ML20037B459
| ML20037B459 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/14/1965 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8009290557 | |
| Download: ML20037B459 (5) | |
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, hir. Rudger Eoyd
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Division of Licensing and Regulation l
U. S. Atomic Energy Co.umission O
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Dear Rodger:
During the recent sautdown on October 7,1005, we experienced some difficulty in inserting J-2 control rod from the full out to the full in position at normal operating pressures.
The plant was shut down to repair a steam leak on a drain line from the high pressure turbine. During the shutdowa period the scheduled scram and friction tests were performed. The control rod in question (J-2) exhibited normal scram and friction test characteristics. After repairing the st eam Ical:, the plant was returned to service. Post startup inspection indicated that the repair of the steam leak was not successful and the plant was shut down again on October 11,19G5. Again vie experienced difficulty in inserting J-2 control rod to the full in position at normal operating pressures. After inserting to the full in position l
it was decided to exercise the control rod to loosen any crud which could contribute to the difficulty. During the fifth exercising, the drive would not insert under normal operating hydraulic pressures.
Two unsuccessful attempts were made to scram the drives in by pulling fuses to actuate the scram valves on Accumulator fill.
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The drive was then scranuned in when the reactor operation mode t
f selector switch was placed in " Shutdown".
a series of tesis were conducted to analyze the operating r
citaracteristics of the control rod drive (J-2). These tests proved l
that the hydraulie system emernal to the drive and the electrical control devices and circuitry performed properly. These tests also indicated that the problem is in the control. rod mechajlism.
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i The control rod difficulties are still present, however, we have scrammed the drive about 80 consecutive times without a failure. We have also found that by introducing an insert signal simultaneously with a scram signal the drive will not scram; liowever, this was done under test conditions.
Our interpretation of the license leads us into the classifi-cation of control rod drives as either (a) normal, or (b) stuck.
This drive (J-2) does not completely fulfill the requirements of being classed as a stuck rod, nor does it fulfill all the require-ments to class it as a normal drive.
We are intending to resume operation on Saturday, October 16,19G5, and will consider this drive (J-2) to be a stuck drive even though we will leave it in a condit, ion capable of being scrammed.
This decision is consistent with our past regard for safe operation of DNPS.
A review has been made of the operation of the reactor in accordance with Section G of DPR-2 considering this drive to be stuck at position 12 along with C-9 at position 8, also a " stuck drive". Critical and suberitical tests on the core indicate that the reactivity limits are easily met. The operation of the reactor is not effected since the control rod is normally fully withdrawn and is not used for vertical power shaping. We will by means of the daily control rod exercise, weekly control rod instrument response test, and monthly control rod worth tests determine any unlikely impairment of performance of the other drives by noting any inability to insert. This particular abnormality was first detected by an increase in difficulty to insert J-2 at normal operating pressures.
In view of the foregoing analysis and the continuing test program, we have determined that operation can be resumed since (1) th9 stuck rod criteria is met, and (2) the anomalous behavior of J-2 does not impair the ability to control the operation of the reactor, and (3) does not indicate that impairment of the other t m.-
trol mechanisms is propagating or is imminent.
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r It is our desire now as was in flie past, to keep you informed on the operation of DNPS and we trust tliat tliis letter serves this purpose.
Sincerely yours,
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Ilarlan'K. II6yt Superintendent Dresden Nuclear Power Station Comnionwealth Edison Company HKII:cew i'
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5Talli Mr. Rodger Boyd Division of Licensing and Regulation U. S. Atomic Energy Commission hw 20545 Washington, D. C.
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