ML19290C108
| ML19290C108 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 10/15/1979 |
| From: | Swart F PUBLIC SERVICE CO. OF COLORADO |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| IEB-79-14, NUDOCS 8001090475 | |
| Download: ML19290C108 (3) | |
Text
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T(C-public service company ce odetree 16805 Weld County Road 191/2, PTatteville, Colorado 80651 October 15, 1979 Fort St. Vrain Unit No. 1 P-79238 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012
Subject:
Safety Related Piping System Audit
Reference:
PSC Letter P-79161 dated Aug. 1, 1979 PSC Letter P-79198 dated Sept.4, 1979
Dear Mr. Seyfrit:
On September 24, 1979, Public Service Company of Colorado notified the NRC Resident Inspector that the inconsistencies noted in the 12 pipe hangers of the random sample audit conducted on the safety related piping systems and reported to the NRC in PSC Letter P-79198 dated September 4, 1979 had been resolved and that the Fort St. Vrain plant would resume power operation effective September 25, 1979.
The resolutions of the discrepancies in the 12 hangers involved in the sample audit were discussed with the NRC Resident Inspector during the week of September 24, 1979.
The lines associated with the hangers in question required the utilization of sophisticated analytical techniques to ascertain system operability which could not be comploted in the alloted time thereby necessitating a plant shutdown until the anlaysis work could be completed.
The lines and hangers have since been analyzed using sophisticated analytical techniques when necessary and, as a result, has allowed PSC Engineering to conclude that there was no system impairment in eleven of the twelve cases.
The twelfth case involved a very complex hanger (llA-H-46130) containing numerous Class I and Class II lines that required model simplification techniques to analyze without exceeding computer core capability on the available computers.
PSC Engineering continued the analysis to the point where it was concluded that the hanger would meet seismic design requirements if eignt fillet welds were increased from 3/16" to 5/16" as originally specified on the hanger drawing.
A craft action was written and the additional weldment was applied to the hanger.
The analysis required to assess the acceptability of the as-found condition of. the hanger was both time consuming and costly.
For these reasons, 1728 191 8 0 010 90 + 75 4
. the analysis to determine operability was discontinued at the point of craft action completion.
At this point in time system operability was arbitrarily assumed to be in jeopardy when, in fact, such might not have been the case.
As a result of the sample audit program PSC concludes: (1) the use of simplified analysis techniques is conservative in that system impairment may be indicated, when in reality, system impairment would not be indicated when analyzed by sophisticated analytical techniques, (2) the simplified tech-niques would have been satisfied had corrective action been taken to correct the discrepancies to return the hangers to it's originally intended configuration and (3) even though discrepancies exist, system operability is not in jeopardy.
Based on the above, PSC intends to implement the requirement of I & E Bulletin 79-14 as follows:
1.
A 100% audit of all accessible 21/2" and larger and 2" and under computer analyzed Class I piping.
The piping audit is being conducted at this time.
The systems or portions of systems required to facilitate reactor primary coolant depressurization and decay heat removal through PCRV liner cooling are being audited on a first priority basis.
2.
Discrepancies found during the field audit shall be resolved by expediently returning the discrepant item to it's originally intended configuration.
Any discrepant item that can not be resolved in this manner will be evaluated per item 3.
3.
An evaluation will be performed based on engineering judgement using the as-built drawings. The evaluation will be completed within two da'ys.
If this evaluation indicates that the affected system operability is in jeopardy, the applicable Technical Specification action will be taken.
4.
If the initial engineering judgement indicates that the system operability is not in jeopardy, an analytical engineering evaluation will be conducted and completed within 30 days.
The technique used in the analytical evaluation will be based upon simplified analytical techniques.
If the simplified analytical technique indicates that the piping or hanger does not meet the design requirements of the simplified technique, corrective action to bring the piping or hanger into compliance with the simplified analytical techniques will be completed within the 30 day period.
If the piping system or hanger analysis and craft action (if required) is not completed within this 30 day period, the applicable Technical Specification action will be taken.
In addition, approximately five per cent of the discrepancies will be analyzed using a sophisticated analytical technique to verify the judgemental evaluations and the conservatism of the simplified analytical techniques.
At the completion of the program, all affected documents will be revised to reflect the as-built conditions in the plant.
PSC's current 1728 192
. engineering and design procedures will be modified, if required, to provide assurance that modifications to systems include updating of piping supports.
The current PSC Engineering procedures are adequate but may be further refined as we proceed through the as-built programs.
All items requiring Technical Specification reporting will be reported in accordance with the applicable directives contained therein.
All
" discrepancies" will be reported to the Commission on 60-day intervals.
The 60 day report shall include a short summary of all discrepancies and corrective actions.
PSC intends to correct all discrepancies in a timely manner throughout the duration of the hanger program.
Based upon the scope and available manpower, we anticipate a projected project completion date of December,1980 with a pessimistic completion date of March,1981.
If there are any questions concerning this program, please contact this office.
Very truly yours, b
[intd A
Frederic E. Swart Nuclear Project Manager FES/LMM/scp 1728 193