ML20086E165

AO 50-267/74/6A:on 750202,gas Waste Vacuum Tank Rupture Disc Ruptured,Releasing Small Quantity of Gas.Caused by Failure of Air Operated Drain Valve to Close Properly.Valve Repaired & Reinstalled

ML20086E165
Person / Time
Site:	Fort Saint Vrain
Issue date:	03/21/1975
From:	Brey H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
AO-50-267-74-6A, NUDOCS 8312060213
Download: ML20086E165 (6)

Text

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REPORT DATE: March 21. 1975 ABNORMAL OCCURRENCE OCCURRENCE DATE: February 2, 1975 a

FORT.ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 s

REPORT NO. 50-267/74/6A

.- Final IDENTIFICATION OF OCCURRENCE:

A gas waste vacuum tank rupture disc ruptured releasing a small quantity of gas. This is identified as an Abnormal Occurrence per Technical Specification definition 2.1.c.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown 1:ot Ghutdcwn Rout.iue I,ved Chaug X Cold Shutdown Other (specify)

Refueling Shutdown

+

Routine Startup

- The major plant parameters at the time of the event were as follows:

Power Rtr -

MWth-Elect. O MWe Secondary Coolant Pressure 1000 psig Temperature 210 *F (Feedwater on pre-boiler recirculation)

Flow 180,000 f/hr.

Primary Coolant Pressure 230 psia Temperature 254 'F Core Inlet 254 'F Core' Outlet Flov 90,000 f/hr. ,

831206d213 750321 t PDR ADOCK 05000267 S PM _

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i* . O O Pega 2 DESCRIPTION OF '

OCCURRENCE:

While attempting to drain "B" helium purification train water separator via HV-2382, with the separator icvel indication of 48", the operator drained the separator to 4" and closed HV-2382. Approximately one minute

• later he received a gas waste vacuum tank high pressure alarm and noticed the gas waste pressure and gas waste flow high. The reactor operator suspected HV-2382 of not closing and dispatched an equipment operator to ch'eck regeneration system pressures. The equipment operator closed PV-2352, the manual isolation for HV-2382 and isolated the blown rupture dise M-63802.

APPARENT CAUSE OF OCCURRENCE: Design Unusual Service Cond.

. Including Environ.

Manufacture X Componen,t Failure Installation /Const. Other (specify)

Operator

'. Procedure The air operated drain valve failed to close properly which allowed primary ecolant heliu= to enter the regeneration aystem and be vented to the' gas waste vacuum tank at a rate which exceeded the capacity of the two gay waste compressors.

• ANALYSIS OF OCCURRENCE:

The release from the rupture dise was about 3 minutes in duration at approx.

100 ACFM. No increase in activity was detectable on the stack radiation monitors (RT,7324-1, 2 or 7325-1). Subsequent analysis of the gas in the gas waste surge tank for release No. 77 showed no measurable7 gamma activity.

The allowable release rate based on tritium was 3.9 (10 ) ACFM.

CORRECTIVE ACTION: .

With the reactor depressurized to atmospheric pressure the valve (HV-2382) was isolated and disassembled for inspection. HV-2382 was found to have a small piece of metal in the seat of the valve which prevented the valve from closing properly. The foreign object was removed, the valve seat repaired and the valve was reassembled and tested. , No further corrective action is planned.

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. .' P gn 3 FAILURE D TA/.

SIMILAR REPORTED OCCURRENCES:

Abnormal Occurrences 50-267/74/21, 50-267/74/22, and 50-267/75/5 No.

involved 74/21 was rupture of this rupture disc but the causes are unrelated.

due to a release of gas from'the gas waste compressor relief valves. -

No. 74/22 was due to a pressure setting error in the operating procedure.

No. 75/5 was due to an improper valve lineup during a purge.

PROGRAMMATIC IMPACT:

None

-CODE IMPACT:

None REC 0!OfENDED: APPROVED:

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H. Larry Brley \

Superintendent-Operations

[FredericE. Swart Superintendent-Nuclear Production Public Service Company _ -

Fort St. Vrain Nuclear Generating Station of Colorado h

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SIMILAR REPORTED OCCURRENCES:

Abnormal Occurrences 50-267/74/21, 50-267/74/22, and 50-267/75/5 involved rupture of this rupture disc but the causes are unrelated. No. 74/21 was due to a release of gas from the gas waste compressor relief valves. -

No. 74/22 was due to a pressure setting error in the operating procedure.

No. 75/5 was due to an improper valve lineup during a purge.

PROGRAMMATIC IMPACT:

None CODE IMPACT:

None k

RECOMMENDED: . APPROVED:

Lv CT _(h; 1,ct- - ~~ v \

H. Larry Brby

' Superintendent-Operations

\ [FredericE. Swart Superintendent-Nuclear Production Fort St. Vrain Nucicar Public Service Company Generating Station of Colorado .

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public service company or ceaendo P. O. Box .161, Platteville, Colo 8u651 April 2, 1975 Mr. E. Morris Howard, Director Region IV, Office of Inspection 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 4

Docket No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Abnormal occurrence Report No. 50-267/75/6A,.

Final, submitted per tne requirements of the Technical Specifications.

Very truly yours,0 L

. U urt Frederic E. swart Supt. Nuclear Production 4

Fort St. Vrain Nuclear Generating Station FES:11 Q __'l) "f f cc: Mr. Angelo Giamousso ,

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