ML20085M577
| ML20085M577 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 09/26/1975 |
| From: | Brey H, Hillyard H, Swart F PUBLIC SERVICE CO. OF COLORADO |
| To: | Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| AO-50-267-75-22, NUDOCS 8311090014 | |
| Download: ML20085M577 (6) | |
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pulAie Service Company *f CeDonnfle i
P. O. Box 361, Platteville, Colorado 80651 I
1 September 26,
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O Mr. E. Morris Howard, Director L./
Nuclear Regulatory Commission 00T9 1975 u 4.1 Region IV c'
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Of fice of Inspection and Enforcenfent t,}.,,'
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Facility Operating License No. DPR-34 Docket No. 50-267
Dear Mr. Howard:
TE FUE O In our letter dated September 25, 1975, regarding Abnormal Occurrence Report No. 50-267/75/22, we erroneously indicated a preliminary report
'was being' transmitted.
Please note that a final was transmitted as indicated on the report itself.
Very truly yours,
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./ < c t 1.lc-p...> %cr. t. 3 Frederic E. Swart Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk cc:
Mr. Roger S. Boyd
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P. O. Box 361, Platteville, Colorado 80651 September 25, 1975 lo,
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Mr. E. Morris Howard, Director Nuclear Regulatory Commission Region IV Office of Inspection.and Enforcement s
Suite 1000 Arlington, Texas 76012 Ref:
Facility Operating License UEM No. DPR-34 Docket No. 50-267
Dear Mr. Howard:
Enclosed please~ find a copy of Abnormal Occurrence Report No. 50-267/75/22, Preliminarf, submitted per the requirements of the Technical Specificationa.
Very truly yours, Frederic E. Svart Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk cc:
Mr. Roger S. Boyd t
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REPORT DATE:
September 25, 1975 ABNORMAL OCCURRENCE 75/22 OCCURRENCE DATE:
September 12, 1975 FORT ST VRAIN NUCLEAR CENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. 0. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/75/22 Final ID8NTIFICATION OF OCCURRENCE:
On September 12,1975, at 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br />, during a gas waste routine release, troubic with the gas waste vacuum tank was observed by the reactor operator.
On September 15, 1975, subsequent examination of rupture disk M-63803 pro-tecting the gas waste vacuum tank from excessive pressure, revealed a rup-tured disk. This is identified as an abnorm'al occurrence per Technical Specification 2.1 (c).
CONDITIONS PRIOR TO OCCURRENCE:
Steady State Power
- Routine Shutdown Hot Shutdown Routine Load Change X
Cold Shutdown Other (specify)
Refueling Shutdown Routine Startup The plant parameters at the time of the event were as follows:
Pcwcr RTR 0
MWTH ELECT 0
MWe Secondary Coolant Pressure N/A psig Temperature N/A
- F Flow N/A f/hr.
Primary Coolant Pressure
+0.5 psig Temperature 83
'F Core Inlet 83
'F Core Outlet Flow 1 ci ren1ntor nr 4 :000 Al'M l
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ABNORMAL OCCURRENCE 75/22 Eage 2 of 4 DESCRIPTION OF OCCURRENCE:
On Friday evening, September 12, 1975, the following sequence of events took place:
1.
A decision was made to make a controlled release from a gas waste surge tank.
2.
The tank was sampled and no radioactivity above background was found.
3.
A surveillance, was performed as required by procedure to insure the availability of the radiation monitors concerned with a gas waste release and the operability of their associated controls.
4.
Af ter completion of all of the above permission was given to start the release of gas waste.
5.
Three (3) minutes after the release was started, an alarm was re-ceived indicating a higher than normal pressure in the gas waste vacuum tank.
The release was immediately terminated.
6.- The pressure in the gas waste vacuum tank continued to rise and both gas waste compresscrs were verified to be 'in operation.
7.
A search for the source of input to the gas waste vacuum tank was started; the regeneration system was not being purged, the fuel handling purge vacuum pumps were discharging to the gas waste blowers, the gas waste release lineup was correct.
8.
Cas was found to be flowing through the fuel handling machine relief valve (PCV-1347).
The downstream block valve for PCV-1347 was closed and the gas waste vacuum tank returned to normal.
9.
The in-service rupture disc of the parallel pair, M-63803 was sus-spected of being ruptured and M-63802 was pl, aced in service and M-63803 isolated.
10.
The gas waste release was restarted and the block valve for PCV-1347 was opened.
The gas waste vacuum tank remained normal.
11.
On Monday morning, September 15, 1975, M-63803 was inspected and found to be ruptured indicating an uncontrolled release had 'taken place.
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ABNORMAL OCCURRENCE 75/22 Page 3 of 4 APPARENT CAUSE OF OCCURRENCE:
Design Unusual Service Cond.
Including Environ.
Manufacture X
Component Failure Installation /Const.
Other (specify)
Operator Procedur'e
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At the time of the occurrence the fuel handling machine was mounted on a reactor isolation valve and connected to a fuel storage well. The fuel handling machine isolation valve and the reactor isolation valve were both open so that the fuel handling machine was at the same internal pressure as the fuel storage wells. The fuel handling machine is protected f rom excessive internal pressure by PIC-1347 and PCV-1347 with PIC-1347 opening PCV-1347 whenever the pressure in the fuel handling machine exceeds O psig.
Pressure in the fuel storage wells and, at this time, in the fuel handling machine-is controlled by PIC-1407 and the combined action of PCV-1407-1 and PCV-1407-2. PCV-1407-1 is the inlet to the fuel storage wells from a low pressure source of helium while PCV-1407-2 is the outlet of the fuel storage wells to the gas waste vacuum tank.
PIC-1407 controls the position of these two valves to maintain the pressure in the fuel storage wells between 5 and 6 inches of water vacuum.
When the excess pressure developed in the gas waste tank, the status of the controls described above was checked and the following conditions found:
PCV-1407-1 25% open PCV-1407-2 25% open PCV-1347 25% open PIC-1347 2 psig pressure in the fuel handling machine From this status it may be seen that the source. cf the excess gas to the gas waste vacuum tank was through PCV-1407-1 which supplied excess helium to the fuel storage wells which resulted in over-pressurizing the gas waste vacuum i
tank.
ANALYSIS 0F OCCURRENCE:
The.' assumed cause of the rupture of M-63803 was a malfunction of the l
helium inlet valve to the fuel storage wells PCV-1407-1.
This allowed helium to flow to the gas waste vacuum tank at a rate in. excess of the pump down I
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ABNORMAL OCCURRENCE 75/22 1
Page 4 of 4 ANALYSIS OF OCCURRENCE (continued):
capacity of both gas waste compressors. The tank pressure increased until the rupture disc ruptured and the safety relief valve lif ted relieving the excess input to the tank. There are no radioactive materials either in the primary coolant or in the fuel storage wells that could have been released by this occurrence.
No increase in the activity of the exhaust stack effluent was detected by the stack monitors.
No effect to the health or safety of the public was caused by this occurrence.
CORRECTIVE ACTION:
We have been unable to determine the cause of the malfunction of PCV-1407-1.
We have been unable to reproduce the failure in numerous check of the per-formance of PIC-1407, PCV-1407-1,,and PCV-1407-2. -No further action is planned.
FAILURE DATA /SIMILAR REPORTED OCCURRENCES:
Abnormal Occurrences 74/21,.74/22, 75/5, and 75'/6 report previous rupture of gas waste vacuub tank rupture discs caused by various malfunctions, not 4
the same as re~ ported in this report.
PROGRAMMATIC IMPACT:
None CODE IMPACT:
Nono Submitted By:
_ _,lyard, j'r.
Harvey W.
Technical Services Supervisor.
Reviewed By:
r-tLvir xy H. Larry Brcy Superintendbut, Operations y,/wo, Approved By:
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Fr/dericE. Swart Mperintendent, Nuclear Production e
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