ML20086B068

AO 50-267/74-22A:on 741129,high Pressure in Gas Waste Vacuum Tank Blew Rupture Disc & Lifted Relief Valve Allowing Release of 750 Scf Uncontaminated Gas.Caused by Design Inadequacy.Pressure Indicator Installed

ML20086B068
Person / Time
Site:	Fort Saint Vrain
Issue date:	02/26/1975
From:	Brey H, Rodgers W PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20086B070	List: ML20086B068 ML20086B073 ML20086B074
References
AO-50-267-74-22, NUDOCS 8311170029
Download: ML20086B068 (5)

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Ref: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Abnormal Occurrence Reports No.

50-267/74/21-A and 59-267/74/22-A, finals, submitted per the

requirements of the Technical Specifications.

Very truly yours, J

J(S H. Larry Brey Superintendent-Operations Fort St. Vrain Nuclear Generating Station HLB:il

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Mr. Angelo Giambusso .,

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G C'.:P.?.L::CR DATE:  ::ovec.ber 29, 1974 "

O NKT ST. VP.AIN NUCLEA.". CE::E21.TI;;C STATION PUDLIC SER*llCE CC::FA'.7 0F COLOT.AD0 _

P. 0. 50X 361 '

PLATTEi'1LLE, COLO UD0 S0651 REPC"I 50. SC-267/74/22A Final IOC:.TIFICATION OF ,

ACCIM?.E: CE:

On ::ovember 29, 1974, hir,h pressure in the gas vaste vacuum tank blev a rupture disc and lif ted a relief valve allowing an unauthori::ed release of approximatcly 750 SCF of uncentacinated gas. This is identified as an abnormal occurrence per Technical Specification 2.1.c.

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CONDITIONS PRIOR O v TO CCCL.nE':CE: Steady St:t: Pe- er P.cutine et.ne.

Hot Shutdown Routine Load Change X Cold Shutdown '

Other (specify)

Refueling Shutdown Routine Startup The major plant parameters at the time of the event were as follows: .

Power PIR, N/A trJch ELECT, M/A WJe Secondary Coolant Pressure F/A psig Tecperaturc N/A 'F Flow N/A #/hr. *

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Primary Coolant

• Pressurc 0 psig Temperature 135 *F Core Inlet.

O ,, 135

• F Core Outlet

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Flow 0 #/hr. . .

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.Sila re ,,enercting th 'A" lov te crature a!sorber of the helium purification s ste-'. the c- er stor w-s pur..in.; the systen to the ges vaste vacut.n tenk.

Tita p:cccdura c2112d for a systcc prcssure of Si psi 2 which was in error.

The presv: 4 shau'.i have bren 1 pai:;.

Th.-re is no local indicatien of hnc'.: he v13 purr,ing tco fast

'vacuu= teah crc.= r:re so the operator/.did ne.:

r. leana of cho:t 750 SCF of eja was tintil tha re,20 ra I'.se vcs br. :en.

reicased to the plant ventilation system cy. haunt. The ventilation enh.ust is c:nitored sn3 ther.2 1--s' r 2 .r.ts shv::  ! re detect..bic cha.nno in count surge tcnk contents confirced rate. Subsequent lab analysis of the "3" that na dctoctable activit/ was preacnt in the Sas.

A"PAeI';T CAUSE Unusual Service Cond OF OCCURRE'CE: X Design

• IncludingEnvironmenf 1

- Manufacture Co=ponent Failure l Installation /Const. Other (specify)

• Operator V X Procedure ANALYSIS OF .

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OCCURRE','CE :

Design: Th.eventins: cnd purging of the helium purification regeneration system is donc frc= a panel which is remote from the control rocc, and although the gas waste system can be overloaded in this process, there is no indication of gas waste vacuun tank pressure at that location. The operator therefore; does not inntediately knew that he is overpressurizing the vacuun' tank. ,

Procedurc: The procedure called for a purge rate of 20 acfm at 88 psig.

Ihis was in error and shculd hava been 10 acfm at 1 psig. The ,

hirln volumetric flow to the vacuun tenk enceeded the capacity of both gas vaste compressors even though the second compressor started properly. ,

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Page 3 i CORRECTIVE ACTION: '

Design: A temporary vacuum tank pressere indicator has been installed for the operater's use and a change notice No. 95 has been issued to make this a permanent instrument.

Procedure: A ciodified System Operating Procedure has been issued to change the purge flow and pressure to the proper values to prevent overloading the gas waste compressors.

FAILURE DATA /

SIMILIAR REPORTED OCCURRENCES:

Abnormal Occurrence #2 was similiar in that a failure of the gas waste vacuum tank rupture disc was involved. The cause of the two Abnormal Occurrences was not the same.

PROGRAMNATIC IMPACT:

None CODE IMPACT:

None

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SUBMITTED BY: . #W ~~

W. Duane Rodgers Operations Supervisor Fort St. Vrain Nuclear Cencrating Station APPROVED BY: _ . , . g Frederic E. Swart j Superintendent Nuclear Production .

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