ML20037B647
| ML20037B647 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/26/1964 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Lowenstein R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8010270591 | |
| Download: ML20037B647 (3) | |
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Dear Mr. Lowenstein
'this letter is to confirm the diffictity emperienced with een of the eighty sontrol rti drives of the Dresden Station as discussed witia your staff perooemel mod myself at the asaanda effise en March 3, 1964.
At 4t15 AM en March 2,1964, during the performones of routine daily l
exercistag of all control rod drives, sentrol red K-4 titich wa in the lully withdrawa position, failed to insert upon the normal "Lasert" sig-mal. Operation of all drives had been satistastery during the previous I
day's exercising. At 7:35 AN of the same day Qhrek 2, 1964) control red drive K-4 was assia gives as " insert" signal with manual hydraulic system pressure senditions and at this time the drive weepended by inserting one match, at ubish ties the "Losert" signal was dissentiamed. After par-forming a de of investigst.ag tests, aussessive attempts to withdrew the drive resulted la progressive insertian, esteh by netsk, under seems1 and under higher-than-mormal hydraulia pressure test oseditions, until the drive was fully inserted. Emah motsk of inserties required at least two " withdraw" signals indicating that the drive was ratehottag in under the influence of the preliminary " insert" impales whisk esists momentarily at the beginaias of each Srithdraw" actuation la order te lift the drive index tube to permit malatching of the locking sollet.
Iaveetinsttoa of Melopersttoo bhile the drive was at positica "9" med subsegment to seaglete insertion to positten "0", the hydraulic system valves associated with the drive were lavestigated and appeared to be functionias properly. The drive was disarmed la the fully inserted position until scheog.ent tests were conducted during a schedaled shutdown for physics tests on March 6 1964. Additional attempts to withdraw drive K-4 failed, and water flow l
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Mr. Ashort Imuenstein learek 26, 1964 asseuremmets indisated aermal hydraulia system valve operaties. Drive E-4 uns agata disarmed for enheepsent reactor operation. During all phases of testing, the reester was maintaiand empable of stustdown within the seguire-meats of lisease DFB-2.
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An evolusties of the results of the investigation todisates that the inoperability of this drive is due to Ameressed fricties.
- 1. is com-sidered prehable that the cause of increased fricties is due to galling of the index tube, such as experienced on C-7 drive on June 17,1962, and f reported to the AEC on Juos 23, 1962, and on March 21,1%3.
N The following factors have been considered regarding continuing operaties of and resumption of eperation of the reactor 1.
All of the other drives have satisfaatory operettamal p
sharesteristics.
2.
The occurrence of increased friction in other drives can be detected by the routine daily or unekly check i
of drive movement. Past experience has demonstrated that drive as1 functions are more readily detested during actual operation than during routine teste performed at shutdown.
3.
Although increased friction la a drive usy impair noems1 metica, it has sever been e h ed to prevent i
scram operation.
l Maving E-4 drive locked out in the full in position has no I
effect on the " stuck cod" criteria and will est impair the ability to control the reactor.
It has been coesladad that the difficulty with K-4 drive does not indicate that impairment of the performance of the other drives may be i==tamar.
Sincere 1 s.
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E. K. Boyt Seputatendent Dresden Nuclear Power Station MKHalssa cc:
E. C. Bailey
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