ML20036C362
| ML20036C362 | |
| Person / Time | |
|---|---|
| Site: | University of Virginia |
| Issue date: | 06/02/1993 |
| From: | Burnett P, Peebles T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20036C360 | List: |
| References | |
| 50-062-93-01, 50-62-93-1, NUDOCS 9306160197 | |
| Download: ML20036C362 (7) | |
See also: IR 05000062/1993001
Text
{{#Wiki_filter:.- . M - [(cd %[o UNITED STATES g NUCLEAR REGULATORY COMMISSION n REGION H $- ,j_ 101 MARIETTA STREET, N.W.
ATLANTA, GEORGI A 30323 \\...../ I Report No.: 50-62/93-01 Licensee: University of Virginia Charlottesville, VA 22901 i Docket No.: 50-62 License No.: R-66
. Facility Name: University of Virginia Reactor UVAR Inspection Conducted: May 3, 1993 , Inspector: g ! //j?,o;tef [ ~ P. T. ' Burnett ~ Date Signed Accompanying Personnel: A. Adams. Jr. ' E. J. McAlpine [ f3 I Approved by: 4 A Tt A. Peebles, Chief Date Signed Operations Branch Division of Reactor Safety 1 SUMMARY- Scope: j This special, announced inspection was conducted in response to the-licensee's timely report of operation with five reactor scram functions disabled. ' Results: The licensee's initial 24-hour report of the event, the thn known causes, and the material condition of the reactor was thorough and truly representative of the status of the facility as observed by the inspectors. The licensee's event . evaluation considered the causes, the significance of the event, and the .l corrective actions. The results of this inspection will be further reviewed , during an inspection scheduled for early June. .
The event may be the basis for future enforcement or escalated' enforcement l action. ' ' 9306160197 930602 PDR ADDCK 05000062 G PDR i i - . - - _ , - .-- - . .
. _ . _ _ . _ . _ . t i i , . REPORT DETAILS 1. Persons Contacted i Licensee Employees 3
- P. E. Allaire, Chairman, MANE
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- P. E. Bannock, Reactor Services Supervisor
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- T. E. Dole, Reactor Operator
- J.
P. Fairer, Reactor Administrator
- R. F. Flack, Associate Chairman, MANE
- J.
G. Gilchrist, Assistant Director, EHS i B. O. Hostika, Research Scientist ,
- R. U. Mulder, UVAR Director
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- R. G. Piccolo, Radiation Safety Officer
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- A. B. Reynolds, Chairman, Reactor Safety Committee
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- D. P. Steve, Reactor Health Physicist
, Other licensee employees contacted during this inspection included operators and administrative personnel.
- Attended exit interview on May 3, 1993.
2. Operation with Safety Systems Disabled , On April 29, 1993, the director of the UVAR informed Region 11 management by telephone that six scram functions required for automatic shutdown of the UVAR were inoperable during a period of operation of about five and one-half hours on April 28, 1993. That report was promptly supplemented by , a written report, which was received on the same day. On April 30, 1993, a t one-page correction to the written report was received by Region II. ' On April 30, 1993, Region II issued a CONFIRMATION OF ACTION LETTER to the University of Virginia listing the Commission's understanding of the actions taken or planned by the University. Those actions listed were: [1] Place the reactor in the shutdown condition as of April 28, 1993,
and will continue to maintain the reactor in a shutdown condition
until you have evaluated the cause of the event, determined the ' extent of the effect on any circuitry on the reactor console and reactor safety systems. e [2] Maintain the reactor in the shutdown condition until your Reactor ' Safety Committee has reviewed the evaluation and corrective
actions implemented. [3] Maintain the reactor in the shutdown condition and not initiate restart of reactor operation until you have discussed the results of your evaluation and your implemented corrective actions with the NRC Region II Regional Administrator or his designee. ' . I i ' -. . . . . - - _-
.. . - -. ~. - - .
I Report Details 2 . f This special inspection was conducted to assure that the events and consequences were as reported by the licensee and to assure that the , licensee understood and agreed with the contents of the CAL. 3. Background Information s Since November 1992, the UVAR has experienced a different type.of spurious , scram. This scram occurs without any annunciator indication, and, thus, ' differs from the usual electrical transient, which always activates an annunciator, sometimes without a scram. According to the designer- , installer of the annunciator system, the response time of the annunciator system is faster that the trip system. That was a deliberate design decision. Hence, it did not seem likely to the licensee staff that the . unannunciated scrams were caused by line noise. To the staff electronics expert, it seemed most likely that the source of the problem was within the scram logic system. When he experienced unannunciated scrams on April 28, 1993, while performing the duties of the SRO, he independently initiated a series of trouble-shooting activities to isolate the source of the problem. With the reactor shutdown and using i figure III-14 (attached), from the SAR as a guide, he first switched the
two SSRs. That action had no effect on the rate of spurious scrams. Next he interchanged the two MDs. The MDs have identical part numbers and external appearance. After a wait of about 30 minutes, no spurious scrams were received. The reactor administrator authorized a restart of the reactor. Neither he nor the SR0 recognized the trouble-shooting activities as maintenance; hence, no post-maintenance testing was prescribed, as required by TS 4.5. Repeating the daily startup checklist would have tested the operability of the scrams driven by console instrumentation.
Full power operation continued for about 5.5 hours, with a change in SR0 every 2 hours. No scram signal was received during this period. The SR0 ' present at the time for shutdown decided to complete the shutdown by introducing a spurious period scram from movement of a test switch on the intermediate range instrument channel. The expected period scram did not occur, and an investigation into the extent and cause of the problem was begun. The following six scrams were found to be inoperative: Two power level scrams ' Intermediate range period scram Primary coolant low flow scram loss of power to the primary pump scram Intermediate channel range switch scram Key switch scram With the MDs interchanged, the following scrams were operable: Pool water temperature Three of three manual scrams Two pool water level scrams Bridge radiation monitor scram -T - - ,e..+ % - e . - - - - 8
_ _ _ _ _ _ _ - _ _ _ _ _ _ , I Rep 6rt Details 3 . . Air pressure to the forced convection flow header scram Face radiation monitor scram Evacuation monitor scram Truck door open/ escape hatch open/ MIF scram None of the operative scrams backed up the inoperative scrams, particularly with respect to power level. The setpoints of the radiation based scrams were equivalent to several times the maximum allowed power level scram
setpoint. i The normal AT across the core is 12.5'F. The high AT alarm, which was - operable, actuates at 13.05 to 13.1*F. For a slow power increase, the - expected operator action of entering a manual scram in response to the
_ alarm would have terminated the excursion a safe power level. For a rapid ' power increase there appeared to be no timely combination of alarm and operator response to assure a scram below the maximum allowed power setpoint. Further investigation by the licensee revealed that the inputs and jumpers in the two MDs were completely different. That observation was confirmed by review of the up-to-date system drawing. That pencil line drawing was revised as work was done over the life of the facility. However, neither the date nor scope of the modifications were entered into the record. The licensee is confident that the non-symmetric use of inputs to the two MDs wes part of the original installation of the updated console in the 1970s. l The licensee, in performing subsequent additions to the MD inputs, .' l consciously used symmetric inputs, and it was those scrams, which were still operable after the MDs were switched. The licensee also concluded that there was no necessity for jumpering the unused inputs, which was done in the original installation. Without ! j jumpers, the switched modules would have worked. l 4. Observations and Conclusions , ' The inspector and accompanying personnel inspected the MD's internals, , I reviewed the detailed drawing, reviewed the operations log book, reviewed the daily checklists completed before during and after the switch, and conducted discussions with all licensee personnel involved in any aspect of the event. They reached the following conclusions: + ' a. The inoperable and operable scrams were as described in the licensee's. letter of 29 April 1993.
b. The licensee has been aggressive in defining and addressing the problem. 1 i c. The licensee is compliant with all aspects of the CAL. 1
_ ._ _ . .- - - . . . - _ - .. -. . - . . . _ _ _ _ . Report Details 4 - . ! d. Neither of the two persons directly involved recognized the process of ! switching modules as maintenance. This was a personnel and personnel training error. ' 5. Potential Corrective Action t The following possible corrective actions were discussed with the licensee, but are not commitments on the part of the licensee: a. Add a RSC member with a strong background in instrumentation to provide an independent overview of licensee activities in that area. - Subsequent to the inspection, the licensee reported this action as complete. b. Dated duplicate copies should be made of the detailed instrumentation drawing, and a copy should be readily accessible in the control room. c. The fact that the increasing frequency of spurious scrams led to this event is of concern. Corrective action to eliminate the source of
unannunciated scrams seems warranted. i ! 6. Apparent Violations , The following apparent violations were identified: a. TS 3.2: The reactor shall not be operated unless the safety system channels described in the following table are operable: The table lists power to the primary pump, primary coolant flow, reactor power level (2), and reactor period. The required scram functions of all of the channels listed above were disabled. , b. TS 4.5: (States in part) Written procedures shall be in effect and ! , followed for preventative and corrective maintenance operations that could have an effect on reactor safety. .; SOPS for maintenance do not specifically require post maintenance ! testing, or identify trouble shooting and diagnostic testing as ' maintenance, j 7. Exit Interview ' , The inspection scope and results were summarized on May 3,1993 with those persons indicated in paragraph 1. The inspector described the areas inspected and discussed in detail the inspection results; the event' ! reviewed may be the subject of future enforcement action. Proprietary , information is not contained in this report. Dissenting comments were not ! received from the licensee.
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i - , 'p6rt Details Re 5 ! , 8. Acronyms and Initialisms , CAL confirmation of action letter MIF mineral irradiation facility , MD mixer-driver, a 28 channel OR gate , NPR non-power reactor ! RSC reactor safety committee
SAR Safety Analysis Report
S0P standard operating procedure SRO senior reactor operator SSR solid state relay , TS Technical Specification (s) UVAR University of Virginia reactor . Attachment 1: SAR Figure III-14 j l . ! > l ) >
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, ATTACIDIENT 1 . . FIGIRE III-1b SCRAM LOGIC DRAWER Cf"AN,
.3 CR f, Ficri AD D LOW CUU:IT RATE Agy, IEVEL TRIP 2 "PS 2 x 10 nv a HIGH POWEB THIPS bh LOW FLUX LE"iEL p1 g, DESEN. ' SWITCH INT. RANGE TRIP EERIOD TRIP ' <> AUX CONT. o o o L ng_4s AUX. COP'T 3 (1) o FLOW OR LEVEL TRIP INT. lWiGE o <, LIGliT AUX. CONT. 1 IOD TRIP LIGHT db o AUX. CONT. 2 -l f- 2 PWR. RANGE TRIP LICIIT ROD PERM. RELAY I 41o . .. . . . . o <, 4, o o o o no . . ... . MIXER DRIVER By f4IXER DRIVER B2 RESET t ' I -{ RESET o o o-> +-- + ci SOLID STATE RELAY 1 . I <> g . Il j i i SOLID STATE RELAY 2 , jp3 N gg w 'uI M. - 1 M ma - s(> f f l W ma g 1 dma j le ma M
j(Scram'Al g arm Relay) -- ,- . _ - . . . - - -- s . }}