ML20149D650
| ML20149D650 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/04/1988 |
| From: | Beck J, Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-115, TXX-88055, NUDOCS 8802090573 | |
| Download: ML20149D650 (2) | |
Text
,
MEE Log # TXX-88055 File # 10110 r
903.7
- I lilELECTRIC DON 7f,1, February 4, 1988 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET N05. 50-445 AND 50-446 4
SEISHIC ANALYSIS OF SERVICE WATER INTAKE STRUCTURE SDAR:
CP-87-115 (FINAL' REPORT)
Gentlemen:
i On October 21, 1987, we. verbally notified your Mr. H. 5. Phillips of a deficiency involving the seismic analysis of the Service Water intake Structure. Our last interim report, logged TXX-6984 was submitted on November 18, 1987. We are reporting this issue under the provisions of i
The required information follows.
DESCRIPTION During the design validation of the seismic analysis of the Service Water Intake Structure (SWIS), it has been determined that the originally calculated natural frequencies of the soil-structure system are high and, in addition, there are discrepancies in the seismic model.
Seismic loads and amplified response spectra were derived from this seismic analysis, thus errors in the seismic analysis would invalidate the seismic loads used in the design of the SWIS and the developed floor response spectra (FRS).
These FRS were used in the qualification of equipment piping and other components.
During our evaluation of this issue a similar modeling error was identified for the seismic Category 1 Concrete Tanks in the yard area.
w The cause of this deficiency is due to underestimating the structural mass and 48 overestimating the subgrade stiffness in the original seismic analysis model.
8R-gg SAFETY IMPLICATIONS
(
mo Failure to correctly calculate the natural frequencies of the soil-structure j
system and discrepancies in the seismic model resulted in errors in the i
$8 seismic analysis of the SWIS which could adversely affect safety.
Since FRS g<
are input parameters used in the qualification of equipment, piping systems i
and components inside the SWIS, errors in FRS could invalidate the design of re such items and adversely affect safety. We are conservatively reporting this ma.m issue under the provisions of 10CFR50.55(e) due to the extensive evaluation required to establish the adequacy of the affected structure, i
S 0
400 hrth Olne Street LB81 Dalla. Tew 1R01 l
m e
TXX-88055 February 4,1988 Pafe 2 of 2 CORRECTIVE ACTION A new seismic analysis.for the SWIS using the revised model with appropriate structural mass and subgrade stiffness has been performed.
New FRS were developed and an assessment of the effects of the revised FRS on the f
qualification of equipment, piping systems, and components have been performed.
All remaining safety related concrete structures were reviewed for this deficiency and were found to be adequate except for the seismic Category I Concrete Tanks. A new seismic analysis was performed and the FRS have been developed for the seismic Category I Concrete Tanks.
An assessment of the i
effects of the revised TRS on the qualification of appurtenances to the Seismic Category I Concrete Tanks is being performed.
Further preventive actions are not required since all models have been evaluated and future medels are not expected to be required.
4 Requ9 red corrective actions will be implemented to satisfy seismic qualification requirements.
All Unit I corrective actions will be implemented j
by Septesber 28, 1988. All Unit 2 corrective actions will be implemented prior to Unit 2 fuel loading.
Very truly yours, i
j W. G. Counsil By: b M,/ b Jobei W. Beck Vice President, Nuclear Engineering l
CBC/grr i
j c-Mr. R. D. Martin, Regiori IV Resident inspectors, CPSES (3) j l
5 L