ML19317G864
| ML19317G864 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek, Rancho Seco |
| Issue date: | 03/07/1973 |
| From: | Schwencer A US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Davis E SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8004020497 | |
| Download: ML19317G864 (2) | |
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UNITED STATES ATOMIC ENERGY COMMISSION
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WASHINGTON. D.C. 20545 ilAR 7 1973
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Docket'No.' 50-312
ld Sacramento Municipal Utility District ATTN:
Mr. E. K. Davis General Counsel j
6201 S Street, P.O. Box 15830 l~
Sacramento, California 95813 Genclemen:
Wo incidents have occurred at a nuclear power plant that indicate a deficiency in the control circuit design that warrants a review of the control circuits of all facilities to assure that these types of defi-
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ciencies do not exist or are corrected. if they do exist.
Both incidents involved the inadvertent disabling of a component by racking out the
' circuit breaker for a. different component.
In one case, this caused the i
loss of capability to isolate secondary containment when this capability was required.
In the second case, the racking out of a breaker for one pump disabled not only= the pump being removed from service but also its i
' redundant counterpart.
Both of these occurrences resulted from the use of auxiliary centacts on the movable portion of the circuit breakers in the control 51u uits of other components. When the breaker is racked out, the control circuit employing these contacts is opened and may be l
rendered inoperable.
Copies of the licensee's reports on these two occurrences are enclosed for your information.
The licensee's corrective j
measures for both of these cases included redesign of the control circuits j
so that racking out the breakers would not render the control circuits of other equipment, inoperable.
As.a result of these occurrences, we request that you perform a review of the control circuits of all safety related equipment at the plant to assure that disabling of one component does not, through incorporation in,other interlocking or sequencing controls, render other components in-opdrable.. All modes of test, operation, and failure must be considered.
i It appsars 'that in the cases cited above, the racked out position of i
breakers had not been included in the failure mode analysis of these control circuits.
j Also, your procedures should be reviewed to ensure they provide that, j
whenever part of a redundant system is removed from service, the portion remaining in service is functionally tested immediately after the dis-abling of the affected portion and, if possible, before disabling of the affected portion.
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1 Sacrargento Municipal Utility District.
The results of your review are requested within sixty days.
This information should be provided with one signed original and thirty-nine additional copies.
Sincerely, Original Signed by LAlbert Schwencer A. Schwencer, Chief Pressurized Water Reactors Branch No. 4 Directorate of Licensing
Enclosures:
' Licensee's reports on occurrences cc: David S. Kaplan, Secretary and Attorney 6201 S Street, P.O. Box 15830 Sacramento, California 95813 DISTRIgUTION4 Docketn PWR-4 R/F EIGoulbourne (2)
Project Manager 6..
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7 Jersey Central Powe'r & Light Company NADISON AV'ENUE AT PUNCN BOWL. R Ao e MORRISTOWN. N.J. 07960 e 539 6118 April 20, 1972 g
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- 1. gg f;.,9.g f> d-. 1 Dr. Peter A. Morris, Director y
Division of Reactor Licensing j
g United States Atocic Energy Commission
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Dear Dr. Morris:
Suaject: Oyster Creek Station O
Docket No. 50-219 '
Loss of Secondary Containment Integrity ThepurposeofthisletteristoreporttoyouavioEation of a Limiting Condition. for Operation in that Secondary Containment Integrity was not maintained as required by Specification 3.5.3.1.
of our Technical Specifications.
s On April 11, 1972, during performance of a routine weekly surveillance test of isolation of the Reactor Building and initiation j
of the Standby Gas Treatment System due to simulated high radiation levels on the Reactor Building Operating Floor and in the Reactor Building Ventilation Exhaust ducts, the supply dampers for the Re, actor' Building Ventilation System failed to close as required.
As a result of this failure, Secondary contain=ent was not in etfect.
Isolation of the Reactor Building Ventilation System supply damper is initiated by "b" contacts from the Reactor Building Ventilation System supply fans, SF1-12, SF1-13, and SF1-14 wired in series.
- However, due to an electrical problem with supply fan 1-13, which resulted in the discovery that the motor was shorted, its supply breaker was racked-out.
Thus, the logic control circuit for the dampers was " opened", the normal situation with the fans in operation. When the remaining fans were trippcd during the surveillance test conducted at 2:00 a.m. on April 11, 1972, the logic control circuit was still open, the da=per control relays remained de-energized, and the dampers did not close.
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The logic circuit was restored by disconnecting the motor leads from the breaker and racking-in the breaker. At 9:20 a.m.
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on April 11, 1972, an operability check of Reactor Building Isolation was conducted and proved to be satisfactory.
A caution tag was placed at the fan control switches in the Control Room to notify operators that if a supply fan breaker is racked-out,the Reactor Building supply damper isolation control logic is defeated unless a jumper is installed in the breaker cabinet. A similar caution note is being stenciled locally on the supply fan breakers.
As noted in the FDSAR, the primary objective of the Secondary Containment System is to minimize ground level re] case of airborne radioactive materials and to provide for controlled elevated release of the building at=osphere under accident conditions.
The containment systet3, Primary and Secondary, provide the principle mechanism for mitilgation of accident consequences.
The off-site accident consequences, howeyer, are relatively insensitive to the Reactor Building in-leakage rate as long as the Standby Cas Treatment System can maintain the building at a vacuum.
In this particular instance, the supply and.
exhaust fans tripped, the exhaust. dampers closed, and the Standby Cas Treatment System was initiated..
With the above situation, the air cupply to the building was not only via the various in-leakage paths but also, and no doubt primarily, via the Reactor Building supply dampers.
Any accident conditions postulated that require sedondary containment in determining environmental releases would, under these conditions, have a second path permitting release of the Reactor Building air at approximately a 60-foot elevation.
,,I,n order to prevent a reoccurrence of this incident, a
circuit design change will be i=plemented that s'ill permit a Reactor Building supply fan breaker to be racked-out for maintenance without defeating the Reactor Building supply da=per isolation logic.
Until this design change can be,imple=ented, a standing order will be issued instructing plant personnel in the appropriate practice to be followed to avoid defeating the Reactor Building supply damper isolation logic.
Very truly yours,
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.41 b Ivan R. Finfrock' Jr.
Manager, Nuclear Generating Stations IRF/pk Enclosures cc: Mr. J. P. O'Reilly, Director Division of Compliance, Region I
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Jersey Central Power & Lignt Company Y.
MADISON AVENUE AT PUNCH SQWL RO AO e MoRRISToWN. N.J. 0796o e 539 4111 y
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Mr. A. Giambusso g
Deputy Director for Reactor Projects g[h* '* '
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Washington, D. C. 20545 s
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Dear Mr. Giambusso:
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Subject:
Oyster Creek Station
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Docket No. 50-219 bb~
Inoperable Standby Liquid Control System g%
The purpose of this letter is to report to yo'u an inciden.
that occurred at Oyster Creek on Septe=ber 26, 1972 in which it was O
discovered that the two pumps in ene standby liquid control system were inoperable at the same time'.
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At.10:45 a.m. on September 25, 1972, the "A" standby liquid control pump was removed from service for replace =ent of the pump packing.
The pump was taken out of service using Technical Specification 3.2.C.3 as the basis.
It states, "If one standby liquid control system pumping circuit becomes in--
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operable during the run mode and specification 3.2.A is met, r
. the reactor nay remain in operation for a period not to excee //
4 seven days, provided the pump in the other circuit is demon
-yc strated daily to be operable".
Specification 3.2.A is met,p
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s therefore, the "A" pump breaker was racked out and the pu=; *-
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was not, co=pleted by the end of the day shif t, and the "A" 6-
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k[A pump was left in an inoperable condition.
At 4:20 a.m. on qqI September 26, 1972', the "B" liquid control system pump was g
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to be run to comply with Technical Specification 3.2.C.3.
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When the operator depressed the start button, the pump did not start.
An interlock in the starting circuitry prevents two standby liquid control pumps from being run simultaneously.
This interlock also prevents the "B" pump from starting when the "A" pu=p breaker is in the racked out position. The interlock is ce= posed of a normally closed contact in the starting circuit of each pump. This contact is operated j
from a relay in the opposite pu=p circuit.
If the "A" standby liquid control pump is started either from the
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control room with the key lock switch or locally frcan the fT (af f- ["
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' October 6, 1972'
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' push button station, a relay is picked up which opens the nor= ally closed contact in the "B" standby liquid control pu=p starting circuit which prevents this pu=p fro operating with the "A" pu=p running.
The reverse is true if the "3" pump is started.
The proble= developed when the breaker for the "A" pu=p was racked out.
It disabled the pu=p and at the sa=a ti=c it physically re=oved the contact in the starting circuitry for the "3" pu=p which si=ulated an open contact. This prevented the "B" pu=p fro: starting.
As soon as the Shif t Fore =an was aware of the inoperability of both pu=ps,-he started a nor=al shut,down of the plant.
In the meanti=e, he received per=ission to clear the =aintenance safety tags and rack the "A" pu=p breaker to its normal position. He then ran a successful operability check on the "B" pupp.
The load reduction was stopped and the plant returned to full load.
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In order to prevent a recurrence of this event, operating procedures have been changed'so that operability tests of redundant engineered safeguards syste= co=ponents will be =ade i==ediately following any action that requires one of the syste=s to be inoperable fo= =aintenance purposes.
We are enclosing forty copies of this letter.
Very truly yours, fG11 }.
i M. Of Ivan R. Finfro'ck, Jy.
.Vice President IRF/pk,
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Enclosures cc: Mr. J. P. O.'Rei,11y, Director Directorate of Regulatory Operations, Ragion 1
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