Text

Response to Request for Additional Information Regarding Generic Letter 2004-02
	ML093220202
Person / Time
Site:	Three Mile Island
Issue date:	11/09/2009
From:	Cowan P; Exelon Generation Co, Exelon Nuclear
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	GL-04-002, TMI-09-107
	Download: ML093220202 (54)
	v • d • e

Exelon Nuclear www.exeloncorp.com Exekln Nuclear 20o Exelon Way Kennett Square, PA 19348 10 CFR 50.54(f)

TMI-09-107 November 9, 2009 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No..50-289

Subject:

Response to Request for Additional Information Regarding Generic Letter 2004-02

References:

(1) Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated September 13, 2004 (2) Letter from K. R. Jury (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Exelon/AmerGen Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated March 7, 2005 (3) Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Exelon/AmerGen Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated September 1, 2005 (4) Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission.

"Exelon/AmerGen Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated December 28, 2007 (5) Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Response to Request for Additional Information Regarding NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors," dated July 27, 2005 (6) Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Three Mile Island, Unit 1 Response to Request for Additional Information Related to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors"," dated November 10, 2008

U.S. Nuclear Regulatory Commission November 9, 2009 Page 2 of 3 (7) Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Supplemental Information to the Three Mile Island, Unit 1 Supplemental Response to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors"," dated February 12, 2009 (8) Letter from P. Bamford (U.S. Nuclear Regulatory Commission) to C. Pardee (Exelon Generation Company, LLC), "Three Mile Island Nuclear Station, Unit 1 -Request for Additional Information Regarding Generic Letter 2004-02, Supplemental Response," dated July 23, 2009 (TAC No. MC4724)

The U.S. Nuclear Regulatory Commission (USNRC) issued Generic Letter (GL) 2004-02 (Reference 1) on September 13, 2004, requesting that addressees perform an evaluation of the emergency core cooling system (ECCS) and building spray system (BSS) recirculation functions in light of the information provided in the GL and, if appropriate, take additional actions to ensure system function. Additionally, the GL requested addressees to provide the USNRC with a written response in accordance with 10 CFR 50.54(f). The request was based on identified potential susceptibility of the pressurized water reactor recirculation sump screens to debris blockage during design basis accidents requiring recirculation operation of ECCS or BSS and on the potential for additional adverse effects due to debris blockage of flowpaths necessary for ECCS and BSS recirculation and containment drainage.

Reference 2 provided the initial AmerGen Energy Company, LLC, now Exelon Generation Company, LLC (Exelon), response to the GL followed by supplemental responses in References 3, 4, and 7. References 5 and 6 responded to requests for additional information regarding the Reference 2 and 4 responses to the GL, respectively.

During the review of the Reference 6 submittal, the USNRC identified various issues that required additional clarification as detailed in the Reference 8 RAIs. Additionally, the NRC staff requested, via email from P. Bamford to W. Croft dated May 27, 2009, Three Mile Island, Unit 1 (TMI, Unit 1) provide a Safety Case that describes how the measures credited in the TMI, Unit 1 licensing basis demonstrate compliance with the applicable USNRC regulations as discussed in GL 2004-02.

The USNRC staff conducted three (3) public meetings (teleconferences) to discuss these remaining issues with TMI, Unit 1 on August 11, 2009, September 23, 2009, and October 19, 2009. The purpose of these.meetings was for Exelon to discuss its proposed path forward for resolving the remaining issues regarding GL 2004-02 at TMI, Unit 1. A written response from Exelon was requested by the USNRC within 90 days of the August 11, 2009, public meeting (teleconference).

The Exelon Safety Case is provided in Attachment 1 to this letter The Exelon responses to the RAIs are provided in Attachments 2 and 3 to this letter.

There is one (1) regulatory commitment provided in this submittal, shown in Attachment 4. The commitment states that within 90 days of issuance of the final USNRC decision on the acceptability of WCAP-16710-P, and its related supplemental information, TMI, Unit 1 will report how it has addressed the set of 10 questions titled "Issues Generic to Westinghouse Debris Generation Testing," issued in the USNRC RAI dated July 23, 2009 (Reference .8).

U.S. Nuclear Regulatory Commission November 9, 2009 Page 3 of 3 In addition to the RAI responses, and the associated commitment, TMI, Unit 1 is providing revised Tables 14 and 15 associated with References 4 and 7, in Attachment 5. The revised tables provide the current data from the TMI, Unit 1 NPSH Margin Calculation and include the newly analyzed configuration (Case V- one operating LPI pump and two operating BS pumps) requested in the attached RAI responses (USNRC Question 8, Attachment 2). In the NPSH Margin Calculation revision, the limiting (minimum excess NPSH) margin remains 0.1 ft-H 20.

Revised Tables 14 and 15 are being provided in Attachment 5 to this letter for use during the continuing USNRC staff review, and supersede previous submittal of these tables.

This information is being provided in accordance with 10 CFR 50.54(f).

If you have any questions or require additional information, please contact Wendi Croft at (610) 765-5726.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 9 th day of November 2009.

Res t ly Pamela B. C wan Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC Attachment (1) Three Mile Island, Unit 1, Response to Request for Additional Information Related to USNRC Generic Letter 2004-02, Safety Case (2) Three Mile Island, Unit 1, Response to Request for Additional Information Related to USNRC Generic Letter 2004-02, Questions Specific to TMI, Unit 1 (3) Three Mile Island, Unit 1, Response to Request for Additional Information Related to USNRC Generic Letter 2004-02, Questions Generic to Westinghouse Debris Generation Testing (4) Three Mile Island, Unit 1, Response to Request for Additional Information Related to USNRC Generic Letter 2004-02, Summary of Regulatory Commitments (5) Three Mile Island, Unit 1, Response to Request for Additional Information Related to USNRC Generic Letter 2004-02, Revised Tables 14 and 15 cc: Regional Administrator, USNRC Region I Project Manager, NRR, USNRC - Three Mile Island, Unit 1 Senior Resident Inspector, USNRC - Three Mile Island, Unit 1 R. R. Janati, Commonwealth of Pennsylvania

ACRONYMS Used for Attachments 1-5 Alion Alion Science and Technology, LLC NPSH Net Positive Suction Head BS Building Spray NPSHa Net Positive Suction Head available BWST Borated Water Storage Tank NPSHr Net Positive Suction Head required CFD Computational Fluid Dynamics NPSHm Net Positive Suction Head margin DDTS Drywell Debris Transport Study OTSG Once Through Steam Generator DH Decay Heat PWR Pressurized Water Reactor Pressurized Water Reactor Owners DP Differential Pressure PWROG Gru Group EQ Environmentally Qualified PZR Pressurizer GL Generic Letter RAI Request for Additional Information GL 2004- TMI, Unit 1 GL 2004-02 Supplemental RCP Reactor Coolant Pumps 02 SR Response dated 12/28/07 (Reference 1)

GR Guidance Report RCS Reactor Coolant System LANL Los Alamos National Labs SE Safety Evaluation LB LOCA Large Break LOCA TMI, Unit 1 Three Mile Island, Unit 1 LDFG Low-Density Fiberglass TPI Transco Products, Inc LOCA Loss-of-Coolant Accident UNM University of New Mexico United States Nuclear Regulatory LPI Low Pressure Injection Commission MSDS Material Safety Data Sheet ZOI Zone-of-Influence X No. of Diameters related to ZOI (e.g.,

7D or 17D)

REFERENCES Used for Attachments 1-5

1. Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy, Company, LLC) to U.S. Nuclear Regulatory Commission, "Supplemental Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors," dated December 28, 2007

2. Letter from P. Bamford (U.S. Nuclear Regulatory Commission) to C. Pardee (Exelon Generation Company, LLC), "Three Mile Island Nuclear Station, Unit 1 -Request for Additional Information Regarding Generic Letter 2004-02, Supplemental Response,"

dated July 23, 2009

3. Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Three Mile Island, Unit 1 Response to Request for Additional Information Related to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors"," dated November 10, 2008

4. Letter from P. B. Cowan (Exelon Generation Company, LLC and AmerGen Energy Company, LLC) to U.S. Nuclear Regulatory Commission, "Supplemental Information to the Three Mile Island, Unit 1 Supplemental Response to NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors"," dated February 12, 2009

5. WCAP-16710-P, Revision 0, "Jet Impingement Testing to Determine the Zone of Influence (ZOI) of Min-K and NUKON Insulation for Wolf Creek and Callaway Nuclear Operating Plants" dated October 2007

6. Letter from W. Ruland (U.S. Nuclear Regulatory Commission) to A. Pietrangelo (Nuclear Energy Institute) "Revised Guidance for Review of Final Licensee Responses to Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" dated March 28, 2008

7. NEI 04-07, Revision 0, Volume 1, "Pressurized Water Reactor Sump Performance Evaluation Methodology," dated December 2004

8. NEI 04-07, Revision 0,Volume 2, "Safety Evaluation by the Office of Nuclear Reactor Regulation Related to NRC Generic Letter 2004-02,"dated December 6, 2004

9. Letter from S. Smith (U.S. Nuclear Regulatory Commission) to M. Scott (U.S. Nuclear Regulatory Commission), "Staff Observations of Testing For Generic Safety Issue 191 During March 8 and March 9 Trip to the Alion Hydraulics Laboratory, 'dated June 12, 2007

10. NUREG/CR 6808, "Knowledge Base for the Effect of Debris on Pressurized Water Reactor Emergency Core Cooling Sump Performance," dated February 2003

ATTACHMENT 1 Three Mile Island, Unit 1 Response to Request for Additional Information Related to USNRC Generic Letter 2004-02 Safety Case

Attachment 1 Three Mile Island, Unit 1 Safety Case Related to Generic Letter 2004-02 USNRC Request: Safety Case This safety case should describe, in an overall or holistic manner, how the measures credited in the TMI, Unit 1 licensing basis demonstrate compliance with the applicable NRC regulations as discussed in GL 2004-02. This safety case should inform your approach to responding to the RAIs, as well as the staff's review of the RAI responses. As appropriate, it may describe how you have reached compliance even in the presence of remaining uncertainties.

TMI. Unit 1 Response:

The recirculation functions for the ECCS and the BS System for TMI, Unit 1 continue to be in compliance with the regulatory requirements listed in the applicable Regulatory Requirements section of the subject GL under debris loading conditions. The response to USNRC-requested information by TMI, Unit 1 in Reference 1, supported by additional information provided in References 3, 4, and this current submittal, describe the completed corrective actions that ensure this compliance.

Conservatisms Listed below are some of the conservatisms, which TMI, Unit 1 has incorporated into its methodology for meeting GL 2004-02:

1. TMI, Unit 1 utilized a bounded loading strategy for testing inputs. The debris quantities for each major debris category were calculated for the limiting break location for the specific debris type. The maximum insulation debris was generated by a hot leg break, the maximum coating debris (excluding structural steel) was generated by a cold leg break, and the maximum coating debris from structural steel was generated by a hot leg break. The debris quantities from the limiting break locations were combined to provide a bounding debris load.

2. TMI, Unit 1 analyses assumed that 100% of unqualified coatings will fail and applied a transport fraction of 100% to this debris. The quantity of unqualified coatings was increased approximately 25% over the amount documented at each elevation in containment. Many of the components that are coated with an unqualified coating are not exposed to direct spray which would minimize the transport of the failed coating to the sump.

3. TMI, Unit 1 utilized a 5D ZOI for qualified coatings which is greater than the 4D ZOI recommended by WCAP-1 6568-P.

4. TMI, Unit 1 utilized a latent debris load of 300 lbs versus a walkdown determined value of approximately 193 lbs. A transport fraction of 100% was applied to latent debris although some surfaces are protected from direct spray by intermediate level floors or other equipment.

5. TMI, Unit 1 utilized a total of 400 ft2 of tags, tape, and labels versus a walkdown determined value of approximately 332 ft 2 . The walkdown report added 25% to the estimated surface area of tags/labels/tape for each of the 3 containment levels outside of the D-Rings. The surface area estimated for the "A" D-Ring was doubled and applied to Page 1 of 3

Attachment 1 Three Mile Island, Unit 1 Safety Case Related to Generic Letter 2004-02 the "B" D-Ring. This is conservative as the "A" D-Ring includes the PZR and associated equipment. An additional 25% was added to the estimated surface area inside the D-Rings. A transport fraction of 100% was applied to tags/labels/tape although it would be unlikely that many of the tags would be washed from upper levels of containment to the sump.

6. TMI, Unit l's minimum 15" submergence of the top hat modules at minimum credited water level is greater than that used in the testing. Testing was conducted at a submergence of approximately 6" above the top hat modules at prototypical plant, conditions, and no vortexing was observed for the postulated operating conditions of the TMI, Unit 1 sump strainer design.

7. The TMI, Unit 1 NPSH analysis conservatively applies the full debris load at the start of recirculation. In an actual event, several pool turnovers would be required before the full debris load would be present on the strainer. The TMI containment pool contains approximately 231,000 gallons (30,885 ft3 ) at minimum level. At the maximum recirculation flow rate of 8582 gpm, it would take approximately 27 minutes for one pool turnover to occur. In the most limiting case, NPSH margin begins to recover after the first BS pump is secured. The NPSH analysis assumes this pump is secured one hour after initiation of recirculation to allow time for the operator to complete the procedurally required actions to secure the pump. Even in the most limiting case, additional NPSH margin would be available before the full debris bed would be present on the strainer.

8. The TMI, Unit 1 NPSH analysis applies the full impact of the aluminum precipitates as soon as the sump temperature is reduced to 1400 F. The full impact is applied even in the maximum cooldown cases where sump temperature is reduced to 140°F within 1 to 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months following the start of the event. Although there would be limited time for the aluminum precipitates to form in these cases, the full impact is applied in evaluating the NPSH margin and strainer differential pressure.

Impact of OTSG Replacement TMI, Unit 1 will replace both steam generators during the fall 2009 refueling outage (T1 R1 8). As part of this effort, the Nukon insulation on the steam generators will be replaced with RMI. In addition, the Nukon insulation on the hot legs near the steam generators will also be replaced with RMI. Approximately 160 ft 3 of Nukon will be removed from the "A" D-Ring and approximately 130 ft3 will be removed from the "B" D-Ring. The reduction in the Nukon debris quantity for the "A" D-Ring, which contains the largest amount of Nukon, is provided in Table I below. Results are provided for both a 17D and 7D ZOI for comparison purposes. Following steam generator replacement, the most significant source of Nukon insulation inside the D-Ring will be the insulation on the pressurizer in the "A" D-Ring.

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Attachment 1 Three Mile Island, Unit 1 Safety Case Related to Generic Letter 2004-02 Table 1: Reduction in Nukon Insulation from the "A" D-Ring following OTSG Re lacement in T1R18 Quantity of Quantity of Quantity of Quantity of Nukon Nukon Debris Nukon Debris Nukon Debris Debris Transported to Generated Transported to Generated the Sump the Sump 17D ZOI 17D Z0I 7D Z0I 7D ZOI Prior to Steam Generator 682* ft3 369 ft3 237 ft3 199 ft3 Replacement (tested quantity)

After Steam Generator 523* ft3 300 ft3 147* ft3 100 ft3 Replacement

These values include 60 ft3 Nukon added as margin.

The Debris Generation and Transport Analyses have been updated to reflect the changes that will occur as a result of the steam generator replacement. TMI, Unit 1 has not conducted additional debris head loss testing based on the lower debris quantities. The existing head loss test, based on the 199 ft3 of Nukon as described in the TMI, Unit 1 Supplemental Response to GL 2004-02 (Reference 1) is bounding for the post-T1 R1 8 condition and remains the test of record. The NPSH Margin Analysis is based on the test results for the 199 ft3 of Nukon and has not been updated based on the post-T1 R18 condition.

NOTE: Although the Debris Generation and Transport Analyses have been revised to reflect the reduction in the Nukon debris quantities, the responses to the RAIs contained in this submittal are based on the debris loading prior to steam generator replacement. This was done so that the information provided would be consistent with previous submittals and discussions with the USNRC.

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A'TACHMENT 2 Three Mile Island, Unit 1 Response to Request for Additional Information Related to USNRC Generic Letter 2004-02 Questions Specific to TMI, Unit 1

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 The USNRC RAI questions specific to TMI, Unit 1 were formatted to correspond to a previous TMI, Unit 1 RAI submittal (Reference 3). Where a previous RAI reference is applicable it is shown in parenthesis (e.g., USNRC Question X (RAI XX)).

USNRC Question 1 (RAI 2)

The NRC staff (the staff) requested that the licensee justify the 60% small fines/40% large pieces size distribution assumed for jacketed low-density fiberglass debris (e.g., Nukon) generated within a 7D ZOI. This assumption made by the licensee is stated on page 10 of the supplemental response dated December 28, 2007. However, on page 8 of the same response, debris size distribution information presented in Table 2 appears inconsistent with the information on page 10. Specifically, Table 2 indicates that 100% small fines were used within 5D of a break for all Nukon insulation systems, and that a 60%1/40% distribution was used between 5D and 7D. In light of the cited information, please clarify the size distribution assumed for jacketed low-density fiberglass debris generated within a 7D ZOI.

Additionally, as shown in Figure 11-2 in Appendix II to the Generic Safety Issue (GSI) -191 Safety Evaluation Report "Confirmatory Debris Generation Analysis," dated December 6, 2004, for ZOIs smaller than 17D (e.g., 7D or a spherical shell from 5D to 7D), a percentage of up to 100%

small fines, higher than the 60/40 distribution assumed by the licensee, may be conservatively expected. Thus, the licensee's assumption of a 60%/40% distribution at distances less than 7D from the break location does not appear consistent with the data in Figure 11-2 in Appendix II to the safety evaluation, and the staff requested further justification for this assumption in RAI 2. In response to the staff's information request, the licensee stated that results from Westinghouse debris generation testing described in WCAP-16710-P were used to justify the assumed size distribution. The staff is reviewing the methodology used for this testing, and the PWROG is currently in the process of generically responding to the staff's questions on this testing. After the PWROG generically responds to the staff's questions on the Westinghouse ZOI testing, the staff expects the licensee to provide plant-specific justification to resolve this item for TM I-I.

TMI, Unit 1 Response:

Clarification of Size Distribution for Jacketed Nukon (LDFG) within a 7D ZOI The size distribution for jacketed Nukon insulation within a 7D ZOI provided in Table 2 (Reference 1) reflects the size distribution applied in the TMI, Unit 1 Debris Generation Analysis.

For jacketed Nukon insulation within a 5D ZOI, a debris size distribution of 100% small fines was applied. This size distribution was also applied to unjacketed Nukon insulation within a 5D ZOI. For jacketed Nukon insulation within the 5D to 7D ZOI, a size distribution of 60% small fines and 40% large pieces was applied. This size distribution is also reflected in Table 2 of Reference 3.

The USNRC noted that the information in Table 2 (Reference 1) appears inconsistent with the information provided in response to Issue 3c.1 (Reference 1, page 10). The information in the previous response to Issue 3c.1 (Reference 1) briefly described the two approaches that were incorporated in the Debris Generation and Transport Analysis. Initially, a 17D ZOI was applied to Nukon in the first versions of the Debris Generation Analysis. Later, the 7D ZOI was applied to jacketed Nukon insulation based on a comparison of the TMI, Unit 1 insulation system to Page 1 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 the insulation tests reported in WCAP-1 6710-P (Reference 5). Both approaches, 17D ZOI and 7D ZOI, are still included in the Debris Generation Analysis.

Discussion of Assumption of 60%140% Distribution within 5D-7D ZOI Based on a review of the results of insulation tests reported in WCAP-1 671 0-P (Reference 5),

an assumption of 100% small fines for Nukon insulation (jacketed and unjacketed) within a 5D ZOI combined with a distribution of 60% small fines and 40% large pieces beyond 5D (i.e., from 5D to 7D for jacketed Nukon and from 5D to 17D for unjacketed Nukon) was considered to be conservative (Table II, below). As noted in USNRC Question 1, above, the size distributions assumed in the TMI, Unit 1 analysis are not completely consistent with the information provided in the SE (Reference 8). For ZOls smaller than 17D, (e.g., 7D or a spherical shell from 5D to 7D), the USNRC noted that data in Appendix II of the SE (Reference 8) indicates a percentage of up to 100% small fines may be conservatively expected.

In response to USNRC Question 1, above, the Nukon insulation sources for the limiting break location were regrouped into two categories (Table III, below). All jacketed Nukon insulation (to which a 7D ZOI was applied) was grouped into one category and a size distribution of 100%

small fines was assumed consistent with Appendix II of the SE (Reference 8). All unjacketed Nukon insulation (to which a 17D ZOI was applied) was grouped into a second category and a size distribution of 60% small fines and 40% large pieces was assumed. The transport fractions of 100% for small fines and 15% for large pieces were applied consistent with Table 2 (Reference 3). The net result is a reduction in the quantity of Nukon debris transported to the sump from 199 ft3 to 187 ft3 .

Based on a comparison of the two methods, the size distribution provided in Table 2 (Reference

3) is slightly more conservative (results in larger amount of debris at the sump) when compared to the result based on the information provided in the SE (Reference 8).

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Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Table II: Nukon Fiber Locations, Characteristics and Transport Fractions as Provided in Previous Response to RAI 4 (Table 2, Reference 3)

Break ZOI Nukon Location wlo f Pl Placed at Components Total Fiber Generated Size 1 %Nukon of Total Transport TrnptTasote Transported w/top of Break Affected Fraction to the Sump Hot Leg Location (ft) Destroyed Boundary OTSG Top Small 5D 5D Head, Hot Leg 125.19 Fines 100% 100% 125.19 Top Loop PZR middle Large 40% 15% 1.96 5D 7D - 5D section 32.7 Pieces (Shadowed by Small 60% 100% 19.62 RCP) Fines PZR Top and Large 40% 15% 2.27 5D 17D Bottom Heads Pieces (no shadowing Small 60% 100% 22.75 credited) Fines Large 40% 15% 0.43 5D 17D PZR Spray Line1.08+1.30+4.81 Pieces Line Small Fines Fines 60% 100% 4.31 Large 40% 15% 0.27 OTSG "A" Pieces 4%1%02 5D 17 D Ma wa 2 .2 4 +2 .2 4 S mall Manway Small 60%

Fines 100% 2.69 Large 40% 15% 0.09 OTSG "A" 0.77+0.77 Pieces Pee 4%1%00 5D 17D OTG""

Handhole Small FinesFns 60% 100% 0.92 Large 40% 15% 1.64 Hot Leg "A" Pieces 5010Blanket 2.7 Small Fines 60% 100%

Fines 16.42 Large 40% 15% 0.0 PZR Surge Pieces 5D 170 Line 1.03 Small 1 1 Fines Fns 60% 100% 0.62 Total Nukon Generated (ft') 237.41 Total Nukon Transported to the Sump (ft') 199.26 Table 2, Reference 3 originally listed the "Small Fines" as "Fines" Page 3 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Table II: Revised Nukon Fiber Locations, Characteristics and Transport I Nukon Trans Total Fiber %of Total Components Affected Generated Size Nukon Fraction to the Sump Destroyed Fraction t thS (ft 3) (ftz)

Jacketed Nukon Insulation - 7D ZOI Applied Hot Leg "A" 57.12* Small Fines 100% 100% 57.12 PZR middle section 32.7 Small Fines 100% 100% 32.7 Unjacketed Nukon Insulation - 17D ZOI Applied OTSG "A"Top 62.04* Large Pieces 40% 15% 3.72 Small Fines 60% 100% 37.2 OTSG "A"Outlet Nozzle 6.03* Large Pieces 40% 15% 0.36 Small Fines 60% 100% 3.62 PZR Top and Bottom heads 37.91 Large Pieces 40% 15% 2.27 Small Fines 60% 100% 22.75 PZR Spray Line 1.08+1.30 Large Pieces 40% 15% 0.43

+4.81 Small Fines 60% 100% 4.31 OTSG "A"Manway 2.24+2.24 Large Pieces 40% 15% 0.27 Small Fines 60% 100% 2.69 OTSG "A"Handhole 0.77+0.77 Large Pieces 40% 15% 0.09 Small Fines 60% 100% 0.92 Hot Leg "A"Blanket 27.37 Large Pieces 40% 15% 1.64 Small Fines 60% 100% 16.42 PZR Surge Line 1.03 Large Pieces 40% 15% 0.06 Small Fines 60% 100% 0.62 (ftd) 237.41 Total Nukon Generated Total NukonTransported to the Sump (ft') 187.19

Included in 5D ZOI in Table II USNRC Question 2 (RAI 4)

The staff requested that the licensee provide the post-transport size distributions for the reflective metal insulation, and jacketed and unjacketed Nukon insulation debris with justifications for the transport fractions (e.g., erosion effects). The GSI-1 91 Safety Evaluation Report, "Pressurized Water Reactor Sump Performance Evaluation Methodology," states that erosion may be neglected if the licensee follows the baseline methodology and considers transport fractions for large debris pieces. The staff noted one apparent inconsistency in the information that was provided regarding the transport of large pieces of fiberglass. Specifically, the information provided in Table 2 of the RAI response indicates that a transport percentage of Page 4 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 15% for large pieces was assumed; however, a note to Table 2 indicates that large pieces are not transported to the sump, and that erosion is also not considered. Further, the licensee has not provided adequate justification (e.g., computational fluid dynamics and experimental debris transport metrics, test results, etc.) for the 15% assumption. The staff requests that the licensee clarify the transport fraction assumed for large pieces of fiberglass debris, state whether it transports as intact large pieces or eroded fines, and provide the technical basis used to derive this transport fraction. Please also clarify whether the transported large debris was modeled in the head loss testing conducted for TMI-1 and identify its prepared size distribution.

TMI, Unit 1 Response:

Clarification of Assumption for Transport of Large Debris Pieces The USNRC Question 2, above, states that the information in Table 2 (Reference 3) is not consistent with the information provided in Note 2, listed under the same Table. Specifically, Note 2 states that large pieces are not transported to the sump, whereas the information in the Table indicates a 15% transport fraction for large pieces.

Note 2 under Table 2 (Reference 3) was taken from a report that evaluated the applicability of WCAP-1671 0-P (Reference 5) to the Nukon insulation systems used on components in the TMI, Unit 1 RCS. The applicability review provided a comprehensive review of WCAP-16710-P (Reference 5)-and provided recommendations for ZOls and damage level for Nukon insulation. This applicability review included the recommendation to assume large pieces of Nukon debris would not be transported to the sump.

The information contained within Table 2 (Reference 3) was taken from the TMI, Unit 1 Debris Generation Calculation. Although the applicability report recommended that large pieces could be assumed to not transport to the sump, the Debris Generation Calculation applied a 15%

transport fraction for large pieces as identified in Table 2 (Reference 3) and Note 2, Table 2 (Reference 3) is not applicable.

Basis for 15% Transport Fraction Applied to Large Pieces of Nukon Debris A transport fraction of 15% for large pieces was determined in the TMI, Unit 1 Debris Generation Calculation. The CFD model showed that turbulence in the pool is not high enough to suspend large pieces of Nukon throughout most of the pool. Since the large pieces of Nukon would settle in most of the pool, the tumbling velocity is the predominant means of transport. The large pieces of Nukon were assumed initially to be uniformly distributed between the locations where it would be destroyed and the sump (Figure 1, below). This area was overlaid on top of the plot showing the tumbling velocity and flow vectors to determine the recirculation transport fraction. The area where large pieces of Nukon would transport is approximately 15% (856/5582 ft3) of the total initial distribution area (Figure 2, below).

Additional description of the transport analysis was provided in the previous response to RAI 5 (Reference 3).

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Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Modeling of Large Debris in Head Loss Testing The 15% of large pieces assumed to be transported was included in the total quantity of Nukon transported to the sump as identified in Table 2 (Reference 3). This total quantity of Nukon (199 ft 3) was used to determine the quantity of debris to be used in the head loss testing based on the appropriate scaling factors. All Nukon debris used in the head loss test was prepared in the same manner, regardless of whether it was assumed to be transported as small or large pieces. The debris preparation procedure was described in the previous response to RAI 7 (Reference 3) and additional information is provided in the response to USNRC Question 3, below.

East and West D-Rtng Break Debris DI~t~bution 5,58 -

Figure 1: Distribution of small and large piece debris in lower containment (yellow area)

Page 6 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Floor area where .

large fiber would be transported to the sump -- totl.

area- 866 f Figure 2: Floor area where large pieces of Nukonwould transport to the sump USNRC Question 3 (RAI 7)

The staff requested additional information on the size distribution of fibrous debris used during testing and requested that the licensee provide information that justified the fibrous debris used during testing. The licensee stated that small fines were used. However, the staff guidance requests that the fibrous debris sizing be further broken down into small and fine debris categories. Current staff guidance states that thin bed testing should be conducted with only fine (easily suspendable) fiber (until all predicted fine fibers have been added to the test). The licensee response to the RAI did not address the referenced guidance. It is possible, but unlikely, that a thin bed test conducted in accordance with the latest guidance could result in Page 7 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 higher head losses than were attained during the TMI-1 testing. It is more likely that the full load test, if conducted with prototypically sized fiber could have resulted in higher head losses. The licensee should provide information that justifies that the head losses attained during testing were not influenced non-conservatively by the sizing of the fibrous debris used during testing.

TMI. Unit 1 Response:

Response Summary:

The USNRC March 2008 guidance (Reference 6) indicated that the use of excessively coarse fibrous debris in testing will likely result in non-conservative results. Compared to the debris size distributions assumed in the TMI, Unit 1 debris analyses, the test debris preparation procedure resulted in debris sizes that were biased toward the smaller debris size classes described in NEI 04-07 (Reference 7). Test photographs and records provide evidence that the material transported to the strainers was not excessively coarse. Therefore, it is concluded that the TMI, Unit 1 test results were not influenced non-conservatively by the sizing of the fibrous debris used during testing.

Although the TMI, Unit 1 strainer tests were conducted prior to the USNRC March 2008 guidance (Reference 6), the extensive test program conducted by TMI, Unit 1 demonstrated that the thin bed head losses are not controlling for the TMI, Unit 1 strainer design. The test preparation procedure and test methodology utilized for TMI, Unit 1 testing did result in covering the strainer with a mat of fine fibers as shown in the photographs provided below. In all cases, the head losses for the thinner beds were less than the head losses measured for the full load tests.

Response Details:

I. Discussion of Full Load Test:

L.A Discussion of LDFG Debris Size Distribution Assumed in the Debris Analyses:

As noted in Table 2 (Reference 1), the debris size distribution for Nukon assumed in the TMI, Unit 1 debris analysis included small-fines and large pieces. The TMI, Unit 1 analysis application of "small-fines" is consistent with the NEI 04-07 GR (Reference 7) which is fibers and small pieces of sufficient size to pass through grating and readily transport. The division between the small-fines and large pieces is nominally 4". Regarding the further classification and size distribution of "small-fines", there is no specific definition or guidance in the NEI GR (Reference 7), associated SE (Reference 8), or the USNRC March 2008 guidance (Reference 6). However, Appendix II, Section 11.3.1.1 of the SE (Reference 8) stated:

"In the debris generation tests conducted during the DDTS, 15 to 25 percent of the debris from a completely disintegrated TPI fiberglass blanket was classified as nonrecovereable. The nonrecovereable debris either exited the test chamber through a fine-mesh catch screen or deposited onto surfaces in such a fine form that it could not be collected by hand (it was collected by hosing off the surfaces). Therefore, it would be reasonable to assume that 25 percent of the baseline small fine debris Page 8 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 (Fzol) is in the form of individual fibers and that the other 75 percent is in the form of small-piece debris."

Small-fines have been considered to be Class 1 through 6 as described in NUREG/CR-6808 Table 3-2 (From Reference 10, reproduced as Table IV, below). Based on the assumed size definition of less than 4" nominally, Classes 1 through 6 represent "small-fines." For illustration, Class 5 debris is shown in Photograph 1 (From Reference 10, reproduced as Photograph 1, below), below, and represents fiberglass fragments that are defined as "transportable" as they tumble and slide along the floor.

Table IV: NUREG/CR-6808 Table 3-2, Size Classification Scheme for Fibrous Debris No. Description 1 Very small pieces of fiberglass material; 'microscopic' fines that appear to be cylinders of varying LID.

2 Single, flexible strands of fiberglass; essentially acts as a suspending strand.

3Multiple attached or interwoven strands that exhibit considerable flexibility and that, because of random orientations induced by turbulent drag, can exhibit low setling velocities.

4Fiber dusters that have more rigidity than Class 3 debris and that react to drag forces as a semi-rigid body-5Clumps of fibrous debris that have been noted to sink when saturated with water. Generated by different methods by various researchers but easily created by manual shredding of fiber matting.

6 Larger dumps of fibers lying between Classes 5 and 7.

L7 *Fragments of fiber that retain some aspects of the original rectangular construction of the fiber matting. Typically precut pieces of a large blanket to simulate moderate-size segments of original blanket-Page 9 of 36.

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Photograph 1: Fiberglass shreds in size Class 5 Page 10 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 1.3B Discussion of Prepared LDFG Debris Size Distribution for Testing:

The Alion Debris Preparation Procedure used for all TMI, Unit 1 prototype tank testing, including the November 2007 test of record, was designed to produce "small-fine" debris of Classes 1 through 4, finer than that required by NEI 04-07 (Reference 7) (i.e., no pieces in Classes 5 through 7 or 4" debris). The following fiber preparation steps are excerpted from the procedure:

3.0 PROCEDURE (Fiber Preparation) 3.1 This section is used to prepare low density fibrous insulation to be used for testing in the vertical test loop or large flume. These low density fibrous insulations include, but are not limited to Nukon, MINERAL WOOL, and THERMAL-WRAP.

3.1.1 Prepare the insulation material for the shredder by cutting it into 12" square pieces.

Note: If material was procured in a shredded form, skip to step 3.1.42.

3.1.2 Process the insulation material through a shredder. If only a small amount of material is required, it is acceptable to shred the insulation by hand.

3.1.3 Collect the shredded insulation.

3.1.4 Using a representative sample of the shredded insulation, compare the size distribution of shredded insulation with that identified in NUREG/CR-6808, Table 3-2, "Size Classification scheme for Fibrous Debris", or NEAICSNI/R (95)11, Table 3.1, "Fibrous Debris Classification' and Figure 3.1, "Examples of Fibrous Debris Fragments Tested". The desired size classification would be Numbers 1 through 4.

Refer to Appendix 1 of this document.

3.1.5 If all of the shredded insulation, or a portion of all of the shredded insulation is too large compared to the classifications of Table 3-2 in NUREG/CR-6808, or Table 3.1 of NEA/CSNI/R (95)11, then process the large pieces of insulation through the shredder or shred by hand.

3.1.6 Using a representative sample of the shredded insulation, compare the size distribution of shredded insulation with that identified in the previously referenced Tables. The desired size classification would be Numbers 1 through 4.

3.1.7 Repeat the insulation shredding as needed to achieve the desired quantity and size distribution of insulation to be used for the testing as required by the Test Plan.

3.1.8 Shredded insulation that does not satisfy the desired size distribution should be removed from the insulation sample and discarded per the MSDS or the ALION Science & Technology Environmental Health and Safety Manual.

3.1.9 Weigh out the required quantity of processed insulation for testing that meets the desired size distribution as required by the Test Plan.

2 All TMI, Unit 1 fibrous debris was procured in bulk form (i.e., not shredded).

Page 11 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 3.1.10 If the insulation is new (i.e. not aged) use one of the following methods as required by the Test Plan or as directed by the Test Engineer.

Method 1: boil the insulation for 60 minutes. (Note: boiling insulation for 60 minutes is part of the debris preparation methodology adopted by the NRC for use at the UNM vertical loop testing facility.)

Method 2: boil the insulation for 5 minutes. (Note: boiling insulation for 5 minutes is part of the debris preparation methodology adopted by LANL for use at the LANL vertical loop testing facility.)

NOTE: Method 2 was used for TMI, Unit 1.

3.1.11 Put the insulation in a bucket of water at a temperature within +/- 10 TF of the temperature of the water to be used in the testing.

3.1.12 Mix / beat the insulation with paint mixer attached to an electric drill for five minutes or until a-homogeneous slurry is formed.

3.1.13 The insulation is now ready for testing.

I.C Comparison of Prepared Test Debris to Debris Analysis Assumptions:

Although the prototype testing for TMI, Unit 1 was performed prior to the USNRC March 2008 guidance (Reference 6), the debris size distribution established by the debris preparation procedure for the head loss testing was consistent and conservative with respect to the TMI, Unit 1 Debris Generation and Transport Analysis per the definition of "small-fines". The analyses definition considers small fines to include Classes 1 through 6 whereas the debris preparation procedure produces Classes 1 through 4. The TMI, Unit 1 Debris Transport Analysis assumes that 100% of the small fines are transported to the sump as shown in Table 2 (Reference 3).

The amount of small fines plus 15% of large pieces were included in the total debris quantity used in the head loss test (see Response to USNRC Question 2, above). Therefore, with respect to the debris size distribution, the analysis and the testing definitions are conservative and in alignment.

I1. Discussion of Thin Bed Test:

The testing of the TMI, Unit 1 prototype screen with Class 1 through 4 fibers at Alion was performed for both the thin and thick bed testing for TMI, Unit 1. The protocol made no attempt to segregate individual fibers through sieving or other means from the debris mixture. The testing involved a series of tests with debris quantities that would produce debris bed thicknesses from 1/8" up to 2.43". Although the test protocol was designed to encourage debris deposition on the screen through tank turbulence (stirring and trolling motors), this was not always successful in the earlier tests, as was witnessed on one of the USNRC visits (Reference 9).

Page 12 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Table V presents the TMI, Unit 1 prototype testing sequences. The November 2006 test series did not include chemical effects. The data provided below for the 2007 tests was recorded after stabilization of the fiber and particulate debris bed but before addition of the WCAP predicted precipitates. The November 2007 Test 2B is the current design basis loading case.

Table V: TMI, Unit 1 Prototype Testing Sequences Test Date Bed Head Loss Debris Volume Thickness (@ nominally 85 0 F).

4 Nov-2006 0.1" 0.22' Latent Only 1 Nov-2006 3/8" 0.22' Amount added to equivalent to 3/8" uniform bed thickness 3 3 Nov-2006 1.3" 0.36' 250 ft 2B Nov-2006 2.03" 2.51' 388 ft3 2C Nov-2006 2.43" 5.98' 465 ft3 1B Mar-2007' 1.4" 0.4' 269 ft33 2B Nov-2007 1.1" 1.7' 218 ft

USNRC Witness It should be pointed out that the USNRC witnessed the March 2007 Test 1B as documented in a USNRC Trip Report (Reference 9). This report indicated that settling occurred with the small pieces in Test 1B. As a result of this report, Alion implemented additional attention to "agitation" in the November 2007 testing to facilitate transport to the sump screen. The differences in settling between the two tests are illustrated in the response to USNRC Question 6, below. As a result of the preferential sedimentation of the small debris fragments from within the "small-fine" debris used for the testing, the debris actually reaching the screen tended to be comprised predominantly of 'fine" debris. This is consistent with the conditions preferred by the USNRC March 2008 guidance (Reference 6).

Review of the 2006 Tests 1, 3, 4 and 2007 Test 1 B indicates that under a variety of load conditions, the screen design is not susceptible to thin-bed effects. This is consistent with Alion's experience with this particular screen design. This is due to the non-uniform approach velocity and debris deposition. The March 2007 1B testing, as well as the earlier 2006 testing, did notice debris settling of small pieces; however, the screen was completely covered in fines, which is a realistic scenario to produce a thin-bed effect considering some settling of small pieces. In all four cases involving small debris quantities with sedimentation of the larger "small/fine" debris fragments (2006 tests 1, 3, and 4 and 2007 test 1B), the thin-bed head loss is consistently much lower than the limiting load cases head losses. Based on these results, it can be concluded that the thin-bed does not produce limiting head losses. In particular, 2006 Test 3 and 2007 Test 1 B produced essentially identical results, and both tests were completely covered in "fines." Photographs 2 and 3 were taken, by Alion, following draindown after the USNRC witnessed 2007 Test 1 B. Note the uniform deposition and 'line" quality of the debris at the screen surface in Photograph 4.

Page 13 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 The debris load from the November 2007, Test 2B (1.1") represents the design full load. This is the latest test and incorporated the USNRC Staff's feedback on non-prototypical settling in the earlier tests identified in the trip report (Reference 9). Alion implemented additional measures (stirring and trolling motor) to ensure transport to the test screen. The increased agitation and attention to settling produced a head loss consistent with the thicker debris loads from the earlier tests (2006 2B & 2C) and provides a limiting head loss. For this reason, it can be concluded from the head losses produced by the Alion testing that the thin-bed head losses are not limiting in this strainer design, and the maximum or full load debris head loss test is the limiting loading condition.

Page 14 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 USNRC Question 4 (RAI 9)

The staff requested additional information on how the extrapolation of head loss results to the strainer mission time would affect the head loss evaluation. The licensee provided additional information that clarified some aspects of the need to perform an extrapolation of the data to the pump mission time. The licensee response to the RAI is reasonable. In addition, the rate of increase of head loss over the last 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months was very small such that less than one foot additional head loss would likely occur over the strainer mission time. However, the TMI-1 supplemental response states that the limiting NPSH margin for the low pressure injection (LPI) pump single operation is 0.1 ft. This is a relatively small margin. The variance of margin related to time was not provided. Because of the low margin available, the licensee should verify that the evaluation of the head loss test data did not include a non-conservative assumption regarding extrapolation that could affect the available pump margin throughout the mission time.

TMI, Unit 1 Response:

Response Summary:

Based on a review of the application of the head loss test data as discussed below, it is concluded that the TMI, Unit 1 NPSH margin and maximum strainer differential pressure analyses did not include a non-conservative assumption regarding extrapolation of the test data throughout the mission time.

Response Details:

During the TMI, Unit 1 prototype testing, the conventional debris (fibrous insulation, Thermolag, coatings, dirt/dust, and latent fiber) was initially batched into the test tank. Next, the calcium phosphate precipitate was batched into the test tank to determine the stable head loss. After the head loss stabilized with the calcium phosphate precipitate, the aluminum precipitates were added to determine the total strainer head loss (Figure 7, Reference 1). As discussed in the previous RAI response to Issue 3f.10 (Reference 1) the head loss value resulting from the calcium phosphate precipitates applies for sump temperatures above 1400 F.

Below 140 0 F, the head loss value including the aluminum precipitates is applied.

Sump Temperatures Above 140°F The maximum stable strainer head loss measured after the addition of the calcium phosphate precipitates in the TMI Unit 1 head loss test was 1.7 ft. As discussed in the previous response to Issue 3f.10 (Reference 1), the test head loss is adjusted for flow rate and temperature when applied in the NPSH analysis: The adjusted head loss due to the total amount of calcium precipitates is applied from the beginning of recirculation to the time when sump temperatures reach 140 0 F. This includes the time of minimum NPSH margin, which occurs in the first few hours following initiation of sump recirculation. No non-conservative assumptions that could affect the available pump NPSH margin were identified in the application of the head loss test data to the time in which sump temperatures are above 140 0 F.

Plots of NPSH margin for the minimum margin cases for both the LPI and BS pumps are provided in the response to USNRC Question 7, below.

Page 15 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Sump Temperatures Below 140°F The maximum strainer head loss measured after the addition of the aluminum based precipitates was applied in the NPSH analysis for sump temperatures below 1400 F. As discussed in the responses to USNRC RAIs 6 and 9 (Reference 3), the test debris bed failed after the addition of about 96.5% of the chemical debris. The maximum head loss value recorded prior to failure of the debris bed (21.3 ft) was applied in the NPSH Margin Analysis. As discussed in the previous RAI response to Issue 3f.10 (Reference 1), the test head loss is adjusted for flow rate and temperature when applied in the NPSH analysis.

The adjusted head loss based on the maximum observed value of 21.3 ft is applied in the NPSH Margin Analysis when sump temperatures reach 140 0 F. The increase in head loss at 140°F is applied as a step change and is not phased in over time. Following the step change in strainer head loss, the minimum NPSH margin for the LPI pumps is 11.9 ft (See Tables in Attachment 5). The minimum NPSH margin for the BS pumps is 13.6 ft (See Tables in Attachment 5). The minimum margins for both pumps occur in the maximum cooldown Case I and are coincident with the step change at 140 0 F. NPSH margin for both pumps increases later in the event as shown in the figures below. With the significant NPSH margins that are available at the lower temperatures, no non-conservative assumptions that could affect the available pump NPSH margin were identified in the application of the head loss test data to the time in which sump temperatures are below 1400 F.

22 LPI NPSHa, NPSHr, NPSHm cv41C cv43C cv45C O

uI f) i O _____ I NPSHa ;

NPSHm 1 03

... ... i 1

" ." I ce ----- I

--- -- -I --. ---. --- .---. .--- . --- --------

. ........ ............... -- i

- -- --- ---. . ..... . .... .. .... . . . . . =. .

0 5 10 15 20 25 30 Time (days)

GOTHIC 7.2a(QA) Nov1/W2008 12:54:50 Figure 3: LPI NPSH - Maximum Reactor Building Cooldown - Case I Page 16 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 BS NPSHa, NPSHr, NPSHm cv42C cv44C cv46C 0

in Si i i in I

1 "ce. . . . .. . . . ... . . . . . .III . . .. . . . . . .i. .. . .. . . . . , ip

I, . . ..

I IIIi CD) . . .. . . . -.

Cq.. .. . .. ... [.. . ..... .. ... l .. . .. .... . ....... .. . .... . . . ... .. ....... T....................

z inI NPSJr 4- - 1 . i LO ---- -- ---- -- -

0 4 8 12 16 20 24 Time After Switchover (hours)

GOTHIC 7.2atQAI NiOWMW002 12:54:50 Figure 4: BS NPSH - Maximum Reactor Building Cooldown - Case I The maximum strainer head loss is also evaluated to ensure thatthe maximum strainer design differential pressure is not exceeded. The maximum strainer head loss always occurs after the sump temperature reaches 140 0 F, but is dependent upon the timing of termination of BS flow and throttling of LPI flow. As discussed in the previous RAI response to Issue 3f.10 (Reference 1), credit is taken for operator action to secure the BS pumps and reduce LPI flow to ensure the structural limit of 16.15 ft (7 psi).is met for all cases. The maximum strainer head loss of 15.6 ft occurs for the maximum cooldown Case I (See Tables in Attachment 5). Strainer head loss decreases and remains below this value due to the action of securing the first BS pump and subsequent operator actions to throttle LPI flow as shown in the plot below. The operator actions credited for maintaining strainer differential pressure below the design value were shown to be effective. No non-conservative assumptions that could affect the maximum strainer differential pressure were identified in the application of the head loss test data to the time in which sump temperatures are below 1400 F.

Page 17 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 28 Strainer Head Loss cv40C 0

Co 0

0i 0

C\1 0 5 Time (days)

GOTHIC 7.2aOA Ncru/062008 12:54:50 Figure 5: Strainer Head Loss - Maximum Reactor Building Cooldown - Case I USNRC Question 5 (RAI 11)

The staff requested additional information on whether containment overpressure was credited for the strainer flashing evaluation. The licensee provided additional information in this area, but it seemed that the question was not understood. The licensee evaluated flashing at the pump suction, but did not address potential flashing in the debris bed or within the strainer. Flashing within the strainer or debris bed can result in additional head losses. The licensee should verify that the potential for flashing at the strainer has been evaluated or provide the parameters such that the staff can verify that flashing will not occur. The minimum margin to flashing at the strainer should be provided. For example, provide strainer submergence, sump temperature, and strainer head loss as a function of time. If required, provide the minimum available containment pressure at the evaluated times.

Page 18 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 TMI, Unit 1 Response:

Response Summary:

An analysis has been performed to evaluate the potential for flashing within the debris bed. The analysis concludes that flashing of the fluid at the debris bed will not occur. The analysis does not take into account any containment overpressure (pressure over the initial containment pressure).

Response Details:

Based on the review of the vertically oriented screen design in the sump pit, the greatest potential for flashing occurs at the top of the strainer due to the minimum submergence. An illustration of the TMI, Unit 1 strainer is provided in Figure 6. The minimum water level is at elevation 283.9' and the top of the strainer top hat is at elevation 282.6' which provides 1.3' of submergence to the top of the strainer top hat.

NMT.S.

[ i.Water Level 283 .9' Figure 6: TMI, Unit 1 Containment Sump Configuration To evaluate the potential for flashing to occur, the following criteria were considered:

1. If the submergence is greater than the debris head loss, then the fluid pressure within the debris bed is greater than the fluid pressure at the pool surface (the containment pressure) and clearly no flashing within the debris will occur, or

2. If the submergence is less than the debris head loss, the potential for flashing within the debris bed does exist. To determine whether or not flashing does actually occur, one must calculate the fluid pressure on the inside of the strainer Page 19 of 36

Attachment 2 Three Mile Island Unit 1 Responseto Request for Additional information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 surface (containment pressure + submergence - debris head loss) and compare this to the fluid vapor pressure. If the vapor pressure is greater than this calculated fluid pressure, flashing would occur unless credit is taken for overpressure. If the fluid pressure is greater than the vapor pressure, no flashing occurs.

Table VI: Containment Flashing Parameters Time Containment Sump Vapor Debris Head Submergence Submergence Pressure Temp Pressure Loss (ft) greater than debris (psia) (OF) (psia) (ft) head loss (Y/N) 1681 sec 42 260 36.4 0.75 1.3 Yes 3433 sec 32 244 27.4 0.79 1.3 Yes Long Term 13.7 208 13.7 0.9 1.3 Yes Long Term 13.7 141 2.9 1.32 1.3 No Long Term 13.7 140 2.9 16.0 1.3 No Temperatures above 140°F:

As described in the previous response to Issue 3o.2.9.i (Reference 1), the head loss across the strainer at temperatures above 140°F is based on the contribution of calcium phosphate precipitates. As described in the Response to Issue 3f.13 (Reference 1), the measured debris head loss is adjusted based on the temperature of the fluid. Due to the effect of fluid density and viscosity, the debris head loss increases as temperature decreases. The submergence of the strainer is greater than the debris head loss until the sump temperature decreases to approximately 141OF. For the temperatures around 141 OF, the fluid pressure determined per criteria 2, above, is above the vapor pressure (see example below for temperatures at or below 140 0 F). Therefore, flashing does not occur for temperatures above 1400 F.

Temperatures at or below 140°F:

As described in the response to Issue 3o.2.9.i (Reference 1), the head loss across the strainer at temperatures below 140°F includes the contribution of aluminum based precipitates. This results in a significant increase in strainer head loss as discussed in the response to USNRC Question 4 (RAI 9). As described in the Response to Issue 3f.10 (Reference 1), operator actions to secure the BS pumps and reduce LPI flow will maintain the strainer DP below the strainer design limit. The flashing evaluation conservatively uses the strainer design DP (16 ft) as the maximum debris head loss. The debris head loss is greater than the submergence of the strainer below 1400 F, therefore criteria 2 is applied. The fluid pressure at the top of the strainer is slightly greater than 7 psia [13.7 psia + 0.5 psia (or 1.3 ft.) - 6.9 psia (or 16 ft.)], which is well above the vapor pressure of 2.9 psia. Therefore, flashing does not occur for temperatures below 140 0 F.

Page 20 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 USNRC Question 6 (RAI 13)

The staff requested justification for why the settlement that occurred during integrated chemical effects testing did not result in non-conservative head loss values. The licensee stated that multiple attempts were made to re-entrain settled debris into the test flume. The staff was present at a test of the TMI-1 strainers. During the test the staff noted non-prototypical settlement of both chemical and non-chemical debris in the test tank. The trip report reference may be found at ADAMS Accession No. ML071230203. As noted in the trip report, the test tank geometry was significantly less conducive to transport than actual plant conditions. The trip report noted that the effects of debris settling should be addressed during the evaluation of the testing. The licensee should evaluate the effects of the settling on the test results.

TMI, Unit 1 Response:

Response Summary:

The USNRC observed head loss testing that was performed for TMI, Unit 1 in March of 2007 and noted non-prototypical settling of chemical and non-chemical debris in the test tank.

Improvements were made to both the test tank configuration and test procedures prior to the test of record for TMI, Unit 1 which occurred in November 2007. Although some minor settling did occur in the November test, the settling is not considered to be non-prototypical and did not significantly affect the test results.

Response Details:

Back-qround USNRC representatives were present at the initial TMI, Unit 1 chemical strainer test performed at Alion in March 2007 (Reference 9). This test was an early implementation of the prototype strainer array tests that utilize both physical (fiber/particulate/dirt/dust) and chemical precipitate debris. During this test, it was observed that significant quantities of debris settled on the floor of the test tank. Subsequent to this test, the design basis (full load) test was performed in November 2007. This test, which was not witnessed by the USNRC, incorporated enhanced methods to agitate the tank throughout the testing process. These methods proved effective in reducing the quantity of settled debris. The TMI, Unit 1 Supplemental Response (Reference 1) and the subsequent RAI response (Reference 3) and supplemental information submittal (Reference 4) were based on the results from the November 2007 test.

Page 21 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Discussions March 2007 Testing The initial test performed in March 2007 utilized an Alion Hydraulic test with a standard, barrel-shaped diffuser. Top hats were mounted vertically on the discharge base plenum to reflect the TMI, Unit 1 sump strainer orientation. A plywood box structure was installed around the top hat array to simulate the TMI, Unit 1 sump pit. The box structure included three "full height" walls that extended above the top of the prototype top hats, and one partial height wall to facilitate the transfer of debris onto the strainers. Flow through the array was discharged from the base plenum and returned to the tank through a flow diffuser to provide a degree of debris mixing.

The diffuser used in this test was barrel shaped, approximately 24" diameter and 36" tall with an array of 2" diameter holes to diffuse the supply water in multiple directions. The diffuser was located near an outer tank wall, away from the plywood box structure to ensure that the discharge from the diffuser did not disturb the debris as it accumulated on the strainer surfaces.

The test configuration previously used in Alion tests employed top hat arrays consisting of 9 total top hats (3 x 3 array). However, in order to accommodate the volume of chemical precipitates introduced to the tank in the March 2007 test, the array size was reduced to utilize a total of 4 top hats (2 x 2 array). This required a lower overall test flow rate to maintain the proper approach velocity at the strainer surface. For the 2 x 2 array, flow was reduced to 44% of the rate associated with the 3 x 3 arrays previously tested. This greatly reduced the effectiveness of the standard diffuser and allowed for the accumulation of settled physical and chemical debris on the floor of the test tank. Manual agitations of the tank were also not effective in suspending the settled debris sufficiently. Photograph 6 and Photograph 7 show the settled debris visible in the tank at the end of the March 2007 testing.

Photograph 6: Settled Debris from TMI, Unit 1 Test Conducted 3/07 (southwest corner)

Page 22 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Photograph 7: Settled debris from TMI, Unit 1 Test Conducted 3/07 (front edge)

November 2007 Testing Alion incorporated improvements to the test tank that would enhance agitation of the water to provide better suspension of debris. The barrel diffuser used in the March 2007 testing was replaced with a "tee-sparger" piping system. This arrangement distributed the water at floor level as it was re-circulated from the strainer plenum back into the tank. This configuration also generates somewhat higher velocities from water entering the tank than were achieved with the barrel diffuser. The distribution piping was configured such that the debris accumulated on the strainer screen would not be disturbed by discharge from the sparger.

The full load test (Test 2B) was initiated in November 2007. As debris was slowly introduced to the tank over approximately 25 minutes, manual agitation was performed with a propeller style trolling motor and a rowing oar to supplement the sparger system. All agitation activities were carefully monitored to ensure they did not affect debris that had accumulated on the strainer.

Review of the test logs reveals that supplemental agitation actions were performed throughout the entire debris addition process until head loss was observed to be stabilized.

At the conclusion of the test, it could be seen that Alion's improvements to tank agitation methods greatly reduced the amount of settled debris. Photograph 8 below illustrates the tank condition after all debris had been introduced to the experiment. This photograph shows the southwest corner of the tank and can be directly compared to Photograph 6 from the March 2007 test (1 B).

Page 23 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Photograph 8: Post Debris Addition TMI "Unit 1 Test 11/07 (southwest corner)

After all debris had been introduced to the tank and consistent attempts to keep the debris in suspension were performed, a small amount of fibrous debris could still be observed in isolated areas of the test tank floor. Photograph 9 shows the final condition of the test. By observation, the only debris component observed to have settled is the largest fiber class. The majority of the fibrous debris, along with the particulate and chemical precipitate debris had accumulated on the sump screen. The amount of settled fiber at the end of TMI, Unit 1 November 2007 Test 2B is estimated to be approximately 10%. Based on the clarity of the water, the particulate has been filtered and the head loss is in general higher with higher particulate to fiber ratios assuming fiber loads that do not fill in the interstitial volume (which is the case here). The head loss at this point is dominated by the tightly packed debris layer on the surface of the screen.

The settled debris on the floor is extremely loose and non-compacted; therefore, the impact of this debris on the measured head loss would not be significant. As seen in Photograph 9, there is already a considerable amount of the non-compacted debris within the sump box. Based on this, the settled debris does not have a significant effect on the results.

Page 24 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Photograph 9: TMI, Unit 1 Test 11 Prototypical Features The TMI, Unit 1 sump pit design incorporates framing and structural components that form surfaces and confined volumes which are all within the volume of the pit, but are elevated above the base of the top hat mounting frame, or isolated from the primary sump volume. Figure 7 shows an isometric representation of the TMI, Unit 1 top hat framing structure that is installed within the sump pit. The entire assembly illustrated below is installed at the bottom of the sump pit, such that approximately 18" of the top of the tallest strainer cylinders extends above the containment floor elevation.

Page 25 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 Figure 7: TMI, Unit 1 Top Hat Framing Structure For reference, Figure 8 below illustrates flow patterns and relative velocities generated within the flooded containment during ECCS operation. From this figure, it can be seen that the majority of the water entering the sump pit approaches from the west side of the structure.

11 P N North Figure 8: Flow Profile during ECCS Operation, RB 281' Elevation Examination of the physical layout reveals that the design contains inherent surface features that result in locations where debris could accumulate without coming into contact with the strainer screen. Specifically, the west side of the structure incorporates multiple flat plate hatches that provide access to the ECCS sump suction inlets (not shown) entering the pit.

Page 26 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 These hatches are closed during operation. On either side of these hatches are the normal sump drain tanks. These tanks have open tops and are cross tied with a discharge (shown) independent from the ECCS discharge. The volume within these tanks is isolated from the general sump volume. As sump water flows into the west edge of the sump pit, the entrained debris will initially interface with these surfaces and volumes of the framing structure.

Since these areas are separated from the base of the top hats, any debris that accumulates on these surfaces within the sump pit would not contribute to head loss. By examination of design drawings, the area of the framing structure above the top hat mounting framework is calculated to be 20% of the total pit cross section. This represents 36 ft2 of surface within the sump where debris with greater settling velocities could accumulate without contributing to head loss across the strainer.

As illustrated by the test, some types of standardized debris, which can analytically be expected to transport to the sump, could in fact settle on available surfaces in the immediate vicinity of the strainer array. The limited amount of settled debris in the November 2007 test is separated from the strainer in a manner similar to what could occur in the actual sump installation.

Therefore, the minor settling noted in the full load test is prototypical and of a relatively small amount, such that the head loss results are not affected in any significant manner.

USNRC Question 7 (RAI 16)

The staff requested that the licensee provide a more detailed description of the NPSH margin calculation methodology, including a description of the time-dependent analysis specifying selected values for NPSHa (NPSH available) and NPSHr (NPSH required) throughout the mission time. Although some information was provided in response to this request, the staff did not consider the response complete because sufficient information was not provided for the dependence of NPSHa on the sump pool water temperature as well as the time-dependence of the NPSH margin. While it is clear that the available margins are very small at the worst point in the limiting accident sequence (i.e., the minimum NPSH margin is 0.1 ft), it is unclear to the staff when this minimum margin occurs, how long it persists, and how much margin exists at other times during the accident. Therefore, to fully resolve this RAI, the staff is requesting that the licensee provide plots of NPSH margin versus time (or sump temperature if this parameter was used in lieu of time) for the limiting case (or cases) for both the LPI and building spray (BS) pumps that demonstrate the periods of minimum NPSH margin and the behavior of the NPSH margin as a function of time (or sump temperature).

TMI, Unit 1 Response:

Plots of NPSH margin for both the LPI and BS pumps for the limiting cases are provided below.

These plots were taken from the most recent revision of the NPSH Margin Analysis.

The TMI, Unit 1 NPSH Margin Analysis has undergone two revisions since the Supplemental Response to GL 2004-02 (Reference 1) was submitted to the USNRC. Both of these revisions to the NPSH Margin Analysis resulted in minor changes to Tables 14 and 15 of Reference 1.

Supplemental information regarding the first revision was provided to the USNRC by Reference Page 27 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1

4. The second revision to the NPSH Margin Analysis is discussed in Attachment 5 to this submittal.

The five system configurations listed below have been evaluated with respect to LPI and BS pump NPSH and maximum strainer differential pressure:

Case I represents two trains of LPI and two trains of BS in service. Each train of LPI is throttled to an indicated flow of 3000 gpm, with the BS pumps independently delivering 1180 gpm. The LPI system is configured with the cross-connect line (DH-V-38A/B) closed.

Case II represents the same LPI configuration as described in Case I with both BS pumps secured. The LPI cross-connect line via DH-V-38A/B is closed.

Case III represents a single LPI pump in operation feeding both trains of injection through DH-V-4A and DH-V-4B (i.e. DH-V-38A and DH-V-38B open). The total indicated flow is 2800 gpm. In this mode, the opposite train LPI pump minimum flow line is open and circulating water back to the DH pump suction. The BS pumps are not operating.

Case IV represents the same LPI pump configuration as described in Case III with the corresponding train BS pump operating at 1180 gpm.

Case V represents the same LPI pump configuration as described in Case III with both trains of BS independently operating at 1180 gpm.

Cases I through IV were included in the previous TMI, Unit 1 Response to Issue 3g.16 (Reference 1). Case V was added to evaluate the one LPI/ two BS pump combination as discussed in the response to USNRC Question 8, below. Each of the cases described above were evaluated for both high temperature and low temperature conditions. As described in the previous response to Issue 3g.16 (Reference 1), the high temperature conditions are referred to as the EQ cases and the low temperature conditions are presented as the Maximum Cooldown cases.

The limiting case for LPI pump NPSH margin is EQ Case V (Table IX, Attachment 5). Short and long term NPSH plots for both Cases IV and V for the LPI pumps are provided.

Page 28 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 30 Short Term LPI NPSHa, NPSHr cv41C cv43C INPSHa

-) - I i I.1 a- z NPSHr

ý -.---------- I I i**--**----*~ I 02 3 4 5 6 Time (hours)

GTI-C72a(oA)SePI17/209 1 1:26 Figure 9: LPI NPSH - EQ Reactor Building Response - Case IV (Hours) 22 U)

LPI NPSI-a, NPSHr, NPSHm I ! I ow41C cv43C cv4SC U) II 0 ---------- -

a . ..............

0 1 2 4_5 U.)

z ~NPSHm i 1- ---

S~ I --

0 5 10 15 20 25 30 Time (days)

IGOTHPC 7.2afOAA Sep(17/MO9 18:0126 Figure 10: LPI NPSH - EQ Reactor Building Response - Case IV (Days)

Page 29 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 5u Short Term LPI NPSHa, NPSHr cv4lC cv43C I i cri UO

"

iNPSHa II U, c) z U,,

C .. .

0 2 3 4 5 6 Time (hours) t~lhrI*II*7 P~(fl&i 4=r171l~d'lOIA-hi-GOTHIC -1 WaM S-Fl? ODIA!

Figure 11: LPI NPSH - EQ Reactor Building Response - Case V (Hours) r2 CD, LO LPI NPSHa, NPSHr, NPSHnm cv41C cv43C cv45C C,)

U,'I z

o* -**_--.... _.. ...

J -. -7 0 5 10 15 20 25 30 Time (days)

GOTHIC 72&fOA) SmN71720O9 18:01:41 Figure 12: LPI NPSH - EQ Reactor Building Response - Case V (Days)

The limiting case for BS pump NPSH margin is EQ Case I (Table X, Attachment 5).

Page 30 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 23 BS NPSHa, NPSHr, NPSHm cv42C c44C cv46C 10 SI ., I. - ------- --

U, I jNPSHa*

UD CO -----.--

I LO ..........................

~NPSHMI Z .......

-o -........ ..---------.-

:-:-:::-"-::-i-I-II ... .' .. . . I I ;

0 - - -___ ___ _ i..... . .. ,.. . . .... .. ... . . .

0 4 8 12 16 20 24 Time After Switchover (hours)

GOTH[C 72a(QA) SepF17/20O9 16:19-20 Figure 13: BS NPSH - EQ Reactor Building Response - Case I (Hours)

USNRC Question 8 (RAIs 17 and 19)

The staff requested that the licensee provide a discussion of how the single failure criterion was used in determining the bounding NPSH margin and why there is confidence that the worst-case single failure was identified and considered. The licensee's response to this item described a single failure of an LPI pump as being the worst-case single failure. Upon considering the NPSH margin results in Table 14 in the supplemental response, as well as the response to RAI 17 that indicates that maximizing reactor building cooling is considered a limiting condition, the staff questioned whether a configuration with one operating LPI pump and two operating BS pumps would be bounded by the results presented. For the case of two operating LPI pumps, having two operating BS pumps led to the minimum NPSH margin, but a corresponding case was not analyzed for single-train LPI operation. Please either (1) provide a basis for considering the configuration of one LPI pump and 2 BS pumps operating to be bounded by the cases analyzed or (2) provide a basis for concluding that this operating configuration will not be implemented following a LOCA (e.g., it would not be allowed by emergency procedures).

TMI, Unit 1 Response:

The TMI, Unit 1 NPSH Margin Analysis has been revised to add the additional case of a single LPI pump operating with both of the BS pumps operating. The minimum NPSH margin for this Case (Case V) was slightly lower than for Case IV as shown in the plots below. However, the minimum NPSH margin remains at 0.1 ft.

Page 31 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 The five system configurations listed below have been evaluated with respect to LPI and BS pump NPSH and maximum strainer differential pressure:

" Case I represents two trains of LPI and two trains of BS in service. Each train of LPI is throttled to an indicated flow of 3000 gpm, with the BS pumps independently delivering 1180 gpm. The LPI system is configured with the cross-connect line (DH-V-38A/B) closed.

Case II represents the same LPI configuration as described in Case I with both BS pumps secured. The LPI cross-connect line via DH-V-38A/B is closed.

" Case III represents a single LPI pump in operation feeding both trains of injection through DH-V-4A and DH-V-4B (i.e. DH-V-38A and DH-V-38B open). The total indicated flow is 2800 gpm. In this mode, the opposite train LPI pump minimum flow line is open and circulating water back to the DH pump suction. The BS pumps are not operating.

Case IV represents the same LPI pump configuration as described in Case III with the corresponding train BS pump operating at 1180 gpm.

Case V represents the same LPI pump configuration as described in Case III with both.trains of BS independently operating at 1180 gpm.

Cases I through IV were included in the previous TMI, Unit 1 Response to Issue 3g.16 (Reference 1). Case V was added to evaluate the one LPI/ two BS pump combination. The limiting NPSH margin conditions occur during the first six hours of operation for EQ Cases IV and V as discussed below. The minimum margin of 0.1 ft occurs in EQ Case V during the first hour of sump recirculation due to the operation of two BS pumps. (Table IX, Attachment 5)

NOTE: The TMI, Unit 1 NPSH Margin Analysis has undergone two revisions since the Supplemental Response to GL 2004-02 (Reference 1) was submitted to the USNRC. Both of these revisions to the NPSH Margin Analysis resulted in minor changes to Tables 14 and 15 of Reference 1. Supplemental information regarding the first revision was provided to the USNRC by Reference 4. The second revision to the NPSH Margin Analysis is discussed in Attachment 5 of this submittal.

A graph of NPSHa and NPSHr versus time for the first six hours of operation in the recirculation mode for EQ Case IV is provided below. The minimum margin for this case was listed as 0.1 ft in Table 14 (Reference 1). When the scale of the plot was expanded and compared to the result for Case V, it is evident that the NPSH margin for Case IV is initially slightly greater than the margin for Case V. The minimum margin for Case IV provided in the revised Table 14 (Attachment 5) is 0.2 ft based on the stable NPSH margin that exists after recirculation conditions are established.

Page 32 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 30 Short Term LPI NPSHa, NPSHr cv4lC o,43C I I I i I I

- I

,-...---.- I I I NPS)-

0..L -

z i i NPSHr 0 1 2 3 4 5 6 Time (hours)

L Zýý Figure 14: LPI NPSH - EQ Reactor Building Response - Case IV (Hours)

A graph of NPSHa and NPSHr versus time for the first six hours of operation in the recirculation mode for EQ Case V is provided below. The minimum stable NPSH margin for the first hour of operation is 0.1 ft. After 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months , the first BS pump is secured as described in the previous response to Issue 3f.10 (Reference 1). After the first BS pump is secured, the configuration is then equivalent to Case IV and the margin increases to 0.2 ft.

Page 33 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 30 Short Term LPI NPSHa, NPSHr cv41C cv43C v-!!

I NPr L0O Cu 0 1 2 3 4 5 6 Time (hours)

GOTHIC 7I2s(QA1 Sed17/2008 I8"1 41 Figure 15: LPI NPSH - EQ Reactor Building Response - Case V (Hours)

The NPSH Margin Analysis uses a GOTHIC model to determine long term NPSH availability during the 30 day mission time for sump recirculation. The transition period from BWST injection to sump recirculation is not included in the GOTHIC model. As seen in the plot above, it appears as if the LPI pump is started at the initiation of sump recirculation at 0.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months as the NPSHr plot makes a step change to approximately 12.9 ft at that time. In actual conditions, the LPI pump will have been running prior to this time taking suction from the BWST. The curve of NPSHa would be decreasing from the value based on the BWST to the value based on the RB sump conditions. As the GOTHIC model does not include the transition time from the BWST to the sump, the minimum NPSH margin during recirculation is based on the stable region of the NPSHa curve when a steady state solution is obtained in the GOTHIC model.

USNRC Question 9 Please evaluate the potential for deaeration of the sump fluid to occur as it flows through the debris bed. The guidance in Regulatory Guide 1.82, Revision 3, Appendix A, states that entrained gas at the pump inlet can result in an increase in required NPSH. Please evaluate whether any adverse effect to pump performance could occur as a result of entrained gas at the pump inlets. If applicable, provide an evaluation of the effects on the pumps.

Page 34 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 TMI, Unit 1 Response:

Response Summary:

An analysis has been performed to determine the air void fraction present in the post-LOCA fluid downstream of the sump strainer. The void fraction is 0% for Reactor Building sump water temperatures above 140°F due to the low debris head losses. At 140 0 F, the strainer head loss increases significantly due to the impact of the aluminum based precipitates. Based on the higher strainer head loss conditions, the average void fraction over the height of the strainer was calculated to be 1.30%.

For temperatures below 140°F when the void fraction at the strainer is greater than 0%, the void fraction at the pump was determined to be 0.97%. The Ideal Gas Law was applied to account for the increased static head and the resultant void compression at the lower elevation of the pump. For both the LPI and BS pumps, the NPSH margin remains greater than 5 ft after applying the RG 1.82 (Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident) adjustment factor to account for the potential effect of air ingestion on required NPSH.

Response Details:

The potential for air void formation downstreamof the strainer was evaluated for the range of sump conditions as shown in Table VII below. Consistent with the NPSH analysis, above 208°F the RB pressure is set equal to the vapor pressure corresponding to the RB sump water temperature (as described in the Response to Issues 3g.1 and 3g.2 in Reference 1). Once the RB sump water temperature has decreased to where the vapor pressure is equal to or less than

-1 psig, then a containment pressure equal to -1 psig is applied. For this initial evaluation, the void fraction is determined at the top of the strainer (1.3 ft submergence).

Table VII: Containment Void Fraction Parameters and Results RB Sump RB Strainer Screen Debris Vapor Void Water Pressure Flow Depth Head Pressure Fraction Temp (OF) (psia) Rate (ft) Loss (psia) (%)

(gpm) (ft) 260 42 8800 1.3 0.75 36.4 0.0 244 32 8800 1.3 0.79 27.4 0.0 208 13.7 8800 1.3 0.9 13.7 0.0 141 13.7 8800 1.3 1.32 2.9 0.0 140 13.7 8800 1.3 16.0 2.9 2.15 The containment pressure of 13.7 psia is the minimum pressure that can exist in containment prior to the event as discussed in the Response to Issue 3g.2 in Reference 1.

The RB3 sump void fraction is 0% at temperatures above 140 0 F. The head loss across the strainer increases significantly at 140°F due to the impact of the aluminum based chemical precipitates. The resulting void fraction at the strainer is 2.15%. Based on these initial results, a Page 35 of 36

Attachment 2 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Specific to TMI, Unit 1 more detailed evaluation of the void fraction at 140°F was performed, including a determination of the void fraction at the pump.

To determine the void fraction at the elevation of the pump, an average void fraction along the height of the strainer top hat was calculated. The typical 83" tall top hat was divided into five equal segments and the void fraction was calculated for each segment. The average of these five values resulted in a void fraction of 1.30%. This void fraction was applied at the vertical midpoint of the top hat.

To extend the void fraction results to the pump inlet, the Ideal Gas Law was applied to account for the increased static head at the pump inlet and the resultant void compression. The resulting void fraction at the pump was determined to be 0.97%.

To evaluate the impact of air ingestion on NPSH margin, the Regulatory Guide (RG) 1.82 relationship was used to adjust the required NPSH for the LPI and BS pumps. The void fraction of 0.97% at the pump was rounded up to 1.0% in the evaluation of required NPSH. The minimum NPSH margin that occurred after the sump temperature reaches 140°F was determined for the LPI and BS pumps for all Cases. For the LPI pumps, the maximum cooldown Cases I and IV(described in the Response to NRC Question 7 (RAI 16), above) are the system configurations that resulted in the lowest NPSH margin at or below 140 0F. Two LPI cases are evaluated due to the different LPI pump flows for the evaluated system configurations. For the BS pumps, the maximum cooldown Case I resulted in the lowest NPSH margin at or below 140 0F. The BS pump flow is the same for all cases. The evaluations of the most limiting NPSH conditions at or below 140°F are provided in the Table below.

Table VIII : NPSH Margin Considering Air Ingestion ECCS Case Pump NPSHr A Adiusted Minimum Adjusted Pump Flow LM Per RG 1.82 NPSHr NPSHm Minimum

¢cSpm) (ft) (ft) NPSHm (ft)

LPI Case I 3247 12.3 1.5 18.5 11.9 5.7 Case IV 3351 13.7 1.5 20.6 20.1 13.2 BS Case I 1180 13 1.5 19.5 13.6 7.1 From Att. From NPSHr x p3 From Att. 5, = Min NPSHm 5, Tables pump P= 1+0.5(1.0%) Tables IX - (adj. NPSHr IXand X curve and X - NPSHr)

Adequate NPSH margin exists for the ECCS pumps when the potential effects of air ingestion are included.

Minimum NPSH margins for sump temperatures above 140°F are discussed in the response to USNRC Question 7, above.

Page 36 of 36

ATTACHMENT 3 Three Mile Island, Unit 1 Response to Request for Additional Information Related to USNRC Generic Letter 2004-02 Questions Generic to Westinghouse Debris Generation Testing

Attachment 3 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Questions Generic to Westinghouse Debris Generation Testing The set of 10 questions titled "Issues Generic to Westinghouse Debris Generation Testing,"

issued in the USNRC RAI to Exelon dated July 23, 2009 (Reference 2), applies to the TMI, Unit 1 credited debris generation testing. The PWROG is attempting to resolve all of the issues identified in these questions generically. The USNRC, the PWROG, and Westinghouse have been conducting regular meetings to reach a resolution of the USNRC issues. Furthermore, the PWROG approved the funding to conduct further jet impingement testing to provide data necessary to answer those USNRC RAIs for which a purely analytical approach has not proven acceptable. Due to the dependence on the PWROG and Westinghouse results and subsequent responses on these issues, TMI, Unit 1 is not able to respond to the 'Issues Generic to Westinghouse Debris Generation Testing' at this time.

TMI, Unit 1 hereby commits to report to the USNRC how it has addressed the set of 10 questions titled "Issues Generic to Westinghouse Debris Generation Testing," issued in the USNRC RAI to Exelon dated July 23, 2009 (Reference 2) within 90 days of issuance of the final USNRC decision on the acceptability of WCAP-1671 0-P (Reference 5), and its related supplemental information. The commitment is documented in Attachment 4 of this submittal.

In the interim, TMI, Unit 1 is evaluating contingency measures for the case where the PWROG and Westinghouse results do not adequately respond to the USNRC issues including potential removal of insulation (as discussed with the USNRC in the public meeting conducted August 11, 2009) in the TMI, Unit 1 Fall 2011 refueling outage.

Page 1 of 1

A'TACHMENT 4 Three Mile Island, Unit 1 Response to Request for Additional Information Related to USNRC Generic Letter 2004-02 Summary of Regulatory Commitments

Attachment 4 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Summary of Regulatory Commitments The following table identifies commitments made in this document.

COMMITMENT TYPE COMMITMENT COMMITTED DATE OR ONE-TIME PROGRAMMATIC "OUTAGE" ACTION (Yes/No) (Yes/No)

TMI, Unit 1 hereby commits to Within 90 days of issuance of the Yes No report to the USNRC how it final USNRC decision on the has addressed the set of 10 acceptability of WCAP-1 671 0-P, questions titled "Issues and its related supplemental Generic to Westinghouse information.

Debris Generation Testing,"

issued in the USNRC RAI to Exelon dated July 23, 2009. -

Page 1 of 1

ATTACHMENT 5 Three Mile Island, Unit 1 Response to Request for Additional Information Related to USNRC Generic Letter 2004-02 Revised Tables 14 and 15

Attachment 5 Three Mile Island Unit 1 Response to Request for Additional Information Related to Generic Letter 2004-02 Revised Tables 14 and 15 The TMI, Unit 1 NPSH Margin Analysis has undergone two revisions since the Supplemental Response to GL 2004-02 (Reference 1) was submitted to'the USNRC. Both of the revisions to the NPSH Margin Analysis resulted in minor changes to Tables 14 and 15 (Reference 1).

Supplemental information regarding the first revision was provided to the USNRC by Reference

4. The second revision to the NPSH Margin Analysis is discussed, below.

A second revision to the NPSH Margin Analysis was recently completed to implement the following changes:

" Incorporate Case V to evaluate the operation of one LPI pump with two BS pumps as described in the Response to USNRC Question 8, Attachment 2.

" Incorporate a change in the flow rate from the Reactor Building Emergency Cooling (River Water) Pumps (shown in Figure 1 of the previous response to Issue 3f.1, Reference 1). This change was unrelated to GL 2004-02 and had minimal impact on the NPSH margin results.

Table IX: Updated Table 14, LPI Pump NPSH Results Initial Reactor Indica Initial Initial Minimum Case Building Train Flow Pump Flow Strainer Flow Excess NPSH Cooling (gpmn) (gpm) (gpm) (ft)

Case I EQ 3000 3247 8582 0.4 Case II EQ 3000 3247 6222 2.4 Case III EQ 2800 3351 3076 2.0 Case IV EQ 2800 3351 4256 0.2 Case V EQ 2800 3351 5436 0.1 Case I Maximum 3000 3247 8582 11.9 Case H Maximum 3000 3247 6222 18.8 Case III Maximum 2800 3351 3076 23.7 Case IV Maximum 2800 3351 4256 20.1 Case V Maximum 2800 3351 5436 20.1 NOTE: Table IXdoes not include the adjustment factor for air ingestion, as described in response to USNRC Question 9, above.

Apart from the addition of Case V, the updated Table 14 is the same as the Table provided in Reference 4 with the exception of the Minimum NPSH margin for EQ Case IV.As discussed in the response to USNRC Question 8, Attachment 2, when the scale of the plot of minimum margin for Case IVwas expanded, the actual margin was determined to be 0.2 ft.

Page 1 of 3

Table X: Updated Table 15, Building Spray Pump NPSH Results Reactor Pump Initial Minimum Case Building Flow Strainer Flow Excess NPSH Cooling (gpm) (gpni) (It)

Case I EQ 1180 8582 2.0 Case IV EQ 1180 4256 2.6 Case V EQ 1180 5436 2.6 Case I Maximum 1180 8582 13.6 Case IV Maximum 1180 4256 22.4 Case V Maximum 1180 5436 22.6 Apart from the addition of Case V, the updated Table 15 is the same as the Table provided in Reference 4 with the exception of the Minimum NPSH margin for EQ Case IV. The minimum margin for EQ Case IV increased slightly from 2.5 to 2.6 ft.

Additional Data Tables The following additional tables are provided to support the information provided in the RAI responses. These tables are from the latest revision of the NPSH Margin Analysis and were not included in previous submittals to the USNRC.

Table Xl: Transient Event Times - EQ Cases*

Event Case I Case II Case III Case IV Case V Time of Peak Sump 48.39 48.39 48.39 48.39 48.39 Temperature (sec)

Time of Switchover to 0.7 0.9 1.7 1.2 0.9 Recirculation (hr)

Time of Minimum Excess** 0.7 0.9 1.7 1.2 0.9 LPI Pump NPSH (hr)

Time of Minimum Excess** 0.7 n/a n/a 1.2 0.9 BS Pump NPSH (hr) 0.7 _____.__

Time When Sump Temperature 22.3 24.5 133.4 133.4 133.4 Reaches 140 *F (hr)

Time When Strainer Pressure 47.3 Never Never Never DoExedIOf(h)22.3 Drop Exceeds 10 ft (hr) ___ ______

Time of Maximum Pressure Drop 23.3 47.3 720 720 720 across the Sump Strainer (hr) 23.3 47.3 720 720_720 Time When First Building 1.7 n/a n/a 25.2 1.9 Spray Pump is Secured (hr)

Time When Second Building 24.7 n/a n/a n/a 24.9 Spray Pump Secured (hr) 9

Event times are from the beginning of event

- Minimum Excess NPSH is determined after switchover operations are complete Page 2 of 3

Table X11: Key Transient Event Times - Maximum Cooldown Cases*

Event -Case I Case 11 Case .11 Case IV Case V Time of Peak Sump 40.19 40.19 40.19 40.19 40.19 Temperature (sec)

Time of Switchover to 0.7 0.9 1.7 1.2 0.9 Recirculation (hr)

Time of Minimum Excess LPI Pump NPSH (hr)

Time of Minimum Excess 1.1 n/a n/a 3.9 3.9 BS Pump NPSH (hr)

Time When Sump Temperature 1.1 1.4 5.6 3.9 3.9 Reaches 140 TF (hr)

Time When Strainer Pressure 1.1 1.6 Never Never Never Drop Exceeds IOft (hr) 1.1_1.6 Neeee_ ee Time of Maximum Pressure Drop 1.7 2.6 720 25.2 24.9 across the Sump Strainer (hr)

Time When First Building 1.7 n/a n/a 25.2 1.9 Spray Pump is Secured (hr)

Time When Second Building 24.7 n/a n/a n/a 24.9 Spray Pump Secured (hr)

Event times are from the beginning of event Table X111: Maximum Strainer Head Loss Initial Maximum Reco Bul Strainer Head Case Building Flow Loss Cooling (gtpr) (ft)

Case I EQ 8582 12.1 Case II EQ 6222 10.0 Case HI EQ 3076 4.2 Case IV EQ 4256 4.2 Case V EQ 5436 4.2 Case I Maximum 8582 15.6 Case I1 Maximum 6222 10.6 Case III Maximum 3076 7.8 Case IV Maximum 4256 8.4 Case V Maximum 5436 7.8 Page 3 of 3