IR 05000156/1981002
| ML20040D924 | |
| Person / Time | |
|---|---|
| Site: | University of Wisconsin |
| Issue date: | 10/16/1981 |
| From: | Boyd D, Janke R, Ridgway K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20040D910 | List: |
| References | |
| 50-156-81-02, 50-156-81-2, NUDOCS 8202020403 | |
| Download: ML20040D924 (3) | |
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
REGION III
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Report No. 50-156/81-02 Docket No. 50-156 License No. R-74 Licensee: University of Wisconsin Madison, WI 53705 Facility Name: University of Wisconsin Nuclear Reactor Inspection Conducted: September 18, 1981 Inspectors:
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& Projects Section IA
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Inspection Summary Inspection on September 18, 1981 (Report No. 50-156/81-02)
Areas Inspected: Special announced inspection of an occurrence (unmanned control room) which occurred September 1, 1981 and was reported to Region III by telephone on September 2, 1981 and by a written report on September 3, 1981. This inspection involved a total of 14 inspector-hours (5 onsite) by two (2) NRC inspectors including 0 inspector-hours onsite during off-shifts.
Results: One item of noncompliance was identified (the control room was inadvertently unmanned for about six seconds).
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DETAILS 1.
Persons Contacted
- R. J. Cashwell, Reactor Director
- S. M. Natusewic, Supervisor, Nuclear Reactor
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M. C. Jensen, Reactor Operator D. E. Range, Reactor Operator
- Denotes those present at the exit interview.
2.
General On September 2 and September 3, 1981, the licensee reported to NRC Region III that the reactor control room was inadvertently unmanned for less than 20 seconds at approximately 2:35 p.m. cn September 1, 1981, while the reactor was operating at 100 percent power. This is in noncompliance with 10 CFR 50.54(k) which states, "An operator or senior operator licensed pursuant to Part 55 of this chapter shall be present at the controls at all times during the operation of the
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facility."
The reactor was at 100% power and on automatic control making a routine run when the operator on duty asked another licensed operator to reliev: him for a few minutes while he delivered a telephone message to another office acr:ss the hallway. The operator agreed to take the watch, but due to the expected short duration of relief, failed to follow written " Standing Operating Instructions, UWNR 001" Revision 5 dated May 20, 1980, which requires formal takeover and signing of the reactor log sheet. When the original operator returned to the control room, about 15 minutes later, another operator was also in the control room. The three operators were having a discussion when a fourth staff member (licensed senior operator) entered the control room and asked about the status of some laboratory equipment.
At this time the operator who had agreed to take the watch assumed the other operator had returned tc take the watch and left the control room. The original operator on watch assumed the se:ond operator was still relieving for him and with the other two operators left the l
control room to look for the equipment in Room 132 (an adjacent room outside the area defined in UWNR 001 as a permissable location for the operators on duty but within hearing of the console annunciators).
The Reactor Director (a licensed senior reactor operator) passed the operators entering Room 132 on his way to the control room (distance between Room 132 and the control room is five steps). Upon entering the control room the Director noted that no operator was on duty and
' assumed control until the first operator returned, about two minutes later. The interval the control room was actually unmanned was about six seconds since the control room door was still closing when the Director arrived. However, only fortuitous circumstance prevented the control room from being unmanned for a longer period of time.
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This particular type of research reactor is, by design, inherently safe. In addition to multiple automatic safety circuit trips, all of which were functional during this event, the TRIGA reactor is intrinsically protected by the large prompt negative temperature coefficient of the hydrided TRIGA fuel sufficient to offset large positive reactivity insertions. During the pulsing mode, where up to two dollars of positive reactivity is inserted in milliseconds, the reactor power reaches the 1000 MW 1evel and is safely shutdown by this negative fuel temperature coefficient.
In the improbable event of an unchecked power rise initiated by failure in the auto-matic controls system and during which both high power safety channels failed to scram the reactor, the negative temperature coefficient of the fuel would limit the power level to approximately 1.4 MW (exceeding the license limit of 1.0 MW but remaining below the technical specifica-tions safety limit of 1.5 MW). In such an event it is estimated that the fuel temperature would remain at less than 400'C (the fuel high temperature scram set point) and no fuel damage would occur.
Thus, while this momentary absence of the operator from the control room did not measurably increase the hazards to the facility or to the public it did provide, albeit small, the very undesirable circumstance whereby the reactor could have operated outside the requirements imposed by the facility license.
The licensee took prompt and proper corrective actions to prevent recurrence by:
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Properly manning the control room in about six seconds.
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Orally reprimanding the individuals involved.
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Placing written reprimands in the involved operator's license files.
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Conducting a training lecture, September 3, 1981, on proper compliance with written procedures. This lecture included a re-review of I&E Circular 81-02, Performance of NRC-Licensed Individuals while on Duty (This circular had been reviewed with all operating personnel during a training session on March 5, 1981. This circular was also to have been mailed to all licensed operators, but, the two operators concerned with this event stated they had not received this circular).
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Reporting to NRC Region III & Licensing.
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During this inspection, the inspectors interviewed facility personnel and reviewed logs, procedures, training records and license files to confirm the reported information and to verify that the reported
., corrective actions had been taken and were appropriate.
3.
Exit Interview The inspectors met with licensee representatives (denoted in paragraph 1) at the conclusion of the special inspection. The abnormal event and corrective actions taken by the licensee were discussed.
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