ML20199D369
| ML20199D369 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 11/17/1997 |
| From: | Quay T NRC (Affiliation Not Assigned) |
| To: | Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| NUDOCS 9711200321 | |
| Download: ML20199D369 (3) | |
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NUCLEAR REGULATORY COMMIS810N WASHINGTON, D.C. m; ?Alset o
Novernber 17, 1997 Mr. Nicholas J. Liparuin, Manager Nuclear Safety and Regulato.y Analysis Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, PA 15230
SUBJECT:
AP600 PASSIVE CONTAINMENT COOLING SYSTEM (PCS) WATER COVERAGE ACCEPTANCE CRITERIA
Dear Mr. Liparulo:
As a result of the staff's continuing review of the AP600 design certification application, the Containment Systems and Severe Accident Branch (SCSB) has identified concems regarding the Westinghouse position on water coverage testing for the AP600 PCS and the use of that information to support the WGOTHIC computer program for design certification.
This issue if further compounded because it spans a number of review areas: (1) the assumptions used in the water coverage model developed for use in WGOTHIC, (2) the initial test and acceptance criteria (ITAAC), (3) the initial test program (ITP), (4) the technical specificationr (TS) and (5) the SSAR.
The limited experimental data available to support water coverage comes from the cold Water Distribution Test (WDT) facility, with some additional support from the Large-Scale Test (LST) facility. The water coverage area fractions used in the wales coverage model, as a func' ion of PCS flow rate, are based on the WDT. The vertical secuon of this test is 4 feet, as compared to about 90 feet in the AP600. The LST has a vertical height of about 12 feet. The PCS has three flow stages during the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> draindown time for the passive containment cooling water storage tank (PCCWST): 442 Cpm for the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />; then as the first standpipe uncovers the flow drops to 122 spm for about 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br />; followed by the uncovery of the second standpipe and a flow of 71.5 gpm to the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> draindown time. Each PCS flow stage has its own unique water coverage area fraction, based on the WDT ebservations.
In SSAR Section 6.2.2.4.2, "Preoperational Testing," it is stated that "With a water level of 6.210.25 feet above the bottom standpipe the containment shell wetted coverage will exceed the amount predicted by the wetting coverage methodology used in the safety analysis." This is not consistent with ITAAC 2.2.2. " Passive Containmint Cooling System," item 8.b), Certified Design Material (CDM) Revision 3, dated May 12,1997, which requires " equal to or greater than" the amount predicted by the wetting coverage methodology used in the refety analysis, in SSAR Section 6.2.2.4.3, " Operational Testing," it is stated that " Operational testing is performed to... ver;fy water flow delivery, cons; stent with the accident analysis." This is further clarified in a response to SCSD comment 47(b) (Westinghouse letter NSD-NRC-97 5263, dated August 19,1997), which states that "SSAR Table 3.9-17 comtrits to verifying the PCS ficw rate
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Mr. Nicholas J. Liparuto 2
November 17, 1997 from each PCS drain line. This test will confirm the c:>oling water flow profile with time remains consistent with the accident analysis. An additional test has been added to the System level inservice Testing Program to confirm the wetted water coverage of the containment shellis equal to or greater than the amount predicted by the wetting coverage methodology used in the safety analysis.'
The Westinghouse position to verify the wetted coverage area for only the minimum PCS flow rate is unacceptable. Further it not known what is meant by "the amount predicted by the wetting coverage methodology used in the safety analysis," or " consistent with the accident analysis."
These phrases are too ambiguous and are also unacceptable.
The staff position is that the wetting coverage area must be verified for each of the three PCS flow rates, in addition to the verificMion of the actual flow rates leaving the PCCWST.
Verification is required during preoperational testing (ITP), and the acceptab!e values must be incorporated into the ITAAC. These values must then be verified at the first refueling outage and at subsequent 10 year intervals (TS). Further, the verification must confirm that the wetting coverage area is uniform along the vertical height as well as around the containment vessel circumference as observed near the upper annulus drain elevation. The performance of the PCS is based on the expectations arising from the WDT (and to a lesser extent, the LST). The acceptable values for the wetted coverage area are equal to or greater than the values observed in the WDT. These WDT values are an integral part of the wetting coverage methodology used by Westinghouse and are an 'ntegral part of the staff's overall understanding of the conservatism in the design certification review. Direct measurement of the expected performance of the water distribution system under conditions similar to the WDT is the only acceptable means for verifying the PCS water coverage.
The AP600 SSAR needs to be updated to reflect the required ITAAC and TS identified above.
Also, tne information provided must emphasize both the water flow rates and the wetted coverage area of the PCS. This has been identified as Open item 480.1084 F. If you have any questions regarding this issue, please call Dino Scaletti at (301) 4151104.
Sincerely, original signed by:
Theodore R. Quay, Director Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No.52-003 cc: See next page QlSTRIBUTION:
- Docket Fileg PDST R/F JWRoe PUBLIC DMatthews TRQuay TKenyon WHuffman JSebrosky DScaletti JNWilson JMoore,015 B18 WDean,0-5 E23 ACRS (ii)
DOCUMENT NAME: A:\\ WATER.WP6 To receive a copy of this document, Indicate in the box: "C" = Copy without attachment / enclosure "E" = Copy with attachment / enclosure
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Mr. Nicholas J. Liparu!o Docket No. 52 003 Wes'Jnghouse Electric Corporation AP600 cc:
Mr. B. A. McIntyre Mr. Russ Bell Advanced Plant Safety & Licensing Senior Project Manager, Programs Westinghouse Electric Corporation Nuclear Energy Institute Energy Systems Business Unit 1776 i Street, NW P.O. Box 355 Suite 300 Pittsburgh, PA 15230 Washington, DC 20006 3703 Mr. Cindy L. Haag Ms. Lynn Connor Advanced Plant Safety & ucensing Doc-Search Associates Westinghouse Electric Corporation Post Office Box 34 Energy Systems Business Unit Cabin John, MD 20818 Box 355 Pittsburgh, PA 15230 Dr. Cralg D. Sawyer, Manager Advanced Reactor Programs Mr. Steriing Franks GE Nuclear Energy U.S. Department of Energy 175 Curtner Avenue, MC-754 NE 50 San Jose, CA 95125 19901 Germantown Road Germantown, MD 20874 Mr. Robert H. Buchholz GE Nuclear Energy Mr. Frank A. Ross 175 Curtner Avenue, MC-781 U.S. Department of Energy, NE-42 San Jose, CA 95125 Office of LWR Safety and Technology 19001 Germantown Road Barton Z. Cowan, Esq.
Germantown, MD 20874 Eckert Seamans Cherin & Mellott 600 Grant Street 42nd Floor Mr. Charles Thompson, Nuclear Engineer Pittsburgh, PA 15219 AP600 Certification NE 50 Mr. Ed Rodwell, Manager 19901 Germantown Roba PWR De.tign Certification Germaritown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 94303
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