ML19208B216

LER 79-035/01T-0:on 790831,field Audit Analysis Indicated Inconsistencies in Hangers of as-built safety-related Piping.Caused by Design & Installation Inconsistencies. Remaining Hangers Being Analyzed

ML19208B216
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/13/1979
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19208B217	List: ML19208B216
References
LER-79-035-01T, LER-79-35-1T, NUDOCS 7909190360
Download: ML19208B216 (4)

Text

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REPORT DATE: September 13, 1979 REPORTABLE OCCURRENCE 79-35 ISSUE O OCCURRENCE DATE: Auguse 31, 1979 Page 1 of 3

- FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/79-35/01-T-0 Preliminary IDENTIFICATION OF OCCURRENCE:

An engineering field audit and preliminary analysis of a random sample of safety related system piping and associated hangers has found inconsistencies that may Jeopardize the operability of systems In the event of a design basis earthquake.

Due to these inconsistencies, Public Service Company has elected to suspend operation of the Fort St. Vrain Unit No. 1, as of 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on Septe=ber 1, 1979.

9 An investigation of these inconsistencies is continuing.

This appears to be reportable per Fort St. Vrain Technical Specification AC 7.5.2(a)9.

EVENT DESCRIPTION:

Public Service Co=pany of Colorado has completed the field audit and a prelim-inary engineering analysis of a random sample of as-built safety related piping isometric and associated hanger drawings as committed to in Public Service Con-pany letter P-79161.

The audit included a field verification of the as-built installation of the piping shown on 26 Class I piping isometric drawings and the 94 associated hanger drawings. The general validity of the seismic design inputs documenta-tion on 18 of the isometric drawings and 64 of the hanger drawings was confirmed.

On the remaining eight isometric drawings and 30 hanger drawings, inconsisten-cies judged to be potentially significant were identified between the field installation and the reference documentation.

An analytical evaluation of the noted isometric drawing inconst. "cies indi-cates that they would not result in invalidation of the seismic qu .ification of the piping depicted on the subject iso =e.tric drawing.

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REPORTABLE OCCURRENCE 79-35 ISSUE O Page 2 of 3 EVENT DESCRIPTION (continued):

An analytical analysis of the inconsistencies identified in the hangers indi-cates that 18 of the hangers of concern fulfill Class I design requirements.

The retaining 12 hangers have inconsistencies that may jeopardize the opera-bility of the associated systems in the event of a design basis earthquake.

Because the sacpling of isometric drawings and associated hangers was made on a rando= basis, no conclusions can be drawn as to the continued operability of those systems or portions of systems required to re=ain operable during and after a design basis earthquake.

On the basis of the results of the audit, Public Service Co=pany of Colorado has determined that the piping systen seistic hanger / support systen for the Class I piping uay not be installed per the design requirements defined in the Final Safety Analysis Report and cay require corrective modifications to bring the "as-built" systems into agreement with the design intent.

Because of the inconsistencies noted, the Public Service Company of Colorado has temporarily suspended operation of the Fort St. Vrain unit as of approxi-cately 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on September 1,1979.

After further analysis, using more sophisticated analytical methods, it has been deter =ined that none of the systems examined to date are impaired per the Final Safety Analysis Report since the individual hangers are acceptable or, the asso-ciated piping and its remaining hangers would re=ain operable during the de-sign basis earthquake.

CAUSE DESCRIPTION:

The inconsistencies between the design and installation of the various hangers required re-analysis of the piping / hanger systems. The time involved did not allow a final resolution of the problem before a report was submitted. There-fore the plant was shutdown pending outcome of the investigation.

CORRECTIVE ACTION:

The re=aining hangers are being analyzed and the outcone of these analyses along with the corrective actions necessary, will be submitted in a future supplemental repo r t.

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REPORTABLE OCCURRENCE 79-35 ISSLT 0 Page 3 of 3 Prepared by: /jZ.

Asa B. Reed Technical Services Technician Reviewed by:

g.W.Miali=

(/ Technical Services Supervisor Reviewed by: b Frank 11. Mathie Operations !!anager Approved by:  % YM Don Warenbourg 9

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