ML20086B073

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

ML20086B073
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/09/1974
From:	Rodgers W, Swart F 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 8311170033
Download: ML20086B073 (4)

Text

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P. O. P,ox 361, Plattcville, Colorado 80651 ,

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i December 9, 1974

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1 Docket >!o. 50-267 50-267 74/22, Enclosed please find a copy of Abnorcal Occurrence Report !!o.

' subnitted per the requirc:aen:s of the Tec'mical Specifications.

.Very truly youra, 4

Frederic E. Svart Superintendent 'Tuclear Production l

, Fort St. Vrain :*uclear

/ Generatinr, Station FES:11

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elo Gianhusso g :' Mr. f.n:; J cc ,

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s REPORT DATE: December 9, 1974 ABNOPJtAL OCCURRE :CE OCCUP2ENCE DATE: November 29, 1974 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE CC:!PANY OF COLORADO P. O. BOX 361

• PLATTEVILLE, COLORADO 80651

. REPORT No. 50-267/74/22 .

Preliminary IDENTIFICATION OF OCCURRE':CE:

On November 29, 1974, high pressure in the gas waste vacuum tank blow a rupture disc and lif ted a relief valvefallowing an unauthoriced release of approxi=ately 750 SCF of uncontaminated gas.

This is identified as 4

an abnor al occurrence per Technical Specification 2.1.c.

CONDITIO::S PRIOR TO OCCURRE.';CE: Steady State Power Routine Shutdown Hot Shutdown Routine Load Chcnge-X Cold Shutdown Other (specify)

Refueling Shutdown

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Routine Startup I 'Ihe major plant paraceters at the time of the event were as follows:

Power PTR, N/A Wth

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ELECT, N/A We

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Secondary Coolant Pressure N/A psig-

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Temperature N/A 'F

'$ Flow N/A #/hr.

Primary. Coolant Pressure O psig Temperature ~135 _ 'F Core Inlet 135 'F Core Outlet Flow - 0 #/hr.

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Page 2 DESCRIPTION OF OCCURRENCE: -

While regenerating the "A" low temperature adsorber of the helium purification system the operator was purging the system to the gas vaste vacuum tank.

The procedure called for a system pressure of 88 psig which was in error.

The pressure should have been 1 psig. There is no local indication of vacuum tank pressure so the operator did not know he was purging too fast until the. rupture disc was broken. A release of about 750 SCF of gas was released to the plant ventilation system exhaust. The ventilation exhaust is monitored and these instruments showed no detectabic ' change in count rate. Subsequent lab analysis of the "B" surge tank contents confirmed that no detectable activity was present in the gas.

APPARENT CAUSE OF OCCURRENCE: X Design Unusual Service Cor.c Including Envirencer Manufacture Component Failure

. Installation /Const. ,0ther (specify)

Operator X Procedurc ANALYSIS OF OCCURRENCE:

Design: The venting and purging of the helium purification regeneration system is done from a panel which is remote from the control roem, and although the gas waste systc= can be overloaded in this process, there is no indication of gas waste vacuum tank pressure at that location. The operator therefore does not immediately know that he is overpressuricing the vacuum tank. .

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

This was in error and should have been 10 acfm at 1 psig. The high volu=atric flow to the vacuum tank exceeded the capacity of both gas waste compressors even though the second compressor started properly.

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9 9 Page 3 CORRECTIVE ACTION:

Design: A temporary vacuum tank pressure indicator has been installed for the operator's use and a change notice will be issued to make this a permanent instrument.

Procedure: A modified Systen Operating Procedure has been issued to. change the purge flow and pressure to the proper values to prevent over-loading the gas waste compressors.

FAILURE DATA /SI'!ILiR REPORTED OCCURRENCES:

- Abnormal Occurrence #2 was similar 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.

PROCPJOSIATIC DCPACT:

None .

CODE DIPACT: .

None ,

Submitted by: M & kN

'- W. Duane Rodgers Operations Supervisor

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j^ Fr9d eric E. Swart ~

, S)crintendent, Nuclear Production G

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