ML060370533

RAI - Response to Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design-Basis Accidents at Pressurized-Water Reactors

ML060370533
Person / Time
Site:	Palisades
Issue date:	02/09/2006
From:	Padovan L Plant Licensing Branch III-2
To:	Harden P Nuclear Management Co
padovan L, NRR/DORL, 415-1423
References
GL-04-002, TAC MC4701
Download: ML060370533 (10)

Text

February 9, 2006 Mr. Paul A. Harden Site Vice President Nuclear Management Company, LLC Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530

SUBJECT:

PALISADES PLANT - REQUEST FOR ADDITIONAL INFORMATION RE:

RESPONSE TO GENERIC LETTER 2004-02, POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN-BASIS ACCIDENTS AT PRESSURIZED-WATER REACTORS (TAC NO. MC4701)

Dear Mr. Harden:

On September 13, 2004, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors, as part of the NRCs efforts to assess the likelihood that the emergency core cooling system (ECCS) and containment spray system (CSS) pumps at domestic pressurized water reactors (PWRs) would experience a debris-induced loss of net positive suction head margin during sump recirculation. The NRC issued this GL to all PWR licensees to request that addressees (1) perform a mechanistic evaluation using an NRC-approved methodology of the potential for the adverse effects of post-accident debris blockage and operation with debris-laden fluids to impede or prevent the recirculation functions of the ECCS and CSS following all postulated accidents for which the recirculation of these systems is required, and (2) implement any plant modifications that the above evaluation identifies as being necessary to ensure system functionality. Addressees were also required to submit information specified in GL 2004-02 to the NRC in accordance with Title 10 of the Code of Federal Regulations Section 50.54(f). Additionally, in the GL, the NRC established a schedule for the submittal of the written responses and the completion of any corrective actions identified while complying with the requests in the GL.

By letter dated March 7, 2005, supplemented by letters dated July 11, and August 25, 2005, Nuclear Management Company, LLC provided a response to the GL. The NRC staff is reviewing and evaluating your response along with the responses from all PWR licensees. The NRC staff has determined that responses to the questions in the enclosure to this letter are necessary in order for the staff to complete its review. Please note that the Office of Nuclear Reactor Regulations Division of Component Integrity is still conducting its initial reviews with respect to coatings. Although some initial coatings questions are included in the enclosure to this letter, the NRC might issue an additional request for information regarding coatings issues in the near future.

P. Harden Please provide your response within 60 days from the date of this letter. If you have any questions, please contact me at (301) 415-1423.

Sincerely,

/RA/

L. Mark Padovan, Project Manager Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-255

Enclosure:

Request for Additional Information cc w/encl: see next page

ML060370533 *per e-mail OFFICE LPL3-1/PM LPL3-1/LA DSS/SSIB DCI/CSGB LPL3-1/BC (A)

NAME MPadovan THarris DSolorio* EMurphy* TKobetz DATE 2/9/06 2/9/06 2/6/06 2/8/06 2/9/06 Palisades Plant cc:

Robert A. Fenech, Senior Vice President Michigan Department of Attorney General Nuclear, Fossil, and Hydro Operations Special Litigation Division Consumers Energy Company 525 West Ottawa St.

1945 Parnall Rd. Sixth Floor, G. Mennen Williams Building Jackson, MI 49201 Lansing, MI 48913 Michael B. Sellman Arunas T. Udrys, Esquire President and Chief Executive Officer Consumers Energy Company Nuclear Management Company, LLC 1 Energy Plaza 700 First Street Jackson, MI 49201 Hudson, MI 54016 Jonathan Rogoff, Esquire Regional Administrator, Region III Vice President, Counsel & Secretary U.S. Nuclear Regulatory Commission Nuclear Management Company, LLC Suite 210 700 First Street 2443 Warrenville Road Hudson, WI 54016 Lisle, IL 60532-4351 Douglas E. Cooper Supervisor Senior Vice President - Group Operations Covert Township Palisades Nuclear Plant P. O. Box 35 Nuclear Management Company, LLC Covert, MI 49043 27780 Blue Star Memorial Highway Covert, MI 49043 Office of the Governor P. O. Box 30013 Lansing, MI 48909 Stephen T. Wawro, Director of Nuclear Assets U.S. Nuclear Regulatory Commission Consumers Energy Company Resident Inspector's Office Palisades Nuclear Plant Palisades Plant 27780 Blue Star Memorial Highway 27782 Blue Star Memorial Highway Covert, MI 49043 Covert, MI 49043 Michigan Department of Environmental Quality Laurie A. Lahti, Manager Waste and Hazardous Materials Division Regulatory Affairs Hazardous Waste and Radiological Nuclear Management Company, LLC Protection Section Palisades Nuclear Plant Nuclear Facilities Unit 27780 Blue Star Memorial Highway Constitution Hall, Lower-Level North Covert, MI 49043 525 West Allegan Street P.O. Box 30241 Lansing, MI 48909-7741 November 2005

GL 2004-02 RAI Questions Plant Materials

1. (Not applicable).

2. Identify the amounts (i.e., surface area) of the following materials that are:

(a) submerged in the containment pool following a loss-of-coolant accident (LOCA),

(b) in the containment spray zone following a LOCA:

- aluminum

- zinc (from galvanized steel and from inorganic zinc coatings)

- copper

- carbon steel not coated

- uncoated concrete Compare the amounts of these materials in the submerged and spray zones at your plant relative to the scaled amounts of these materials used in the Nuclear Regulatory Commission (NRC) nuclear industry jointly-sponsored Integrated Chemical Effects Tests (ICET) (e.g., 5x the amount of uncoated carbon steel assumed for the ICETs).

3. Identify the amount (surface area) and material (e.g., aluminum) for any scaffolding stored in containment. Indicate the amount, if any, that would be submerged in the containment pool following a LOCA. Clarify if scaffolding material was included in the response to Question 2.

4. Provide the type and amount of any metallic paints or non-stainless steel insulation jacketing (not included in the response to Question 2) that would be either submerged or subjected to containment spray.

Containment Pool Chemistry

5. Provide the expected containment pool pH during the emergency core cooling system (ECCS) recirculation mission time following a LOCA at the beginning of the fuel cycle and at the end of the fuel cycle. Identify any key assumptions.

6. For the ICET environment that is the most similar to your plant conditions, compare the expected containment pool conditions to the ICET conditions for the following items:

boron concentration, buffering agent concentration, and pH. Identify any other significant differences between the ICET environment and the expected plant-specific environment.

7. (Not applicable).

ENCLOSURE

Plant-Specific Chemical Effects

8. Discuss your overall strategy to evaluate potential chemical effects including demonstrating that, with chemical effects considered, there is sufficient net positive suction head (NPSH) margin available during the ECCS mission time. Provide an estimated date with milestones for the completion of all chemical effects evaluations.

9. Identify, if applicable, any plans to remove certain materials from the containment building and/or to make a change from the existing chemicals that buffer containment pool pH following a LOCA.

10. If bench-top testing is being used to inform plant specific head loss testing, indicate how the bench-top test parameters (e.g., buffering agent concentrations, pH, materials, etc.)

compare to your plant conditions. Describe your plans for addressing uncertainties related to head loss from chemical effects including, but not limited to, use of chemical surrogates, scaling of sample size and test durations. Discuss how it will be determined that allowances made for chemical effects are conservative.

Plant Environment Specific

11. Provide a detailed description of any testing that has been or will be performed as part of a plant-specific chemical effects assessment. Identify the vendor, if applicable, that will be performing the testing. Identify the environment (e.g., borated water at pH 9, deionized water, tap water) and test temperature for any plant-specific head loss or transport tests. Discuss how any differences between these test environments and your plant containment pool conditions could affect the behavior of chemical surrogates.

Discuss the criteria that will be used to demonstrate that chemical surrogates produced for testing (e.g., head loss, flume) behave in a similar manner physically and chemically as in the ICET environment and plant containment pool environment.

12. For your plant-specific environment, provide the maximum projected head loss resulting from chemical effects (a) within the first day following a LOCA, and (b) during the entire ECCS recirculation mission time. If the response to this question will be based on testing that is either planned or in progress, provide an estimated date for providing this information to the NRC.

ICET 1 and ICET 5 Plants

13. (Not applicable).

Trisodium Phosphate (TSP) Plants

14. Given the results from the ICET #3 tests (Agencywide Document Access and Management System (ADAMS) Accession No. ML053040533) and NRC-sponsored head loss tests (Information Notice 2005-26 and Supplement 1), estimate the concentration of dissolved calcium that would exist in your containment pool from all containment sources (e.g., concrete and materials such as calcium silicate, Marinite',

mineral wool, kaylo) following a large-break LOCA and discuss any ramifications related to the evaluation of chemical effects and downstream effects.

15. (Not applicable).

16. Given an active strainer design, discuss your evaluation of potential downstream effects resulting from chemical products that pass through the active strainer into the ECCS system.

Additional Chemical Effects Questions

17. (Not applicable).

18. (Not applicable).

19. (Not applicable).

20. (Not applicable).

21. (Not applicable).

22. (Not applicable).

23. (Not applicable).

24. (Not applicable).

Coatings Generic - All Plants

25. Describe how your coatings assessment was used to identify degraded qualified/acceptable coatings and determine the amount of debris that will result from these coatings. This should include how the assessment technique(s) demonstrates that qualified/acceptable coatings remain in compliance with plant licensing requirements for design basis accident (DBA) performance. If current examination techniques cannot demonstrate the coatings ability to meet plant licensing requirements for DBA performance, licensees should describe an augmented testing and inspection program that provides assurance that the qualified/acceptable coatings continue to meet DBA performance requirements. Alternately, assume all containment coatings fail and describe the potential for this debris to transport to the sump.

Plant Specific

26. (Not applicable).

27. (Not applicable).

28. (Not applicable).

29. (Not applicable).

30. (Not applicable).

31. You indicated that you would be evaluating downstream effects in accordance with WCAP 16406-P. The NRC is currently involved in discussions with the Westinghouse Owner's Group (WOG) to address questions/concerns regarding this WCAP on a generic basis, and some of these discussions may resolve issues related to your particular station. The following issues have the potential for generic resolution; however, if a generic resolution cannot be obtained, plant-specific resolution will be required. As such, formal RAIs will not be issued on these topics at this time, but may be needed in the future. It is expected that your final evaluation response will specifically address those portions of the WCAP used, their applicability, and exceptions taken to the WCAP. For your information, topics under ongoing discussion include:

a. Wear rates of pump-wetted materials and the effect of wear on component operation

b. Settling of debris in low flow areas downstream of the strainer or credit for filtering leading to a change in fluid composition

c. Volume of debris injected into the reactor vessel and core region

d. Debris types and properties

e. Contribution of in-vessel velocity profile to the formation of a debris bed or clog

f. Fluid and metal component temperature impact

g. Gravitational and temperature gradients

h. Debris and boron precipitation effects

i. ECCS injection paths

j. Core bypass design features

k. Radiation and chemical considerations

l. Debris adhesion to solid surfaces

m. Thermodynamic properties of coolant

32. An active strainer effectively reduces all debris that reaches the active screen into fine fibers and small particulates, then passes them on through the screen into the reactor vessel. Therefore, all the topics highlighted above must also include an evaluation for long-term erosion/degradation of all debris that is postulated to reach the active screen

33. The NRC staffs SE discusses a systematic approach to the break selection process where an initial break location is selected at a convenient location (such as the terminal end of the piping) and break locations would be evaluated at 5-foot intervals in order to evaluate all break locations. For each break location, all phases of the accident scenario are evaluated. It is not clear that you have applied such an approach. Please discuss how the limiting break locations listed as being evaluated in your GL response were selected.

34. Were secondary side breaks (e.g., main steam, feedwater) considered in the break

selection analyses? Would these breaks rely on ECCS sump recirculation?

35. The staff SE refers to Regulatory Guide 1.82 which lists considerations for determining the limiting break location (staff position 1.3.2.3). Please discuss how these considerations were evaluated as part of the Palisades break selection analyses.

36. The licensees GL response provides an illustration showing the analyzed break locations. The sump is shown in the pressure relief valve compartment. Please discuss the basis for not evaluating a break in this compartment, as a break in this compartment seems likely to have the most direct path to the sump.

37. The licensee includes an analyzed break called alternate break. Is this break analyzed in accordance with the Alternate Methodology (Section 6) of the NRC staffs SE? It is not clear from the GL response how the alternate approach is being applied. Please provide a detailed discussion of how the SE Section 6 methodology is being applied.

38. The licensee did not provide information on the details of the break selection, zone of influence and debris characteristics evaluations other than to state that the Nuclear Energy Institute and SE methodologies were applied. Please provide a description of the methodology applied in these evaluations and include a discussion of the technical justification for deviations from the SE-approved methodology.

39. How much passive strainer area will be available to complement the active strainer?

Describe the passive portion of the strainer. Also, describe whether/how this area was or will be credited during plant-specific testing.

40. What specific sources of hold-up are accounted for in the containment minimum water level calculation?

41. Is it possible for large pieces of insulation or other large pieces of latent or foreign material debris to be transported to the active strainers (e.g., via blowdown from the break, sheeting flows that might occur during the initial phase of an accident, or floatation)? If so, are the active strainers protected from large pieces of debris, for example, with trash racks or other interceptors? If protection does not exist, then to what extent are the strainers capable of withstanding large pieces of debris, and to what extent has this capability been demonstrated by testing?

42. What is the minimum submergence depth for the active strainers? Describe the testing and analysis that has been performed to demonstrate that large pieces of debris and/or high concentrations of debris at the strainer surface would not prevent the entry of water into the strainer under shallow submergence conditions.

43. Please explain the derivation of the maximum concentration of debris that will arrive at the active strainer and justify that the analyzed maximum concentration is conservative.

How much margin exists between the analyzed maximum concentration and the estimated point of failure of the active strainer?

44. How much margin (i.e., water volume) is available between the maximum containment

water level and the level at which the active strainer motors would become flooded?

45. Are there any vents or other penetrations through the active or passive strainer control surfaces which connect the volume internal to the strainer to the containment atmosphere above the containment minimum water level? In this case, dependent upon the containment pool height and strainer and sump geometries, the presence of the vent line or penetration could prevent a water seal over the entire strainer surface from ever forming; or else this seal could be lost once the head loss across the debris bed exceeds a certain criterion, such as the submergence depth of the vent line or penetration. According to Appendix A to Regulatory Guide 1.82, Revision 3, without a water seal across the entire strainer surface, the strainer should not be considered to be fully submerged. Therefore, if applicable, explain what sump strainer failure criteria are being applied for the vented sump scenario described above.

46. What is the basis for concluding that the refueling cavity drain(s) would not become blocked with debris? What are the potential types and characteristics of debris that could reach these drains? In particular, could large pieces of debris be blown into the upper containment by pipe breaks occurring in the lower containment, and subsequently drop into the cavity? In the case that large pieces of debris could reach the cavity, are trash racks or interceptors present to prevent drain blockage? In the case that partial/total blockage of the drains might occur, do water hold-up calculations used in the computation of NPSH margin account for the lost or held-up water resulting from debris blockage?

47. Has debris settling upstream of the sump strainer (i.e., the near-field effect) been credited or will it be credited in testing used to support the sizing or analytical design basis of the proposed replacement strainers? In the case that settling was credited for any of these purposes, estimate the fraction of debris that settled and describe the analyses that were performed to correlate the scaled flow conditions and any surrogate debris in the test flume with the actual flow conditions and debris types in the plants containment pool.