ML20085M563

AO 50-267/75/24:on 751108,static Seal on Helium Circulator B Inadvertently Released.Cause Presently Undetermined. Circulator B Brake & Seal Manually Set

ML20085M563
Person / Time
Site:	Fort Saint Vrain
Issue date:	11/18/1975
From:	Brey H, Hillyard H, Swart F, Swrt F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
50-267-75-24, AO-50-267-75-24, P-75008, NUDOCS 8311090008
Download: ML20085M563 (4)

Text

-

o O

/

,/

. P. O. Box 361, Platteville, Colorado 80651 4Q{\ s$i:]

. ~1!

.~ e, ,

,kN' / '^<

/'

p.5//.,,,'.0'.,.c.y l 7 c., , ~ November 18, 1975

',' .

• 77);.2 } Fort St. Vrain

.-: < >, n, * ,' eq :.Q" Unit No. I h ..h

\%'

P-75008

' ' /g ,_,_-)-

"M ~

Mr. E. Morris Howard, Director Nuclear Regulatory Coctnission Region IV Office of Inspection and Enforcement Suite 1000 Arlington, Texan 76012 Ref: Facility Operating License No. DPR-34 i

Docket No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Abnormal Occurrence Report No. 50-267/75/

24, Preliminary, submitted pcr the requirements of the Technical Speci-fications. .

Very truly yours,

-Frederic E. Swart

' Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk cc: Mr. Roger S. Boyd i

I 8311090008 751118 PDR ADOCK 05000267 g PDR 13476 L. .h

" ': O o. l ABNORMAL OCCURRENCE 75/24 REPORT DATE: November 18, 1975 Page 1 of 3 OCCURRENCE DATEi November 8, 1975 FORT ST. VRAIN NUCLEAR CENERATING STATION PUBLIC SERVICE COMI'ANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/75/24 .

Preliminary IDENTIFICATION OF OCCURRENCE:

On November 8, 1975, the static seal on "B" helium circulator was apparently inadvertently released,which is one of the primary coolant boundaries when the helium circulator is shutdown.

This is identified as an abnormal occurrence per section 2.1.c of the Fort St. Vrain Technical Specifications.

CONDITIONS PRIOR ,

Routine Shutdown

- TO OCCURRENCE: Steady State Power Routine Load Change Hot Shutdown 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 0 MWe 210 psig Secondary Coolant Pressure

~

Temperature 70 *F Flow 80,000 #/hr.

46 psia Primary Coolant Pressure Temperature N/A *F Core Inlet

' 84 'F Core Outlet Flow 1 circulator at 4,000 rpm #/hr.

G

o o

. . ~ .

ABNOlGIAL OCCURRENCE 75/24 Page 2 of 3 DESCRIPTION OF OCCURRENCE:

During reactor shutdown, "B" helium circulator was shutdown to reroute cables for segregation reasons. At 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br />, while PCRV was approximately 35 psig during pressurization, the reactor operator noticed a positive increase of buffer /mid buffer AP, which indicates flow down the circulator shaf t. The brake and seal set position indicating lights were inoperable' due to a construction work authori-zation, so an operator was sent to the local location and the brake and seal were set manually.

APPARENT CAUSE OF OCCURRENCE: Design Un_ usual Service Cond.

Including Environ.

Manufactur.e Component Failure Installation /Const. X Other (specify)

'- Operator Undetermined at this: time.

, Procedure P With the cable reroutes in progress, one of the redundant circuits which had a holding circuit that was relied on to set the brake and seal, was apparently interrupted. This appears to have released the static seal on "B" circulator.

ANALYSIS OF ,.

OCCURRENCE: .

The following conditions existed when the buffer /mid buffer increasing differential pressure was observed:

1. - One cable reroute work authorization removed the "X"' circuit on circulator auxiliary isolation valvci. It also -included position indication on the brake and seal valves. -

2. A'second cabic reroute work authorization removed the channel'"A"Linput of "B" circulator -buf fer/mid buffer (scal- malfunction)(module. - This module removal also nullified the' channel "A" input of "B"_ circulator

~

loss of bearing water.

3. A third cable reroute work authorization removed the channel "B" input of "B"l circulator loss of bearing water module. Removal of this module also removed the "B" channel of "B" circulator buffer /mid buf fer (scal malfunction) input.

These conditions in'themselves should not have released the brake and seal be~

-cause thc."B" circulator trip should not have reset. The brake and seal shouldf have remained set- by the holding circuit. _ .

ad . - '-'

~

o o ABNORMAL 0,CCURRENCE 75/24

• Page 3 of 3 ANALYSIS OF OCCURRENCE (continued):

Investigation into the cause of the release is still in progrer.s.

CORPICTIVE ACTION: .

. The "B" circulator brake and seal was manually set as a follow up to the increase of the buffer /mid buffer differential pressure. This action closed the static seal, which returned the primary coolant boundary + o normal.

Investigation into the cause and any possibic further corrective action is in progress.

FAILURE DATA /SIMILAR REPORTED OCCURRENCES:

~

Abnormal Occurrence 50-267/74/24A - similar, but not the same.

Abnormal Occurrence 50-267/74/10 - related, but not similar.

Abnormal Occurrence 50-767/74/13A - related, but not similar.

Abnorm.al Occurrence 50-267/75/9 - related, but not similar.

PROGRAFDfATIC IMPACT:

None CODE IMPACT:

None

~

Submitted by: e M~ .

Harvey E/ Hillysid, Jr.

Technical Services Supervisor 11 Reviewed by: h 4\  %

H. Larry Bt y j

Superintend nt, Opera ions Approved by: /n .

. . k k.enn (

_/redericE. Swart

}

fuperintendent, Nuclear Production G

4

-*Y y

_ _ _