ML20002E378
| ML20002E378 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/21/1981 |
| From: | Hukill H METROPOLITAN EDISON CO. |
| To: | Novak T Office of Nuclear Reactor Regulation |
| References | |
| TLL-671, NUDOCS 8101270674 | |
| Download: ML20002E378 (3) | |
Text
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Metropolitan Edison Company Post Office Box 480 Middletown, Pennsylvania 17057 717 944-4041 Wntvs Direct Dial Number January 21, 1981 TLL 671 T.M.[ovak,AssistantDirector Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Atmospheric Dump Valves This letter is in response to your letter of August 15, 1980, concerning the automatic opening of the atmospheric dump valves during a failure of the nonnuclear instrumentation or the integrated control system.
We have investigated the problem identified in your letter and concur with your finding that the TMI-l ADV (MSV-4A and MSV-4B) will move to midposition corresponding to an input signal of 0 vde (power equivalent) on loss of ICS power. We will correct this situation by providing automatic transfer of the control of the ADV from the ICS to manual controls located in the control room upon loss of power. The manual loaders will be powered from a power supply independent of the ICS. Attachment 1 depicts the proposed modification.
Relay ARIO will deenergize on loss of hand power allowing relay 86 to drep the ICS and allow the manual loaders to assume control. Relay 86 shall be a latching type and will be reset by the operator from the relay room. The operator will be advised by indicating lights whether the total ICS bus or a portion thereof has failed. The operator will clearly know that the ADV's are under manual control-- Administrative control will insure that the manual loaders are kept at the closed position to keep the ADV's closed af ter the transfer. The atmospheric dump valves currently actuate position indicating lights on the main control board at the closed and open position. These lights are powered independently from the ICS. The manual loading stations which will be installed as proposed will provide an indication (0 to 100%) of the signal being applied to the valve from which valve position can be inferred.
Thesc modifications and administrative controls will be put in place as equipment is delivered. We currently expect to complete the modifications and adminstrative controls before restart.
N Sincerely, g
k 2
. D.
ukill Director, IMI-l HDH:DGM:1ma Attachment Metrecontan Ecson Ccmcany s a Mer er of the Ceneral Putte Ltit:es System f
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R. W. Reid B. H. Grier B. J. Snyder D. DiIanni H. Silver L. Barrett
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