ML20072K008
| ML20072K008 | |
| Person / Time | |
|---|---|
| Site: | University of California - Irvine |
| Issue date: | 06/27/1983 |
| From: | Geoffrey Miller CALIFORNIA, UNIV. OF, IRVINE, CA |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| NUDOCS 8307010168 | |
| Download: ML20072K008 (23) | |
Text
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UNIVERSITY OF CALIFORNIA, IRVINE NR A f tf Y . fwls . IRslNE 11Pi AM.fl.Is . Ris t Rsilit . uN (JIK,0 . MN FR AVN u MNTA IL4RRAR A . MNTA Ott'Z i
DEPAllTitKNT OF C11Eht!5TitY ll(VINF, CAI.lf 0)(NI A *> 2 ' I '
June 27th, 1983 U.S. Nuclear Regulatory Comission, Director, Office of Inspection and Enforcement, ATTN: Document Control Desk Washington, D.C. 20555 Ref: Docket 50-326, License R-116 Annual Report, U.C.Irvine Reactor Facility Gentlemen, Twelve (12) copies of an annual report for our facility as required by Technical Specifications Section 6.7f and as indicated by Reg Guide 10.1, Item 171 are being submitted to this address.
Sincerely yours,
( .kb .
George E. Miller Lecturer in Chemistry and Reactor Supervisor cc: The Vice Chancellor, W. Lillyman F.S.Rowland, Reactor Administrator American Nuclear Insurance, attn: R. Waite P. Rogers, Senior Reactor Operator Reactor Operations Comittee d< OY y
8307010168 830627 PDR R ADOCK 05000326 PDR w __________________ - _______-__ _ _ _ _ _
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?' ,4 i U.C.IRVINE Nuclear Reactor Facility Annual Report for 1
July 1st,1982 to June 25th,1983 4
Facility License: R-116 i
Docket: 50-326 Prepared in Accordance with Part 6.7f of the facility Technical Specifications - *
.i by Dr G.E. Miller Reactor Supervisor l
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. 1 Section 1.
OPERATIONS I Operation of this facility is in support of the Department of Chemistry program in research and education in the use and application of radiochemical techniques and radioisotope utilization in chemical studies.
Reactor utilization, apart from operator training and maintenance, is thus entirely for sample irradiation. Samples come from diverse origins related to forensic science, fossil fuels, geochemistry, art and archeological studies, chemical synthesis, industrial quality control, enzyme studies, trace element pollution, etc.
The reactor was also used in class work by undergraduates learning tracer and activation analysis techniques using small quantities of short-lived activated materials.
10 graduate students and 2 post-doctoral associates have used the facility under the guidance of three faculty in Chemistry. These include-visiting students from Taiwan, Brazil, Ireland, West Germany, and the Peoples Republic of China.
- Currently the facility has 2 licensed senior operators including the Reactor Supervisor.
No major changes have been made in this period to the facility. The ;
annual inspection of core components indicated that all fuel elenents and 1 control rods were in good condition. !
A major accomplishment this year has been the repair of the rotating specimen rack. A graphite sleeve bearing was inserted in the unit to provide suppport for the drive shaft instead of the failed ball race. The repair necessitated removal of the rotating specimen rack from the reactor pool for several days. The unit is now fully operational. A full report is included as Appendix A to this docunent.
- Operations in general have been slightly reduced from last year, partly because of the rotating specimen rack difficulties. Data on the operations is presented in Section 2.
Sacurity system difficulties were encountered in May and June, 1982 resulting in a Notice of Violation dated July 7th, 1982. A security inspection was conducted by NRC inspectors in August, 1982. By the inspection date, all physical security items were in order. ,
A radiological safety inspection was conducted by an NRC inspector in ' '
December, 1982. As a result of this inspection a Notice of Violation was ;
issued with regard to Reactor Operations Committee activities. No other items of non compliance or deviations were noted. 1
~ An incident report was filed in July,1982 regarding a brief operation at higher than licensed power level during power calibration. . This was reported -
fully'in the last annual report.
i- An incident report was made, dated June 16th 1982, with a follow-up report on June 25th, regarding difficulties on June 2nd and again on June 24th with the fast transient rod air cylinder causing failure of complete rod drop on reactor scram. This abnormal occurrence was also reported to NRC by telephone on . June 3rd. This is more fully described in ' the maintenance
- section of this report.
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On December 2nd 1982, an experimenter received a modest ( but high for our facility ) extremity exposure (420 mrem ), accompanied by a whole body exposurer of 15 mrem as a result of handling a sample handling device that had been inadvertently irradiated to a high level ( several R/hr).
The rotating specimen rack repair operation necessitated quite high exposures, again very abnormal for this facility, to several operation personnel. The maximun was 2.75 Rem hand extremity, and 110 mrem whole body to any one individual, and a total of 3.6 man-rem extremity and 0.345 man-rem whole body exposure for the complete operation. Details are given in the special report ( Appendix A).
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Section 2.
Data Tabulations for the Period July 1st,1982 to June 25th,1983 TABLE I.
Experiment approvals on file 7 Experiments performed (including repeats) 268 Samples irradiated 2148 Energy generated this period (Megawatt hours): 28.8 Total, 69 element core 127.0
>74 element cores 767.6 -
Total energy generated since initial criticality: 894.6 Mwh Pulse operation this period: 10 of which greater than $2.00 insertion: 10 Tots 1 pulses to 6/25/83 675 Hours critical this period: 179 , .
Total hours critical to date: 4720 Operator training and requalification, hours: 35 Inadvertent scrams: 32 Visitors to reactor - adnitted: 260 Maximum dosimeter recorded for visitors: 1 mrem Visiting researchers (dosimeter issues): 124 Maximum dose recorded: 49 mrem Visiting researchers (badged): 4 1
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i TABLE II.
Reactor Status 6/25/8_3 Fuel elements in core (including 2 fuel followers): 80 Fuel elements in storage (reactor tank) - used: 28 Fuel elements unused (instrumented element): 1 Graphite reflector elanents in core: 34 Graphite reflector elements in reactor tank storage: 0 Experimental facilities in fuel elsnent positions': 4 Water filled fuel element positions: 7 Core excess, cold, no xenon: $2.77 Control rod worths (6/26/83):
REG $2.77 SHIM $3.76 -
- ATR $1.97 FTR $0.67 Total: $9.17 Maximtm possible pulse insertion: $2.64 Maximum peak power attained (4/15/83 - $2.60 insertion): 1008 Mwatts Maximun peak temperature observed (B-ring): 240 C Page 5 l-u_-
Section 3.
Inadvertent Scrams and Unplanned Shutdowns TABLE III.
Date Time Power Type and Cause 1982 T/T- 12:07 <3 watts Period scram. Operator error during start-up.
7/5 19:38 174 kw Linear Power scram. On switching to AUTO mode - mode switch contacts.
7/8 9:51 250 kw Same as 7/5 7/8 10:09 9.50 kw External (seismic) scram. Improper reset during start-up. No seismic activity.
7/8 10:13 <5 kw Linear Power scram. On switching to AUTO mode - mode switch contacts.
7/30 10:28 250 kw % Power scram. Gamma build up not noticed by operator.
Other power indications at <250 kw.
8/6 14:19 100 kw Period scram. Operator error during power level change.
9/3 10:38 250 kw Linear Power scram. Same as 7/8.
9/3 10:44 250 kw Linear Power scram. Same as 7/8.
9/9 8:51 250 kw % Power scram. Ganna build up and drift not noticed by operator. Other power indications at <250 kw.
9/15 9:28 240 kw Linear Power scram. Same as 7/8.
9/15 9:38 250 kw % Power scrom. Drift up not noted by operator. Other power indications at <250 kw. , .
9/22 16:35 250 kw % Power scram. Same as 9/15. -
9/30 9:35 Period scram - operator error during .
10/14 9:12 250 kw % Power scram. Same as 9/15.
10/18 18:05 1 watt Linear Power scram. Trainee range switching error.
10/18 18:15 250 kw Linear Power scram. On switching to AUTO mode.
10/23 7:57 1 kw Linear Power scram. Same as 10/18.
10/23 8:02 1 kw Li'near Power scram. Sample removed from core (worth
$0.19) before manual scram performed.
10/26 12:10 250 kw % Power scram. Same as 9/15.
11/5 9:18 250 kw % Power scram. same as 9/15.
11/18 15:43 15 kw Period scram. Operator error during power level change.
12/30 13:33 130 kw Period scram. LOG channel signal lead disturbed at reactor bridge while adjusting chamber position.
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F Inadvertent scrams (continued):
1983 T/2T 11:05 10 kw Linear Power scram. On switching to AUTO mode.
1/26 18:41 1 watt Period scram - operator error during start-up.
1/26 18;52 250 kw % Power scram. Gamma build-up/ circuit drift, now observed carefully to occur at less than 105%P on meter even though scram set at 110% P. Other power levels indicated less than 250 kw.
2/8 10:53 250 kw Same as 1/26.
3/1 13:31 250 kw Same as 1/26. Observed carefully to trip at 103.5% P.
4/22 14:59 250 kw Same as 1/26.
S'/28 15:18 10 w Console Power scram indicated. Magent current / scram reset key switch contact problem.
5/31 16:23 250 kw Same as 5/28, 6/1 10:28 3 watt Same as 5/28.
6/6 9:10 10 w Period scram. LOG channel HV connector loose. Not properly refastened after monthly voltage measurements.
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Section 4.
Maintenance and Survelliance.
All critical items ( fuel elements , control rods, detector systems) continue to be found in good condition during routine inspections. There are a few new and recurring items given special attention this year.
The following special items were noted this year:
(a) Console Mode Switch. This switch continues to be a source of undesired reactor scrams when switched between steady-state and automatic mode. The main wafer section was replaced with a new unit during the year and this has reduced the frequency of difficulty considerably. Undesired scrams still occur, however, if the switching is done with the power level close to 100% on any range of the linear channel.
(b) False Security Alarms. A ntaber of false alarms were received. The cause of many was finally traced to the presence of certain liquid nitrogen storage tannks within the facility. One or two of these tanks appear to have pressure relief valves that release with abnormal noise - enough to trip the facility ultrasonic motion sensors. One or two power failures caused alarms to be turned ja, also. A few circuit changes ' were made in the security central computer, to try to reduce the sensitivity to power changes.
(c) LOG Channel. Abnormal noise in this channel circuit was discovered on 12/29/82. Cleaning all BNC connectors in the signal path cured this problem.
(d) Fuel Element Location Record. An error in fuel element location record was discovered during annual core surveillance. The locations of two "B" ring fuel elements had been interchanged. As a final check on this mistake, the serial numbers on the elenents 'were read by placing them in a temporary rack about 2 feet under water and using a small mirror.
(e) REG control rod drive positix o indicator potentiometer. Thi.s was replaced on 12/27/82 during annual maintenance, as it appeared to be loose
- during part of travel. This replacement resulted in straightening of a " kink" 1 which had always been present in REG rod calibration curves for some years.
The rod curve obtained now looks much more normal.
(f) FTR Rod Drive. This rod drive cylinder was oiled once, and then about 20 days later, dismantled and all "0" ring and piston seals thoroughly cleaned, reoiled and reinserted after a problem occurred in which the FTR did 1 not drop properly after scram. Since this event constituted an abnormal occurrence, an incident report was filed with NRC.
(g) Rotary Specimen Rack. As noted in a previous report, on 6/24/82 the
! entire rack was removed from the core structure following approved procedures and stored at the side of the reactor tank for decay before repair. Work on the repair was begun on 12/20/82 and completed 12/26/82. The reactor was-reloaded and recalibrated by 12/30/82. A separate report (Appendix A.)
describes the repair operations in detail.
(h) Deionized Water Release. On July 8th, 1982 a report was submitted to NRC regarding an accidental release of deionized water on June 29th,1982.
This event was described in the previous annual report for the facility.
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F Section 5.
Facility Changes and Special Experiments Approved.
As noted under maintenance, the rotating specimen rack was reinstalled during December,1982. Operation of this repaired facility appears nomal.
No other changes or special experiments were approved during this period.
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Section 6.
Radioactive Effluent Releases.
(a) Gases. The major direct release to the environs is Argon-41 produced during normal operations. Very small amounts of other short-lived geses may be released from irradiated materials in experiments.
Releases are estimated based on original estimates at point of origin within the facility and taking only dilution into account. An integrated dose estimate is provided by an environmental dosimeter (calcium sulfate-dysproaltn) hanging directly in the exhaust at the point of stack discharge. This is changed and read quarterly. The results substantiate the projection that the submersion dose to an individual standing continuously in the stack discharge for one year would be less than the combined reliability limit of the four dosimeters, or less than 20 mrem per year.
The exact quarterly dose readings obtained are given in Section 7 of this report. The location is location 5 in Table IV.
Release estimates are as follows:
(1) Operation of pnematic transfer system (7/1/82 - 6/25/83):
Total time of operation (assmed to be at 250 kw): 1686 minutes.
Release rate assumed -8 6 x 10 microcuries/ml 6
Flow rate of exhaust air 2 x 10 ml/sec Total release computed 4 1.2 x 10 microcuries (2) Release from pool surface (7/1/82 - 6/25/83)
Total hours of operation at power (Mwh x 4) 116 hours0.00134 days <br />0.0322 hours <br />1.917989e-4 weeks <br />4.4138e-5 months <br />
- Release rate assmed <1 x 10-8 microcuries/ml Flow rate of exhaust air 2 x 10 6 ml/sec Total release computed <0.8 x~104 microcuries Total of (1) + (2) = 2 x 10 4 microcuries Concentration averaged over 12 months = <4 x 10-10 microcuries/ml i
This is lower than the level reported last year because of reduced operations and remains lower than MPC even assming no additional p1me dilution at the stack.
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(b) Liquids and Solids. Liquid and solid wastes from utilization of by-product materials are disposed through a University contract. Waste is transferred to the custody of the Campus Environmental !!calth and Safety Office for final packaging and shipping. Wastes from filters in the pool water cooling system are also disposed in this way. Spectrometric measurements indicate that these are contaminated with medlun and short-lived by-product isotopes in low quantities. Also disposed during this year were a number of end fittings taken from "used" fuel elements received in March, 1974 from General Atomic. These. had been in facility storage for several years. 26 such fittings, with an estimated activity of 70 microcuries (mostly c'obalt-60) each were disposed.
Some of the materials generated in experiments in this facility are transferred to other users operating under State of California license and final disposal of such materials is not under the control of this facility.
Disposals by the facility were as follows: (activities are estimated as of time of transfer to E, H and S control).
Dry wastes: 7 cubic feet 1920 microcuriesm' ixed activation products.
Liquids: 7 gallons 75 microcuries mixed activation products.
Total: 1995 microcuries l
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r Section 7.
Environmental Surveillance.
Calcium-sulfate: Dysprosium thermoluminescent dosimeters in packs supplied by the Radiation Detection Company, Sunnyvale, California are placed at nine locations around the U.C.I. campus. One pack is kept. off-campus in a wood frame house (second story) as a control. The average of the remotely located packs on campus is in fact used as a " concrete environment" background for comparison purposes for evaluation of packs placed closer to the facility.
Table of Locations.
- 1. Window of reactor room ( inside the facil'ity ).
- 2. Between reactor labcratories and radiochemical laboratory, in hallway.
- 3. Loading dock, adjacent to west wall of reactor facility.
- 4. Classroom 152, over reactor facility.
- 5. In roof exhaust air flow from reactor room.
- 6. Steinhaus Hall ( Biological Sciences building ), 4th floor.
- 7. Library building across Campus, 5th floor office. -
- 8. Computer Science building, 4th floor.
- 9. Fume Hood exhaust, roof level, from reactor laboratory.
- 10. 17941 Spicewood Way, Irvine. (Control location about 2.5 miles from Campus)
Table IV shows the data as received from RDC for the period. All levels are as ex pected. Those above background reflect the neutron generator operating schedule (nitrogen-16 formed in the cooling water) and are essentially similar to those reported in prior years. As noted before, areas -
1 and 2 are partly controlled so that the maximun possible annual dose to an individual in a true 'off-site' location would be estimated to be less than 40 mrem ( above background ) from operations at this facility, using this data. The main and fune hood exhaust dosimeters continue to show no detectable dose, above background, in the exhaust stacks from the facility.
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r-TABLE IV.
Environmental Dosimetry Report Data.
198233.
Average Exposures in mr.
Location. Quarter. -
Total. Total less
Background
2 3 4 1* 1 (41 + 20)
I 123 79 60 77 47 309 268 2 53 29 57 45 25 169 128 3 9 9 0 36 16 24 0 4 3 5 6 29 9 23 0 5 7 7 7 31 11 32 0 6 14 15 14 31 11 54 (13) 7 12 15 17 33 11 55 (14) 8 3 5 3 23 3 14 (0) 9 5 7 8 (missing) (20) 0 10 3 6 7 10 26 0 Average of locations 6,7,8 used for background.
- These dosimeters appear to have received approximately 20 mr of exposure all together except for the location 10 which had been removed to the off campus location. This probably occurred during rotating specimen rack repair operations but before the dosimeters were changed at their locations. -
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i Section 8.
Radiation Exposure to Personnel.
The annual exposures reported as a result of finger-ring and film badge dosimetry are presnted in Table V. Essentially all of these exposures with the exception of those accunulated during the repair of the rotary specimen ' i rack (see Appendix A) are acquired in the course of isotope handling experiinents and in some instances will have been accunulated in areas outside the facility, licensed by the State of California.
Twenty-eight (28) persons were monitored on a continual basis using film badges, of these twenty-two (22) were also issued finger rings. These were required to be worn while handling isotopes. Film badges were generally worn at waist level by all personnel. An additional twenty-eight (28) students were issued badges and finger rings for nine weeks during a laboratory course [
in Radioisotope Techniques. They entered the facility for some of their ' '
experiments, but not for all. Their exposure records have not been included i in this listing.
3 Contamination surveys consisting of wipe tests and G-M surveys have shown significant removable contamination in isotope handling areas. No other ,
contamination areas have been found. *
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TABLE V.
Personnel Exposure Summary for 6/1/82 to 4/31/83 (in mrem) ~*
Individuals Whole Body Finger-Ring * ,
Pen Non-pen 1 70 0 2750 1 35 0 310 1 25 0 150 1 20 0 280 1 15 0 630 1 0 0 200 .
16 0 0 0 6 0 0 not issued
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. Univera5ty' of California, Irvine Ce'partment of Chemistry Nuclear Reactor Facility
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Report on
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Rotary Specimen Rack Repa'ir s, ,. :
N N l ', t r Completed: Cecember, 1982
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The rotating specimen rack was removed from the reactor core structure on June 24th,1982 and stored at the free end of the reactor pool supported on a temporary wooden bridge across the pool. Parts for the repair were machined at UCI. They consisted of a graphite sleeve fitting closely around the drive and locking shafts and a stainless steel bushing to support the drive shaft cn this sleeve. A replacement shaft support bracket was also fabricated to accomodate the bushing.
On December 20th,1982 wrenches were obtained on loan from Harlan Rogers and General Atomic to fit the tube connector nuts (Weatherhead fittings). The upper sections of the drive shaft and loading tubes were removed. Some difficulty was encountered in removing the aluninm tube sleeves from over the connecting links on the drive and locking shafts as these had been crimped in severly on both top and bottom ends, and access to them was not easy since the lower shaft does not extend much over the lower guide tube. Eventually, with much levering and banging, these sleeves were persuaded to slide, and the dowel pins could be accessed. No trouble was encountered in removing the dowel pins.
The rack was then raised until under about 38 inches of water ( at the top of the rack ). Readings with a Cutie-Pie monitor just above* water .
indicated 12 mr/hr. Rough calculation indicated a level of about 0.75 R/hr in air at the same distance. This would be too high to work with no shielding.
In addition, it was apparent that since so much difficulty was encountered in removing the sleeves covering the dowel pins in the upper tube, it was likely to be equally difficult at the lower junction, and to try to do this while leaning over the side of the pool and keeping the unit underwater would not be possible. A decision was mada, therefore, to build a shield with 2 inches thick lead equivalent at the side of the pool to house the entire rack. The shield was 30 inches inside dimension square and 20 inches tall, and had steel plates for a lid which could support 2 inches of lead. An attenuation factor of 24 would be provided by this shield. Additional shielding was provided for working operators while working close to the unit. Estimates were made of the dose rates expected at the walls of the reactor facility with the rack in the shield, and these were less than 2 mr/hr, except for the period when the rack was being transferred into the shield.
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For the transfer operation, two persons only were used within the facility. The surrounding area - corridoors and room over the facility were cleared and guarded by personnel from E, H and S. The operation was performed late in the day so few persons were in the vicinity anyway. The initial shield was constructed without top or front, so the rack could be inserted.
Polypropylene ropes were fed through the lifting lugs on the rack (3 in all) by use of a long handling tool. These ropes were then looped over the hoist hook with the hoist positioned directly over the rack. Ropes were j attached to the drive shaft guide tube and the loading tube both near the top and at the water line to act as guide ropes. at this point the facility was cleared except for the two handling personnel and the surrounding areas patrolled by E, H and S personnel with geiger monitors. Operation of the hoist and use of the guide ropes then enabled th'e operators to maneuveur the rack into the shield while remaining at a minimum of about two meters from the rack. Wnile the rack was still under water, it remained sufficiently bouyant that there was some probica keeping it upright. Once out of the water, this was no problem. The operation took between 5 and 10 minutes. Readings of various radiation measuring devices during this operation were as follows:
Maximum observed monitor readings:
l Location During transfer After transfer' (unshielded) (in shield) hallway 10 mr/hr 0.4 mr/hr control room 50 mr/hr 1.5 mr/hr classroom overhead 1.5 mr/hr background outsioe on dock 15 mr/hr 1.5 mr/hr (one spot 6' high by door)
Personnel dosimeters / exposures:
1 49 mrem upper torso 25.5 mrem waist level 2 conservatively asstned same exposures These readings were taken after completion of building of the shield top and front which involved approaching much closer to the rack.
Estimated dose rate at about 1 meter from the shield = 20 mr/hr.
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1 With the initial flat cover design of the shield, it was still not possible to accees properly the lower joint fitting on the drive shaft tube.
It was therefore decided that the top must be rebuilt. Two 1/4th inch thick steel plates were fabricated to fit on the top of the rack, with holes to go over the lifting lugs. They fitted each side of the tube outlets from the rack. Three personnel - different from those removing the rack - worked on removing the top as it existed, placing the plates in place, and replacing the lead bricks on the new plates. while the tcp was uncovered, the classroom overhead and surrounding corridoors were cleared and patrolled as before. With the top uncovered, the RAM on the facility ceiling reached about 40 mr/hr indication in the control room. The maximm reading found at the floor of the classroom overhead was 1.8 mr/hr ( geiger monitor ). Total personnel exposures during this operation were: '
3 90 mrem upper torso 75 waist level 4 40 mrem upper torso 5 31 mrem upper torso l With the new lead cover in placs, monitor readings weret overtank RAM - 1.2 mr/hr, storage RAM - <0.5 mrem /hr, cleasroom - background.
Working alone, the Reactor Supervisor was now able to loosen the* nut on ,
the lower Weatherhead fitting. the alumina sleeves over the connecting link on this joint had not been so heavily crimped, so were more ersily lifted with pliers. The dowel pins were pressed out with a specially modified C-clamp which could be operated from about 12 inches away. The dowel pins themselves measured 20 mr/hr at contact.
The locking pin shaft was now gripped with a " vise grip" wrench and lifted. This easily lifted off the almina shaft support bracket. This piece measured only 3 mr/hr at contact. The lower locking pin shaft was removed completely at this point. at its lower end it measured 20 mr/hr at contact. -
All these items were placed in a lead container for storage.
During the above, and subsequent, operations, the lone worker crouched behind an additional lead shield consisting of a low cart with wheels on which a lead container and several bricks were built up. This shielded much of the main body leaving only arms, hands, and head exposed. Finger ring dosimeters were used, and the self-readinn dosimeter _ was clipped to the shirt collar to estimate head exposure.
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At- this juncture, the fabricated parts were checked for fit without actually being inserted. One modification was needed to the alminum support bracket as the locating pins had been made larger than specified. The stain 1'ess steel bushing was too tight a fit onto the drive shaft and was reamed out slightly to 0.395" diameter.
The remaining shaft guide tube was next cleaned out as well as possible using tissues on a flex handling tool. Then the graphite sleeve was inserted.
In order to get it to fall properly, the drive shaft had to be lifted so that the gear could engage properly with the drive chain in the rack. once this was done, the sleeve fitted in eesily and the locking shaft was also inserted. Now the new support barcket was tapped lightly to a snug fit into the guide tube.
The stainless steel bushing was then slid over the drive shaft. The drive shaft was lifted slightly ( to approximately
- the mid-point of its free movement) and the shaft locked up in this position using a " vise grip". The shaft was then drilled through the pilot holes in the bushing for the 3/32 inch diameter pin. Some effort was made to place plastic bags around this shaft to catch drillings, but this was difficult without increasing hand exposure. It was decided to clean up afterwards using a small brush. The chips were radioactive and could be traced easily once away from the rack. After the first hole was drilled, a 3/32 inch diameter dowel pin was pressed in using ,
the modified C-clamp. The final portion was tapped home using a 9 inch long alunine red as an anvil. A second hole was then drilled and a second pin inserted.
The upper drive rods were next reconnected, their dowel pins reinserted, and the cover sleeves dropped back in place. It was found convenient to hold up the sleeves with " vise grips" while the dowel pins were being tapped back in place. For all dowel pins, it was necessary to use an alinement probe to get the first hole lined up properly. Again, it was difficult to do this and minimize hand exposure. When this had been accomplished, the threads of the -
Weatherhead fittings were cleaned off as much as possible with tissues in long forceps and long " swab" sticks. Fresh "molykote" was then added and the unit reassembled. With the long wrenches, and added extensions, it was relatively easy to tighten the nut satisfactorily.
During the above operations, one individual recorded 19 mrem whole body exposure and.2750 mrem hand exposure.
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Following the reassembly, an attempt was made to test the joints for leakage by pressurizing the whole rack with nitrogen gas and using " snoop" around the joint. Because of restricted vision, it was not possible to be j
totally certain of absence of leaks, but none were obvious.
On December 26th, the rack was maneuvered back into the reactor pool after first removing the top lead cover and front (facing the pool) shielding.
This was done this time by attaching a polypropylene line only to the front '
lifting lug ( instead of to all three lugs ). The guideropes were then used to tilt the whole rack backwards until the tubes could be held by hand at floor level at their upper ends. The hoist then lifted the front rack, and the two persons, one on each tube, the rear. This technique kept persons slightly further from the rack, and less instability was 'noted. With the rack forward over the pool, it could be lowered as the tubes were tilted back upright. A j wooden plank at the edge of the pool prevented the almine tubes and the rack from scraping on the tank wall. With the rack under several feet of water, a complete test of joint integrity could be more easily performed with the unit repressurized. No bubbles were observed. to pressurize the system, special auto radiator hose was clamped over the tube ends.
The upper sections of the loading and drive shaft tubes were next ,
reassembled. Again, the Weatherhead fittings were carefully cleaned off and re covered in "molykote". Burrs caused by the efforts to remove the almine sleeve covers from the connecting linkages were removed. When the tubes were -
first removed, they were marked as to exact alinement. During the reassembly, this alinement was maintained as far as possible on the theory that any distortion of tubes or fittings would reassemble better if in the same location. The whole rack was lowered so the upper joints were also under i water, and the pressure test conducted again. An exciting moment occurred when one of the auto hoses blew off
- hile the unit was under pressure. The plastic plugs included in the drive shaft guide tube to provide neutron shielding came
' boiling" out of the tube and spilled into the pool. Fortunately, they are of light plastic and float! They were retrieved, dried, and replaced in the tube.
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At' this point, the rack was declared " leak tight" and was ready to be inserted into core. As part of annual maintenance, the reactor core had been stripped of its B ring fuel elements , all four control rods, the central thimble dry tube, the pneunatic temini and the neutron source. It was thus a simple matter to lower the rack almost to the bottom, thread the drive tube and loading tubes up through their respective access holes in the reactor bridge, lift the rack by about 10 feet above the core to clear the FTR guide tube still in core, and lower it into its slot in the reflector assembly. some difficulty was encountered in fastening the three clamps onto the rack because, with the clamp turned over the rack, the clamp leans backwards sufficiently that it prevents access of the wrench onto the clamp bolts. To solve this, the wrench had to be put in place before the clamp was over the rack, then the clamp was knocked around with a long pole, and then the bolt tightened taking great care not to let the wrench slip off. After some trials, the three clamps were tightened. Total recorded personnel exposures during this whole operation, most of which were sustained during transfer of the rack into the tank were:
1 31 mrem 2 40 mrem 5 18 mrem -
The remaining reactor core items could now be replaced. no additional exposure to personnel was involved. Complete reassembly, check-out and calibrations were accomplished by 12/30/82.
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o d.
Event Exposure Summary
- 1. Estimated from local self reading and digital dosimeters. Upper torso locations, in mrem:
Individual mrem 1 105 2 90.5 3 90 4 40 5 49 TOTAL 374.5 or 0.3745 man-rems Any offsite exposure: less than 2 mrems.
j 2. Film badge and finge! ring data, in mrem:
l Individual -badge ring 1 70 2750 3 110 280 5 35 240 2 65 130 -
- 4 65 180 TOTALS 345 3580 i
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