ML20207L802

Special Rept:On 880923,main Steam Line post-accident Radiation Monitor RM-064 Turned Off Due to Apparent Power Supply Failure.Caused by Inherent Characteristics of Electronic Ratemeter.Monitor Turned Back on

ML20207L802
Person / Time
Site:	Fort Calhoun
Issue date:	10/10/1988
From:	Morris K OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LIC-88-907, NUDOCS 8810170447
Download: ML20207L802 (2)

Text

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l l Omaha Public Power District l 1623 Harney Ornaha. Nebraska 68102 2247 402/536 4000 October 10, 1988 LIC-88-907 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station PI-137 Washington, DC 20555

Reference:

Docket No. 50-285 Gentlemen:

SUBJECT:

Special Report on Inoperability of Main Steam Line Radiation Monitor RM 064 for Post-Accident Monitoring The Omaha Public Power District (0 PPD), holder of Operating License DPR-40, submits this special report pursuant to the requirements of Fort Calhoun Station Unit No. 1 Technical Specification 2.21 "Post Accident Monitoring Instrumentation." Fort Calhoun Station Unit No.1 Technical Specification l Section 2.21, Table 2-10, item 3 requires that a minimum of I channel for main steam line radiation post-accident monitoring instrumentation be operable in Modes 1, 2 and 3. With the number of OPERABLE channels less than required by the minimum channelt operable requirements, OPPD must either restore the inoperable channel (s) to OPERABLE status within 7 days of the event, or prepare and submit a special report to the Commission pursuant to specification 5.9.3 within 14 days following the event.

On September 23, 1988 at 0635 hours0.00735 days <br />0.176 hours <br />0.00105 weeks <br />2.416175e-4 months <br />, the main steam line post-accident radia- I tion monitor RM-064, was turned off due to an apparent power supply problem.

$v The monitor was logged as inoperable and a maintenance order was written to Spp investigate the problem, but it was not assigned a high priority. In accor-  ;

c6 dance with Technical Specification Table 2-10, footnote (a), a preplanned  ;

M Mo alternate method of monitoring the appropriate parameter was verified to be in l place per 01-PAP-8. l Ne '

N The apparent inoperability was due to inherent characteristics of the elec- l R@ tronic ratemeter, resulting in inappropriate actions to repair an operable in-

- strument. RM-064 is designed primarily to be used following a steam generator 2x tube rupture. Normally, the monitor is electronically 'on' but does not per-

$pg form its post-accident sampling function until required by Emergency Operating Procedures. It usually indicates near the bottom of the ratemeter scale. When the ratemeter scale falls below 10 counts por minute (CPM) an internal circuit generates an alarm, which in turn causes the panel annunciator to alarm. This action also turns off the "Fail" light on the ratemeter. When this light is

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,U. S. Nuclear Regulatory Commission LIC-88-907 Page 2 out, it leaves the impression that the power supply has failed. The technician

performing the maintenance order could not duplicate the problem. The monitor was turned back on and declared "operable" on September 30, 1988 at 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br />,

, which exceeded the 7 day time limit by approximately 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />.

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On October 1,1988 Fort Calhoun entered Mode 4, and Technical Specification l q 2.21 for operability of RM 064 was no longer applicable. Fort Calhoun Station i is currently in refueling shutdown (Mode 5). Further investigation indicates a i possible problem with a pre-amplifier in the monitor. Results of the i investigation are not yet available and will be provided within 30 days. l

if you have any questions, please do not hesitate to contact us.

l Sincerely, ,

i

. Morris [

Division Manager  ;

Nuclear Operations KJM/sa c: LeBoeuf, Lamb, Leiby & MacRae '

1333 New Hampshire Ave., N.W.

Washington, DC 20036 l 2

R. D. Martin, NRC Regional Administrator i P. D. Milano, NRC Project Manager i

P. H. Harrell, NRC Senior Resident Inspector l

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