ML20084T496
| ML20084T496 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/08/1972 |
| From: | Worden W COMMONWEALTH EDISON CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084T499 | List: |
| References | |
| NUDOCS 8306230230 | |
| Download: ML20084T496 (3) | |
Text
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o Commonwealth Edison Company 72 WEST ADAMS STREET
- C H I C A G O.
ILLINOIS Amen Eselp een j
cost orrecs som ist
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Dresden Nuclear Power Station l
R. R. #1 Morris, Illinois 60450 C
December 8, 1972 g
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50-249
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W DEC L.,,.. e Hr. A. Giambusso Deputy Director for Reactor Projects g
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Directorate of Licensing CMal.
u U. S. Atomic Energy Commission
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SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6.6.C.1 0F THE TECHNICAL SPECIFICATIONS,
Dear Mr. Giambusso:
This is to report a condition relating to the operation of the station, when during surveillance testing, main sesam isolation va'.ve (MSIV) 3-203-1B was found to have a closure time of 2.1 seconds, which is outside the limits specified in the Technical Specifications.
PROBLEM AND INVESTICATION
]O At 0530, November 11, 1972, with the reactor at a power P
level of 1113 MWe, quarterly MSIV timing surveillance was being O
fk) conducted. During these tests, it was discovered that MSIV 3-203-1B had a closure time of 2.1 seconds, faster than theyecond to 5 second limits specified in the Technical Specifications (Table 3.7.1).
Both valves in the "b" steam line were promptly closed in accordance with f
section 3.7.2 of the Technical Specifications, and maintained in that condition until a subsequent shutdown.
The MSIV's on the other three steam lines had closure times within the 3 second to 5 second limits.
The limits specified on fast closure of the MSIV's are intended to prevent a rapid reactor isolation, and subsequent rapid reactor pressurization and resulting relief valve operation.
Closure of one MSIV in 2 seconds instead of 3 seconds does not significantly increase the pressure spike or the potential for relief valve operation.
Additionally, any pressure transient from the fast closure of one MSIV would be " softened" by the slower MSIV closure on the other three lines.
Consequently, it is concluded that the fast ciceure of the 3-203-1B MSIV was of no safety significance.
G306230230 721200 PDR ADOCK 05000249 7
0 PDR C0PY SEgr nEGION
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O Mr. A. CiambussaO
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- Dezember 8, 1972 CORRECTIVE ACTION On November 19, 1972, during a subsequent plant shutdown, MSIV 3-203-1B was inspected and found to have a slight oil leak in a fitting (see attached figure).
This fitting is in the valve's hydraulic speed j
control system. On loss of oil, the speed control system causes the valve to closa faster. The fitting probably leaked due to insufficient tighten b
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ing during installation. The slight leakage eventually resulted in j
sufficient loss of oil to affect closure time.
l The fitting was tightened, oil added, and the valve retimed.
The valve operated satisfactority and the 2 valves on "B" steam line were opened for startup. This problem is considered a one time occurrence and no further action is planned at this time.
Sincerely,
).. hp VN fW.P.Werden Superintendent
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