ML20204B437

Responds to NRC Re Reactor Protection Sys Power Supply.Possibility of Undetected or seismic-related Failures Remote.Probability & Possible Effects Still Under Analysis. No Facility Mods Proposed at Present Time

ML20204B437
Person / Time
Site:	Cooper
Issue date:	10/06/1978
From:	Pilant J NEBRASKA PUBLIC POWER DISTRICT
To:	Ippolito T Office of Nuclear Reactor Regulation
References
TAC-08938, TAC-8938, NUDOCS 7810170152
Download: ML20204B437 (2)

Text

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GENEHAL OFFICE I 1 Nebraska Public Power District " " fe1%'nE%"Wi%a"^ """

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l October 6, 1978 i

i Director, Nuclear Reactor Regulation l Attention: Mr. Thomas A. Ippolito, Chief ,

Operating Reactors Branch No. J  !

Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Reactor Protection System Motor - Generator Sets Cooper Nuclear Station NRC Docket No. 50-298, DPR-46 i

Dear Mr. Ippolito:

i Your letter of August 7, 1978 requested the Nebraska Public Power District to evaluate the reactor protection system (RPS) power supply at Cooper i Nuclear Station ~and determine if a potential exists for either undetected single failures or earthquake initiated events which would adversely affect the system. Our initial evaluation has.shown that this potential, -

however remote, does exist in the system due to the RPS Motor-Generator sets being non-Class 1E; however, the probability of such an event and its effects are still under analysis. For this reason no facility modifications '

are being proposed at this time. NPPD will submit the results of the further analytical efforts upon their completion. If deemed necessary, NPPD will also submit proposed facility modifications by approximately February 1,1979.  !

Attachment 1 to your letter listed four items in a surveillance program which Cooper Nuclear Station was to commence. Items one and two of this 4 program were being performed by the Station prior to receipt of your letter.

Data supplied by General Electric shows that this equipment has operated a total of 136 reactor years without a reported failure, including operations during severe earthquakes. Based upon this long history of trouble-free '

operation, it is NPPD's belief that performance of items three and four i of the surveillance program is not warranted. Cooper Nuclear Station will ,

continue to monitor the output voltage and current of each RPS M-G set once per shift and will remove an M-G set from service if the output voltage cannot be adjusted to.withiu 110% of its nominal value.

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, Mr. Thomas A. Ippolito 2 tober 6, 1978 Page 2 If you have any questions or require additional information relative to the RPS power supplies, please contact me.

Sincerely,

.. Pilant Director of Licensing and Quality Assurance JDW/cl i

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