ML20216H389

Submits Rept of Safety Sys Failure.On 870618,during Testing of New Safety Equipment,Determined That No Output Voltage from LOG-N to Period Generator.Caused by Broken Circuit Ground at Two Prong End of Cable.Diagram Encl

ML20216H389
Person / Time
Site:	Ohio State University
Issue date:	06/24/1987
From:	Redmond R OHIO STATE UNIV., COLUMBUS, OH
To:	Michaels T NRC
References
NUDOCS 8707010393
Download: ML20216H389 (3)

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• Ov The Ohio State University Engineering Experiment Station 142 Hitchcock Hall 2070 Neil Avenue Columbus, Ohio 43210 Phone 614 422-2411 June 24, 1987 1

l Mr. Ted Michaels Standardization and Special Projects Branch Division of Licensing U.S. Nuclear Regulatory Commission Washingtcr; DC 20555 RE: Report of Safety System Failure, License R-75, Docket 50-150 The Ohio State University Research Reactor (OSURR)

Dear Mr. Michaels:

This letter is to report a findhg as required by the R-75 license

(#3D(1) Reports). It is a follow-up to the telephone communication you had with Mr. Richard Myser of the OSURR on June 18, 1987. Please be advised that Mr. Robert Gregor of the US NRC Region III was also noti-fied by telephone on June 19, 1987. j On June 18, 1987, during testing of new safety equipment (Power Level and Period Safety) while the reactor was shutdown, it was deter-mined that there was no output voltage from the LOG-N (80 volt output) to the Period Generatar (see enclosed block diagram). The trouble was isolated to the cable t.nd checks indicated an intermittent opening in the " ground" side. Inspection of the cable indicated circuit ground was broken at the "two prong" end of the connecting cable into the LOG-N Amplifier.

Testing of new sa'fety system equipment has been in progress for approximately the last three months. This has, on occasion, required movement of the LOG-N Amplifier which may have contributed to this problem. Notes from snr testing procedures indicate the Period Safety system was functioning properly as late as May 13, 1987. To determine that the Slow Scram system was functioning properly since May 13, we have checked the period recorder chart paper for indication of any short

(<5 second) periods and reactor pre-start checkouts - calibration check of LOG-N-Period recorder.

During the subsequent eleven (11) reactor operations, no short g period indications were observen on the recorder paper. Additionally, j P

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College of Engineering

g 44-E Mr. Ted Michaels June 24, 1987 1 Page Two each pre-start checkout prior to an operation resulted in a period recorder " spike" indicating proper Slow Scram system operation. There-fore, we conclude that the Slow Scram system was functional during this entire time. We could not determine if the Period Safety functioned during this time since no curtate (<1'second) periods occurred.

However, proper response during pre-start checkouts indicated correct system operation from the Period Generator to control rods.

The problem was' corrected by fabrication of a new connecting cable.

After installation, all voltages were checked and instrument calibration checks performed satisfactorily. The staff of OSURR have reviewed this problem and all individuals have been instructed to observe certain responses during pre-start checkouts indicating that the Period Safety system cabling is connected properly and that signals are being fed from the LOG-N Amplifier through the Period Generator to the Period Safety Amplifier.

For the future, we are investigating an instrument' supplied by Kiethly (manufacturer of 25012A LOG-N Period Amplifier)-that will provide a period signal to the input of the LOG-N-Amplifier. This will test the entire' system instead of the Period Safety Amplifier.

If you have any questions on this matter, please contact Mr.

Richard Myser or Mr. Joel Hatch at 614/292-6755.

Sincerely, 3 Robert F. Redmond Director RFR/sh enclosure c: 'D. Miller, Director, NRL  !

R. Myser, Associate Director, NRL R. Gregor, US NRC, Region III l

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