TXX-6512, Interim Deficiency Rept CP-87-12 Re Containment Pressure/ Temp Analysis Computer Error.Initially Reported on 870513. Reanalysis of Main Steamline Break to Be Completed 870701. Next Rept Will Be Submitted by 870805
| ML20215A718 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/12/1987 |
| From: | Counsil W, Keeley G TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-12, TXX-6512, NUDOCS 8706170048 | |
| Download: ML20215A718 (2) | |
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Log # TXX-6512 FE File # 10110 906.2
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Ref # 10CFR50.55(e) nlELECTRIC June 12, 1987 wmn c. c-m Eucunve %ce Preskknt U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKETS NOS. 50-445 AND 50-446 CONTAINMENT P/T ANALYSIS COMPUTER ERROR SDAR: CP-87-12 (INTERIM REPORT)
Gentlemen:
On May 13, 1987, we verbally notified your Mr. Ian Barnes of a deficiency involving a containment pressure / temperature analysis computer error. We are reporting this issue under the provisions of 10CFR50.55(e) and the required information follows.
DESCRIPTION OF PROBLEM During recent validation efforts, an apparent error was observed in the computer program used to analyze containment pressure and temperature transients from a spectrum of main steam line breaks (MSLB) as presented in the FSAR table 6.2.1-2.
These efforts, conducted as part of the Design Basis Consolidation Program, consist of a comprehensive review of calculation inputs, assumptions, methodology, and results.
The original analysis utilized the computer program CONTEMPT-LT/M0D 26. The main steam line break of "0.908 ft2 split rupture at 70% power" produced the maximum peak containment temperature of 333 degrees F.
Using the same inputs, assumptions, and a later version'of CONTEMPT-LT/ MOD 26, a peak containment temperature of 366 degrees F (33 degrees F higher) was observed.
Further evaluation initiated to investigate the difference in the peak temperature results revealed that three FORTRAN lines in the HEAT subroutine were left out of the earlier CONTEMPT edition. This error directly affects the results when the Uchida heat transfer option is used.
In order to evaluate the effects of this error, the three FORTRAN Lines were 2
removed from the later edition of CONTEMPT and the "0.908 ft " main steam line split case was rerun. The results from this operation matched the original results (i.e., peak containment temperature of 333 degrees F).
Based on this evaluation, we have concluded that the earlier edition of CONTEMPT LT/ MOD 26, used in the process of establishing current containment pressure and temperature transients contained.the error.
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TXX-6512 June 12, 1987 Page 2 of 2 The version of CONTEMPT-LT/ MOD 26 used in the earlier analysis was developed by EG&G Idaho, Inc., obtained from the NRC, and used by Gibbs & Hill during the original design phase at CPSES.
The application of this computer code in other nuclear-installation design programs is unknown.
Although our corrective actions are specified below, a preliminary reanalysis has been conducted which indicates the revised peak temperature is actually only 342 degrees F.
This peak temperature has been calculated using the LOCTIC computer code (with an 8% revaporization) and revised as-built containment heat sinks.
SAFETY IMPLICATIONS In the event this condition had remained undetected and the original analysis uncorrected, the deficiency could have resulted in the inability of safety-related systems to perform as required following postaccident conditions.
CORRECTIVE ACTION The. reanalysis of the main steam line break is scheduled to be completed on July 1,1987. Upon completion of our evaluation, we will determine corrective actions as required. Our actions will include a proposed revision to Section 6.2.1 of the FSAR after the main steam line break analysis is completed. We will identify all areas / items where the results of the program CONTEMPT-LT/ MOD 26 have been used as a design basis.
We will' submit our next report by August 5, 1987.
Very truly yours, W. G. Counsil By:
I G. S. Keelev
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Manager,Nucleaycensing JCH/gj c - R. D. Martin, Region IV Resident Inspectors, CPSES (3)
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