United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9604090325

Commonwealth Edison Company

1400 Opus Place

Downers Grove, IL 60515-5701


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 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.


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.


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



                    10CFR Part 21 Final Notification

                    RWST Level Setpoint Uncertainties

                       10CFR Part 21 File No. 9514


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




                    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.


Questions pertaining to this notification should be addressed to:

Kenneth A. Ainger

Part 21/Technical Issues Committee

Nuclear Engineering Services


1400 Opus Place, Suite 400

Downers Grove, IL 60515

(708) 663-7217



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