GNRO-2003/00002, Updated Risk Metrics for Extending the Emergency Diesel Generator Allowed Outage Time

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Updated Risk Metrics for Extending the Emergency Diesel Generator Allowed Outage Time
ML030500322
Person / Time
Site: Grand Gulf Entergy icon.png
Issue date: 01/28/2003
From: Roberts J
Entergy Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
GNRO-2003/00002, TAC MB3973
Download: ML030500322 (4)
v • d • e


Text

Entergy Operations, Inc.

SEntergy Waterloo Road PO Box 756 Port Gibson, MS 39150 Tel 601 437 6470 Jerry C. Roberts Di rector Nuclear Safety Assurance GNRO-2003/00002 January 28, 2003 U.S. Nuclear Regulatory Commission Attn. Document Control Desk Washington, DC 20555

SUBJECT:

Grand Gulf Nuclear Station, Unit 1 (GGNS)

Docket No. 50-416 Updated Risk Metrics for Extending the Emergency Diesel Generator Allowed Outage Time (TAC No.MB3973).

REFERENCES:

1. Letter GNRO-2002/00007 from William A. Eaton to U.S. NRC Document Control Desk, "License Amendment Request Emergency Diesel Generator Extended Allowed Out-of-Service Time" dated January 31, 2002
2. Letter GNRO-2002/00056 from Jerry C. Roberts to U.S. NRC Document Control Desk, "Supplement to Amendment Request - Emergency Diesel Generator Extended Allowed Outage Time, TS 3.8.1", dated June 20, 2002.

Dear Sir or Madam:

By letter (Reference 1), Entergy Operations, Inc. (Entergy) proposed a change to the Grand Gulf Nuclear Station, Unit 1 Technical Specifications (TS) to extend the allowed out-of-service time for a Division I or Division II Emergency Diesel Generators (EDGs) from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 14 days (TAC No MB3973). The NRC approved and issued the change as Amendment No. 151. The NRC approval was based in part on the evaluation of risk impacts associated with the change. These risk impacts were evaluated by Entergy using an interim Probabilistic Safety Analysis (PSA) model. Prior to issuance of the amendment, Entergy committed in a letter (Reference 2) to evaluate the risk metrics using the updated PSA model, when available, and provide a summary of the results to the NRC staff.

Revision 2 of the GGNS PSA model is now complete and has been used to evaluate the risk of an extended EDG AOT. A summary of the results of the evaluation are contained in Attachment 1. As expected, the risk metric values are less than the results reported using the interim model and continue to show that the increase in plant risk is small and consistent with regulatory guidance. _ (

There are no new commitments contained in this letter.

January 28, 2003 GNRO-2003/00002 Page 2 of 2 If you have any questions or require additional information, please contact Ron Byrd at 601-368-5792.

Sincerely, JCR/RWB/amt attachment: Updated Risk Metrics cc: U. S. Nuclear Regulatory Commission ATTN: Mr. Ellis W. Merschoff Regional Administrator, Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 U. S. Nuclear Regulatory Commission ATTN: Mr. David H. Jaffe NRR/DLPM (w/2),

ATTN: U.S. Postal Delivery Address Only Mail Stop OWFN/7D-I Washington, D.C. 20555-0001 Mr. T. L. Hoeg, GGNS Senior Resident Mr. D. E. Levanway (Wise Carter)

Mr. L. J. Smith (Wise Carter)

Mr. N. S. Reynolds Mr. H. L. Thomas Dr. E. F. Thompson (w/a)

State Health Officer State Board of Health P. 0. Box 1700 Jackson, Mississippi 39205

Attachment I To GNRO-2003100002 Updated Risk Metrics to GNRO-2003/00002 Page 1 of 1 Updated Risk Metrics for EDG AOT Extension By letter dated January 31, 2002 (Reference 1), Entergy requested a Technical Specification Amendment to extend the Emergency Diesel Generator (EDG) allowed outage time (AOT) from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 14 days. The request was a risk informed submittal which relied upon an interim Probabilistic Safety Analysis (PSA) model to develop the risk metric values for NRC review. In a supplemental letter dated June 20, 2002 (Reference 2) GGNS committed to evaluate the risk metrics for the EDG extended AOT using the updated risk model, when available, and provide a summary of the results to the NRC staff. Revision 2 of the GGNS PSA model is now complete and has been used to evaluate the risk of an extended EDG AOT. A summary of the results is provided below.

Updated PSA Results:

Model Updated CDF Updated LERF Baseline 4.27E-6/yr 5.30E-8/yr EDG A OOS 6.17E-6/yr 1.35E-7/yr EDG B OOS 5.99E-6/yr 1.31 E-7/yr Updated Risk Metrics for EDG Extended AOT:

Risk Metric Significance GGNS Initial GGNS Updated Guidance Criterion 1 Results Results ACDFAVG <1 .OE-06/yr 2.73E-7/yr 1.09E-7/yr ICCDP <5.OE-07 2.15E-7 7.30E-8 ALERFAVG <1.OE-07/yr 1.04E-8/yr 4.74E-9/yr ICLERP <5.0E-08 8.32E-9 3.15E-9 These results are based on EDG A, Division I, which still provides the limiting values for the risk metrics. As can be seen from the above table, the GGNS updated results continue to show that the increase in plant risk is "small and still within the significance guidance of Regulatory Guides 1.174 and 1.177.

1 Reference RG 1.174 & RG 1.177

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