ML083380671

Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors, Request for Additional Information (TAC Mc 4725)

ML083380671
Person / Time
Site:	Turkey Point
Issue date:	12/22/2008
From:	Mozafari B Plant Licensing Branch II
To:	Stall J Florida Power & Light Co
Paige, Jason, NRR,301-415-5888
References
GL-04-002, TAC MC4725
Download: ML083380671 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 22, 2008 Mr. J. A. Stall Senior Vice President, l'Juclear and Chief Nuclear Officer Florida Power and Light Company P.O. Box 14000 Juno Beach, Florida 33408-0420

SUBJECT:

TURKEY POINT NUCLEAR PLANT, UNIT 3 - GENERIC LETTER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE OI'J EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS," REQUEST FOR ADDITIONAL INFORMATION (TAC NO.

MC4725)

Dear Mr. Stall:

By letters dated February 28,2008, as supplemented June 30,2008 and August 11,2008 (Agencywide Documents Access and Management System (ADAMS) Accession Nos.

ML080710429, ML081960386, and ML082310488), Florida Power and Light (FPL, the licensee) submitted responses to Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors," for Turkey Point, Unit 3.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensee's submittals.

The process involved detailed review by a team of approximately 10 subject matter experts, with a focus on the review areas described in the NRC's "Content Guide for Generic Letter 2004-02 Supplemental Responses" (ADAMS Accession No. ML073110389). Based on these reviews, the NRC staff has determined that additional information is needed in order to conclude there is reasonable assurance that GL 2004-02 has been satisfactorily addressed for Turkey Point, Unit 3. The enclosed document describes these requests for additional information (RAls).

The NRC requests that the licensee respond to these RAls within 90 days of the date of this letter. If the licensee concludes that more than 90 days are required to respond to the RAls that are being addressed by new testing, the licensee should request additional time, including a basis for why the extension is needed.

The exception to the above response timeline is RAI 33 in the enclosure. The NRC staff considers in-vessel downstream effects to not be fully addressed at Turkey Point, Unit 3, as well as at other pressurized-water reactors (PWRs). The licensee's submittal refers to draft WCAP-16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous, and Chemical Debris in the Recirculating Fluid" At this time, the NRC staff has not issued a final safety evaluation (SE) for WCAP-16793.

J. Stall -2 The licensee may demonstrate that in-vessel downstream effects issues are resolved for Turkey Point, Unit 3, by showing that the licensee's plant conditions are bounded by the final WCAP-16793 and the corresponding final NRC staff SE, and by addressing the conditions and limitations in the final SE. The licensee may also resolve RAI 33 by demonstrating, without reference to WCAP-16793 or the NRC staff SE, that in-vessel downstream effects have been addressed at Turkey Point, Unit 3. The specific issues raised in RAI 33 should be addressed regardless of the approach the licensee chooses to take.

The licensee should report how it has addressed the in-vessel downstream effects issue and the associated RAI referenced above within 90 days of issuance of the final NRC staff SE on WCAP-16793. The NRC staff is currently developing a Regulatory Issue Summary to inform licensees of the staff's expectations and plans regarding resolution of this remaining aspect of Generic Safety Issue 191, "Assessment of Debris Accumulation on PWR Sump Performance."

renda L. Mozafari, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-250

Enclosure:

RAI cc w/encl: Distribution via ListServ

TURKEY POINT NUCLEAR PLANT UNIT 3 REQUEST FOR ADDITIONAL INFORMATION SUPPLEMENTAL RESPONSES TO GENERIC LETTER (Gl) 2004-02 DOCKET NO 50-250 DATED FEBRUARY 28, JUNE 30, AND AUGUST 8. 2008

1. Please provide clarification of whether the containment spray system (CSS) is required to operate in recirculation mode for a secondary system high energy line break (HELB). If the CSS is required to operate in recirculation mode following a secondary system HELB, please describe your evaluation of this event including the performance of the new sump strainer.

2. Please provide your evaluation that establishes that breaks at or near the reactor nozzle will not result in a more limiting debris generation condition than the breaks presented in the supplemental response. Explain the insulating material(s) for the reactor vessel.

3. Please provide information that illustrates how the debris that would be generated from a pressurizer surge line break was considered in the break selection process, or verify that that the only target material for a surge line break is reflective metal insulation (RMI).

4. Please provide information that justifies ignoring the potential fibrous debris generation from break locations not considered in the break selection process. It is possible that fibrous debris outside of the currently selected break zone of influences (ZOls), when combined with relatively small amount of Cal-Sil (calcium silicate) debris, could result in a more limiting debris load on the strainer. It is a staff position that a fiber bed much less than 1/8 inch in thickness, when combined with microporous or particulate insulation debris, could result in significant head losses (see Enclosure 1 of ADAMS Accession No. ML080230112).

5. Please provide the materials and construction of the jacketing systems for the insulation within the lOis for the selected breaks. Provide the type of debris expected to be generated if the jacketing systems are damaged. Also, provide information that justifies that the jacketing material itself will not contribute to strainer head loss, or that the head loss effects of the jacketing material have been appropriately considered.

6. The debris characteristics discussion in the supplemental response dated June 30, 2008, did not provide a debris size distribution for Cal-Sil and Microtherm debris, as was requested in the NRC's Revised Content Guide. Provide the assumed debris size distribution and characteristic size for Cal-Sil and Microtherm debris generated during a loss-of-coolant accident (LOCA) so that the staff can verify the prototypicality of the debris used for head loss testing. Also, specifically identify the quantity of individual fines assumed to be generated for each of these types of debris for comparison to the debris used for head loss testing. Provide a technical basis for any assumptions made that are not consistent with approved guidance in the Nuclear Regulatory Commission (NRC) staff's approved safety evaluation (SE) on NEI [Nuclear Energy Institute] 04-07.

Enclosure

-2

7. On page 37, the June 30,2008, supplemental response indicates that debris size distributions were assumed for Nukon and RMI in the downstream effects evaluations.

Provide these assumed debris size distributions. Specifically, for each type of debris, provide the percentage of debris assumed in each debris size category, and the characteristic size for each debris type, and provide a technical basis for these values.

8. Given that at Turkey Point Unit 3 there appears to be no margin between the walkdown latent debris value and the input value to the transport/head loss analysis, describe the statistical methodology used to compute the sample mass used in the estimates of total latent debris mass. Provide the accuracy of the individual sample mass measurements and the influence of the uncertainty in the samples on the total calculated mass of latent debris.

In responding to this question, state any assumptions made or conservatisms taken during the analysis.

9. Please provide a more detailed discussion of the technical basis for the total area of tapes, stickers, etc., beyond just the values used in the calculation of strainer sacrificial area, including any assumptions that would reduce the quantity of material transported to the sump screen.

10. The June 30, 2008, supplemental response assumed 0% paint chip transport, but does not provide adequate basis to substantiate this assumption. Provide the following information to justify this assumption:

a. An explanation of how the transport calculation accounts for the washdown of paint chips into the outer annulus near the strainer. A curb lift velocity metric does not apply for paint chips that wash down from upper elevations onto or near the strainer.

b. The velocities quoted in the supplemental response for the regions beneath the strainers and between strainer disks appear to be average velocities. However, local velocities typically vary significantly from these average values and can be much higher near the suction of the emergency core cooling system (ECCS) piping and along flow channels in the sump pool where much of the flow from the spray or break moves toward the strainers. Explain how local variations in the flow velocity have been accounted for.

c. A justification that the paint chips at Turkey Point Unit 3 are physically similar to the paint chips for which the test results in NUREG/CR-6808 were derived.

d. Given the information in Table 3.e-1 in the supplemental response, the unqualified coatings debris transport fraction appears to be 1 because the quantity transported is equal to the quantity generated. In light of this information, please clarify how the conclusion that paint chips are nontransportable is applied in the transport calculation.

11. The extrapolation of test results to different conditions is discussed in the supplemental response. The supplemental response states that the sector test head loss was scaled to the full-sized strainer system based on velocity and bed thicknesses. State all other extrapolations or scaling that was performed for the head loss evaluation (e.g., temperature

-3 and mission time). Provide the methodology for all scaling including the inputs and assumptions used.

12. Please provide the clean strainer head loss (CSHL) calculation methodology. Include information that shows that CSHL is independent of debris build up on the strainer, or provide justification that the CSHL calculation was conservative or prototypical.

13. It was implied that the debris was added to the sector test prior to starting the recirculation pump. Provide details on the test sequence and also provide justification that adding debris prior to starting the recirculation pump would result in prototypical or conservative head loss values during the test.

14. Provide documentation for the testing methodology including:

a. debris introduction sequences (debris type and size distribution) including time between additions

b. description of test facility

c. general procedure for conducting the tests

d. debris introduction zones

e. fibrous size distribution and comparison to transport evaluation predictions showing that non-prototypical fiber sizes were not added to the test.

f. particulate debris size distributions

g. amounts of each debris type added to each test

h. test strainer area for each test

i. test flow rates

j. description of debris introduction (including debris mixes and concentrations) showing that agglomeration did not occur

15. Provide documentation of the amount of debris that settled in the agitated and nonagitated areas of the test tank. The supplemental response stated that debris was maintained in suspension using stirring. No information was provided to show that the stirring did not drive nonprototypical debris onto the bed nor prevent debris from collecting naturally on the strainer. Please provide information that verifies that the stirring did not result in nonprototypical bed formation.

16. Please provide the test termination criteria and sufficient data to show that the tests were run in accordance with that criteria.

17. Provide information that shows that flashing will not occur within the strainer. The flashing evaluation did not provide the margin to flashing through the strainer. The supplemental response stated that a small amount of containment air pressure was credited, but the amount of overpressure credited was not provided, nor was the available margin to flashing.

The total head loss, including chemical effects, was not provided. Submergence was stated to be less than 1 foot. Include the inputs and assumptions used to make this determination.

Provide the margin to flashing at the limiting point during recirculation.

18. The supplemental response stated that the vortexing evaluation was conducted with submergence levels less than those expected during recirculation. However, the flow rate assumed for the vortexing evaluation was not provided. Strainer modules hydraulically closer to the pump suctions would have higher flow rates early in debris bed formation. The

-4 supplemental response did not provide the actual flow rates through the modules under clean conditions nor state whether some modules could experience higher flow rates than others. Provide the maximum flow through the vortex limiting strainer module in the array under clean conditions. Verify that the flow rates used for the vortexing evaluation and strainer testing bound the actual flow rates expected.

19. Provide final integrated chemical effects head loss values and updated head loss, vortexing and flashing evaluation based on these values.

20. Provide the assumptions and methods used to evaluate the maximum recirculation sump flow rates. Please discuss the basis for specifying a change in sump flow from 2697 gpm to 3750 gpm at the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> point in the event, as well as the pump operating configurations, assumptions, and methodology used to calculate the flows for both cases.

21. Provide the method used for estimation of the head losses in the suction lines.

22. The licensee states that the net positive suction head required (NPSHr) for the pumps were based on pump test curves. While use of NPSHr data provided by the manufacturer may be acceptable, it is not clear that the equivalent of the Regulatory Guide 1.82, Revision 3, 3%

criterion has been used. Provide more detail as to the basis for the pump test curves and state whether the 3% criterion was applied.

23. The supplemental response does not discuss the distinction between cold-leg and hot-leg recirculation scenarios, in which the pump lineups and, therefore, the flow rates, may be different. If plant procedures address both scenarios, NPSH results for both scenarios should be presented, or a basis should be provided establishing that one or the other scenario is limiting.

24. Provide technical justification in support of the assumption of "no blockage of the refueling pool canal drains." Identify the type, physical characteristics (size, shape, etc.) and amounts of debris that may be blown into the refueling cavity during a LOCA. If it is determined that drainage from the refueling cavity could be blocked, specify the volume of water held up in the cavity and state the effect on minimum containment sump pool level.

25. Your June 30,2008, response to GL 2004-02 states that the final sump fluid pH is achieved by manual addition of sodium tetraborate (STB) following a LOCA rather than by dissolution of STB already stored in the lowest elevation of the reactor building. Provide the procedure for addition of sodium tetraborate following a LOCA. Where is the sodium tetraborate stored during normal plant operation? How is the sodium tetraborate transported to the containment building and how is it physically added to the sump?

26. What surveillance requirements are in place to ensure that the required quantity of sodium tetraborate is available to provide adequate sump bUffering?

27. What surveillance requirements are in place to ensure that the sodium tetraborate's chemical and physical properties are maintained in a manner that allows for timely addition, dissolution, and adequate pH control? Are chemical tests performed periodically to ensure the buffer capacity of the stored sodium tetraborate? Are physical tests performed to ensure that densification of the sodium tetraborate has not occurred over time? If the sodium

-5 tetraborate is exposed to humid conditions in the storage facility the pellets/granules may solidify, which would impede both dissolution and addition to the sump. How is this potential phenomena addressed at Turkey Point?

28. Because addition of the sodium tetraborate is performed manually (as opposed to a passive system in the containment) the amount of time required to add the required amount to buffer to the sump pool may be longer. Provide the amount of time needed to manually add the required amount of sodium tetraborate. Has the dose for the personnel performing the manual addition process been estimated? Does the time dependant sump pH profile used to determine material dissolution (e.g., aluminum, calcium, silica) consider the time required to manually add the sodium tetraborate?

29. The June 30, 2008, GL 2004-02 response states that buffer addition occurs until a pH of 7.2 is achieved. How is the sump fluid pH monitored following a LOGA to ensure that an adequate quantity of sodium tetraborate has been added to achieve a pH of no lower than 7.2?

30. The licensee made the statement on page 68 of the June 30 supplemental response that aluminum ladders are above the LOGA flood level, so there is no adverse impact on the sump strainers from these ladders. Describe how the possible contact of containment spray water with these aluminum ladders was considered with respect to chemical effects.

31. Page 29 of the June 30, 2008, supplemental response states that the replacement strainer design does not have trash racks. The supplemental response also states that the original sump design did not include trash racks. However, the staff noted that existing TS 4.5.2.e.3 refers to trash racks being present. Are there plans to revise TS 4.5.2.e.3 to remove the reference to a trash rack being present to be consistent with the current design of the Turkey Point Unit 3 sump?

32. Page 26 of the June 30, 2008, supplemental response indicates that the replacement EGGS strainer design is a common, non-independent strainer assembly shared by both trains. The response indicates that this design is not a departure from the current licensing basis because the original EGGS sump intake design included a permanent cross-connection between trains that was located outside of containment. Provide the following additional information concerning the original EGGS sump intake design:

a. Please provide a piping system diagram that includes the cross-connection line between the EGGS sump suction lines.

b. Please state whether the original EGGS sump suction lines were normally isolated, independent lines during sump recirculation mode that could be cross-connected by operator action, or whether the cross-connect was normally open in recirculation mode.

c. Please identify the type of valves installed on the cross-connect line (if any) and whether remote or manual operation would be necessary to operate the valves.

d. If the cross-connection line was a normally isolated line during recirculation, then this would indicate that the original EGGS sump screens were independent screens that

-6 could be shared if desired during an event, which is a different configuration than the current replacement strainer design that does not have independence. Justify any change to the plant licensing basis that is necessary if the independence of the original sump screens was reduced.

33. The NRC staff considers in-vessel downstream effects to not be fully addressed at Turkey Point Unit 3 as well as at other pressurized-water reactors. Turkey Point Unit 3's supplemental response refers to draft WCAP-16793-NP, "Evaluation of Long-Term Cooling Considering Particulate, Fibrous, and Chemical Debris in the Recirculating Fluid." The NRC staff has not issued a final SE for WCAP-16793-NP. The licensee may demonstrate that in-vessel downstream effects issues are resolved for Turkey Point Unit 3 by showing that the licensee's plant conditions are bounded by the final WCAP-16793-NP and the corresponding final NRC staff SE, and by addressing the conditions and limitations in the final SE. The licensee may alternatively resolve this item by demonstrating, without reference to WCAP-16793 or the staff SE, that in-vessel downstream effects have been addressed at Turkey Point Unit 3. In any event, the licensee should report how it has addressed the in-vessel downstream effects issue within 90 days of issuance of the final NRC staff SE on WCAP-16793. The NRC staff is developing a Regulatory Issue Summary to inform the industry of the staff's expectations and plans regarding resolution of this remaining aspect of Generic Safety Issue-191 .

J. Stall -2 The licensee may demonstrate that in-vessel downstream effects issues are resolved for Turkey Point, Unit 3, by showing that the licensee's plant conditions are bounded by the final WCAP-16793 and the corresponding final NRC staff SE, and by addressing the conditions and limitations in the final SE. The licensee may also resolve RAI 33 by demonstrating, without reference to WCAP-16793 or the NRC staff SE, that in-vessel downstream effects have been addressed at Turkey Point, Unit 3. The specific issues raised in RAI 33 should be addressed regardless of the approach the licensee chooses to take.

The licensee should report how it has addressed the in-vessel downstream effects issue and the associated RAI referenced above within 90 days of issuance of the final NRC staff SE on WCAP-16793. The NRC staff is currently developing a Regulatory Issue Summary to inform licensees of the staff's expectations and plans regarding resolution of this remaining aspect of Generic Safety Issue 191, "Assessment of Debris Accumulation on PWR Sump Performance."

Sincerely, IRA by JPaige fori Brenda L. 1VI0zafari, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-250

Enclosure:

RAI cc w/encl: Distribution via ListServ DISTRIBUTION:

Public RidsNrrLABClayton Resource RidsAcrsAcnwMailCenter Resource LPL2-2 RlF RidsNrrDorlLpl2-2 RidsNrrDssSsib Resource RidsOgcRp Resource RidsNrrPMBMozafari Resource JPaige RidsRgn2MailCenter RidsNrrDeEmcb RidsNrrDciCsgh ADAMS Accession No ML083380671 OFFICE LPL2-2/PE LPL2-2/PM NRR/LPL2-2/LA NRRlDSS/SSIB NRR/DCI/CSGB LPL2-2/BC JPaige BMozafari BClaylon DHarrison AHiser TBoyce NAME by clPaiqe for By RSoia for by BMozafari for DATE 12/22/08 12/22/08 12/22/08 12/09/08 12/19/08 12/22/08 OFFICIAL RECORD COpy