ML13309B235
| ML13309B235 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/14/1983 |
| From: | Knighton G Office of Nuclear Reactor Regulation |
| To: | Bernath L, Cotton G, Dietch R San Diego Gas & Electric Co, Southern California Edison Co |
| References | |
| NUDOCS 8302250496 | |
| Download: ML13309B235 (6) | |
Text
DISTRIBUTION Document Control 50361/362 NRC PDR Attorney, OELD L PDR ACRS (16)
PRC System Taylor, IE NSIC Jordan IE LB#3 Reading Docket Nos. 50-361 JLee and 50-362 RMattson FEB 1 4 1983 HRood OParr Mr. Robert Dietch Mr. Gary D. Cotton Vice President Mr. Louis Bernath Southern California Edison Company San Diego Gas & Electric Company 2244 Walnut Grove Avenue 101 Ash Street Post Office Box 800 Post Office Box 1831 Rosemead, California 91770 San Diego, California 92112 Gentlemen:
SUBJECT:
AFW PUMP MOTOR BEARING QUALIFICATION AND CPC SOFTWARE ERROR The purpose of this letter is to inform you of recent conclusions reached by the NRC staff regarding the two subject issues:
to request that you make certain changes in San Onofre 2 and 3 relating to each area; and to request that you provide us with schedules for implementation of changes in each area.
AFW Pump Motor Bearing Qualification In May of 1982 you informed us that the Babbitt bearings in the electric motors of the AFW pumps were not qualified for the conditions which are predicted to result from a postulated steam line break in theAFW pump room.
Under these.conditions the San Onofre 2 and 3 auxiliary feedwater system does not meet Position 5 of Branch Technical Position ASB 10-1, "Design Guidelines for Auxiliary Feedwater System Pump Drive and Power Supply Diversity for Pressuized Water Reactors" which requires that the AFWS be able to perform its safety function following a high energy line break and a single failure.
This position applies to San Onofre 2 and 3 because the AFWS is used during the startup and shutdown of the plant.
Various modifications to the AFWS have been discussed with you as ways of resolving this problem. In your letter of January 11, 1983 you presented the results of a revised AFWS reliability study which indicated that the contribution to AFWS unreliability is low enough that a pipe break in the AFWS pump room need not be considered.
Your analysis indicated that the constribution from the effects of a pipe break to unreliability when con sidering the loss of offsite power as the initiating event is only 10%.
We have reviewed your January 11, 1983 letter, and while we have no technical difficulties with the information submitted we do not believe that PRA should be substituted for the NRC's deterministic criteria such as Position 5 of BTP ASB 10-1.
In particular, in the Commission's introduction to NUREG-0880, "Safety Goals for Nuclear Power Plants: A Discussion Paper" the Commission states (Page xi) that:
8302250496 830214 PDR ADOCK 05000361 P
PDR DATE... *
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NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981-335-960 FEB 141983 "Since the completion of the Reactor Safety Study, further progress in developing probablistic risk assessment and in accumulating relevant data has led to recognition that it is feasible to begin to use quantitative reactor safety guidelines for limited purposes. However, because of the sizable uncertainties still present in the methods and the gaps in the data base-essential elements needed to gauge whether the guidelines have been achieved-the quantitative guidelines should be reviewed as aiming points or numerical benchmarks which are subject to revision as further improvements are made in probabilistic risk assess ment. In particular, because of the present limitations in the state of the art of quantitatively estimating risks, the numerical guidelines are not substitutes for existing regulations."
There are a few cases where probability numbers are used in the Standard Review Plan, such as external event hazards (Section 2.2.3), tornado missile spectrum selection (Section 3.5.1.4) and auxiliary feedwater system unreliability (Section 10.4.9). In these cases probability is used as a supplement to guide the review in determining what potential risks should be considered in meeting the general guidance of the General Design Criteria. This use is consistent with the Commission's guidance and differs from your use of PRA. Your proposal attempts to replace a specific requirement with the results of a probability analysis.
As a result of our conclusion given above, we require that you meet the deter ministic requirements of the SRP. A hardware modification such as the cooling system for the AFW pump motor bearing lubrication oil described in your letter of January 11, 1983 is a potentially acceptable method of meeting the SRP.
We request that you identify the method whereby you will meet the SRP, and provide a schedule for its implementation by February 18, 1983. We also rquest that you submit a detailed description of the selected method for staff review as soon as is reasonably achievable.
Correction of CPC Software Error
References:
- 1. Letter for A. E. Scherer (CE) to R. C. DeYoung (NRC)
"Core Protection Calculator Software Decrepancy,"
August 4, 1982.
- 2. Letter From J. R. Marshall (AP&L) to W. C. Seidle (NRC), "Arkensas Nuclear One, Unit 2 Licensee Event Report No. 82-026/03L-0," August 30, 1982.
- 3. Letter from L. V. Mausin (LP&L) to R. L. Tedesco (NRC) "Waterford Steam Electric Station - Unit No. 3, CPC Software Functional Inconsistency,"
September 3, 1982.
OFFICE I..........................................
SURNAME DATE.......................................................
NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD CO PY USGPO: 1981-335-960 FEB 14 1983 By reference 1, Combustion Engineering informed the NRC staff of the discovery of a discrepancy in the Core Protection Calculator (CPC) software of four CE plants (Waterford -
Unit 3, Arkansas Nuclear One - Unit 2, San Onofre Units 2 and 3). This decrepancy was also reported by Arkansas Power & Light (Ref.2) and Louisiana Power and Light (Ref. 3).
The discrepancy involves penalty factors (PF) associated with the Control Element Assembly Calculators (CEAC).
When both CEACs are failed (CEAC testing is also considered as "fail"), the functional requirements specify that the CPCs are to use DN3R (departure from nucleate boiling ratio) and LPD (local power density) PFs stored in the CPC data base. These PFs are the largest possible PFs that the CEACs could calculate during normal operation. However, it has been found during the testing of the Waterford-3 CPC software that the CPC software does not provide for the application of the LPD PF to the LPD calculation in accordance with the design specifications. Despite this condition, CE has concluded that there is adequate protection provided by CPC reactor trip logic to permit plant operation with the CPC software error.
Their justification is based on their conclusion that DNB trips would occur prior to any LPD trips that might be initiated when applying the LPD PF.
The staff has not reviewed this justification and doubts that the evaluation can be thorough, though the conclusion is probably true.
The nature of the CPC software protection logic is not amenable to an evaluation or test program which can provide complete assurance that all circumstances requiring LPD trip protection have been adequately analyzed.
Even if the conclusion is valid, we believe that the error degrades the protection provided by the CPCs by effectively eliminating one software trip path to the protection circuit.
Based on discussions regarding the CPC software error during a recent CPC startup test audit for San Onofre 2 and 3, the staff understands that ANO-2 intends to continue operation in their next cycle without correction of the error.
While the safety concern does not appear serious enough to warrant plant shutdowns until the correction is implemented, we do believe that the software should be corrected as soon as practical without impairing operation.
Therefore, we request that you correct the errors for San Onofre 2 and 3 at the earliest reasonable opportunity and inform us of your schedule for the correction by February 18, 1983.
George Knighton, Branch Chief Licensing Branch No. 3 Division of Licensing cc:
See next page
- See previous concurrence.
OFFCEDL:LB#3 DS DL:LB, SURNAME~
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//-1/83 217f83 I
NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981-335-960
-3 By reference 1, Combustion Engineering informed the NRC staff of the iscovery of a discrepancy in the Core Protection Calculator (CPC) software four CE plants (Waterford - Unit 3, Arkansas Nuclear One - Unit 2, Sa Onofre Units 2 and 3). This decrepancy was also reported by Arkansas P wer & Light (Ref.2) and Louisiana Power and Light (Ref. 3). The descrep cy involves penalty factors (PF) associated with the Control Element Assembly C culators (CEAC).
When both CEACs are failed (CEAC testing is also consider d as "fail"), the functional requirements specify that the CPCs are to us DNBR (departure fro'm nucleate boiling ratio) and LPD (local power density) Fs stored in the CPC data base. These PFs-are the largest possible PFs at the CEACs could calculate during normal operation. However, it has been fou d during the testing of the Waterford-3 CPC software that the CPC softwa does not provide for the application of the LPD PF to the LPD calculati in accordance with the design specifications.
Despite this condition, CE s concluded that there is adequate protection provided by CPC reactor trip loo c to permit plant operation with the CPC software error. Their justificat' n is based on their conclusion that DNB trips would occur prior to any PD trips that might be initiated when applying the LPD PF. The staff h s not reviewed this justification and doubts that the evaluation can be th ough, though the conclusion is probably true. The nature of the CPC softwa e protection logic is not amenable to an evaluation or test program whi can provide complete assurance that all circumstancesrequiring LPD trip rotection have been adequately analyzed.
Even if the conclusion is valid we believe that the error degrades the protection provided by the CPCs by effec vely eliminating one software trip path to the protection circuit.
Based on discussions rega ding the CPC software error during a recent CPC startup test audit for S n Onofre 2 and 3, the staff understands that ANO-2 intends to continue ope ation in their next cycle without correction the error.
While the safety conc rn does not appear serious enough to warrant plant shutdowns until the correctio is implemented, we do lbljeve that the software should be corrected as so as practical without if pateng operation.
Therefore, we ruest that you correct the errors for San Onofre 2 and 3 at the earliest r,'asonable opportunity and inform us of your schedule for the correctio by February 18, 1983.
George Knighton, Branch Chief Licensing Branch No. 3 Division of Licensing DL:LB#3 DSI:AD DL:LB#3 OFFICE.
SURNAME
.HRood/yt LRubenstein GWKnighton DATE NRC FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY USGPO: 1981--33-960
San Onofre Mr. Robert Dietch Vice President Southern California Edison Company 2244 Walnut Grove Avenue P. 0. Box 800 Rosemead,,California 91770 Mr. Gary D. Cotton Mr. Louis Bernath San Diego Gas & Electric Company 101 Ash Street San Diego, California 92112 cc:
Charles R. Kocher, Esq.
Mr. Mark Medford James A. Beoletto, Esq.
Southern California Edison Company Southern California Edison Company 2244 Walnut Grove Avenue 2244 Walnut Grove Avenue P. 0. Box 800 P.-0. Box 800 Rosemead, California 91770 Rosemead, California 91770 Mr.-HeneryPete rs Orrick, Herrington.& Sutcl.iffe San Di.ego Gas & Electric Company ATTN:
David R. Pigott, Esq.
P. 0. Box 1831 600 Montgomery Street San Diego, California 92112
-San Francisco, California 94111 Ms. Lyn Harris Hicks Mr. George Caravalho Advocate for GUARD City Manager 3908 Calle Ariana City of San Clemente San Clemente, California 92672 100 Avenido Presidio San Clemente, California 92672 Richard J. Wharton, Esq.
University of San Diego School of Law Alan R. Watts, Esq.
Environmental Law Clinic Rourke & Woodruff San Diego, California 92110 Suite 1020 1055 North Main Street Phyllis M. Gallagher, Esq.
Santa Ana, California 92701 Suite 222 1695 West Crescent Avenue Lawrence Q.
Garcia, Esq.
Anaheim, California 92701 California Public Utilities, Commission 5066 State Building Mr. A. S. Carstens San Francisco, California 94102 2071 Caminito Circulo Norte Mt. La Jolla, California 92037 Mr. V. C. Hall Combustion Engineering, Inc.
Charles E. McClung, Jr., Esq.
1000 Prospect Hill Road Attorney at Law Windsor, Connecticut 06095 24012 Calle de la Plata/Suite 330 Laguna Hills, California 92653 Mr. S. McClusky Bechtel Power Corporation Resident Inspector, San Onofre/NPS P. 0. Box 60860, Terminal Annex do U.S. Nuclear Regulatory Commission Los Angeles, California 90060 P. 0. Box 4329 San Clemente, California 92672 Mr. Dennis F. Kirsch U.S. Nuclear Regulatory Comm. - Reg. V Regional Administrator-Region V/NRC 1450 Maria Lane, Suite 210 1450 Maria Lane/Suite 210 Walnut Creek, California 94596 Walnut Creek, California 94596
-~
I SAN ONOFRE
-2 Mr. 'C. B. Brinkman Combustion Engineering, Inc.
4853 Cordell Avenue Bethesda, Maryland 20814