ML20086D932
| ML20086D932 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/18/1973 |
| From: | Riley B VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086D933 | List: |
| References | |
| AO-73-28, VYV-3026, NUDOCS 8312050679 | |
| Download: ML20086D932 (2) | |
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Gentlemen:
U1 As defined by Technical Specifications for the Vermont Yanime
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Abno rru l Occurrence as AU- / _i-as.
At approximately 1330 on September 10, 1973, while perf orcing a monthly functieaal tent on the Low P re:,n u re Coolant Injection Syutem (LPC1) break detect ion logic (i.'.,
A>ll d/p acrow riset s), a microswi tch
. mtalled in DPIS 2-12913 failed to tetuate at the required setpoint of 1 (+J.5) psid aa specified in Table 3. 2.1 of t.he Technical Specifications.
The mim oswit.ch actuating arm uas mechanically bound and fniled to drop into the cam valley.
Function.tlly, this swi t ch ope rat es in conjunction wi t h DP f S 2-129D to act.uat e a relay in thei r respect he logic strings to close t he Loop "il" LPCI valve and actuate the Loop "A" Recircu lation val vea.
Th. reactor was shut down at the time of this incident.
The nensor wa'. nade operable by replacing the r:icroswitch assembly t;hi ch includen the suitch, the switch actuatiin arm and backplate assembly.
Operation was natislactory af ter repeated actuations and the inatrument channel was declared operable at 1619 on f>eptembe r 10, 1973.
The Plant Operations Review Commit tee (PORC), r..eet ing t o revjew the ineident, noted that this was the samt 11arton swit ch and actunt ing assemb.ly which h.td f ailed twice previously during aurvell]nnce t e s t. in g. These incidents were reported as A0-73-09 and A0-7 3-21.
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.I VERMONT YA$KEC NUCLEAR POWCR CCT4 F'ORATIOT Directorate r.1 Licensing September 18, 1973 Page 2 Whe rais, in the previous two incidents, corrective action consisted of replacement of the nicrosult h only and/or re :'.ignment of the actuating, arn, in this case, the complete subasseubly was replaced when inspection revealed excessive binding f ra the switch actuating arm.
The committee ar, reed that this more extensive rep lacement should correct the probh n and reccamended that the defective assembly be returned to the vendor for analysis to determine the cause of the mechanical binding.
Very truly yours, VERMONT YANKEE NUChEAR POWER CORPORATION bb3.
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Bradford W.
Riley Plant Superintendant WFC/hbd i
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