IR 05000139/1988001

Insp Rept 50-139/88-01 on 8880111 & 0216.No Violations & Deviations Noted.Major Areas Inspected:Review of Events Reported by Licensee Involving Excessive Insertion Time of Shim Rod 3 & Gradual Loss of Excess Reactivity of Reactor

ML20148G705
Person / Time
Site:	05000139
Issue date:	03/10/1988
From:	Crews J, Yuhas G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:
Shared Package
ML20148G680	List: IR 05000139/1988001 ML20148G676
References
50-139-88-01, 50-139-88-1, NUDOCS 8803290206
Download: ML20148G705 (4)

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U. S. NUCLEAR REGULATORY COMISSION

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REGION V

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j Report No. 50-139/88-01

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Docket No. 50-139

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License No. R-73

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l Licensee: University of Washington i

Seattle, Washington 98195

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Facility Name:

University of Washington Research Reactor

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Inspection at:

Sea.tt'le, Washington

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InspectionConducid:

Janu y and February 16, 1988

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Inspector:

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nsse L. Cre s / Reactor Inspector Date Vigned Approved by:

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G. P. Yuhas CFfef Date Signed i

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Facilities RadM1ogical Protection Section l

i Summary:

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Inspection on January 11 and February 16, 1988 (Report No. 50-139/88-01)

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Areas Inspected:

This routine, announced inspection involved the review of events reported by the licensee involving excessive insertion time of shim rod No. 3 and the gradual loss of excess reactivity of the reactor due to apparent leakage of water from the fuel f.ax gasket (s) into the graphite moderator.

Results:

Of the areas inspected, no violations or deviations were identified.

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8803290206 se0310 f

PDR ADOCK 0500

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DETAILS 1.

Persons Contacted

• Dr. M. A. Robkin, Director, Nuclear Engineering Laboratory

• Dr. P. Miller, Associate Director, Nuclear Engineering Laboratory and Reactor Supervisor Dr. A. L. Babb, Chairman, Reactor Facility Advisory Committee

• Present at Exit Interview.

2.

Review of Operational Events On January 4,1988 the licensee reported, by telephone, to the Region V office two events relating to operation of the reactor facility.

One event which occurred on January 4, 1988 involved excessive insertion drop time (in excess of the one second limit of the technical specifications)

of shim rod no. 3.

The second event involves apparent graoual leakage of water from the fuel box gasket (s) into the graphite moderator, resulting in a corresponding

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l decrease in the excess reactivity.

Facility records were examined and discussions were held with licensee representatives, from which the following information relating to the above events was obtained, a.

Excessive Insertion Drop Time of Shim Rod No. 3 Tne licensee representatives attribute the observed increase in insertion drop time of shim rod No. 3 to the solidification of

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l lubricating grease in the rod drive bearing mechanism.

Supporting l

this determination by the licensee is recent experience over the past several months, wherein inspection and replacement of the l

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bearing mechanism of the regulating rod when it exhibited similar l

behavior resulted in drop times substantially less than one second I

(see Inspection Report No. 50-139/87-01).

Exercising the rod l

several times has consistently resulted in a reduction in drop time to less than one-second, as well.

The licensee attributes the most recently observed, on January 4, 1988, incresse in rod drop time to in excess of one second (up to approximately 1.2 seconds) to an extended period of approximately two weeks during which the reactor was not operated.

Discussions with licensee representatives revealed that plans call for potential termination of reactor utilization at the end of the current academic year - in June 1988.

For this reason, disassembly of the reactor to permit bearing replacement on the No. 3 shim rod is not considered to be a desirable corrective action at this time.

Licensee representatives have concluded that a preferable option is to propose a change to the technical specifications, with l

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accompanying safety analysis, which would increase the insertion

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drop time limit for shim rod No. 3 to 3 seconds.

During a

conference call on January 11, 1988 between representatives of the

licensee, the Office of Nuclear Reactor Regulation (NRR) and the

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j Region V office this option was discussed.

i By letter dated February 4, 1988, the licensee submitted a proposed amendment to the technical specifications to increase the drop time limit for shim rod No. 3 to 3 seconds.

The proposed change was j

granted by the Office of NRR by letter dated February 24, 1988.

At the time of the current inspection, the licensee committed to not resume operation of the reactor, pending NRC review and action on

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the licensee's submittal of a proposed technical specification change.

This commitment was-reconfirmed by the Associate Director in a telephone discussion with the NRC inspector on February 16, 1988.

In a subsequent telephone discussion on February 26, 1988 the

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i Associate Director informed the NRC inspector of plans to resume l

cperation of the reactor on that day.

At that time it was also j

confirmed by the Associate Director that shim rod No. 3 would be exercised during each work day to better insure the rod's reliable performance (e.g., breakdown solidification of bearing grease), and j

that the rod would also be drop time tested prior to each reactor operation as part of the checkout procedure.

This matter is considered closed.

No violations or deviations were

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identified in those areas excmined by the inspector.

b.

Water leakage Into the Graphite Moderator

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Discussions with !icensee representatives and a review of facility j

records revealed that a gradual decrease in excess reactivity of the i

reactor has occurred over a period of the past approximately

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seventeen months.

The rate of reactivity loss has been measured by

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the ifcensee at approximately 0.12% AK/K for the 12 months period of

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August 1986 through August 1987, i

j The reactivity loss has been attributed by the licensee to water J

1eakage past onc or more fuel box gaskets into the graphite

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moderator during reactor operation.

Loss of reactivity due to water

d in contact with the graphite moderator is a condition experienced and described to the NRC on previous occasions by the licensee in

letters dated July 23, 1979 end December 21, 1979.

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The recent experience was reviewed by the licensee's Safety Advisory

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j Committee during a meeting on June 16, 1987.

The licensee j

representatives exhit,ited a good understanding of the mechanism for

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and safety significance of the condition during discussions with the

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inspector at the time of the current inspection.

The current i

condition and its safety significance was described in a letter to l

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the NRC dated January 14, 1988.

l No violations or deviations were identified in those areas examined i

by the inspector.

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3.

Exit Interview Results of the inspection as described in this report were discussed with those persons indicated in paragraph 1 at the conclusion of the inspection on January 11, 1988.

Licensee representatives stated that the rear.ar would not be operated until an appropriate proposed amendment to '.he technical 'i eci'icatio::s, discussed paragraph 2, above, has been acted upon kv the NRC staif.

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