Part 21 Report - 1996-141

ACCESSION #: 9604090325 Commonwealth Edison Company 1400 Opus Place Downers Grove, IL 60515-5701 ComEd April 5, 1996 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attn.: Document Control Desk Subject: Braidwood Station Units 1 and 2 Byron Station Units 1 and 2 Zion Station Units 1 and 2 Commonwealth Edison 10 CFR Part 21 Final Report File 95-14 PWR Refueling Water Storage Tank (RWST) Analysis Assumptions NRC Dockets 50-456 and 50-457 NRC Dockets 50-454 and 50-455 NRC Dockets 50-295 and 50-304 Reference: Letter from I. M. Johnson to USNRC Document Control Desk dated December 22, 1995. In the referenced letter, pursuant to 10 CFR 21.21(a)(2), ComEd notified the NRC Staff of concerns regarding the use of incorrect assumptions related to the PWR Refueling Water Storage Tank (RWST) in several analyses for Braidwood, Byron, and Zion Stations. The analyses were performed by Westinghouse Electric Corporation, Sargent & Lundy, and ComEd. ComEd has concluded this issue is not a substantial safety hazard. Sufficient margin was available in the analyses to bound the impact of the incorrect assumptions. Work is in progress to update the impacted analyses. At this time minor changes to Byron and Braidwood RWST level setpoints are being incorporated to improve plant margins. Provided as an attachment to this letter is ComEd's final notification in accordance with the requirements of 10 CFR Part 21. k:\generic\nrc0405.doc A Unicom Company Document Control Desk -2- April 5, 1996 If there are any questions regarding this notification, please direct them to Kenneth A. Ainger at (708) 663-7217. Respectively, Irene M. Johnson Licensing Operations Director Attachment: 10 CFR Part 21 Final Report cc: H. J. Miller, Regional Administrator - RIII C. Phillips, Senior Resident Inspector - Braidwood H. Peterson, Senior Resident Inspector - Byron R. Westberg, Senior Resident Inspector - Zion Office of Nuclear Facility Safety - IDNS k:\generic\nrc0405.doc Attachment 10CFR Part 21 Final Notification RWST Level Setpoint Uncertainties 10CFR Part 21 File No. 9514 Applicability This notification is submitted in accordance with the requirements of 10CFR 21, sections 21.1(a), 21.3a(3), and 21.3d(1). Identification of Facility and Component This notification concerns non-conservative assumptions in Refueling Water Storage Tank (RWST) level uncertainties and the RWST switchover time used in safety analyses for Byron Station Units 1&2, Braidwood Station Unit 1&2, and Zion Station Unit 1&2. Identification of Component Manufacturer Westinghouse Nuclear Safety Analysis: Sargent and Lundy: Westinghouse, NTD, NSA Randall Kurtz, QA Manager P. O. Box 355, Mail Stop E4-13 55 East Monroe Pittsburgh, PA 15230-0355 Chicago, IL 60603 Nature of Defect Discrepancies exist in the time of Safety Injection (SI) Switchover and Refueling Water Storage Tank (RWST) level setpoint uncertainties in a number of analyses. The time of SI switchover from RWST to containment sump impacts analyses because of the enthalpy difference between the two SI sources. The Small Break LOCA, Post-LOCA Sump Boron, LOCA Mass and Energy Release, and Ultimate Heat Sink analyses are impacted by these discrepancies. The Containment Sump pH and Containment Flooding analyses are also impacted. Safety Significance ComEd has concluded that this issue is not a substantial safety hazard. Sufficient margin existed in the analyses to offset the impact of this issue. k:\generic\nrc0405.doc Attachment 10CFR Part 21 Final Notification RWST Level Setpoint Uncertainties Time of Discovery On October 31, 1995, while investigating the possibility that RWST level setpoint uncertainties at Braidwood may be larger than previously assumed, ComEd determined that these uncertainties had not been previously included in a number of safety analyses. Corrective Actions ComEd has calculated appropriate RWST levels, switchover times, and ECCS/CS flows and uncertainties. The results of these calculations are being used as bases for detailed evaluations and reanalyses. ComEd is working with Westinghouse and Sargent & Lundy to complete analyses applicable for all applicable plant operating conditions. The corrective actions associated with this report are being tracked at ComEd to ensure the issues are completed. Contacts Questions pertaining to this notification should be addressed to: Kenneth A. Ainger Part 21/Technical Issues Committee Nuclear Engineering Services ComEd 1400 Opus Place, Suite 400 Downers Grove, IL 60515 (708) 663-7217 k:\generic\nrc0405.doc *** END OF DOCUMENT ***

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