United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9812300224


Westinghouse Electric Company,
a division of CBS Corporation
Box 355
Pittsburgh Pennsylvania 15230-0355

NSD-NRC-98-5819
December 22, 1998

U.S. Nuclear Regulatory Commission
Attn: Document Control Desk
Washington, DC 20555

Subject: Interim Report of an Evaluation of a Deviation or Failure to Comply Pursuant to 10CFR21.21(a)(2).

The following information is provided pursuant to the requirements of 10CFR Part 21 to submit an Interim Report on issues for which an evaluation of reportability will not be completed within 60 days from the discovery of the deviation or failure to comply. An Interim Report is enclosed for the following Potential Issue under Westinghouse evaluation:

LOCBART Computer Code Error - Interim Report 98-029

If you have any questions regarding this matter, please contact me at 412/374-5282.

Sincerely,

H. A. Sepp, Manager
Regulatory and Licensing Engineering

Attachment 0124S
NSD-NRC-98-5819 December 22, 1998


Westinghouse Electric Company
Energy Systems
P.O. Box 355
Pittsburgh, PA 15230-0355

Interim Report No. 98-029
Date: 12/22/98

SUBJECT: Interim Report of an Evaluation of a Deviation or Failure to Comply Pursuant to 10CFR21.21(a)(2).
TITLE: LOCBART Computer Code Error
BASIC COMPONENT SUPPLIED BY: Westinghouse Electric Company
NATURE OF DEVIATION: Westinghouse has identified a potential issue related to a logic error discovered in the LOCBART code which causes the cladding zirc-water oxidation calculations to be performed three times per timestep. Preliminary investigation has shown that, while correcting the error is expected to result in a reduction in local cladding oxidation, the corresponding heat deposition in the cladding is expected to increase, which could result in an undetermined increase in large break LOCA peak cladding temperature.
DATE OF DISCOVERY OF DEVIATION: October 23, 1998
EVALUATION STATUS: Westinghouse is continuing to evaluate the deviation to fully characterize the impact of the deviation. Westinghouse is currently evaluating a possible revision to the model used to interpolate blowdown fluid boundary conditions onto the finer axial nodalization that is modeled in LOCBART. Preliminary studies have shown that the reduction in cladding temperatures resulting from this revision is sufficient to offset the increase in cladding temperatures that results from correcting the error in the zirc-water oxidation logic.
In addition, the Westinghouse Owners Group (WOG) PI Core Team has been apprised of this situation.
EVALUATION COMPLETION SCHEDULE DATE: June 30, 1999


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