ML060380017

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

ML060380017
Person / Time
Site:	Surry
Issue date:	02/09/2006
From:	Stephen Monarque Plant Licensing Branch III-2
To:	Christian D Virginia Electric & Power Co (VEPCO)
Monarque, S R, NRR/DORL, 415-1544
References
GL-04-002, TAC MC4722, TAC MC4723
Download: ML060380017 (10)

Text

February 9, 2006Mr. David A. ChristianSenior Vice President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

SURRY POWER STATION, UNITS 1 AND 2, REQUEST FOR ADDITIONALINFORMATION RE: RESPONSE TO GENERIC LETTER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN-BASIS ACCIDENTS AT PRESSURIZED-WATER REACTORS" (TAC NOS. MC4722 AND MC4723)

Dear Mr. Christian:

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 NRC's efforts to assess thelikelihood 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 issuedthis 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-accidentdebris 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 evaluationidentifies as being necessary to ensure system functionality. Addressees were also required tosubmit information specified in GL 2004-02 to the NRC in accordance with Title 10 of the Codeof Federal Regulations Section 50.54(f). Additionally, in the GL, the NRC establis hed aschedule 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 4, 2005, as supplemented by letter dated September 1, 2005, VirginiaElectric and Power Company provided responses to the GL. The NRC staff is reviewing andevaluating your responses along with the responses from all PWR licensees. The NRC staffhas 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 Regulation's Division of Component Integrity is st ill conducting its initial reviews with respect tocoatings. 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 nearfuture.

D. Christian-2-Please provide your response within 60 days from the date of this letter. If you have anyquestions, please contact me at (301) 415-1544.Sincerely,/RA/Stephen Monarque, Project ManagerPlant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket Nos. 50-280 and 50-281

Enclosure:

Request for Additional Informationcc w/encl: See next page D. Christian-2-Please provide your response within 60 days from the date of this letter. If you have anyquestions, please contact me at (301) 415-1544.Sincerely,/RA/Stephen Monarque, Project ManagerPlant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket Nos. 50-280 and 50-281

Enclosure:

Request for Additional Informationcc w/encl: See next pageDistribution

PUBLICBSingal, DORL DPRRArchitzel LPL2-1 Reading FileWBatemanTHaffera RidsNrrDorlLplcRidsNrrPmJHopkinsJLehning RidsNrrLAMO'BrienRidsNrrDorlDprHWagage RidsNrrPSMonarqueMMurphySLu RidsOgcRpPKleinJHannon RidsAcrsAcnwMailCenterMYoder RidsRgn2MailcenterMScottAccession No.: ML060380017*by emailNRR-088OFFICELPL2-1/PMLPL2-1/LADSS/SSIBDCI/CSGBLPL2-1/BCNAMESMonarqueMO'BrienDSoloris*EMurphy*EMarinos DATE2/9/062/9/062/6/062/8/062/9/06OFFICIAL RECORD COPY Surry Power Station, Units 1 & 2 cc:

Ms. Lillian M. Cuoco, Esq.Senior Counsel Dominion Resources Services, Inc.

Building 475, 5th Floor Rope Ferry Road Waterford, Connecticut 06385Mr. Donald E. JerniganSite Vice President Surry Power Station Virginia Electric and Power Company 5570 Hog Island Road Surry, Virginia 23883-0315Senior Resident InspectorSurry Power Station U. S. Nuclear Regulatory Commission 5850 Hog Island Road Surry, Virginia 23883ChairmanBoard of Supervisors of Surry County Surry County Courthouse Surry, Virginia 23683Dr. W. T. LoughVirginia State Corporation Commission Division of Energy Regulation Post Office Box 1197 Richmond, Virginia 23218Dr. Robert B. Stroube, MD, MPHState Health Commissioner Office of the Commissioner Virginia Department of Health Post Office Box 2448 Richmond, Virginia 23218Office of the Attorney GeneralCommonwealth of Virginia 900 East Main Street Richmond, Virginia 23219Mr. Chris L. Funderburk, DirectorNuclear Licensing & Operations Support Dominion Resources Services, Inc.

Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, Virginia 23060-6711 EnclosureGL 2004-02 RAI QuestionsPlant Materials1.Identify the name and bounding quantity of each insulation material generated by alarge-break loss-of-coolant accident (LBLOCA). Include the amount of these materials transported to the containment pool. State any assumptions used to provide this response.2.Identify the amounts (i.e., surface area) of the following materials that are: (a) submerged in the containment pool following a 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 concreteCompare the amounts of these materials in the submerged and spray zones at yourplant 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 scaffoldingstored 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 insulationjacketing (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 cooli ng syst em(ECCS) recirculation mission time following a LOCA at the beginning of the fuel cycleand 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 theexpected containment pool conditions to the ICET conditions for the following items:

boron concentration, buffering agent concentration, and pH. Identify any othersignificant differences between the ICET environment and the expected plant-specificenvironment. 7.For a LBLOCA, provide the time until ECCS external recirculation initiation and theassociated pool temperature and pool volume. Provide estimated pool temperature and pool volume 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after a LBLOCA. Identify the assumptions used for these estimates. Plant-Specific Chemical Effects 8.Discuss your overall strategy to evaluate potential chemical effects includingdemonstrating 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 containmentbuilding 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 howthe 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 determi ned 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 partof 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 producedfor 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 resultingfrom 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 ontesting 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.Results from the ICET #1 environment and the ICET #5 environment showed chemicalproducts appeared to form as the test solution cooled from the constant 140 oF testtemperature. Discuss how these results are being considered in your evaluation of chemical effects and downstream effects. Trisodium Phosphate Plants14.(Not applicable).15.(Not applicable).

16.(Not applicable).Additional Non-Coatings 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 Plants25.Describe how your coatings assessment was used to identify degradedqualified/acceptable coatings and determine the amount of debris that will result fromthese 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 requirementsfor DBA performance, licensees should describe an augmented testing and inspection program that provides assurance that the qualified/acceptable coatings continue to meetDBA performance requirements. Alternately, assume all containment coatings fail and describe the potential for this debris to transport to the sump.Plant Specific26.(Not applicable).

27.(Not applicable).

28.(Not applicable). 29.Your GL response indicates that you may pursue a reduction in the radius of the zone ofinfluence (ZOI) for coatings. Identify the radius of the coatings ZOI that will be used foryour final analysis. In addition, provide the test methodology and data used to support your proposed ZOI. Provide justification regarding how the test conditions simulate or correlate to actual plant conditions and will ensure representative or conservativetreatment in the amounts of coatings debris generated by the interaction of coatings anda two-phase jet. Identify all instances where the testing or specimens used deviate from actual plant conditions (i.e., irradiation of actual coatings vice samples, aging differences, etc.). Provide justification regarding how these deviations are accounted for with the test demonstrating the proposed ZOI.30.The NRC staff's safety evaluation (SE) addresses two distinct scenarios for formation ofa fiber bed on the sump screen surface. For a thin bed case, the SE states that all coatings debris should be treated as particulate and assumes 100% transport to the sump screen. For the case in which no thin bed is formed, the staff's SE states that the coatings debris should be sized based on plant-specific analyses for debris generated from within the ZOI and from outside the ZOI, or that a default chip size equivalent to the area of the sump screen openings should be used (Section 3.4.3.6). Describe how your coatings debris characteristics are modeled to account for your plant-specific fiber bed (i.e. thin bed or no thin bed). If your analysis considers both a thin bed and a non-thin bed case, discuss the coatings debris characteristics assumed for each case. If your analysis deviates from the coatings debris characteristics described in the staff-approved methodology, provide justification to support your assumptions.31.Your submittal indicated that you had taken samples for latent debris in yourcontainment, but did not provide any details regarding the number, type, and location of samples. Please provide these details.32.Your submittal did not provide details regarding the characterization of latent debrisfound in your containment as outlined in the NRC SE. Please provide these details.33.Will latent debris sampling become an ongoing program?34.You indicated that you would be evaluating downstream effects in accordance withWCAP 16406-P. The NRC is currently involved in discussions with the WestinghouseOwner'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 berequired. As such, formal RAIs will not be issued on these topics at this time, but maybe needed in the future. It is expected that your final evaluation response willspecifically address those portions of the WCAP used, their applicability, and exceptionstaken to the WCAP. For your information, topics under ongoing discussion include:a.Wear rates of pump-wetted materials and the effect of wear on componentoperationb.Settling of debris in low flow areas downstream of the strainer or credit forfiltering leading to a change in fluid compositionc.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 clogf.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 coolant35.Your response to GL 2004-02 question (d)(viii) indicated that an active strainer designwill not be used, but does not mention any consideration of any other active approaches(i.e., backflushing). Was an active approach considered as a potential strategy or backup for addressing any issues?36.You stated that for materials for which no ZOI values were provided in the NuclearEnergy Institute (NEI) guidance report or the staff SE, conservative ZOI values are applied. Please provide a listing of the materials for which this ZOI approach was applied and the technical reasoning for concluding the value applied is conservative.37.You did not provide information on the details of the debris characteristics assumed intheir evaluations other than to state that the NEI and SE methodologies were applied. Please provide a description of the debris characteristics assumed in these evaluations and include a discussion of the technical justification for deviations from the SE-approved methodology.38.Has debris settling upstream of the sump strainer (i.e., the near-field effect) beencredited or will it be credited in testing used to support the sizing or analytical designbasis of the proposed replacement strainers? In the case that settling was credited foreither 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 plant's containment pool.39.Are there any vents or other penetrations through the strainer control surfaces whichconnect 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 entirestrainer 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.40.What is the basis for concluding that the refueling cavity drain(s) would not becomeblocked 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, aretrash racks or interceptors present to prevent drain blockage? In the case thatpartial/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?41.What is the minimum strainer submergence during the postulated LOCA? At the timethat the re-circulation starts, most of the strainer surface is expected to be clean, and the strainer surface close to the pump suction line may experience higher fluid flow than the rest of the strainer. Has any analysis been done to evaluate the possibility of vortexformation close to the pump suction line and possible air ingestion into the ECCS pumps? In addition, has any analysis or test been performed to evaluate the possible accumulation of buoyant debris on top of the strainer, which may cause the formation of an air flow path directly through the strainer surface and reduce the effectiveness of the strainer?42.The September 2005 GL response stated that the licensee performed computationalfluid dynamics analysis of which outputs included global (entire containment) and local (near sump pit) velocity contours, turbulent kinetic energy contours, path lines and flow distributions for various scenarios. Please explain how you used these outputs to determine the amount of debris that transports to the sump screen.43.In GL 2004-02, item 2.d.iv, the NRC requested licensees to provide the basis forconcluding that the water inventory required to ensure adequate ECCS or ContainmentSpray System recirculation would not be held up or diverted by debris blockage at choke-points in containment recirculation sump return flowpaths. Surry responded that even though no choke-points or flow diversions were identified, the licensee may choose to perform additional verification walkdowns for Unit 1. Provide a date when the NRC will get a supplemental response (if additional walkdowns identify choke points or flowdiversions) with the results of the verification walkdowns.