ML17252A528
| ML17252A528 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/03/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | O'Leary J US Atomic Energy Commission (AEC) |
| References | |
| BBS Ltr. #483-74 | |
| Download: ML17252A528 (3) | |
Text
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~Jee Commonwealt.Aison One Firs~ National fir Chicago, Illinois P.tddress Reply to: Post Office Box 767 Chicago, Illinois 60690 Mr. J. F. O'Leary, Director Directorate of Licensing
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U.S. :'. *::s1.' c..
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U. S. Atomic Energy Conunission Washington, D. C.
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SUBJECT:
- LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, REPoRT OF UNUSUAL EVENT PER SECTION 6.6.B.2 OF THE TECHNICAL SPECIFICATIONS.
FAILURE OF 3B CONTAINMENT COOLING SERVICE WATER PUMP TO START.
Reference:
Drawing: P6alD M-368
Dear*Hr. O'Leary:
This letter is to report a condition relating to the operation of the unit at about 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> *on June 17, 1974. At this time, a contaimnent cooling pump failed to star.t during surveillance testing of. the pump.
This malfunction is contrary 'to section 2.a. l. c of Regulatory Guide 1.16 which states that "any condition involving a single possible failure which, for a system intended t_o be designed against assumed single failure, could re.sult in a loss of the capability of the system to perforin its safety function;".
PROBLEM.
With Unit 3 at approximately 632 MWe, preparations were made to take the Unit 3 diesel generator out of service 'for its annual inspection.
The Technical Specification (section 3.5.F.l) states in part "when any unit or shared diesel generator is inoperable, continued reactor operation is permissible only during the succeeding seven days provided that all of
. the low pressure core cooling and containment cooling subsystems shall be operable".
As part of the station's normal procedure, the LBCI and contain-ment cooling service water pumps were started to demonstrate system operabi-lity. When the equipment attendent attempted to start the 3B containment cooling service wat~r pump, the pump failed to start. The other three containment cooling service water pumps and the other components of contain-ment cooling functioned normally.
This action brought.the status of the CCSW pumps into compliance with the Technical Specification (Section 3.5.B.2) which states: "When it is determined that one containment cooling service water pump is operable, the remaining components of that subsystem and the other containment cooling subsystem shall be demonstrated to be operable immediately and daily thereafter." This action was completed by 4:10 a.m.
on June 17, 1974.
The normal function Qf the containment cooling system 6334
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Mr. J. F. O'Le~ry
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- July 3, 1974 is to provide cooling water to the LPCI he.-!l! __ ~~c;l_un1ge_r_. ___ The-containment--- - -----*
-. ____.:__ ____ cooling--service-water* pumps--circulate water from the crib house, through the LPCI heat exchanger and discharge the water to the main service water discharge piping.
INVESTIGATION Following the failure of the 3B CCSW pump to start, an equipment operator was sent to check the circuit breaker for this pump.
He found that the racking screw cover was not closed all of the* way.
This cover includes a safety device which prevents the breaker from being electrically charged when the cover is not completely closed. This *cover is spring loaded and is supposed to close automatically when the racking screw tool is withdrawn.
In this case, the spring failed to closeSthe cover completely.
CORRECTIVE ACTIONS The equipment operator closed the cover completely.
The 3B CCSW';:
pump was then started without further problems.
This work was completed by 4:45 a.m. on June 17, 1974 and the Unit 3 diesel generator was taken out-of-service shortly thereafter. A work request has been initiated by shift personnel to 'nspect the 3B CCSW pump circuit breaker.
This work request is not yet completed. Additionally, a procedure change has been initiated which will require.inspection of the racking screw cover operation every time the 4KV air circuit breakers are inspected.
Both the breaker inspection and procedure revision should be completed by July 31, 1974.
EVALUATIONS There -was no effect on the safety of operation during the period of uncorrected.condition.
Surveillance revealed that the other three CCSW pumps were operatioiµil.. Thus,: neither the CCSW system nor the subsystem consisting of A and B CCSW pumps was inoperable at any time.
The ~diate. actions.to correct the :~ondition. and:'b~i~g~ the status into compliance *~ith*the Technical-Specificationswere'appropriate.
The Technical sp:ecifiCations prov.ide for' certain actions in. event of a CCSW pump failure and these actions were followed.
The problem with the pump was investigated.and established quickly and the pump was returned to operational status very soon after discovery of its failure to start.
Follow-up actions have been appropriate and should minimize the
- probability of future failures of this.type.
A review of station records revealed that no prior occurrances of this nature have been reported.
Because of the lack of any previous history of failure of the racking screw cover to close, the continued operation of the unit is justified. The remaining investigations and actions involve inspection of the breaker racking screw cover and a pro~
cedure change to insure this inspection will be performed during each
.rj]ci4-Mr. J. F. O'L~ry
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July 3, 1974 maintenance o_L.El _ _JJimilar tY-p_e_of __ breaker--even--t-hough-,---judging--by-past ___ his-tot'y,- ---- ---
-- ---- - --tnl.s was -an isolated faiiure.
In addition, the 4KV breaker checklist associated with the equipment outage check-off list will have a column added to include checking for closure of the racking screw cover when returning 4KV circuit breakers to service.
Sincerely, BBS:JMD:do