ML20045A157
| ML20045A157 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/28/1993 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-88-20, NUDOCS 9306090451 | |
| Download: ML20045A157 (2) | |
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BALTIMORE OAS AND l
ELECTRIC 1650 CALVERT CUFFS PARKWAY. LUSBY, MARYLAND 20657-4702 ROBERT E. DENTON VICE PREstDENT NUCLEAR ENERG' May 28,1993 foo) 260 445S U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Contmi Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2: Docket Nos. 50-317 & 50-318 Notification of coposed Schedule for Generic Ixtter 88-20, Individual Plant Examinations (IPE) for Severe Accident Vulnerabilities (TAC Nos. M74392; M74393)
REFERENCES:
(a)
Letter from Mr. G. C. Creel (BG&E) to NRC Document Control Desk, dated July 21,1992, " Generic Letter 88-20, Individual Plant Examinations (IPE) for Severe Accident Vulnerabilities; Notification of Proposed Schedule Change" (b)
Letter from Mr. D. G. Mcdonald, Jr. (NRC) to Mr. G. C. Creet (BG&E), dated July 30,1992, " Revised Schedule for the Submittal of the Individual Plant Examination for Severe Accident VuNerabilities, Generic Letter 88-20
Gentlemen:
1 in Reference (a), Baltimore Gas & Electric Company notified you that a revision to our submittal date for the summary report of the Individual Plant Examinations (IPE) was required. We proposed l
a new date of May 31,1993. In Reference (b), the Nuclear Regulatory Commission (NRC) informed us that the revised schedule was acceptable.
The purpose of this letter is to inform you that additional factors have been encountered that have led to further delays in the completion of the Probabilistic Risk Assessment (PRA) for Calvert Cliffs.
i Although significant progress has been made in the area of adjusting the PRA model to ensure it accurately reflects the plant configuration, substantial additional work is required to explore modeling changes and the effects of crediting appropriate operator actions in the model. This work is very time-consuming due to the fact that, with the high degree of detail presently built into the model, any changes in one portion of the model can have significant effects in other portions, which in turn must be addressed.
From the insights currently available from the preliminary model, we have determined that the overall risk profile for Calvert Cliffs is relatively flat with no single plant function or issue dominating.
We recently had a third-party review performed by an external PRA consultant to assess the quality of the model and recommend changes to detail, conservatisms, methodology and inputs. This review 9306090451 930528 fd
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Document Control Desk May 28,1993 Page 2 concluded that the model was highly detrailed. Additionally,it concluded that the methodology is typical of that used by many plants, support documentation is excellent and a strength of the IPE is liuman Reliability Analysis. The consultant also agreed that the preliminary result indicates a flat risk profile with no dominating vulnerabilities.
In the best interest of those who will use or evaluate our PRA, we have concluded that only a realistic study that truly reflects the actual plant configuration should be submitted for NRC review.
Therefore, we will continue refining the model. A staff of six engineers have been and remain assigned to this effort. As stated in Reference (a), we are committed to the involvement ofinhouse engineers and operations staff in the development and review of the PRA with minimal support from contractors. This approach meets the spirit of the NRC's recommendation to develop a continuing appreciation of severe accident behavior by having utility engineers involved in the analysis as well as the technical review.
We anticipate that an additional seven months will allow sufficient time to adequately refine our PRA. Consequently, we are notifying you that we have revised our schedule and now plan to submit the summary report of the IPE by December 31,1993.
Should you have any questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, s
Q AM RED /JMO/jmo/ dim /bjd cc:
D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC T. T. Martin, NRC P. R. Wilson, NRC R. I. McLean, DNR J. II. Walter, PSC i
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