ML20125D432
| ML20125D432 | |
| Person / Time | |
|---|---|
| Site: | University of Virginia |
| Issue date: | 12/11/1992 |
| From: | Mulder R VIRGINIA, UNIV. OF, CHARLOTTESVILLE, VA |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9212150194 | |
| Download: ML20125D432 (15) | |
Text
- . _- _ _ . - - - - -- - . ._ ._
SCllODI.0F ENGINEERING @
& APPLIED SCIENCE December 11, 1992 Sycj,gggjuggc7ggf;;cffffy Department A Mechanical, Actmpace A Nuclear lingineering
- U.S. Nuclear Regulatory Commission Uniscrg d Virginia
! Document Control Desk Charlottenille VA 2NO-2442 i
Washington, D.C. '
uu.9c.sm I Auum:-sm
- 20555 L
I
Subject:
Final report from tt.9 University of Virginia Reactor Facility (Reactor Docket Nos. 50-62 and 50-396) relating the recovery of ceramic beads spilled in the UVAR pool.
- Gentlemen
I A special written report was made to the NRC on October 9,1992 that described the in-pool disassembly of two canisters used for neutron activation of ceramic beads. This resulted in the dispersion of small, insoluble and non-floatable aluminum oxide / silicon dioxide beads to the research reactor's pool i
floor and primary coolant system. A final report covering the l bead recovery operation in detail was promised in the special report.
UVAR Technical Specification 6.4.2 did not require reporting of this occurrence because an unsafe condition was not created and was unlikely to be generated in the future. This because the UVAR pool is designed to contain safely radioactive irradiation experiments, cobalt sources and nuclear fuel. A special report to the NRC was made because considerable reactor downtime to perform the recovery of the beads was anticipated.
Written procedures for a safe recovery of the beads with an underwater suction device were planned, reviewed, approved by
- the Rea e :r Safety Committee (RSC), and then practiced in dry-runs. The bead recovery operation was completed on October 21, 1 1992. Return of the UVAR to operation at power was authorized by the RSC on October 26, 1992. The RSC authorization was based on a review of the cleanup operation and a determination that the very small amount of beads which were not recovered.
could remain at the bottom of the pool without affecting reactor safety or posing a radiological risk.
Iridium bead irradiations will resume once the company providing the material accepts improved canister soecifications and QA/QC forms approved for use by our R :ctor Safety Committee. Attached to this report please find copies of the following documents considered by the RSC: New canister t
3 50H
- 9212150194 921211 l DR ADOCK0500g2 {g l
- (Cover letter to Final Report, page 2, cont.)
specifications; Changes to the Facility's QA/QC checklist based on 10CFR50.59 and; Modifications of the Irradiation Request Form.
Sincerely,
/
/
/
k Robert U. Mulder, Director U.VA. Reactor Facility Q ( {q n u g_ ,_
( gn,n;.mwmth of Virginia i hm Uy certifftimt the attached docurnent is a true arvj
( tart copy of a o.,w dChr a e n
- presented tx.'kwe me this I day of _ f_G 190b. .
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- i inc: Canister Specifications & QA/QC Checklist QA/QC Form changes j
Revised Irradiation Request Form i Final Report i
CC:
U.S. Nuclear Regulatory Commission Region II Regional Administrator 101 Marietta St. N.W.
Atlanta, Georgia
- - 30323 1
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FINAL REPORT OF IRIDIUM BEAD RECOVERY FROM UVAR POOL Ifealth Physics considerations Recovery of activated aluminum / silicon oxide beads from the reactor pool Mgan on Tuesday, October 13, 1992 and was fully concluded on October 21, 1992. Two health physics personnel from the office of Environmental Health and Safety observed all phases of the operation. All personnel involved in the operation were issued self-reading dosimetry. The suction system's water filters were monitored by an audible radiation dose rate meter throughout the recovery process. Four portable radiation survey instruments were used to monitor radiation dose rates while work was in progress. The highest individual personnel exposure during the entire recovery process was 1.7 mR, as measured with self-reading dosimetry. Total measured personnel dose was 2.9 mR. These readings are consistent with expectations for the work performed.
The (1-inch diameter) hoses connecting the suction nozzle to the collection chamber, and the chamber to the water ,
filter / pump, were kept suspended under a minimum of about 4 feet of water (see Figure 3). This was sufficient to reduce the dose rate at the pool surface to very small levels. The pF ysical principle for bead recovery was bead drop-out of water tiow in the (3 in. diameter) collection chamber pipe, and into a removable recovery can at the base of the collection chamber, due to decreased waterflow velocity with the increase in flow crossectional area. A fine-mesh metallic filter was located at the exit of the collection chamber to prevent very small beads from passing to the water filters and pump located above poolwater level. The audible doserate meter strapped to the filters confirmed that no beads were passing beyond the collection chamber.
Recovery Timetable:
The recovery, using special RSC approved procedures, was performed as follows:
10-13-92 Beads lying on the in-pool underwater table located at a wall at the north-end of the pool were the first to be collected with the suction system.
These beads came from the canister which had been successfully retrieved from reactor gridplate position 74, but which had fallen onto the table when an attempt was made to secure the canister.
(In the attempt to envelop the canister in a sock, the bottom of the canister came loose.) Following the recovery of these beads, the recovery can was removed from the suction system's collection chamber while submerged and visually inspected. It was almost full of beads, indicating near complete l
I -
4 (Final Report, page 2, cont.)
recovery of one canister. The can was capped while i underwater, tagged and stored in the pool. Next, an 1 empty second recovery can was installed in the collection l l chamber to recover beads on the pool bottom below the !
underwater table. The highest individual personnel exposure during this phase of the recovery process was
- 0.4 mR. The monitor placed on the water filters 4
registered 0.5 mR.
i l 10-14-92 Suctioning of the pool floor beneath the underwater table and buttress area adjacent to the primary flow return line was initiated. The recovery can was removed, visually inspected (and found to be about 20% filled),
capped and stored. The amounts recovered up to this
] point corresponded to one canister.
i l Next, the suction system was relocated from the north end i of the pool to the south end. Suction of beads from around gridplate positions 64 and 74 (where the canisters had been irradiated) was performed. Fuel and graphite elements adjacent to grid positions 64 and 74 were removed from the gridplate. Each element was visually inspected underwater. As expected, no beads were present
- on the elements. The elements were stored at the north end of the pool in racks. The freed area on the gridplate was then suctioned, following which the gridplate was completely unloaded of the remaining elements. The highest individual personnel exposure during this phase of the recovery process was 0.2 mR.
The monitor at the vacuum filters registered 5.0 mR.
10-15-92 The empty grioplate was suctioned. Visual obcervation with a scope indicated no beads on the gridplate. The
! collection chamber was moved to the underwater table and 1
the recovery can removed. It was about 1/5 full. The can was capped, tagged and moved to storage at the side of the pool. An empty can was installed in the collection chamber and the reactor bridge moved toward the center of
. the pool. Visual inspection with a scope revealed some beads on the header " funnel" and at the bottom of the primary piping underneath the header. The header and
! primary piping were suctioned clean. The collection l chamber was then moved to the underwater table and the recovery can removed. It appeared to be about 90% full.
Like the other cans, it was capped, the stringer labelled and the can stored underwater at the side of a pool wall.
The highest individual personnel exposure during this phase was 0.6 mR. The monitor at the vacuum filters registered 6.5 mR.
] '(Final Report, page 3, cont.)
i 10-16-92 The primary pump was started and run for about 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. A j detector placed by the heat exchanger shell to record activity variations indicated a tenporary rise in activity for about 14 seconds followed by a drop to a level slightly higher than the one before the pump was s
started. This behavior showed that a few beads not recovered by suction from the primary piping were passed
! through the heat exchanger and carried to the exit of the primary water return line at the bottom of the pool.
Personnel in the reactor room observed these beads
, exiting the flow diverter and fall to the bottom of the pool. A few beads were retained by the flow baffles in the heat exchanger (see Figures 2). The reactor coolant
' pump was then " jogged" on and off about 15 times to pass tha heads trapped by the baffle plates and the heat changer was then surveyed again (see Figures 3 and 4).
The pool floor area underneath the header and the primary piping was suctioned for about an hour. No beads were found in this area. The highest individual personnel exposure for the day was 0.2 mR. The monitor at the
, vacuum filters registered 1.9 mR.
10-19-92 To collect the beads that traversed the primary coolant system (the heat exchanger), the pool floor at the north
+
end of pool adjacent to primary water return line and the area around center buttress was suctioned. The highest 4
individual personnel exposure for this operation was 0.2 mR. The monitor at the vacuum filters registered 2 mR.
, 10-20-92 The primary pump was started and run for about 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
L The primary floor area at the north end of pool adjacent to flow return line and conter buttress were
- inspected and suctioned. The recovery can was removed
- from the suction system and inspected underwater. A small layer of beads, about 1/2 inch in depth, was found in the can. The can was capped, tagged and stored at the side of pool. The suction system was again relocated to the south end of pool and the pool floor at this end suctioned. Highest individual personnel exposure for the day was 0.3 mR. The monitor at the vacuum filters
! registered 5.1 mR.
10-21-92 A thorough visual inspect.on was made, with a scope, of the gridplate and areas arcund the header and primary l piping. No indication of beads was found in those areas.
4 I
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{ '(Final Report, page 4, cont.)
)
summarv:
j All :easonable actions to recover beads from the reactor pool were taken. The recovery process went very smoothly and the staff did an excellent job. Poolwater conditions remained within TS limits l throughout. Surveys indicated no contamination at poolside. From 1
the mass collected, it was possible to estimate (by weight and i
neutral balance) that about 98% of the beads were recovered.-
j Unirradiated beads from unused canisters were available for this comparison. The amount of material present in the irradiated L canisters was estimated from an average of the amount in the
{ remaining unirradiated canisters, and may have been overestimated.
1 i
j It is likely that the actual recovery was greater than 98% (as indicated by visual inspection and spot sampling of the pool i
floor). A better estimate of the percentage recovered would have been possible if the irradiated bead mass had been known more precisely. Recovery estimates based _on activity would not.be more accurate activity than the one obtained, given the greater uncertainty in measurements.
1 I
i The few beads still retained in the heat exchanger (about 1 gram or i 1 mci) pose no radiological hazard. When they eventually complete j
passage through the heat exchanger, they will settle out on the j-floor at the north end of the pool and decay over a period of time.
These beads will not enter the reactor coolant flow, given their t high (2.5) specific gravity (Were this not so,- there still would be
] no impact, i.e. no significant reactivity effects, tramp j
j activation, coolant flow blockage or control rod jamming, because j of the trace levels of iridium involved and the small maximum diameter of the beads compared to the relevant reactor dimensions) .
The beads which were recovered will most likely be kept within the l
i UVAR pool and permitted to decay to disposal level.
A complete file on the iridium bead spill will be kept with the Reactor Facility records.
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/ .g Calibration due 4-22-93 Survey by: 'y *~
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screen in 8b 1 foot out from Hx midpoint at waist height = 0.4 mR/hr I foot below Hx midpoint = 0.85 mR/hr Figure 4: Heat Exchanger Survey Results Following Operation of Coolant Pump for 125 hrs.
QUALITY ASSURANCE CHECKLIST FOR ALUMINUM CONTAINERS CONTAINING 3
IRIDIUM OR SCANDIUM IN CERAMIC MEDIA FOR 1RRADIATION AT THE 4
UNIVERSITY OF VIRGINIA NUCLEAR REACTOR FACIUTY i
j CAN ID: DATE:
CONTENTS: (circle one) lRIDIUM SCANDIUM l (check) QUALITY ASSURANCE ITEM j Proppant materialis 65% Al,0, 35% SiO, manufactured for Protechnics International by Norton Alcoa Proppant material contalr.o no visible foreign matter and is free of " fines" Proppant bead diameter is between 20 and 100 mesh l
Aluminum can is made of either alloy 6061,6063 or 1100 j Bottom of can is welded in place with a circumferential weld (no grinding)
Empty can with bottom is weighed (insert weight below) 4 Can liiied with proppant iald weighed (Insert weight below) i i Lifting lug wi'.h a 1/8" hole is welded to tcp center of can -
Can lid is welded in place with a circumferential weld Assembled can is weighed (insert weight below)
Max. can diameter is measured to be s 3.1 inches (record below)
Max. can length is measured to be s 10.25 inches (record below) l Can ID # gross and net weights are imprinted on the can No leaks found upon completing leak test
- 1. Weight of empty can grams
- 2. Weight of unsealed can plus proppant grams t
- 3. Weight of sealed can grams I 4. Weight of contained proppant (item 2 - item 1) grams
- 5. Maximum diameter of can ( s3.02' or s3.1" ) inches _
- 6. Maximum length of can ( s10.25') inches 1
j Checklist completed by:
I Signature Date Name printed Position title 444444444444444444444444444444444444444444444444444444444 Reviewed for UVA by (signature) Date 9
~ - - - . - - , , , - , . . - - . , ,n, , , . , , . ..n. . ., . - - , , . , ,..,w - - - r-,,- g + ---.,.e-, , - - , -~
FACILITY DESIGN. CONSTRUCTION OR MODIFICATION EVALUATION FORE (This Q/A Form based on 10 CFR 50.59 requirements was approved by RSC on 12/05/85 and revised (item a4.16) and approved by RSC on - 11 24-92 ]
- 1. Requested by: Date:
2.
Description:
- 3. Safety Analysis:
a) is the facility to be designed, constructed or modified described in the SAR?
yes, in section no N/A b) is a change required in SOP as referenced in the SAR?
Yes, updated S0p to be reviewed by RSC on / /
No N/A c) Does the proposed change,-test, experiment or facility involve a change in Technical Specifications?
Yes, to Tech. Spec. ,
(therefore a license amendment pursuant to 10 CFR 50.90 is required)
No d) is-the probability of an accident with or malfunction of the equipment such that it may bear on safety items considered in the SAR?
Yes, bearing exists on SAR items No e) Are the consequences of a malfunction of'this equipment important to safety _ evaluations previously made in the SAR?
Yes, affects evaluation in SAR section No f) Is an accident or malfunction of a different type than previously evaluated in the SAR possible?
Yes, the scenario not previously considered is No-g) Is the margin for safety as defined in the basis for any Techn8 cal .
Specification reduced?
Yes, margin of safety for T.S. (is, are) reduced.
-No-
1 l
Revised 11/92 !
, UNIVERSITY OF VIRGI!11A REACTOR FACILITY DPECIAL IRRAD_ULTJSN REOURST TORM --(SIRF1 IRF # page # .1. o f _
l Requestor _ Authorized, _ Qualified, _ Restricted Supervisor of work _ Authorited, Quellfled
, Work performed for _ no direct charges, bittable l Sanple description Irradiation times (nominal), (maxiran) Power levels (nominal), (max) l Location (s): Encapsulation: Reactivity worth:
Special handting:
4 Additional CA/QC requiremente are applicable and these are attachtd: (circle) tES N3
. _ Materlat or en esperiment of thla type has been previously irradiated, IRF# __
1 1
_ A trial irradiation of 1 min or less will t4 performed.
- 1f neither blank is checked, Reactor Health rhysicist arprovat to irradiate is required.
i Known isotope (s) AND/OR estimated matirsn dose rate on retrievat of sanple, escluding std. container (s)
Primary isotopes produced:
Maximum espected dose rates r#/hr G 1 f t based ont cattutations orlor experience 4
j The above information accurately describes the material to be irradiated.
'I
- Esperimenter Date The irradiation described above meets the requirements of the UVAR SOP's and tech. Spect.
APPPOVALS: Reactor Supervisor Date Two of Senior Operator Date three required i
- Health Physicist Date 1
Corinents Sanple Irradiation time Dose final Disposition Init. 2 1 ft
- Identification Loc. Date in Out Total Disp. mr/hr Init. Date Location init.
1 Container + sanple Date of measurement xxxxx4 xxxxxxxxxxx xxx 1
2 Container + sample Date of measurement: xxxxxx xxxxxxxxxxx xxx 2
3 Container + sampte Date of measurement: xxxxxx xxxxxxxxxxx xxx 3
7
- Thermal pneatatic rabbit CR = Counting rocm E = Epithermal pneumatic rsbbit HU = Hotdup station F# = Flua trap or irradiation basket and grid position SP = Side of pool H = Hydrautle rabbit SC = Shipping container LS = Lead shletd
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Revised 11/92
. UllIVERSITY OF VIBGIllIA REACTOR FACILITY ROUTllG IRRADlATlQiLJGELEFT FORli_@IBJ).
.lRF # page # 1 of _
Requestor ,,,,,_,, Author i t ed, _Quall f l ed, _ Rest r ic ted Supervisor of work _ Authorized, _ Quallfled 4
Work perf orned f or _ no direct charges, _ billable Servle description irradiation times (nominal), (maxirm) Power levelt_ (nominal), (man)
(Mat ion (s): E nc apsula t ion: Reactivity worth:
Special handling:
Additional QA/QC requirements are applicable and these are attached: (circle) TES NO
_ Material or en esperiment of this type has been previously irradiated, 18t#
_ A trial 4"adiation of 1 min or less wll1 be perf ormed.
- 1f neither blank is checked, Reactor Health F-hysicist afprovst to irradiate is reqJired.
Known isotope (s) AND/OR estimated meAlrm dose rate on retrieval of Sa"ple, escluding std. container (s)
Primary isotopes produced:
Maxirm espected dose ratet ff/hr a 1 f t based ont calculations _ J rlor esperience The above information accurately describes the material to be irradiated.
Esperimenter Date The Irradiation described above meets the reesirements of the UVAR 50P's and Tech. Specs.
i APPROVALS: Reactor Supervisor Date j
two of
( 5enior Operator Date three required
' Health Physicist Date Comments l
l Sanple Irradiation fire Dose Final Disposition Init. G 1 ft
- Identification Loc. Date In out total Disp. mc/hr Init. Date Location Init.
1 l
2 3
4 5
1 6 l
1 = Thermal pnematic rabbit CR e Counting roo.n E = Epithermal pnematic rabbit HU = Holdup station F# = Flux trap or irradiation basket and grid position $P a Side of pool H s HydraullC rabbit $C a Shipping container LS = lead shield