ML20059A913
| ML20059A913 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Catawba, McGuire  |
| Issue date: | 10/18/1993 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9310270210 | |
| Download: ML20059A913 (3) | |
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DukeIbwer Company M S Tixxnw P.O Box 1006 Senior 1ke President Quarlotte, NC21'01M NudearGenerahon (704)38222000fhce (704)3324360 Fax DUKEPOWER October 18 1993 r
U. S Nuclear Regulatory Commission Washington D.
C.
20555 Attentions Document Control Desk h
Subject McGuire Nuclear Station Docket Numbers 50-369 and -370 Catawba Nuclear Station Docket Numbers 50-413 and 414 Report Pursuant to 10 CFR 50.46, Changes to or Errors in an ECCS Evaluation Model Westinghouse Electric Corporation recently issued Nuclear Safety Advisory Letter 93-018, Safety Injection in the Broken Loop, which describes a significant change to the NOTRUMP SBLOCA ECCS evaluation model. The change to the evaluation model resulted from the discovery that the historic assumption of no safety injection into the broken loop was non-conservative rather than conservative, such that explicitly modeling the safety injection into the broken loop was a significant peak clad temperature (PCT) penalty (approximately 150 *F).
This change was evaluated with respect to the analyses documented in the FSARs for the McGuire and Catawba Nuclear Stations. The results of this evaluation are presented in the Attachment. The results show that even with the penalty, the PCTs for each station are well below the 2200 'F limit imposed in 10 CFR 50.46.
Duke is continuing to review and discuss this issue with Westinghouse and the Westinghouse Owners Group (WOG). WOG, in turn, is evaluating the development of a generic program to resolve the issue for affected licensees. Further details will be forwarded to the NRC as they become available.
If there are any questions, please call Scott Gewehr ((704) 382-7581) or Jacky Lee ((704) 382-7565).
1 Very truly yours, f'k.
Ok &wn M.
S.
Tuckman ec:
Mr. V. Nerses, Project Manager Office of Nuclear Reactor Regulation U.
S.
Nuclear Regulatory Commission Mail Stop 14H25, OWFN Washington, D.
C.
20555 Mr. R. E. Martin, Project Manager Office of Nuclear Reactor Regulation U.
S. Nuclear Regulatory Commission Mail Stop 14H25, OWFN j
Washington, D. C.
20555 264102 9310270210 931018 PDR ADOCK 05000369
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Attachment l
l SBLOCA EM Chances The 1985 Westinghouse ECCS EM analyses apply to all fuel types in the McGuire and Catawba cores.
The analyses shown in the McGuire FSAR are for a case in which a 1488 *F PCT is calculated. As shown in Table 15-32, EM changes previously reported to the NRC could result in an increase in this value by up' i
to 102
- F.
The analyses shown in the Catawba FSAR are for a case in which a 1304 'F PCT is calculated. As shown in Table 15-39, EM changes previously reported to the NRC could result in an increase in this value by up to 136 *F.
Per a letter from Westinghouse (Reference DPC-93-226, September 22, 1993, letter from J. M.
Hall (Westinghouse) to W. M.
Sample (Duke), " Safety Injection in the Broken Loop"), assuming that the safety injection flow directed to the broken RCS loop actually reaches it, rather than spilling into i
the containment sump, increases the PCT by 150
- F.
The increase occurs because the SI flow reduces the ability of the steam generated in the partially uncovered core to vent through the break. A model change to the NOTRUMP EM, based on COSI facility test data, to credit condensation of the venting steam by the colder SI liquid introduces an offsetting decrease in PCT of at least the same 150 *F magnitude.
It is unclear how this offset will be allowed by the NRC to be credited.
This change is obviously above the 50 *F "significant" change threshold of 10 CFR 50.46, necessitating the 30 day t
report.
An error was corrected (
Reference:
DPC-93-228, September 27, 1993, letter from Westinghouse (J. M.
Hall) to Duke Power (W. M. Sample), "10 CFR 50.46 Notification and Reporting Information") in the. computation of countercurrent flow in vertical flow links.
The C. parameter in Equation G-65 of NOTRUMP EM topical report was set to its correct maximum value of 1.3926.
This error i
correction results in a benefit in PCT of at least 13 'F.
Because the change could be greater, as much as 55
'F in some cases, Westinghouse recommends treating it as a significant change.
The net effect of the two changes is shown in the following tables McGuire-Catawba-(*F)
(*F)
Analysis result on which FSAR figures are 1488 1304 based Prior changes in PCT
+102
+136 Effect of putting SI in the broken loop
+150
+150 l
Effect of correcting vertical countercurrent
-13
-13 flow error
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Resulting PCT 1727 1577 Effect of crediting condensation per COSI test
-150
-150 3
data Resulting PCT 1577 1427 i
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U.
S.
Nuclear Regulatory Commission October 18, 1993 Page 2 Mr. S.
D. Ebneter, Regional Administrator U.S. Nuclear Regulatory Commission - Region II 101 Marietta Street, NW - Suite 2900 Atlanta, Georgia 30323 G.
F. Maxwell Senior Resident Inspector McGuire Euclect Station R.
J.
Freudenberger Senior Resident Inspector Catawba Nuclear Station
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