ML20037A920
| ML20037A920 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/23/1962 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | |
| References | |
| NUDOCS 8008080721 | |
| Download: ML20037A920 (3) | |
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Dresdem Nuclear Power Station R. R. #1
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Morris, Illinois June 23, 1962
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.a W !hl Mr hohert lowenstein, Director
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Divisioe of Licensing and Regulation
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U. S. Atomic Emergy f%==f asion
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Washington 25, D. C.
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Dear Sir:
This letter is to awdvise the ABC that we have experienced difficulty with one of the eighty control rod drives of the Dresdes amenlear Power Plant's reactor.
Qa June 17, 1962, just prior to a scheduled plaat shutdown (January 20-25, inclusive) for quarterly i
control rod drive testing, as specified in DPR-2 as ammaded June 9, 1%1, C-7 control rod drive exhibited abnormal operation in that it chewed sluggish response to normal insertion and withdrawal signals.
This sluggish operation was alleviated by checking for proper valve operation and exercising om June 13, 1962. Centrol rod followin; was verified by in-core and out-of-core chader and megewett electria al instrummat response during control rod drive exereising.
Af ter plant shutdown at 4:58 PM, ca June 20, 1962, the friction testing of the control rod drives was started on June 21.
During this testing, C-7 eontrol red drive again showed abnormal operation by being i
sluggish as withdrawal, and during insertion it stuck at positica 6.
The drive was inserted to full in position by raising the drive-ia pressure to 250 peig.
Investigation of this difficulty was initiated; sad during the sourse of the invegtigation, operability of this drive (C-7) became more diffisult. At no time during such testing did pres-suree used for insertion of this drive exceed 250 posada.
(Pressure for normal scram operation is 1400 peig). After having inserted it to position 0 a nuder of times, the drive could not be withdraum with normal pressure and with pressures up ts 275 peig.
An evali ation of the results of the investigation indicates that the inoperability of this drive is due to increased friction. A number of possibilities to explaim this have been considered,-- and it is comaluded that the cause of the high friction is galling of the indes tube in the drive.
Sach galling has been observed om essastaa in test
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t Mr. Robert imeera. coin t
, Juno 23, 1962 l
l operations at General Electric's AftD plant in San Jose the behavior of drive C-7 has characteristics similar
, Califormit, and such test operations.
to those observed io tude which can be overcome by the application oi drivIt should be a t
imately 507,above normal.
e-in pressure approx-exists in capability to scram since the scram pressure is morThis l
times normal drive-in pressure.
l e than sia the design is such that the force acting in this directiThe drive cannot be w drive-in force for normal drive-im pressure.
on is 1/3 of that 1/3 the effective pistem area in the " insert" directionthe e s approximately L. teeults.sf the tut 6 them to be in good operating conditiou;os the other 79 eontrol rod drives showwi behavior as was experienced by C-7 drive.none of them exhibited sluggish 22, 1962, It that this drive would be left was decided et 6:00 PM, June 1
other scheduled work is completed which is expecte n
as soon as June 25, 196 ?.
omtay aftaracon, of operation of the reactor:h following fa'ctors Lee bua considere.d regardin on I
l 1.
All of the other drives have actisfscrory operational t
ch:rscterirtica.
2.
h cccurrence or increased frictier. in other drives usa be detected by the routine daily or weekly check of drive noveneat.
3.
Although increased friction in a drive may impair normal l
motion, it has never been obsarved to l
operation which utilizes pressures app: prevent seven that required to driva C-7 in.
roximately 5 times on the " stuck rod" criteria and will actRaving C-7 drive lockM out in the effect It has been concluded that the difficulty with C-7 drive doesimpa reactor.
indicate that impairasat of the performanca of the other driv not aussiment.
Procedures and Limitations" of Appendix A to DPR-2 as aTheref es may be
" Operating resuming operation of the Dresden Nuclear Power Station on June 25 mended, we are t
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l Sincerely yours, l
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