ML20101N594

Special Rept:On 920615,briefly Unidentified High Radiation Area Noted During Reactor Startup.Caused by Human Error. Self-critical Evaluation Conducted & Controls in Place to Prevent Reccurrence

ML20101N594
Person / Time
Site:	University of Virginia
Issue date:	07/01/1992
From:	Mulder R VIRGINIA, UNIV. OF, CHARLOTTESVILLE, VA
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 9207100061
Download: ML20101N594 (9)

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Subject:

Special Report from the University of Virginia -Reactor.

Facility [ Reactor Docket Nos. 50-62=and 50-396).

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Gentlamen:

UVAR Technical Specification (TS) 6.4.2. describes _ action to-be taken by a licensee in-the event of.a reportable occurrence.

One-condition meriting report is delineated in this TS's subsection (5) as "an observed inadequacy in the implementation.of either 3

administrative or procedural controls, such:that the inadequacy 3

could have caused the existence-or development ' of an unstfa i

condition in connection with the' operation-of the-reactor" 4-l Please find in attachment a report-of an_ occurrence involving the UVAR which is related to this technical 1 specification.

It is related in the sense that an inadequacy.-in proi::edurul-controls was found.

While the safe operatic'n of the reactorcwas not' challenged i-by the inadequacy, because-all TG parameters pertaining-to-it.had.-

been measured and found to be:in'confermance with specifications, a

radiological safety concern was. generated ; inadvertently ~in connection with an installed irradiation facility..

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The radiological-. aspects of the incident were discussed with the i

U.Va-Radiation-Safety?OfficerEandsthelReactorl Health' Physicist.

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In - the; RSO's opinion, an junsafe condition was: noti generated (further data 1le are n attachment).-

Also,. the. radiological-3 conditions were not _ of a nagnitude: - or, consequence Emeriting_

a reporting,.as per regulations., _Hence, thefoccurrence is not;-a=TS-U

"- reportable occurrence" '

However, to? document commensurate 3

' administrative concern -anda responser to' the levent,c this speci'al.

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report is being submitted to the NRC.

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-(page 2, cover letter to Special Report)

Corrective actions taken and to be taken are listed in the special report which is in attachment.

These actions inclurie adoption of additional procedural controls, the holding of a staff meeting to examine root causes and to review other aspects of reactor operations for potential problems of a similar origin, and the

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start of a process to upgrade UVAR procedures.

Since the incident was minor in nature, we expect that NRC inspectors will follow up on our resolution of the case at their next inspection.

Until then, any questions you may have may be called in to uc at (804)-

982-5440.

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l{ m) r hY Robert U. Mulder, Director U.VA. Reactor Facility i

viy/Gounty of _hi.rw /r Lomotonwealth cf Virginia I hercby certfv that the Wached document is a true atd exact copy of a

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Special Report Survey results New checklist cc:

U.Va. Reactor Safety Committee Mr. Alexander Adams, Project Manager, U.S.

NRC,. Wash. - D.C.

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SPECIAL REPORT TO Tile NRC PERTAINING TO l

A BRIEFLY UNIDENTIFIED HIGH-FADIATION AREA AT THE UVAR BRIDGE GENERATED IN CONNECTION WITH A REACTOR STARTUP 1

Dac}Lqr_qua_d1 During the week of June 15, 1992, a WAR core configuration change was initiated.

Five fuel elements were removed from the reactor and three fresh fuel elements were installed with control rods 1, 2,

and 3.

First, the control rods were visually inspected.

Next, rod drop tests were performed after inst 11ation of the control rods.

Then, subcritical multiplication measurenents were taken during the addition of the remaining fuel to estimate the final i

fuel configuration.

Rod calibrations were performed on June 16 and 17 with the reactor at power levels below 1 kW.

Subsequently, calculations were made of the shutdown margin and excess reactivity.

All reactor parameters 'were well within the UVAR Technical Specification limits.

i In association v!th the configuration change, various irradiation facilities were installed next to the

core, ar91:g them an epithermal pneumatic " rabbit" facility suited ft-NAA sample activation.

Prior to the installation, the epits mal rahN t facility had.been out of the core for three months-because of a water leak at a connector.

This leak was repaired and the facility installed in reactor grid position 65.

Becuuse this facility had to be removed and inserted in the grid plate in order to determine its reactivity worth (at low reactor power), full bowing of its tube to prevent radiation streaming was postponed until just prior to taking the reactor to power. [ Note: The epithermal f acility tube is bowed by tensioning it with a stainless stnel wire, like a bow.

handling the epithermal f acility with its. tube tensioned is not possible.

The tube reaches the bridge in the area directly above the core, next to the control rod drives.)

4 The Occu,rJence Under the impression _ that all core and experimental facility 4

manipulations had been concluded successfully,

_the reactor administrator had the UVAR started up by a reactor operator on the i

morning of June 18, 1992 and taken to full power (2 MW) for the purpose of checking instrument re dings.

Power range #1 and #2 and linear detectors had to be adjuM ed.

-For this, both f.he reactor administrator and supervisor went to the reactor bridge to make adjustments.

Concurrently, a visual inspection of the reactor core was made at this time by the supervisor. ~ For this operation, the reactor was at full power (2 MW) from 09:44 until 10:39 and-then shut-down.

At approximately 13:30 on June 18, a staff member noticed that the epithermal rabbit had not been tensioned (bowed) and clamped off on the side of the bridge.

Concurrently, it was recognized that with t

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its partially bent tube extending from the core to the bridge, radiation could have streamed to the reactor bridge during the startup that morning.

Thus, the reactor supervisor who had done the core visual could have gotten exposed unnecessarily.

To check on the potential high-radiation field created,'a special radiation survey was made at the top of the two inch diameter tube, i

first with the reactor in the shutdown state, later at low power, i

With the reactor shutdown the following results were obtained:

Gamma-2 mr/hr l

Neutron-O mr/hr Next, tne

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• or was started up, taken to 100 kW, ope::ated from 14:17 to 14:23, then shut down.

Radiation readings taken at the top of the epithermal rabbit were as follows:

Gamma-45 mR/hr Neutron-45 mR/hr Extrapolation of these readings to 2 MW yield:

k Gamma-900 mR/hr Neutron-900 mR/hr The beam was highly collimated, approximately two inches in diameter, located alongside the bridge, almost directly over the reactor core.

[A copy of the survey that was_ taken is in attachment.]

The supervisor who performed the visual inspection of the core during the morning operation at 2 MW estimates that he might have been in the thin beam emanating from the epithermal facility for a maximum of 10 seconds.

Thus, using the survey data presented above, it is estimated that he could have gotten a total dcse equivalent of approximately 5 mrem.

It is noted that both supervisors were wearing appropriate dosimetry at the time.

As a precaution, film badges belonging to the reactor operator who did the reactor startup and both supervisors Vere sent to_U.VA.'s dosimetry film processor, Landauer, for immediate reading.

The results reported back indicate 20 mrem readings for both supervisors and a minimal reading for the operator.

The 20 mrem readings are consistent with work perforamed by the supervisors involving handling and shipping of radiactive sources and control rods visuals earlier in the month of June.

Therefore, the results.

Indicate-that no appreciable exposure of personnel occurred as a result of the slip in proccdural control.

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(page 3, Special Report)

Following the taking of the special survey, notifications of reactor managers were made and evaluations were initiated.

Consultz.tlons with the U.VA. Radiation Safety Officer resulted in a determination that, wnile undesirable, the high-radiation field had not been unsafe due to the beam geometry and maximum time the supervisor may have been in the beam while performing the core visual inspection.

Neverthelese, an unidentified high-radiation area had been created on the reactor bridge which had therefore gone unposted.

A check was made of wording of UVAR TS and federal regulations, with a determination that the event was not reportable, since the field was not savero, had been localized in a restricted area which has minimal personnel occupancy, and the exposure, if any, was minor to a single individual.

Aralysjs of Occurrence y

The reactor director was informed of the event soon after the survey was completed.

Discussions with reactor staff encued.

It was concluded that the root causes of the evert were:

1) The requirement that the epithermal rabbit facility tube be fully bowed by tensioning had been overlooked (human error).

This requirement exists in the documentation reviewed and approved by the RSC which authorized its operation.

The requirement was overlooked because it was not listed on any checklists.

It was not placed on a checklist because staff inattentiveness to this condition had not been foreseen.

2)

The reactor administrator nas a practice of. direct personal involvement in fuel manipulations and felt secure in positively knowing all aspects that concerned the core change.

During the past twenty-sven years, his decinions to take the reactor to power following core changes had been uneventful.

The need for a procedure (checklisc) pertaining specifical)y to such startupa, covering a second check of TS parameters as well as requirements on experiments, went unrecognized until this incident.

Corrective Actions A self-critical evaluation was conducted by the React ~r Staff and the Director.

For now,. procedural controls specific to precluding I

a repeat of_a similar situation have been adopted.

The controls consist of placing an additional requirement on the Daily Reactor Checklist, that of confirming proper tensioning (bowing) of pneumatic irradiation facility tube (s), as well as introducing inte permanent use a special startup checklist to be used prior to taking new core conf 3gurations to high reactor power. levels.

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s (page 4, Special Report)

These procedures are being submitted to the U.VA. Reactor Safety Committee for review and approval.

However, since this new checklist is passive in nature, the Reactor Director detcermined that it be implemented forthwith, prior to its review and approval by the RSC.

Accordingly, the checklist was completed and used on r

June 19, 1992 before restarting the UVAR.

Prior to the restert, the epithermal rabbit tube-was tensioned, fully bowed and. clamped off on the side of the bridge.

The reactor reached full power at 08:23.

After stabilizing the reactor at 2 MW, as per the new procedure, a complete radiation survey was taken at the top of the reactor bridge.

The results of this survey are in attachment.

During future requalification meetings greater emphasis will be placed on requirements for proper operation of experimental =

facilities.

Where possible, hands-on practicume will be held to supplement theory given in the classroom.

Each staff member has been asked to become.more self-critical, and-to question rather than assume conditions pertaining to reactor operations.

They also are asked to continuously evaluate the adequacy of the procedures they are using, and to question which staf f activities might require formalization into procedures.

Each t

member has been urged to call for a staff meeting to - discuss nignificant personal concerns when these should arise.

One senior operator has voluntered to begin an upgrade (re-write) of the procedures involving re-formanting and adequacy review, current practice call for procedures to be reviewed by staff members prior-to submittal to the' RSC.

This will serve as a didactic exercise as well.

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q CHECKLIST FOLLOWING REACTOR CORE CHANGE New ' core d esignation......,............,....,.

l C. Rod calibrations complete C ' Shutdown margin calculated and found to be greater than 0.4%.

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O Excess reactivity calculated and found to be less than 5%

O neactivity of experiments and experimentai facilities measured and <2%:

C All 64 grid locations filled.

C All elements, facilities, and plugs in proper locations and seated i

Any systems bypassed or otherwise taken out of service for the core change _have been L

placed back into service l

Core gamma monitor connected and placed into apprcpriate location over core, L

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Headerindication pole free of obstructions a

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Any materials placed into experimental facilities ior reactivity 'measurernents have been=

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Pneume. tic rabbit facilities have been tensioned and secured to provide a bow to the tubing.

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to limit radia_ tion streamingL

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-(When installed in core) Hot thimble in-line lead shielding in place Senior reactor operations staff members polled to inquire if.they know of any reason that tiie reactor should not be taken to power Reactor Director informed of reactor readiness for full power operation s O

j3 Approved for startup and operation at power (t_wo senior operators):

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(Date of first operation above one kilowatt:

< Radiation survey on reactor bridge performed after the reactor is broughtLto poweripayingi L

particular attention to the areas around the instrument tu_bec, the rod guide tubes and the-experinJental facilities.t

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