ML20004B903

Ro:On 810518,pressurizer High Pressure Scram Switch 939 Was Found Isolated.Caused by Failure to Reopen Valve 599B After Insp.Valve 599B Reopened & High Pressure Scram Protection Restored

ML20004B903
Person / Time
Site:	University of Missouri-Columbia
Issue date:	05/26/1981
From:	Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8106010279
Download: ML20004B903 (2)

Text

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Research Reactor Facility UNIVERSITY OF MISSOURI Researen Park May 26, 1981 columei.. ussoun 65211 wennene pio 882a211

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Director of Licensing fs U. S. iluclear Regulatory Commission Washington, D.C. 20555

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f2-mi N y,2SJSSImI-o, ~i Re ference: Docket 50-186 University of Missouri Q ".,s ***oe %"D g,/ [

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License R-103 N

Subject:

Report as required by Technical 9 :s Specification 6.1.h(1).

Descriotion On May 18, 1981 at approximately 0100, the pressurizer high pressure scram switch 939 was found isolated. Operating the reactor with the pressurizer high pressure scram protection isolated is not in compliance with Technical Speci-fication 3.3. ,

Analysis .

On May 18,1981, the primary mechanical equipment area was being inspected before a reactor start-up following a loss of facility electrical power. The pressure gauge in parallel with the pressurizer high pressure scram switch 939 was found to be reading zero. Investigation found the corresponding isolation valve 599B to be shut. There is no indication of the pressure sensed at this pressure switch in the control room. Valve 599B had been closed on a mainte-nance day, April 27, 1981, while performing a compliance check. The compliance check requires the Heise gauge to be connected to plug (A) to measure pressurizer pressure.

Pressure Gauge PS 939 Valve o Plug (A) 599B Pressurizer X N $

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- Director of Licensing May 26, 1981 Page 2 4

At the completion of the Compliance Check Procedure, valve 599B was closed to disconnect the Heise gauge and was not reopened. The procedure step was " Remove Heise test rig".

The high pressure transient analysis is contained in Hazards Su:mtary Report, Addendum 5. Section 4.4. With PS939 isolated, there are three levels of pro-tection against a high pressure transient exceeding the primary system pressure limit of 110 psig. First, the automatic venting system was operational as veri-fied by all log readings (taken during the time PS939 was isolated) being within the normal operating band. Second, the pressurizer high pressure alarn (77.5 psig) was operational and a high pressure condition could be corrected by oper-ator action. Third, the two primary relief valves and the pressurizer relief valve were operational. Low pressure protection was not affected by this error.

Corrective Action Upon finding valve 599B closed, it was immediately reopened and high pres-sure scra'n protection restored. The operators who performed the Compliance Check were interviewed by their shift supervisor and made aware of the importance of this type of mistake. A review of the Reactor Safety System sensors was made to 4

see if any others could be isolated without indication in the control room being affected. The pressurizer low pressure scram switch could also be isolated with-out affecting control room indication. The Reactor Startup Checksheet was re-vised to check both isolation valves for the pressurizer high and low pressure scram switches. The Compliance Check Proce, dure was revised to specify opening valve 599B after disconnecting the Heise gauge. Additionally, all other ;ompliance Check Procedures are being reviewed for this type of problem. ,

Sincerely, -a 6

J. C. McKibben Reactor Manager JCMK:vs

- cc: James Keppler, Director Regulatory Operations - Region III

Doc; ment Management Branch, NRC Reactor Advisory Committee Reactor Safety Subcommittee

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