ML20247F708
| ML20247F708 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/07/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-87-062, CP-87-62, TXX-89651, NUDOCS 8909180246 | |
| Download: ML20247F708 (2) | |
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Log # TXX-89651 C
File # 10110 C
C 903.9 Ref. # 10CFR50.55(e) 7UELECTRIC September 7, 1989 Esecaudve Mce President U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 CLASS 5 PIPE SUPPORTS SDAR:
CP-87-062 (SUPPLEMENTAL REPORT)
Gentlemen:
On September 30, 1987, TU Electric notified the NRC by report logged TXX-6731 of deficiencies in the use of nomographs to design seismically supported Class 5 piping systems. The last report on this issue logged TXX-88471, dated June 16, 1988, described preventive and corrective actions which were being taken to resolve this issue. The purpose of this report is to revise the corrective action specified in TXX 88471.
TU Electric has elected to implement a new program to demonstrate tb9 adeqracy of large bore non-nuclear non-ASHE (Class 5) piping systems in lieu of the corrective action previously specified in TXX-88471. The objective of the
. program is to demonstrate the adequacy of the total population of large bore Class 5 pipe supports by selecting a bounding sample consisting of the least conservative seismic design configurations, and proving the acceptability of those configurations by analysis. Demonstration of the acceptability of the bounding sample will provide adequate assurance that the remaining pipe support systems are also acceptable and will not catastrophically fail during a seismic event.
To implement this new program, a walkdown was conducted for Unit 1 and Common areas within Seismic Category I structures to identify design configuration anomalies in large bore Class 5 piping systems which, based on earthquake engineering database experience, have less conservative seismic designs.
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'TXX-89651-September 7, 1989 Page.2 of 2 A bounding sample was then selected from the observations recorded during the walkdown
- A_ detailed analysis will be performed on each anomaly in the bounding sample to demonstrate its structural design adequacy during a seismic event.
If any anomaly in the bounding sample is determined-by analysis to be unacceptable, the affected piping / support (s) will be modified as required.
In that event the anomaly with the next least conservative design will then be selected for analysis from the walkdown. observations to replace the unacceptable anomaly in the bounding sample.
The above program supersedes the corrective action specified in TXX-88471.
The Unit I and Common bounding sample analyses and modifications (if any) will be completed prior to Unit I fuel load. The corrective action required for Unit 2-wi11 be assessed upon resumption of the balance of Unit 2 engineering activities.
As indicated in TXX-88471, recurrence of this deficiency has been precluded by changing the applicable Design Basis Document to require that nomographs be utilized only in accordance with' approved engineering procedures.
Sincerely, William J. Cahill, Jr.
DJE/ddm c - Mr. R. D. Martin, Region IV Resident Inspectors CPSES (3)
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