ML20086B424
| ML20086B424 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 10/08/1974 |
| From: | Brey H, Rodgers W PUBLIC SERVICE CO. OF COLORADO |
| To: | Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| NUDOCS 8311170208 | |
| Download: ML20086B424 (5) | |
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i October 8, 1974 Mr. E. Morris lloward, Director Direct. orate of Regulatory Operations, Region IV USAEC 3 0395 L'est Col f ar., Room 203 Denver, Colorado 6021S Ref:
Facility Operating License No. DPR-34 Docket No. 50-267
Dear Mr. Iloward:
Eucl.oned please find a copy of Abnorraal Occurrence Report No. 50-267/74/13a, Final, cubmitted per the requirencats of the Technical Specifications.
Very truly yours,
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- 11. Larry Brey Superintendent-Operations Fort St. Vrain Nuclear Generat.ing Station IILD :ll cc:
Mr. Angelo Giambusso 8311170208 741000 bh
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COPY SENT REGION 2
1 O
O REPORT DATE:
10-3-74 ABNOPJ1AL OCCURRENCE OCCUIUtENCE DATE:
7-7-74 FORT ST. VRAIN NUCLEAR GENERATINC STATION PUBLIC SERVICC COMPANY OF COLOPADO P.O. Box 361 PLATTEVILLE, COLORADO 80651 4
REPdRT No. 50-267/74/13a FINAL IDENTIPICATION OF OCCURRENCE:
The following is considered an Abnormal Occurrence under definition 2.1 e of the' Technical Specifications.
On July 7, 1974, excessive loss in the static seal actuator pressure for "A" lic11un Circulator was observed.
CONDITIONS PRIOR TO OCCliRRESCE-Steady State Power Routine Shutdown Hot Shutdown Routine Load Change Cold' Shutdown X
Other (specify).
Refueling Shutdown Reactor shutdown with PCRV Routine Startup at atmospheric uressure The major plant parancters at the time of the event were as follows:
Power PTR N/A MWth r
Elect.
N/A MWc Secondary Coolant Pressure N/A pain Temperature N/A
- F Flow N/A
- /hr.
Primary Coolant Pressurc 0
psig-Temperature 125
- F Core Inlet 125
'F Core Outlet Flow 0
- /hr.
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DESCRIpTIO:; CF OCCURRE::C!..
On Ju]y 7,1974, an excessive increase in the bleed off rate of the helium gcs bottle supp]ying the static neal actuator on "A" belium circulat or was observed.
Subsequent leah checking on this system indicates that the leakage point in internal to the nachine.
APPARENT CAUSC OF OCC URRI::s'CE :
Design X
Unusual Service Cond.
including Environ.
Manufacture X
Component Failure Installation /Const.
_0ther (specify)
Oporator Procedure ANALYSIS OF OCCunnE::C E -
The static neal was renoved from the circulator and was found to be cracked in three placts.
(See attached picture)
A metallurgical exanination of a section taken from the bellows revealed no abnormali ies.
The physical examination indicated the bellea:s was deformed in the nrca of the failures and that it had apparently been overpressured.
Discussions held with a bel. tows manufacturer confirmed this observation.
A new bellows assembly was used to confirm that overpressurization vould cause a failure with t he same appearance as was found in the f ailed bellous.
The neu bellows was pressure tested to 1700 psig per the acceptance specification requirements with its motion restrained.
It was then cycled 500 times, using 1135 psig operating pressure.
The be] lows extension, uhen pressurized, was limited to.060", the anme as in the circulator.
The bellows was then pressurized in the extended position to 1600 - 1650 psig when it failed.
The mode of fallure was exactly as seen on the bellows that had been installed.
A search of the records did not indicate a specific time at which the bellows could have been overpressured.
An examination of the bellow actuating gas cupply s'7:: tem was nade.
No failure mechanism of the pressure regulator could be defined that could overprescure the system unless the relief valve capacity uas inadequate.
Relief valve capacity was tested and found to be acceptabic.
It was the conclusion that the hellows had been overpressured at time unknown and this had caused the failure.
Attention was turned to the condition of the bellows operators of the remaining three helium circulators installed in t he PCRV.
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Page 3 Diccussionn with a Le]1ous manufacturer pointcd out t.he fact a heavy walled high pressure bello'..;, if overprersured and defort:ed, will f all within a f eu operatin: cycler, because of the final heat treat uncd in the fabricatien of the bz]1ous. Thin heat tsre a t r e n t Jowers the maxinum tenulle strength to the approximat e value of the yield ctrengt h.
This fact was confirr:ed by an independent authority.
If the bellown is over-prensured and deforred, thin indicates the yleld strene,th of the material has been exceeded and possibly the uaxit um t ensile strength.
If the bc]10ws did not fail at the t ice of defornation, it will in a few operat.ine, cycles.
I The bellmm operators of U, C, and D helium circulator static seals were each Jeak tented in place and t. hen operated twenty tines each and re-leak tested.
No change in leak t.ightnes =, was observed.
From t.his test it pas determined that the three hellun circulator static seal bellous operators had not experienced the overpressure condit. ion that "A" had and were operable.
CORIGCT1VE ACTIO:i:
l The "A" hulium cir'ulntor has been replaced with the spare unit.
c In addition, to assure prevention ar;ainst overpressurization from the normal operating gas source, the relief valve setting has been reduced to 1300 1 50 psig.
FAILURE D/,TA/ ST"II./3 PJPORTED OCCPPM SCES :
This mode of static ceal f ailure has not occurred before.
The subject of Abnormal Occurrence #50-267/74/10, dated. lune 3, 1974, was leakage of pr.iuary coolant by the static seal on "B" helium circulator due t o particulate natter between the sealing surfaces. These two types of failure are not considered similiar.
PROGRAMMATIC 1MPACT Approximately 35 days are required to completely change out a helium circulator.
Due to our present schedule, this circulator change out will delay t.he overall testing program approxicately two weeks.
CODl: IMPACT:_ _ _ _.
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Im mn U. Duane Rodgers, Operations Supervisor II. Larry Brey, S perinteddent-Operations
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