ML17238A728
| ML17238A728 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/12/1972 |
| From: | Worden W Commonwealth Edison Co |
| To: | Morris P US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17238A728 (2) | |
Text
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Commonwealth Edison Co~
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72 WEST ADAMS STREET
- CHICAGO, ILLINOIS Addreu Reply to, POST OFFICE BOX 767 *CHICAGO,. ILLINOIS 60690 Dresden Nuclear Power Station Dr. Peter A. Morris, Director.
Divi_sion of Reactor Licensing
- u. S. Atomic Energy Commission Washington, D.C.
20545 R. R. 411
- Morris, May 12,
Subject:
License DPR-25 DNPS Unit '#3 Section 6.6.B.2 of the Technical
Dear Dr. Morris:
meKEniD WBAliC 60450 MAY 161972 e.
J:raov OOCKrt CURie This is to report a condition relating to the operation of the 1
station, when isolation condenser valve 3-1801.;.3 failed to open electrically following a spurious reactor scram, thus rendering the isolation condenser inoperable contrary to section 3.5.E.l of the Dresden Unit 413 Technical Specifications.
PROBLEM AND INVESTIGATION On May 4, 1972, Unit #3 was operating in a base load condition at 802 MWe and 2300 MWt.
At. 09ll, _the. unit underwent'" a.scr.am. which. was followed by a Group I isolation, causing the reactor pressure to rise.
An attempt was made to place tli"e isolation condenser in service, but valve 3-1301-3 would not open.
An operator was dispatched to the valve and manually moved the valve off its s~at. Once the valve was manually moved off its seatr~a!ld its breaker reset, *_ !..'"!.J it appeared to function properly.
The isolation condenser was then used to reduce reactor pressure in an orderly fashion.
CORRECTIV~ ACTION Following the plant shutdown, investigation of the isolation condenser valve 3-1301-3 discillosed that the "B" auxiliary contact on.the closing circuib~i6or the valve motor operator circuit breaker was not consis;.
tently closing properly.
This contact is in the electrical interlock circuit for the open contactor.
The auxiliary contact arm was adjusted and proper op.~ration of the valve was verified.
lhe last surveillance performed on this valve prior to the scram was on 1/15/72 when the valve operated satisfactorily.
Subsequent to the
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Dr. Peter May 12' 1972 sfutup following the scram the valve was aga*in operated electrically and performed properly.
ADDITIONAL INFORMATION
'llle spurious scram on 5/4/72 and the ensuing pressure transient caused an electromatic relief valve to operate.
One safety valve prematurely opened at 1108 psig reactor pressure resulting in pressurizing the drywell to 2~ psig.
'lllere was no drywell damage except for a piece of insultion which was blown off an adjaeent relief valve.
'llle transient was reviewed by?the Station Review Board and the Nuclear Review Board. t.FQ__~gi~~~~view, startup was approved and the plant returned to service.
A complete report of the event is being developed at this time and will be forwarded to you by 6/1/72.
WPW:sds Sincerely, a:JJ.*rvt~
0_,.., W. P. Worden
'\\ ' 'Superintendent