ML20085M538

RO 50-267/75/16:on 751009,apparent Failure of Control Sys for Circulator High Pressure Separator C Resulted in Flooding of High Pressure Separator.Low Selector Removed, Disassembled,Inspected & Cleaned

ML20085M538
Person / Time
Site:	Fort Saint Vrain
Issue date:	10/17/1975
From:	Brey H, Hillyard H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20085M528	List: ML20085M525 ML20085M538
References
RO-50-267-75-16, NUDOCS 8311080625
Download: ML20085M538 (5)

Text

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P. O. Box 361, Platteville, Colorado 80651 l

l October 17, 1975 l 1

lo-33-,s

'Mr. E. Morris Howard, Director '

1 Nuclear Regulatory Commission l

. Region IV .

Office of Inspection and Enforcement  ;

Suite 1000 i Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 l

Docket No. 50-267

~

Dear Mr. Howard:

Enclosed please find a copy of Unusual Event Report No. 50-267/75/16,

, Final, submitted per the requirements of the Technical Specifications.

Very truly.yours, l

I Frederic E. Swart Superintendent, Nuclear Production Fort St. Vrain.Nucicar Generating Station FES/alk l

cc: Mr. Roger S. Boyd l

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l 8311080625 761014

l hDRADOCK 05000267 '

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REPORT DATE: October 17, 1975 UNUSUAL EVENT 75/16 Page 1 of 4 OCCURRENCE DATEi October 9, 1975 i

FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO -

P. O. BOX 361 PLATTEVILLE, COLORADO 80651

. REPORT No.- 50-267/75/16 Final 4 IDENTIFICATION OF OCCURRENCE:

Apparent failure of control system for "C" circulator high pressure separator resulted in flooding of the high pressure separator.

In discussion with NRC on October 9,1975, this was identified as an unusual event per section 7.6 of the Technical Specifications, paragraph (C) 2, Non-Routine Reports.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown 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:

RTR 0 MWth Power -

ELECT' O MWe Pressure _ 2,700 psig .

' Secondary Tem'perature 1,100 *F Flow 40,000 #/hr.

Primary Coo] ant Pressur~e -0.4 'psig

- Temperature 104 'F Core Inlet i.

106 'F Core Outlet

. Flow 42,000 f/hr.

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UNUSUAL EVENT 75/16

• Page 2 of 4 DESCRIPTION OF OCCURRENCE:

On August 30, 1975, with "C" helium circulator operating et 4,000 rpm on the Pciton wheel drive, the reactor operator cal, led the Results Department to re-port "C" high pressure separator flow was high. .

Results Department personnel reported to the control room and found the reactor operator had placed IIC-2176 ("C" circulator main drain valve controller) in manual and to the full open position. (See attached drawing for schematic of

, controls.) ,

Results went to check operation of PCV-2176 ("C" circulator main drain valve) and PDC-2176 local controller. Results also verified that LV-21304 ("C" high pressure separator drain valve was open and controlling level. PDV-2176 was full open and the setpoint on PDC-2176 was at -5 AP (equivalent to 3 psi or less from current to pneumatic converter, XEP-2176), which is a full open sig-nal.

The a'ir line from the XEP output (setpoint for PDC-2176) was leaking. The air line was repaired and PDV-2176 was then manually operated from IIC-2176 in the c' ontrol' room and af ter satisfactory operation, was placed in " auto". The high pressure separator level and flow were controlling near normal.

Approximately twenty minutes later "C" high pressure separator level began to rise. The reactor operator placed HC-2176 in manual and drove the output to " fully open" signal for PDV-2176. The high' pressure separator level rose to 60", and the buf fer/mid-buf fer measurement was reduced to a slightly positive pressure.

This represented a flooded condition which persisted for about.five minutes before the reactor operator manually tripped "C" circulator.

Since an increase in PCRV moisture level was observed, "D" circulator speed was increased to 4,000 rpm and the purification system. flow was increased to 120 ACFM to remove the moisture and maximize system cleanup rate.

APPARENT CAUSE OF OCCURRENCE: Design Unusual Service Cond.

Including Environ.

Manufacture Component Failure

' Installation / Cons t. X Other (specify)

Operator Unable to identify cause.

Procedure It was first believed that a control offset signal was generated by a failure of the pneumatic low selector. A manual regulator in the system, set-at 12 psig (equivalent to a 25% . open position on .Pl}V-2176) supplies an input to the low selector to prevent the main drain valve from going beyond 75% shut. Ilowever, ,

no failures could be'found to support this supposition.

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UNUSUAL EVENT 75/16 Page 4 of 4 ANALYSIS OF OCCURRENCE:

Analysis indicated that the high pressure separator flooding probably occurred during the manual stroking of PDV-2176 with the "C" circulator operating at 4,000 rpm. The valve was stroked'arter repairs were mnje on the broken air line to the XEP. Although PDV-2176 is a fail-open valve, a control signal of fset could have caused.the valve to fail shut. This could cause the high pressure separator to flood.

CORRECTIVE ACTION:

The low selector was removed, disassembled, inspected, and cleaned since failure of this component could be the only way PDV-2176 could have shut.

No prob] ems of any kind were found with the pneumatic low selector. The main drain control system and valve were completely checked out and operated under simulated conditions for all inputs. The system operated correctly as de-signed. LV-21304, high pressure separator drain valve, was observed to be operating properly.

FAILURE DATA /SIMILAR REPORTED OCCURRENCE:

None PROGRA>&fATIC IMPACT:

None CODE IMPACT:

None Submitted by- -_ . .

arveyW. Hilly 8d ..Jr. V Technical Services Supervisor r .

Reviewed by: M M -

H. Larry Brky NuclearProduction

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. Superintenddnt, i f ,

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L Approved by: //. - .iN m, s F cdcric E. Swart uperintendent, Nuclear Production- ~

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