05000267/LER-1976-012, Handwritten LER 76-012:on 760527,circulator 1B Tripped. Caused by Buffer Seal Malfunction.Sys Operating Procedure for Reset Following Trip Will Be revised.W/760607 Ltr

Handwritten LER 76-012:on 760527,circulator 1B Tripped. Caused by Buffer Seal Malfunction.Sys Operating Procedure for Reset Following Trip Will Be revised.W/760607 Ltr

ML20086A051
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/07/1976
From:	Hillyard H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20086A050	List: 05000267/LER-1976-012, Handwritten LER 76-012:on 760527,circulator 1B Tripped. Caused by Buffer Seal Malfunction.Sys Operating Procedure for Reset Following Trip Will Be revised.W/760607 Ltr ML20086A044
References
LER-76-012, LER-76-12, P-76122, NUDOCS 8311110225
Download: ML20086A051 (5)

LER-2076-012, Handwritten LER 76-012:on 760527,circulator 1B Tripped. Caused by Buffer Seal Malfunction.Sys Operating Procedure for Reset Following Trip Will Be revised.W/760607 Ltr

Event date:
Report date:
2672076012R00 - NRC Website

text

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- . . .. , 9 REPORT DATE: June 7,1976 ABNORR\L OCCURRENCE 76/12 Page 1 of 3 OCCURRENCE DATE: (Determined) May 28, 1976 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT NO. 50-267/76/12 Final IDENTIFICATION OF OCCURRENCE:

On May 27, 1976, an unexpected trip of helium circulator 1B occurred. This is identified as an abnormal occurrence per Fort St. Vrain Technical Speci-fications, Section 2.1, paragraph g.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown Hot Shutdown Routine Load Change I Cold Shutdown Other (specify)

R'efueling Shutdown

Routine Startup

^

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

T;,.

Power RTR 0 MWth s.

.x ELECT 'I 0 MWe .I Secondary Coolant Pressure O peig .

Temperature 90 *F Flow 0 f/hr. f,I, Primary Coolant Pressu're 283 psig

'4 Temperature 94 *F Core Inlet 103 *F Core Outlet Flow 0 f/hr.

4 (contimmed) d' k

. .. . O O ABNORMAL OCCURRENCE 76/12 Page 2 of 3 CONDITIONS PRIOR TO OCCL'RRENCE (continued):

Helium Circulator Status Circulator 1A Shutdown Circulator 1B Self-turbining Circulator 1C Sel f-turbining Circulator ID Self-turbining DESCRIPTION OF -

OCC'JRRENCE:

A loss of electrical power test (LOEP) was run on the af ternoon of May '27,1976, which tripped helium circulators 1C and 1D, and initiated a Loop 2 automatic shutdown from the Plant Protective System as expected. Af ter the surveillance test was concluded, the Loop 2 helium circulators were returned to self-turbining operation. When the Loop 2 helium circulator steam turbine trips were reset, 1B circulator tripped on buffer seal malfunction.

APPARENT CAUSE OF OCCURRENCE: Design Unusual Service Conc Including Environme:

! Manufacture Component Failure Installation /Const. - Other (specify)

Operator X Procedure

• ANALYSIS OF OCCURRENCE: ,...

A Loop 2 shutdown initiates an inhibit signal to prevent the seal malfunction trip of the Loop 1 helium circulators, and vice versa. In addition, a recent modification to the 2 of 3 logic output for seal malfunction of each circulator, added a holding circuit such that following a buffer seal malfunction, it is necessary to manually reset the holding circuit before returning the circulator to service. During the loss of electrical power test, the buffer seal malfunc-tion of B circulator was tripped causing the holding circuit to be energized.

No circulator trip of 1B occurred, however, because the Loop 2 shutdown inhibit j was also energized. (Note circulator lA was shutdown at the time.) '

1 l

A

o

. -. O

. ABNORMAL OCCURRENCE 76/12 Page 3 of 3 ANALYSIS OF OCCURRFl CE (continued):

Following the loss of electrical power test, circulator auxiliaries were restarted and self-turbining speeds were achieved for helium circulators 1C and 1D. When the operator manually reset the Plant Protective System steam /

water drain latching bistables on circulators 1C and ID, the Loop 2 shutdown signal reset as it should, which cancelled the inhibit of seal malfunction for helium circulator 1B. Because the holding circuit was energized, a buffer seal malfunction trip signal was actuated for circulator 1B, even though the buffer seal differential pressure was normal, and the circulator tripped.

The procedure governing operator action for this situation, which is alarmed in the control room, was found to be inadequate. Because of the lag in issuing procedural changes corresponding to hardware changes, the revised reset procedure incorporating the changed nomenclature had not been issued.

CORRECTIVE ACTION:

The system operating procedure will be revised to provide correct reset action for the holding circuit, following its actuation. No further corrective action G planned or required. . -

FAILURE DATA /SIMILAR REPORTED OCCURRENCES: .

None i PROGRAMATIC IMPACT: .

r.-

, None CODE IMPACr: #

None i

Submitted by:

• C W.11hfard, Jr. /

• Technica1L.8'ervices Supervisor .'

Reviewed by: . ly Ig/4,<.

H. Larry lirey # '

Superintendent, Operations Approved by:-. -

f o/m n. C . v ,m ' '

F94deric E. Swart S6perintendent, Nuclear Production i:

j

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_k

O O NN puNie Service Comp my 2 Ochemde P. O. Box 361, Platteville, Cororado 80651 q,

e June 7, 1976 Fort St. Vrain Unit No. 1 P-76122' 7, ,

Mr. E. Morris Howard, Director ' '

Nuclear Regulatory Commission .

Region IV Office of Inspection and Enforcement

.s

\, -

Suite 1000 x, . .

Arlington, Texas 76012 -

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

Dear Mr. Howard:

Enclosed please find a copy of Abnormal Occurrence Report No. 50-267/

76/12, Final, submitted per the requirements of the Technical Specifi-cations. ,

Also please find enclosed one copy of the Licensee Event Report for Abnormal Occurrence Report No. 50-267/76/12.

Very truly yours, E

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

cc: Mr. Roger S. Boyd 5956 COPY SENT REGION ~ m

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