ML20085L725
| ML20085L725 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/04/1975 |
| From: | Brey H PUBLIC SERVICE CO. OF COLORADO |
| To: | Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML20085L723 | List: |
| References | |
| RO-50-267-75-3, NUDOCS 8311020383 | |
| Download: ML20085L725 (4) | |
Text
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' O C) public service company oe ochmea P. O. Box 361, Platteville, Colorado 80651 March 4, 1975 q,-( M %
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p n U jf';' " C r-Mr. E. Morris Howard, Director I
"'d Nucicar Regulatory Commission s
Region IV Office of Inspection & Enforcement
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611 Ryan Plaza Drive Suite 1000
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Arlington, Texas 76012
Dear Mr. Iloward:
REF:
Facility Operating License No. DPR-34 Docket No. 50-267 Enclosed please find a copy of Unusual Event Report No. 50-267/75/3, submitted per the requirements of the Technical Specifications.
Very truly yours, Y
My ($9
- 11. Larry Brey Superintendent-Operations Fort St. Vrair. Nucicar Cencrating Station llLB:11 cc:
Mr. Angelo Ciambusso 0
8311020383 770630 28 PDR ADOCK 05000 S
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- i REIMT DATE : rebrunry 22,,,__1975 UNUSUAL EVENT 0CCUlutE?:CE DATE February 3, 1975_
1 FORT ST. VRAIN NUCLEAR CENFPATING' STATION
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.g ej REPORT 1;0. 50-267/75/3 l.
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Preliminary
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IDENTIFICATION OF OCCURRENCE:
OnFebruary3,1975,bidr in the Loop 2 instrunent bus volta:;c caused a Loop 1 llelium Circulator to trip This is identified as' an Unusual Event per Technical Specification definition AC 7.6.C.3.
CONDITIONS PRIOR TO OCCURRENCE:
Steady State Power Routine Shutdown Hot Shutdown Routine Load Change Cole :.diardv.a Other (specity)
Refueling Shutdown Routine Startup The major plant parameters at the time of the event were as follows:
Power
- PTR, MWth
. ELECT, MWe Secondary Coolant Pressure psig Temperature 140*h'MainSteam 500'F Rcheat-Flow f /hr. -
Primary Coolant Pressure jsig Temperaturc
'F Core Inlet' l
'F Core Outlet
' _ Flow
- /hr.
- A, B, D, Helium Circulators self turbining between 300-500 rpm i
C llelium Circulator,at 2000 rpm 1
250s c
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j Page 2 DESCRIPTION OF OCCUPJ:ENCE:
At 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> en February 3,1975, a construction electrician accidently grounded the Loop 62 instrument bus.
Helium Circulators B, C and D Tripped of f primarily due to a buf fer/mid-buffer upset.
A fault on the Loop Inst rument Bus should not have af fected a Loop 1 liclium Circulator ("B" Helius Circulator).
APPARENT CAUSE OF OCCUERECE:
Design Unusual Service Cond.
Including Environ.
Manufacture Component railure Installation /
Const.
X Othcr (Specify)
Operator The cause of this occurrence in Procedure presentiv unknown.
ANALYSIS OF OCCUnnFNCE:
The upset in the buffer system caused by the instrument bus voltage dip some how reflected from Loop 2 into Loop 1.
This incident along with a Helium Circulator upset uhich occurred on January 15, 1975, wher. firing of a Loop 2 bearing water accumulator to meet a Technical Specification Surveillance Test requirerent caused an upset in the buffer systea which could be seen on the Loop 1 Helium Circulators was presented to the Plant Operations Review Committee.
The Committec-revitued both incidents and determined them to be " Safety Significant",
The NTSC was appraised of the situatlon and has recommended that the system vendor be notified cf the problems and that the risc-to-power testing program be delayed until the problems are satisf actorily resolved.
CORRECTIVE ACTION:
The Corrective Action has not, as yet, been determined.
This will be transmitted with the " Final" Unusual Event correspondence for Unusual Event No. 50-267/75/1.
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- i FAILUn_E DATA /SIMILAR REPORTED OCCUllRENCES:
None PROGPR fATIC IMPACT:
Unknown CODE IMPACT:
None RECO.TIENDED :
APPROVED:
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~_urri. J H. L. Brey, puperintendent, Operations
[ Fort.St.
rederic C. Swart, Superintendent, Production Fort St. Vrain Nuclear Station Vrain Nuclear Station l
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DATE:
DATE:
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