IR 05000062/1988004
| ML20204J932 | |
| Person / Time | |
|---|---|
| Site: | University of Virginia |
| Issue date: | 10/04/1988 |
| From: | Burnett P, Jape F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20204J929 | List: |
| References | |
| 50-062-88-04, 50-62-88-4, NUDOCS 8810250290 | |
| Download: ML20204J932 (7) | |
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UNITED STATES
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NUCLEAR' REGULATORY COMMIS$10N
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REGION 11 101 MARIETTA ST,. N.W.
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ATLANTA OEOAQlA ta323 i
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i Report No.: 50-62/88-04 l
Licensee: University of Virginia l
Charlottesville, VA 22901
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Docket No.: 50-62 License No.:
R-66 Facility Name: University of Virginia Reactor UVAR and Cavalier i
Inspection Conducteu: August 22 to 25, 1988
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Inspector:
Md N
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P.T. Burnet {
Date Sign NM8 i
Approved by:
Af83UV>
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Date Signed
i F. Jape, CWe~f'
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Test Programs Section
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Engineering Branch
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Division of Reactor Safety i
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SLMMARY
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Scope:
This routine, unannounced inspection addressed tbs areas of the j
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j annual operations inspection of Class ! research reactors.
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Results: No violations or deviations were identified. One issue was referred j
to NRR for resolution.
Both the unscrarenabla regulating rod and the i
i shim safety rods are described as control rods in the TS, and the t
i shutdown margin is described in tenns of reactivity inserted by I
control rods. The Itcensee has been using the witndrawn worth of the
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regulating rod in the shutdown margin calculation.
This practice appears to be supported by TS, but is contrary to the concept of
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shutdown margin being instantaneously available; since on power a
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failure the regulating rod would not drive in at all and would
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require operator action at other times (See paragraph 2.b.).
Two licetisee comitments were obtained to improve procedures (See i
paragraph 6).
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REPORT DETAILS
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1.
Persons Contacted
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Licensee Employees
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- P. E. Benneche, Reactor Adninistrator
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J. S. Brentzer, Jr., Assistant Professor, Department
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of Nuclear Engineering
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0. T. Hale, Reactor Health Physicist
- T. G. Williamson, Chaiman, Department of Nuclear Engineering
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J. P. Farrar, Supervisor, Reactor Operations
- B. Hosticka, Research Scientist l
l Other licensee employees contacted included faculty members and office personnel.
- Attended exit interview L
Acronyms and initialisms used throughout this report are defined in the
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final paragraph.
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2.
Organization Logs, and Records (39745)
a.
Organization l
The Organization of the reactor facility is as described in TS 6.1.
Since the last inspection, the persons filling the positions of
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reactor supervisor and reactor administrator have exchanged jobs, but
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the requirements for the position of reactor supervisor are satisfied by the current incumbent.
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b.
Review of Operations Logs
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l UVAR Log #27 was reviewed for the period 30 June 1987 to 28 July 1988, inclusive, and Log #28 from that period to date. Most routine data entries were facilitated by the use of rubber-stamp entry forms
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to assure all required data were entered.
Typical stamp forms
included the startup checklist, powr checklist, irradiation data, l
and shutdown margin.
I One freqaent entry in the log was the notation, "Completed CVE." On i
occasion. this entry was cccorpanied by an entry noting debris was I
observed on top of the fuel and would be monitored during operation.
CVE stands for core visutI examination, and appears to be a long standing practice at the facility to periodically examine the core
for flow blockage, bubbles, and other abnormalities every four hours, j
when illuminated by Cherenkov glow.
It is basically a good practicei i
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since it does show up loose items or debris in the pool or on the
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fuel.
But, the practice is not procedura11 zed and, hence, may mean different things to different people.
Further there are no criteria on what observations should lead to reactor shutdown or on what
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constitutes an unacceptable volume of debris on or potentially
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accessible to the fuel.
The reactor coolant flows downward, and
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debris greater than some limiting size may interfere with fuel l
cooling if drawn into the fuel.
Current plans are to increase the number of fuel plates per assembly to 22 from 18 for the t.EU fuel.
This will make the coolant channels more vulnerable to blockage.
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Folbwing discussion of this subject at the exit interview, the liernsee rade a commitment to make the CVE part of a procedure and to l
provide acceptance criteria for the examination. This action will be completed by October 31, 1988 (Inspector Followup Item 062ied 04-01).
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I Another frequent entry in the logbook was a stamp showing the calcu-
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I lation of shutdown margin.
The good practice of calculating and
I logging shutdown margin at every practical opportunity appears to be l
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followed routinely.
Some of the entries indicated that some of the
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l operators were having difficulty following the procedure to adjust l
shutdown margin for the reactivity of unsecured experiments. Discus-
sions with management confirmed that the adjustment was intended to
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be conservative, but is so only for those experiments having a negative reactivity effect on insertion into the reactor. It is not conservative for positive-reactivity experiments, and in one extreme
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case an allowance of +0.14 %dK/K for an experiment was noted.
This
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is about one-third the minimum allowable shutdown margin of 0.4
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%dK/K.
Following discussion at the exit interview, the licensee mode
a corm 11tment to change the shutdown margin procedure to assure the f
reactivity from experiments is always treated conservatively in the f
calculation.
This action is to be completed by November 30, 1988 (Inspector Followup Item 062/88-04-02).
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Another issue with shutdown margin was identified.
The procedure t
includes the withdrawn worth of the regulating rod in the calculation i
of shutdown margin.
In the definitions section of the TS, the i
regulating rod is defined as a control rod of low reactivity worth, t
but makes no mention of its scram capability; it has none.
The TS j
define the shim safety rods as control rods with scram capability.
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TS 3.1(1) requires the minimum shutdown margin piovided by control
rods be 0.4 %dK/K under prescribed conditions.
It appears then that
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the licensee's procedure conforms to TS 3.1(1), but it does not I
confom to the generally accepted concept that shutdown margin be l
dttained instantaneously at scram.
In the limiting case, the margin
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would be obtained at UVAR onl/ after driving in the regulating rod.
j During a power failure, that would not be possible.
Currently, the i
I licensee's calculeted shutdown margin is in excess of 1 %dK/K. and the reasured reactivity worth of the regulating rod is 0.2 idK/K, or half the limiting value of shutdown margin.
However, there is no TS obstacle to increasing core excess and decreasing the shutdown
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margin.
Furthermore, the licensee's calculations fnr the forthcoming l
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LEU core indicated the regulating rod worth could be in excess of 1 i
%dK/K.
At the exit interview, the insptctor expressed the view that shutdown margin should be defined in tems of the capability of the scrammable shim rods rather than control rods and further stated
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l the issue would be brought to the attention of NRR for review.
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opinion was restated by Region !! supervision to the facility direc-tor in a telephone conversation on September 20,19:3.
Licensee
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management responded that the issued would be brought before the RSC during its next meeting.
On the same date, the NRR project manager was infomed of this concern.
Other uncertainties in determining shutdown margin are addressed in Paragraph 4.
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The log books record the shipment of four bttches uf nine fuel bundles each from the facility in the period September 23 to October 6,1987.
The licensee stated that, with those shipments
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and the assembly of the cu. rent core, 22A, all fuel currently astigned to UVAR at the facility was loaded on the grid.
The last two pages of each logbook record the reactor scrams.
In the
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period August fi,1987 to July 22, 1987, there were 31 scrams.
Most
here due to instrument noise, particularly in the intermediate ranga
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nuclear instruments.
None were indicative of significant operator error.
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UVAR Operations Notebook
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The VVAR Operations Notebook was reviewed as an adjunct to the
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operations and irradiations 109 It contains a list of authorized
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users of the various irrediation facilities signed by the director.
l The last update was in.*une 1988. There is clso a Itst of the three
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permanent staff members authorized to handle raterials producing more than 1 R/hr at one foot.
The notebook also contains the most recently measured values of significant parameters such as the i
integral worth of each control rod, minimum pemissible critical rod
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position, and excess reactivity.
The contents also include the measured reactivity worths of incore or core-adjacent experimental facilities and the mass limits for the amount of boron or caMium absorber to used in any facility.
The notebook appears to function
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as a useful operations reference, which is kept up-to-dato.
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d.
Review of Reactor Irradiations j
The Irradiation Log for the period was reviewed, and cased upon that review about 30 Irradiation Request forms were selected for further inspection.
Most of the foms were acceptable, but many could have been made out more legibly, for the cona n19nce of the operators as
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well as the inspector, and with more attention to details that 15, fill in all blanks. None of the foms recorded a measurable reactivity
effect from the experiment.
In one case, the actual radiation
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level was approximately three times the predicted radiation tevel (90
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and 35 mR/hr at one foot). Thsre was no indication of further action by the licensee.
Discussion with licensee se'sonnel disclosed that
their practice is not to respond to errors 'n estimates of radiation t
level unless a factor of five is exc eded, but they do havo that revisw criterion.
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t No violatioas or deviations were identified.
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3.
Reactor Safety Comittee Review and Audi; Activities (40745)
i Review of the minutes and audits of the Reactor Safety Committee showed that the RSC met eleven times during the review period.
The meetings of i
l August 19, 1987 and January 29, 1988 addressed the completed, required
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semi-annual audits.
In the first audit, the auditor and RSC questioned l
the application of the regulating rod to the minimum pemissible critical
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rod position.
In another audit the RSC questioned the calibration of
I the flow orifice plate and the measurement of reactor power, which appeared to be dropping, and requested a procedure for calibrating the plate.
That procedure is to be presented to the RSC for review at their next. meeting. The conclusion drawn from this review of RSC activities,
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which appear to be well documented, is that the RSC has performed
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thoroughly and capably in both its routine and audit activities.
No violations or deviations were identified.
4.
Surveillance Activities (61745)
f Control rod worth measurements were performed on October 19 - 20, 1987 I
following assembly of core 22A and in response to the requirements of TS l
4.l(2).
The licensee's practice is to construct only integral rod worth t
curves from the measurements.
The inspector chose to independently
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reanalyze the data at.d from that reanalysis construct differential as well i
as integral rod worth curves.
The integral results were in good agreement l
with the licensee's, but the differential curves were more revesling. The
plots show considerable rod to rod interaction as the rod being measured l
passes a fixed red or is passed by the compensating rod. (The curve for
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Shira 3 is provided as Attachment I to this report as an example.) Thus it I
appears that the actual reactivity worth of all of the rods inst.rted i
together is less than the sum of the integral worths obtained from the rod
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worth measurements.
The rrdhod of measurement is the best available, but
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its securacy is limited.
It is these practical measurteent uncertainties j
that must be addressed in determining what the required shutdown margin i
must be, l
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After tne red worth measurements. the licensee measured the reactivity worth of core-adjacent experimental facilities and confirmed that the limiting arount of absorber, boron or cadmium in these facilities had i
minimal reactivity effect.
The ?,emi-annual rod drop time tests and annual visual red inspections were i
carried out satisfactorily and with acce.ntable frequency during the review period.
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On November 24, 1987, the annual practice evacuation was conductedn and
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acceptable results reported to the RSC.
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Experiments (69745)
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No new kinds of experiments were conducted during the review period. The
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routine irradiation experiments, a major portion of facility activity, are
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discussed in paragraph 2.d above.
Special procedures were written and
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app oved for the operation of the neutron radiography facility and the
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mine,al irradiation facility.
No violations or deviations were identified, i
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6.
Exit Interview l
t The inspection scope and findings were summarized on August 25,1988, wi th those persons indicated in paragraph 1 above.
The inspector described the areas inspected and discussed in detail the inspection findings.
No
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dissenting coments wer* received from the licensee.
The licensee did not identify as proprietar, any of the materials provided to or reviewed by i
the inspector during this inspection.
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Two licensee comitments were obtained to improve procedures:
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Inspector Tollowup Item 062/88-04-01: Make the CVE part of a procedure and provide acceptance criteria for the examination. This
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action will be completed by October 31, 1988.
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inspector Followup Item 062/88-04-02: Change the shutdown margin j
proc dure to assure the reactivity from experiments is always Weated
e conservatively in the calculation.
This action is to te completed by
November 30, 1988, i
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Acronyns and Initialisms Used in This Report
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t core visual examination i
CVE
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reactivity unit - dimensionless l
idK/K
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low-enriched uranium, less than 20 percent U-235
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milli-Roentgen per hour l
mR/hr
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U. S. Nuclear Regulatory Comission, NRR r
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Office of Nuclear Reactor Regulation R/hr Roentgen per hour
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RSC Reactor Safety Comittee i
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technical specification (s)
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UVAR University of Ytrginia Reactor
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ATTAChNENT*
I Shin 3 Differential Worth
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SHIM 3
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UVAR 19 OCTOBER 198~7
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