ML20198B583
| ML20198B583 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1998 |
| From: | Wen P NRC (Affiliation Not Assigned) |
| To: | Sepp H WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| References | |
| TAC-M99107, NUDOCS 9812210020 | |
| Download: ML20198B583 (3) | |
Text
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4 November 24, 1998 p
g Mr. Henry A. Sepp, Manager t
ny;, y' p q-Regulatory and Licensing Engineering Westinghouse Electric Corporatiorp fP-1 l'!l 0: 05
'A Mail Stop ECE 4-07A Post Office Box 355 PU?LIC 00CUiiOiT f:00M Pittsburgh, Pennsylvania 15230-0365
SUBJECT:
SUPPLEMENTAL REQUEST FOR ADDITIONAL INFORMATION REGARDING WCAP-14882, REV. O,"RETRAN-02 MODELING AND QUALIFICATION FOR WESTINGHOUSE PRESSURIZED WATER REACTOR NON-LOCA SAFETY ANALYSIS"(TAC No. M99107)
Dear Mr. Sepp:
l-Following the staff's initial review of WCAP-14882, the staff prepared a set of 21 RAls which l
were transmitted to Westinghouse dated June 1,1998. These were answered dated August 26,1998, October 30,1998, and November 12,1998. The Westinghouse responses identified modeling assumptions regarding reactor core mixing, decay heat, the accumulators and the pressurizer which were not described in the WCAP. The staff has determined a need for additional information in this regard. The enclosure to this letter identifies the information i
requimd. Please address your response to the NRC Document Control Desk.
If you have any questions, please contact me at 301/415-2832 (email, pxw@nrc. gov) or Wa!t lensen at 301/415-2856 (email, wij@nrc. gov).
Sincerely, 1
/
1 Peter C. Wen, Project Manager Generic issues and Environmental Projects Branch l
Office of Nuclear Reactor Regulation
Enclosure:
Supplemental RAI on topical report WCAP -14882, Rev 0 cc w/ encl: See next page
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Mr. Nicholas Liparulo, Manager Equipment Design and Regulatory Engineering.
Westinghouse Electric Corporation-Mail Stop ECE 4-15 P.O. Box 355 Pittsburgh, PA 15230-0355 Mr. Jack Bastin, Director i
Regulatory Affairs Westinghouse Electric Corporation 11921 Rockville Pike Suite 107
- Rockville, MD 20852 Mr. Sumit Ray, Manager
' Fuel Licensing -
Westinghouse Electric Corporation l
PO Box 355 Pittsburgh, PA 15230-0355 L
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e Supplemental Request for information Regarding WCAP-14882 Rev. O RETRAN-02 Modeling and Qualification for Westinghouse Pressurized Water Reactor Non-LOCA Safety Analysis
- 1. For analysis of feedwater system malfunctions, RETRAN is run with "no inlet mixing" for the coolant entering the core and with " perfect outlet mixing" for the coolant exiting the core.
Justify that these assumptions are conservative for calculating DNBR by comparison to the assumption of " design mixing" which is based on experimental data.
2, Please provide the equation used to generate the Westinghouse decay heat curva which will be used with your RETRAN analyses. Provide a graphical comparison with the ANS 5.1 decay heat standard using conservative inputs for ANS 5.1, Justify that the inputs to the
' ANS 5.1 standard are conservative for analysis of Westinghouse PWRs.
- 3. Following a main steam line break, core power generation is reduced by injection of boric acid from the accumulators. The accumulator modelin RETRAN assumes the accumulator gas to be at the same temperature as the water. This assumption may result in accumulator flow rates that are too high and which may be non-conservative for main steam line break analysis. We understand that Westinghouse makes an adjustment to the accumulatorjunction loss coefficient to account for this effect based on reactor plant data. Provide comparisons of RETRAN results to the plant data showing the development of the adjusted loss coefficient.
Justify that the plant data represents an accumulator blowdown representative of that which would occur during a postulated main steam line break accident. Justify that your evaluation is inclusive of 2-and 3-loop plants as well as for the 4-loop plant analyzed in WCAP-14882.
- 4. The pressurizer model in RETRAN appears to assume instantaneous flashing of liquid when saturation conditions are reached. Pressurizer flashing might result from a sudden reactor system depressurization produced by an overcooling transient. Instead of being instantaneous, flashing of the liquid might be delayed for a time as the steam bubbles form on nucleation sites within the pressurizer. Delayed flashing could cause the reactor system pressure to be lower than that predicted by RETRAN. Justify that RETRAN predictions for reactor system pressure will be conservative for use in DNBR calculations for rapid overcooling transients.
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ENCLOSURE 4
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