ML20039C628

Forwards LER 81-072/03L-0.Detailed Event Analysis Encl

ML20039C628
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/17/1981
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20039C629	List: ML20039C628 ML20039C632
References
P-81318, NUDOCS 8112290534
Download: ML20039C628 (6)

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@g # ! 16805 Road 19 1/2, Platteville, Colorado 80651-9298 December 17, 1981 Fort St. Vrain Unit No. 1 P-81318 e rs

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S f Mr. John T. Collins, Regional Administrator p El ./ ~ , \

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Nuclear Regulatory Commission ggg201361% ,d 611 Ryan Pla::a Drive Q q,j,c 7,,,i';

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Reference:

Facility Operating License O #

No. DPR-34 Docket No. 50-267

Dear Mr. Collins:

Enclosed please find a copy of Repcetable Occurrence Report No. 50-267/81-072, Preliminary, subT.itted ;.e r the requirements of Technical Specification AC 7.5.2(b)1.

Also, please find enclosed one copy of the Licensee Event Report for Reportable Occurrence Report No. 50-267/81-072.

Very truly yours, bOV {Wdh%MA G by f3(Cf5h Don Warembourg Manager, Nuclear Production DW/cls Enclosure cc: Director, MIPC O!ddhh67 I PDR

OCCURRENCE REPORT DISTRIBUTION Su* er of Corteg De pa r tme n t o f E n e r gy - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 (P Letter)

San Francisco Operations Of fice Attn: California Patent Group 1333 Broadway Oakland, California 94612 De p a r tmen t o f Ene r gy - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 (P Letter)

Mr. Glen A. Newby, Chief riTR Branch Division of Nuclear Pcver Development Mail S tation B-107

• • .ashin gton, D.C. 20545 De pa r tme nt o f Ene r gy - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 (P Letter)

Attn: Project Manager 110 Vest A Street, suite 460 San Diego, California 92101 3~ TCOUCn5

& F2rl_" q ,4 g yeeter -------------------------

9 1 (Original of P Letter Region IV and Copy of LER)

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Nuclear Regulatory Cot:nission 611 Ryan Plaza Drive Suite 1000 Arlington, Texas .N ](poll Director - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 (P Letter, LER)

Of fice of Management Information and Program Control U. S. Nuclear Regulatory Cornission Washington, D.C. 20555 Mr . 11 cn a rd P he lp s - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 10 (Original of FP5.G 1etter FS7, CA. Site plus Two Copies, One Representative Copy of P letter, One General Atomic Company Copy of LER)

P. O. Box 426 Platteville, Colorado 80651 Mr. Sill Lavalee - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 (P Letter, LER)

Nuclear Safety Analysis Center 3412 Hillview Avenue i

P. O. Box 10412 Palo Alto, California 94303 NRC Resident Site Inspe cto r ------------------------ - 1 (P Letter, IIR) f7

REPORT DATE: December 17, 1981 REPORTABLE OCCURRENCE 81-072 ISSUE O OCCURRENCE DATE: November 17. 1981 Page 1 of 4 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO 16S05 WELD COUNTY ROAD 19 1/2 PLATTEVILLE, COLORADO 80651-9298 REPORT NO. 50-267/81-072/03-L-0 Preliminary IDENTIFICATION OF CCCURRENCE:

Ouring a routine surveillance check performance on November 17, 1981, the setpoint of the PCRV rupture disk assembly M-11701 was found to

, be 847 psig. Since this setpoint is higher than the 832 psig 2 1%

allowable by Fort St. Vrain Technical Specification LSSS 3.3, Table 3.3.1.2(c), it is being reported per Fort St. Vrain Technical Specification AC 7.5.2(b)1.

EVENT i DESCRIPTION:

With the reactor shutdown and depressurized for scheduled maintenance, the high set rupture disk M-11701 was removed from service for a scheduled surveillance calibration bench test. The "as found" pressure setpoint was 847 psig. The acceptance criteri.n of LSSS 3.3, Table 3.3.1.2(c) requires the set pressure co be 832 psig 1% (824 psig to 840 psig).

Refer to Figure 1. Before the test gas pressure is applied, the cutter, ([) , is removed, and a special ring is installed to limit the travel of the Belleville washers 2 . The washers snap-over when the set pressure is reached. Adjustment of the set pressure is made by positioning of the threaded ring ([) . When the set pressure is reached, the diaphragm and washers travel a few thousandths of an inch, which produces an audible " thump." The plant instrumentation personnel know from previous experience that the setpoint of the Belleville washers decreases slightly with subsequent snap-overs during testing. Therefore, the snap-over test was conducted two additional times with snap-overs occurring at 831 psig and 831 psig, respectively. The last two tests were within the specified acceptable range. The average of the three tests was 836 psig, which is satisfactory, so no further adjustments were required. The remainder of the surveillance was completed, and the rupture disk assembly was returned to service.

During this surveillance interval, the low set rupture disk, M-11702, was operable and provided the required overpressure protection.

M-11702 was last calibrated in 19d0, and was left within the specified setpoint range.

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REPORTABLE OCCURRENCE 81-072 ISSUE O Page 2 of 4 CAUSE DESCRIPTION:

The rupture disk movement setpoint being out of tolerance was caused by drift of the Belleville washer operating point over the period since its' last calibration surveillance.

CORRECTIVE ACTION:

The snap-over test was conducted three times with the last two of the tests within the required setpoint band. The remainder of the surveillance was completed, and the rupture disk assembly was returned to service.

An evaluation of the rupture disks is being conducted by the Public Service Company of Colorado's Nuclear Engineering Division. The results of this evaluation will be included in a future supplemental report.

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REPORTABLE OCCURPINCE 81-072 ISSUE 0 Page 3 of 4 e

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REPORTABLE OCCURRENCE 81-072 ISSUE O Page 4 of 4 Prepared By: ' d / $ < r //

Robert A. Dickerson h h Technical Services Technician Reviewed By: t[A fIm Charles Fuller Technical Services Engineering Supervisor Reviewed By: b 0's 9 kShibMh._

Edwin D. HiU Station Manager Appraved By: Nt1 &QA.Lw()OUAc, bJ Don Warembourg ' '

Ekh Manager, Nuclear Production