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.
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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
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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.
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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
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