05000267/LER-1979-016-01, /01T-0 on 790521:punch Gap of Pcrv Rupture Disc M-11702 Found Out of Tolerance W/Vendor Specs.Caused by Undocumented Change of Punch Gap Specs.Tolerances Returned to Original Specs

/01T-0 on 790521:punch Gap of Pcrv Rupture Disc M-11702 Found Out of Tolerance W/Vendor Specs.Caused by Undocumented Change of Punch Gap Specs.Tolerances Returned to Original Specs

ML19259C144
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/01/1979
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19259C142	List: 05000267/LER-1979-016, Forwards LER 79-016/01T-0 05000267/LER-1979-016-01, /01T-0 on 790521:punch Gap of Pcrv Rupture Disc M-11702 Found Out of Tolerance W/Vendor Specs.Caused by Undocumented Change of Punch Gap Specs.Tolerances Returned to Original Specs
References
LER-79-016-01T, LER-79-16-1T, NUDOCS 7906120409
Download: ML19259C144 (5)

LER-1979-016, /01T-0 on 790521:punch Gap of Pcrv Rupture Disc M-11702 Found Out of Tolerance W/Vendor Specs.Caused by Undocumented Change of Punch Gap Specs.Tolerances Returned to Original Specs

Event date:
Report date:
2671979016R01 - NRC Website

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'S REPCRT CATE 80 EVENT DESCRIPTION AND PACBABLE CONSEQUENCES h a

2 l During refueling shutdown, shile performin g routine surveillance testing on PCRV rup-I o

3 lture disc, 11-11702, the punch gap was found to be out of tolerance specified by canu-l l f acturer which could have prevented relief valve frem fulfilling the functional re-I 0

A l quirements of the sys tem as required by Technical Specification AC 7.5.2(a) 5.

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s 3 i,3 ! l disc 11-11701 was also recoved and tested and was also out of tolerance.

No over-i o;7 l pressurization of the PCRV occurred.

This had no affect on plant operation.

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o l The oroblem occurred because of an undocumented chance o? ounch eso soecifications.

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, l vised tolerances.

Because of deficiency in documentation at. this time tolerances werel l returned to the original specifications and the punch gaos modified to.085 inches.

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REPORT DATE:

June 1, 19 79 REPOKIABLE OCCURRENCE 79-16 ISSUE O OCCURRENCE DATE:

May 21, 1979 Page 1 of 4 EDRT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLAITEVILLE, COLORADO 80651 RP. PORT No. 50- 26 7/ 79-16/01-T-0 Final IDENTIFICATION OF OCCURRENCE :

On iby 21,1979, while the reactor was shutdown and depressurized for refueling, surveillance tes ting and preventive maintenance was being performed on the PCRV relief valve sys tem.

The cutting edge for the rupture discs was found out of tolerance, which could have prevented either relief valve from fulfilling the functional requirements of the system.

Since the reactor has been operated at power during the surveillance interval, this is reportable per Fort St. Vrain Technical Specifica tion AC 7. 5.2(a)5.

EVENT DES CRIPTION :

Whil.e the reactor was shutdown and depressurized for refueling the low set rup-ture disc, 1911702, was removed from service for a scheduled surveillance bench test.

See Figure 1.

During this tes t the punch gap, ([l, was found out of tolerance.

The cutting edge, ([), was farther from the rupture disc, (}),

than allowed by manuf acturer's specifications.

Since the low set rupture disc punch gap was out of tolerance, the high set rupture disc, M-11701, was also removed and bench tested. Its punch gap, 0 6

, was also out of tolerance with

(]l), being farther from the rupture disc,The punch gap toleran the cutting edge, by manufacturer's specification.

ments are listed below.

Punch Cao Allowed

• Actual Low Set Rupture Disc Fhil702 0.065/0.085 in.

0.111 in.

High Set Rupture Dise M-11701 0.065/0.085 in.

0.105 in.

• Per Ametek/Calmec Operation and Maintenance Manual PS-239 for M-11701 and M-11702 (Calmec Part Number 2002-503).

The manufacturer's representative was contacted and indicated that because of the large size and movement of these discs the punch would have probably cut the disc in both cases.

2285 086

REPORTABLE OCCURRENCE 79-16 ISSUE O Page 2 of 4

CAUSE

DESCRIPTION:

During initial installation and testing, and subsequent surveillance testing of these rupture discs, the punch gap was checked per approved procedures.

How-ever, during the initial installation and testing some confusion resulted over the correct punch gap tolerances.

Some of the procedures were changed from the original 0.065 to 0.085 inch punch gap to allow a 0.100 to 0.120 inch punch gap.

This was apparently done on a verbal authorizacion of the technical representa-tive present as no authorizing documentation can be found.

These undocumented limits were still present on some of the approved procedures.

The problem was dis covered when the engineer supervising the surveillance this year used a pro-cedure having the original tolerances as listed in the manual.

Because the manufacturer has gone out of business and all records are in storage, it would be extremely difficult to document the higher specifications at this time.

Th erefo re, the punch gaps have been decreased to a maximum of 0.085 inches.

CORRECTIVE ACTION:

The punch has been cachined to produce a punch gap of 0.085 inches on both M-11701 and FF11702.

The procedures concerning these rupture discs have been reviewed and the correct specifications for the punch gap verified.

Since there is no mechanism for the punch gap measurement to change in service, no further corrective action is anticipated.

2285 087

REPORTABLE OCCURRENCE 79-16 ISSUE O Page 2 of 4

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REPORTABLE OCCURRENCE 79-16 ISSUE O Page 4 of 4 Prepared by:

>M Asa B. Reed '

Technical Services Technician

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Frank M. Mathie Operations Manager Approved by: uk ' 'd i h f

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Don Warerbourg f/

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Manager, Nuclear Product' ion 2285 089