris in the testing facility is representative or conservative with respect to the expected flow and transport in the plant-specific conditions.

2.21.i 30-Day Integrated Head Loss Test: Licensees should provide the plant-specific test conditions and the basis for why these test conditions and test results provide for a conservative chemical effects evaluation.

2.21.ii 30-Day Integrated Head Loss Test: Licensees should provide a copy of the pressure drop curve(s) as a function of time for the testing of record.

2.22 Data Analysis Bump Up Factor: Licensees should provide the details and the technical basis that show why the bump-up factor from the particular debris bed in the test is appropriate for application to other debris beds.

Response to Issue 3o1:

Debris and other containment sources which could contribute to the formation of chemical precipitates in the sump pool were evaluated using the methodology of Reference (12), WCAP-16530-NP-A. The results of these analyses showed the elemental amounts silicon (Si) and aluminum (Al) expected to be released into the sump pool as well as the predicted quantity of NaAlSi 3 O 8 precipitate. The Argonne Page 126 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 National Laboratory (ANL) solubility equation was also used to credit delayed chemical precipitation until sump pool temperatures of 140°F and below.

Strainer chemical effects head loss testing was conducted in 2008 and 2010 as discussed in the response to Issue 3f4 using NaAlSi 3 O 8 surrogate chemical precipitate prepared in accordance with Reference (12).

This head loss testing showed acceptable strainer performance for all breaks within both Region I, and Region II.

Response to Issue 3o2.1:

Calvert Cliffs is not crediting a simplified chemical effects analysis.

Response to Issue 3o2.2:

The strainer head loss with only non-chemical debris (e.g., fiber and particulate) is negligible for all break sizes and locations. Therefore, the strainer head loss test program was focused on determining locations having maximum head loss when chemical debris was included. As discussed in response to issue 3f4, the chemical effects head loss test program performed in 2008 and 2010 tested multiple plant debris loads to determine the bounding strainer head loss with chemical effects included, and to optimize forthcoming insulation replacements with RMI.

A chemical precipitate calculation was prepared for each debris load option/configuration. The head loss test results show a fairly consistent pattern that tests that resulted in higher conventional debris head loss also had higher combined chemical plus conventional debris head loss.

As discussed in response to issue 3f6, thin bed effects were investigated by using low quantities of the postulated fibrous debris and the entire particulate loading to verify that the CCI strainer does not produce a thin bed effect for the debris from Calvert Cliffs. This also ensures that a break that produces little debris does not produce an unexpectedly high head loss.

Response to Issue 3o2.3:

Calvert Cliffs conducted multiple head loss tests with chemical precipitates, and determined that to minimize the impact of chemical precipitates the existing tri-sodium phosphate buffer would be replaced with sodium tetraborate. The following assumptions or results of calculations were used to determine the chemical effects loading for each break analyzed:

• 100% of the debris dislodged from targets was assumed to transport to the post-LOCA containment pool.

Page 127 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

• The containment spray pH were initially set to 4.5, and the containment sump pool pH was initially set to 7.56. At a recirculation actuation signal (RAS) the containment spray pH was changed to also be 7.56. The buffer is sodium tetraborate (i.e., not TSP). Sump is assumed mixed one full time step after RAS.

• Sump pool water temperature, and containment vapor temperature are determined from the containment accident analysis. The maximum sump water temperature is approximately 276°F and the maximum sump water temperature at the start of recirculation is approximately 209°F.

• The maximum sump pool volume is 69,758 ft3.

• Continuous containment spray for the full duration of the accident.

• Materials in Containment considered in the calculation of chemical effects precipitate with quantity of each as determined in calculations.

o Aluminum metal exposed to sprays - 150 ft2.

Aluminum metal submerged - 0 ft2.

o Fibrous debris, Nukon, Thermal Wrap, generic fiberglass, and mineral wool, except for intact blankets of Nukon and Thermal Wrap. These intact blankets are encased in a tightly woven mesh that does not allow for fluid in the sump to readily pass through the blanket.

o Concrete - 66,300 ft2.

o Calcium silicate from Marinite boards.

o Insulation (for bounding Region II break)

Generic Fiberglass 198.6 ft3 Nukon 655.8 ft3 Temp-Mat 12.9 ft3 Thermal Wrap 912.4 ft3 Mineral Wool 10.06 ft3 o The fiberglass jacketing on permanent lead shielding was assumed to not contribute to chemical effects. This material is specifically designed for high temperature (500°F) and is resistant to attack by acidic and alkaline solutions. This material was included in Calvert Cliffs specific autoclave chemical dissolution testing where no dissolution was observed in test of 10-day duration.

Page 128 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.4:

CCI performed plant-specific chemical effects strainer head loss testing for Calvert Cliffs.

Response to Issue 3o2.5:

The methods of Reference (12), WCAP-16530-NP-A, were used to assess the plant specific chemical effects precipitate loading and testing. Chemical precipitates were produced using the methods of Reference (12). Aluminum solubility was credited for sump fluid temperatures >140°F (see Issue 3o2.8) .

Response to Issue 3o2.6.i:

Calvert Cliffs did not use an AECL model.

Response to Issue 3o2.6.ii:

Calvert Cliffs did not use an AECL model.

Response to Issue 3o2.7.i:

Calvert Cliffs did not deviate from the WCAP base model spreadsheet. The entire precipitate amount generated from a 30-day mission time was added to the test loop and the resulting peak head loss was used to evaluate NPSH margin at the earliest time of precipitate formation (i.e., at a sump pool temperature of 140°F).

Response to Issue 3o2.7.ii:

For all debris cases considered the WCAP-16530 spreadsheet predicted only NaAlSi 3 O 8 (sodium aluminum silicate) precipitate to form. The largest quantity of NaAlSi 3 O 8 predicted from Region I breaks was 46.6 lbm, and for Region II breaks it was 75.3 lbm. The precipitate quantity generated for each of the four limiting Region I and Region II breaks are provided in Tables 4a and 4b contained in Issue 3b4.

Response to Issue 3o2.8:

Calvert Cliffs utilizes one refinement to the methods of WCAP-16530-NP-A [Reference (12)]. Chemical precipitate effects are not considered until the sump pool temperature drops to 140°F and below. This is based on the temperature at which the aluminum based precipitates would be expected to begin forming.

Page 129 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Argonne National Laboratory (ANL) presented aluminum solubility data as a function of pH and temperature in NUREG/CR-7172. This report provides the following equation for aluminum solubility as a function of pH and temperature for temperatures equal to or below 175°F:

[Al(ppm)] = 26980 x 10pH-14.4+0.0243T The break that produces the largest quantity of chemical precipitate (DEGB at Weld 42-RC-11-4) has an aluminum concentration of 1.834 ppm. For conservatism this is doubled to 3.67 ppm. The minimum sump pool pH after 30 days of radiolysis acid generation is 7.18. Using the aluminum concentration and sump pH in the ANL equation yields a precipitation temperature of 138.0°F. Therefore, assuming aluminum precipitation at 140°F is conservative. When determining the total strainer head loss, the chemical debris head loss was included for sump pool temperatures up to 140°F.

Response to Issue 3o2.9.i:

There were no plant-specific refinements used other than those discussed in Issue 3o2.8.

Response to Issue 3o2.9.ii:

Inhibition or passivation of aluminum was not used in determining aluminum corrosion and the resultant chemical precipitates.

Response to Issue 3o2.9.iii:

Solubility was not credited to reduce the quantity of chemical precipitate predicted to form in the containment sump pool.

Response to Issue 3o2.9.iv:

Calvert Cliffs did not deviate from the WCAP Base Model. See Response to Issue 3o2.7.ii for type and maximum amount of precipitate predicted to form.

Response to Issue 3o2.10:

Precipitates are formed in a separate mixing tank.

Page 130 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.11.i:

Precipitates were not formed by injection into the test loop.

Response to Issue 3o2.11.ii:

Precipitates were not formed by injection into the test loop.

Response to Issue 3o2.11.iii:

Precipitates were not formed by injection into the test loop.

Response to Issue 3o2.12:

No exceptions to the procedures of Reference (12) were taken.

Response to Issue 3o2.13:

Credit for near-field settlement in the plant is not taken. Debris and chemical precipitates in the tests were transported to the strainer and lodged in the strainer pockets, on the face of the strainer, or at the base of the strainer. The debris found at the base of the strainer could not be made to enter the strainer pockets even with mechanical agitation. This debris behavior was observed and could not be eliminated. All credited tests demonstrated repeatability. Similar quantities of debris at the base of the strainer under test were observed in all tests.

Near-field settlement of chemical precipitates was not credited in the tests. Chemical precipitates accumulated on the fibrous debris in all locations similar to the accumulation on the debris bed captured by the strainer.

Response to Issue 3o2.14.i:

Calvert Cliffs chemical effects head loss testing did not credit near field settlement.

Response to Issue 3o2.14.ii:

Calvert Cliffs chemical effects head loss testing did not credit near field settlement. No chemical precipitate settled away from the strainer.

Page 131 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.15.i:

The strainer pockets were full of fibrous and particulate debris and a debris bed greater than 6 inches thick had formed on the outside of the strainer immediately prior to chemical precipitate addition.

Agitation was unable to move more debris into the strainer pockets because of the low strainer flow rates. The strainer face flow speed is about 0.002 feet per second and the approach speed for the strainer as it transitions to a more simple shape once it is full is about 0.02 feet per second. Neither flow speed is adequate to maintain debris in suspension for long. Debris that does not get into the pockets during initial loading and subsequent agitation cannot move into pockets later. A typical debris bed from the testing at CCI prior to the introduction of chemical precipitates is shown in Figure 23. This shows that the majority of the debris is on the strainer.

Page 132 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Figure 23: Typical Debris Bed Before Chemical Precipitate Addition Page 133 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.15.ii:

One hour precipitate settling of sodium aluminum silicate (NaAlSi 3 O 5 ) for the 2010 tests is provided in Table 23a below, and in Table 23b for the 2008 tests. The settling tests were performed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of precipitate addition to the test flume.

Table 23a: One-Hour Chemical Precipitate Settlement Volume Percentages for 2010 Tests Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 95% 97% 99% 98% 90% 90% 96%

Table 23b: One-Hour Chemical Precipitate Settlement Volume Percentages for 2008 Tests Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 90% 98% 98% 95% 97% 98% 97%

These results all satisfy the 60% of the total volume or greater within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> acceptance criterion.

Additionally, all results are within 15% of the freshly prepared surrogate volume.

Response to Issue 3o2.16:

Test termination criteria was developed to ensure that the head loss test was only terminated after the strainer head loss had either stabilized, or was decreasing. Test termination criteria were as follows:

1) At the discretion of the Test Director and after consultation with the Calvert Cliffs Representative and with the Test Monitor.

2) Once the final chemical addition has occurred and either of the following conditions is achieved:

a) The test strainer head loss has stabilized to less than a 1% increase per hour for head loss values

>60 mbar or 0.6 mbar for head loss values 60 mbar. If 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> has elapsed since the final chemical addition was completed and the head loss trend is extrapolated to be increasing greater than the allowable stabilization criteria then Calvert Cliffs shall be contacted to decide on test continuation.

b) The strainer head loss is clearly and significantly greater than 50 mbar and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> have elapsed since the final chemical addition was completed.

Page 134 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.17.i:

Calvert Cliffs performed seven strainer head loss tests during the summer of 2010 and seven strainer head loss test during late-2008. Five of these tests from the 2010 testing are being used, and one of the tests from the 2008 testing is being used to qualify the various break cases. Head loss plots were created from data from these tests, and are presented in Section 3f4.

Response to Issue 3o2.17.ii:

Calvert Cliffs did not use data extrapolation methods because the head loss had either stabilized, or was decreasing prior to test termination. Calvert Cliffs uses area-based scaling between the test and the plant design for debris quantities, chemical precipitate quantities, and flow rate through the strainer.

Calculations dependent on head loss testing use the head loss test results without modification. The scaled test parameters were bounding on the containment emergency sump strainer especially for debris loading and flow.

Response to Issue 3o2.18:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Response to Issue 3o2.19.i:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Response to Issue 3o2.19.ii:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Response to Issue 3o2.20:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Response to Issue 3o2.21.i:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Page 135 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Response to Issue 3o2.21.ii:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Response to Issue 3o2.22:

Calvert Cliffs did not perform Alion style Integral Generation testing.

Page 136 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 NRC Issue 3p:

Licensing Basis The objective of the licensing basis section is to provide information regarding any 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) regarding changes to the plant licensing basis. That is, provide a general description of and planned schedule for any changes to the plant licensing bases resulting from any analysis or plant modifications made to ensure compliance with the regulatory requirements listed in the Applicable Regulatory Requirements section of this generic letter. Any licensing actions or exemption requests needed to support changes to the plant licensing basis should be included. The effective date for changes to the licensing basis should be specified. This date should correspond to that specified in the 10 CFR 50.59 evaluation for the change to the licensing basis.

Response to Issue 3p:

No changes to the plant licensing basis requiring prior NRC approval are made.

The description of the containment sump strainer in the UFSAR was updated to reflect the new design that was installed in response to Generic Letter 2004-02. ECCS pump NPSH margin values will be updated once the response to Generic Letter 2004-02 has been completed.

The Chapter 14 UFSAR Accident analyses that reference long-term ECCS cooling, and the containment sump (LOCA & Containment Response) do not require revision, and are not impacted by Generic Letter 2004-02.

The Containment Response accident analysis requires that the Containment Structure be capable of withstanding the pressure and temperature conditions resulting from a postulated LOCA, or main steam line break. The acceptance criteria for the containment response analysis is that the containment pressure and temperature remain below 50 psig and 276°F respectively to ensure that the containment response analysis is performed in accordance with General Design Criteria 10, 40, and 52 with respect to containment heat removal and design margin. The Chapter 14 containment response analysis inputs and assumptions are not impacted by Generic Letter 2004-02 requirements. The peak pressures and temperatures occur 1 - 3 minutes after the LOCA break, and are not impacted by post-accident debris effects. When the containment sump pool temperature has cooled to a temperature where chemical precipitates might form, the containment pressure and temperature will have fallen to values near those before the accident started, and containment design limits will not be challenged.

The LOCA accident analysis requires that the ECCS design meet the 10 CFR 50.46 Acceptance Criteria.

The analysis criterion is applicable to the transient phase of the LOCA. The transient phase is of sufficiently short duration that it is over before the switchover to sump cooling occurs. Therefore, the only 10 CFR 50.46 criterion applicable to the containment sump is Long-Term Cooling which requires decay heat to be removed for the extended period of time required by long-lived radioactivity remaining in the core. The Chapter 14 analysis does not provide any details or requirements on the assumptions Page 137 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 and methodologies used to achieve long-term core cooling, it only stipulates that the core temperatures remain low, and decay heat be removed. As discussed in this response, the testing and analyses performed in response to Generic Letter 2004-02, combined with emergency operating procedures demonstrate that at Calvert Cliffs the containment sump will be able to support long-term core cooling under the most limiting LOCA conditions.

The principles and assumptions required by Generic Letter 2004-02 were used to evaluate the effects of post-accident debris generation on the containment sump recirculation system. NEI 04-07 (Reference 1), Section 6, was used to evaluate LOCA breaks using the Alternate Break Size Approach. Under this approach LOCA breaks less than or equal to a 14" Sch. 160 break (a Region I break) must meet the full deterministic criteria required by Reference 1 without qualification whereas breaks larger than a 14" Sch. 160 Break (a Region II break) must still demonstrate successful strainer performance using for the most part design basis rules, but some latitude in crediting operator actions and non-safety-related equipment to accomplish successful event mitigation.

Calvert Cliffs can show successful mitigation of all Region I and Region II LOCA break sizes. For the limiting Region II LOCA break (11 / 21 Hot Leg break at SG) it is necessary to secure the remaining Containment Spray pump shortly after containment atmospheric conditions permit. However, even if this action were not taken and pump distress resulted, operator actions that currently exist in station procedures would be implemented. These actions include turning off and/or reducing unnecessary flows to the strainer in the event that ECCS pump distress is detected including stopping Containment Spray flow. These actions are currently in station procedures and are addressed in operator training.

Additional defense-in-depth actions are also identified, and are currently in station procedures (e.g.,

injection from a refilled RWT). Any additional actions required for a Region II break are not expected until the recirculation sump pool would cool below 140°F (approximately 11-18 days into the event for the design basis case).

The implementation of NEI 04-07, including the Alternate Break Size Approach, was reviewed under 10 CFR 50.59 and determined not to be an adverse change as it is a new evaluation methodology that does not replace any existing post-accident debris mitigating strategy currently in the UFSAR. Prior to Generic Letter 2004-02 Calvert Cliffs did not have a LOCA-break debris generation analysis. Previously, the only analytical detail for the containment sump strainer in the ECCS pump NPSH evaluation was to assume 50% blockage of the sump screen. With the advent of Generic Letter 2004-02, plant specific debris generation analyses and conservative plant specific head loss testing have been performed to demonstrate that the containment sump strainer will be able to support long-term core cooling and containment heat removal during a LOCA. The response to Generic Letter 2004-02 and the use of NEI 04-07 to evaluate post-accident debris effects on LOCA mitigation efforts will be summarized in the UFSAR.

Furthermore, at Calvert Cliffs with the application of Leak-Before-Break the mechanical structural loads associated with the dynamic effects of a large-break LOCA in the RCS Hot Legs or Cold Legs is no longer part of the plant design basis. Instead, only breaks of piping connected to the RCS Main Loop piping are Page 138 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 postulated. Therefore, use of the Alternate Break Size methodology is congruent with the existing plant design basis.

In summary, all LOCA break sizes can be successfully mitigated using station procedures and standard accident recovery principles. Successful mitigation of the limiting Region II break size during long-term core cooling may require use of existing operator actions to prevent ECCS failures when the sump pool is cooled below 140°F. The UFSAR will be updated to summarize the response to Generic Letter 2004-02 and reflect the use of NEI 04-07 as a new methodology to evaluate post-accident debris effects on the containment sump system. No prior NRC approval is required for the changes discussed herein, and no need for exemption from regulations is identified.

Page 139 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02

REFERENCES:

(1) Safety Evaluation on NEI 04-07, Revision 0, December 2004, Pressurized Water Reactor Sump Performance Evaluation Methodology, ADAMS Accession Number ML043280007.

(2) C.D.I. Report No. 9606, Revision A, Air Jet Impact Testing of Fibrous and Reflective Metallic Insulation, included in Volume 3 of GE Nuclear Energy Document No. NEDO32686A, DRF A74 00004, Utility Resolution Guide for ECCS Suction Strainer Blockage, dated October 1998.

(3) WCAP16727P, Revision 0, Evaluation of Jet Impingement and High Temperature Soak Tests of Lead Blankets for Use Inside Containment of Westinghouse Pressurized Water Reactors.

(4) NRC Audit Report, Indian Point Energy Center Corrective Actions for Generic Letter 2004-02, ADAMS Accession Number ML082050433.

(5) Wyle Laboratories Report No. 54497R07, Revision B, dated August 31, 2007, Jet Impingement Test of Electromark Labels and Thermal and Fire Barrier Insulation.

(6) SL-009195, Revision 0, dated November 9, 2007, Wyle Jet Impingement Testing Data Evaluation.

(7) SP-0898, Revision 2, dated April 18, 2004, Specification for the Safety-Related Level 1 coating Applications inside reactor Containment Building..

(8) WCAP-16406-P-A, Revision 1, dated March 2008, Evaluation of Downstream Debris Effects in Support of GSI-191 with associated NRC SER dated December 20, 2007.

(9) No Longer Used.

(10) No Longer Used.

(11) CA10216, Rev. 0000, Technical Report ALION-REP-CCNPP-7636-01, Calvert Cliffs Low Density Fiberglass Debris Erosion Testing Report, Revision 0, July 30, 2010.

(12) WCAP-16530-NP-A, Revision 0, dated March 2008, Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191.

(13) NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing, dated March 2008.

(14) I. E. Idelchik, Flow Resistance, a Design Guide for Engineers.

(15) No Longer Used.

(16) Regulatory Guide 1.82, Revision 4, Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident, March 2012.

(17) NUREG/CR-6916, dated December 2006, Hydraulic Transport of Coating Debris.

(18) Letter from Mr. C. H. Cruse (CCNPP) to Document Control Desk (NRC), dated November 13, 1998, Response to Generic Letter 98-04, Potential for Degradation of the Emergency Core Page 140 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 Cooling System and the Containment Spray System after a Loss-of-Coolant Accident Because of Deficiencies and Foreign Material in Containment.

(19) WCAP-16793-NP-A, Revision 2, dated July 2013, Evaluation of Long-Term Cooling Considering Particulate, Fibrous and Chemical Debris in the Recirculating Fluid.

(20) Letter from Mr. G. H. Gellrich (CCNPP) to Document Control Desk (NRC), dated July 23, 2010, Request for Additional Information Regarding Generic Letter 2004-02.

(21) ASME B&PVC Section III, Division I, Subsection NF, "Supports," 2004 Edition including 2005 Addenda.

(22) ASME B&PVC Section III, Division I, Subsection NB, Class 1 Components, 2004 Edition including 2005 Addenda.

(23) Keeler & Long PPG Report No. 06-0413, Design Basis Accident Testing of Coating Samples from Unit 1 Containment TXU Comanche Peak SES, April 13, 2006.

(24) Generic Letter 2004-02, PWR Containment Sump Performance.

Page 141 of 141

ATTACHMENT 1 SUPPLEMENTAL RESPONSE TO GENERIC LETTER 2004-02 ENCLOSURE 1 ECCS and CSS SYSTEM FIGURES

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CCNPP Final Response and Close-out to Generic Letter 2004-02 Attachment 2 November 12, 2020

SUMMARY

OF REGULATORY COMMITMENTS The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRCs information and are not regulatory commitments)

COMMITMENT TYPE COMMITTED One-Time COMMITMENT DATE OR Programmatic Action "OUTAGE" (Yes/No)

(Yes/No)

CCNPP EOP-05, Loss of Coolant By 03/31/21 Yes No Accident, will be revised to ensure operating pumps and pump flow rates during a LOCA are consistent with this supplemental response. These include actions to reduce and later secure LPSI flow on a failure of a LPSI pump to stop on RAS, secure Containment Spray flow earlier in event, and additional throttling of HPSI flow.