ML20210K077
| ML20210K077 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 07/30/1999 |
| From: | Krich R COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9908060001 | |
| Download: ML20210K077 (3) | |
Text
r Commonwealth lidison Company 1400 Opus Place e
Downers Grove. 11. 60515-5701 July 30, l' U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
30-Day Report of an Emergency Core Cooling System Evaluation Model Error Required by 10 CFR 50.46
References:
(1)
Westinghouse Electric Company letter to USNRC, " Interim Report of an Evaluation of a Deviation or Failure to Comply Pursuant to 10 CFR 21.21(a)(2)," dated December 22,1998 (2)
Westinghouse Electric Company letter to USNRC, " Update and Schedule Revision Regarding Westinghouse Interim Report No.98-029,"
dated June 29,1999 In accordance with 10 CFR 50.46(a)(3)(ii), we are submitting a 30-day report following the discovery of an Emergency Core Cooling System (ECCS) Evaluation Model error for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2. Westinghouse Electric Company I
(Westinghouse), in Reference 1 initially reported the error to the NRC pursuant to 10 CFR 21,
" Reporting of Defects and Noncompliance," and recently provided a status update in Reference b
- 2. We received notification from Westinghouse on June 30,1999, of their discovery of the error and its potential impact. The error could potentially result in a greater than 50*F change in calculated Peak Cladding Temperature (PCT) for the limiting Large Break Loss of Coolant Accident (LBLOCA) analysis for the Byron and Braidwood Stations. The 0-day report is due July 30,1999,30 days from June 30,1999, the date we were notified of the discovery of the O;
error. Therefore, this report is being submitted by July 30,1999.
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9908060001 990730 PDR ADOCK 05000454 P
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July 30,1999 U.S. Nuclerr Regulatory Commission Page 2 Westinghouse, as described in References 1 and 2, identified a logic error in their LOCBART computer code. This code is used in the Byron and Braidwood Stations' LBLOCA analysis to
' calculate the fuel rod heatup and confirm the resultant PCT is less than 2200 F, the 10 CFR 50.46 acceptance criterion for PCT. The LOCBART logic error causes the cladding metal-water oxidation calculations to be performed three times per time step. Correcting the error is expected to reduce the total cladding oxidation while increasing the heat deposition in the cladding. This could potentially result in exceeding the 10 CFR 50.46 acceptance criterion of 2200 F for PCT.. The discovered error does not affect any other LOCA or non-LOCA analyses for the Byron and Braidwood Stations.
Preliminary LBLOCA scoping studies performed by Westinghouse indicate that PCT results are acceptable when fuel assembly average burnup levels are greater than 4000 MWD /MTU or
' when the total peaking factor (F ) is less than 2.45 for beginning of life conditions. We have a
determined that for the current Byron and Braidwood Stations' operating cycles, the reload value for Fa is less than 2.45. Further, we confirmed that all assembly average burnups for Byron Station Unit 2 and Braidwood Station Unit 1 are beyond 4000 MWD /MTU. As an interim compensatory measure until the actual impact of the error upon PCT is known, the Core
~ Operating Limits Report limit for the monthly surveillance of F, has been reduced from 2.6 to 2.45 for Byron Station Unit 1 and Braidwood Station Unit 2.
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Based on the above evaluations and interim compensatory measure, we conclude that the Byron and Braidwood Stations can continue to operate without further restriction and still meet the 2200 F PCT acceptance criterion.
Upon final validation / verification and the resolution of the LOCBART logic error, the Byron and Braidwood Stations' plant specific LBLOCA PCT impact will be determined by Westinghouse.
These activities are scheduled to be completed by August 31,1999. Based upon the final results, we may withdraw this report if the error correction results in a PCT difference of less than 50 F from the previously calculated LBLOCA PCT temperatures for the Byron and Braidwood Stations.
Should you have any questions concerning this letter, please contact Mr. P. R. Simpson at (630) 663-7971.
Respectfully, p&
R.M. Krich Vice President - Regulatory Services
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Regional Administrator - NRC Region lli NRC Senior Resident inspector-Braidwood Station NRC Senior Resident inspector - Byron Station t.l..
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NRC Project Manager, NRR - Braidwood and Byron Stations Manager of Energy Practice -Winston & Strawn
' Office of Nuclear Facility Safety -IDNS Senior Reactor Analyst-IDNS Site Vice President - Braidwood Station Site Vice President - Byron Station l
Vice President - Regulatory Services Vice President - Nuclear Fuels Management l
Regulatory Assurance Manager - Braidwood Station Regulatory Assurance Manager-Byron Station Director, Licensing and Compliance - Braidwood and Byron Stations Comed Document Control Desk Licensing (Hard Copy)
Comed Document Control Desk Licensing (Electronic Copy) l I
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