TXX-6929, Interim Deficiency Rept CP-87-57 Re Inaccurate Modeling Methods in Environ Analysis W/Computer Code Compare MOD1A. Initially Reported on 870814.Validation of All Affected Sys Will Be Performed.Next Rept Will Be Submitted by 880301

Interim Deficiency Rept CP-87-57 Re Inaccurate Modeling Methods in Environ Analysis W/Computer Code Compare MOD1A. Initially Reported on 870814.Validation of All Affected Sys Will Be Performed.Next Rept Will Be Submitted by 880301

ML20236Q172
Person / Time
Site:	Comanche Peak
Issue date:	11/16/1987
From:	Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
CP-87-57, TXX-6929, NUDOCS 8711190222
Download: ML20236Q172 (2)

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5 File # 10110 909.4-MfELECTR/C- Ref # 10CFR50.55(e) mmam c. camsu November 16, 1987 Eucutive Vice Persiktu U. S. Nuclear Regulatory Commission l  ;

ATTN: Document Control Desk Washington,.D.C. 20555

SUBJECT:

' COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NOS. 50-445 AND 50-446 .'

COMPUTER MODELING ERROR: COMPARE MODIA SDAR: CP-87-57 (INTERIM' REPORT)

Gentlemen:

On August 14, 1987, we verbally notified yo.ur'Mr. H. S. Phi.llips of a potentially reportable item involving inaccurate modeling methods in the environmental analysis using the computer code COMPARE M001A. After further ,

evaluation, we have determined this item to be reportable'under the provisions i of 10CFR50.55(e), and the required information follows.

Description of Deficiency i Inaccurate modeling of the tornado dampers in the COMPARE M001A: computer code I has been discovered which may have resulted in non-conservative room temperatures and/or pressures. The version of the code used, assumes that the damper v ens at a set pressure, then relatches when the pressure falls below the set pressure. However, the t-ornado dampers installed in the field do not relatch when the pressure drops below the set pressure. In the unlatched condition the damper vanes allow flow in either direction in response to any l applied differential pressure. This condition affects various rooms in the Auxiliary, Safeguards and Fuel Buildings in Units 1 and 2.

The cause of this deficiency was failure to adequately reflect plant design in the computer modeling. This deficiency affects only the tornado dampers; therefore, no other implications have been identified.

Safety Implications

In the event this deficiency had not been discovered, a preliminary evaluation has shown that post-accident pressures and/or temperatures for the affected rooms _may have exceeded the design limits calculated by the computer runs.

This, in turn, could have resulted in the inability of safety-related systems .

to perform as required following post-accident conditions.

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TXX-6929 November 16, 1987 Page,2 of 2 Corrective Action After further evaluation we have decided to perform a 100% validation of all systems affected by this issue. This will be performed in_ lieu of an evaluation to determine the safety significance of this issue as a whole.

This effort is not yet complete.

We will submit a follow-up report by March 1, 1988, to provide the results of l our verification effort.

Very truly yours, N

l W. G. Counsil MCP/mgt c - Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3)