ML20246J113
| ML20246J113 | |
| Person / Time | |
|---|---|
| Site: | 05000112 |
| Issue date: | 08/28/1989 |
| From: | Skierkowski P OKLAHOMA, UNIV. OF, NORMAN, OK |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8909050040 | |
| Download: ML20246J113 (9) | |
Text
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. iyw g w Th y ; university ofOklafwma RADIATION SAFETY
,. 905 Asp, Room 112 L Norman, Oklahoma 73019
[ (405) 325 1015' p
p 28 August 1989 p.
L U.S. Nuclear Regulatory Commission'
- Office.of Nuclear Reactor Regulation Division;of Licensing
. Washington, DC 20555 e
Subject:
Application.for License Amendment to terminate License R-53 g (Docket 50-112)
' Gentlemen:
! - The University of Oklahomc.hereby submits this application for a L-license amendment to terminate License R-53 for the University of
- Oklahoma Research Reactor.
/ The-attached documents detail the activities conducted in compliance with our Dismantling and Decommissioning Plan authorized by order dated'5 June 89 from the Office of Nuclear Reactor Regulation.
Should'you'have any questions concerning this' submission please ad-
!. vise me at the above listed address / telephone number.
l lT Sincerely, l
W Paul Skierkowski, Ph.D.
Radiation Safety Officer PS/cs foY
' \
890905o04o 990828 *
[DR ADOCK 05000112 PDC
P-f; 'Q Page 1 of 8 DISMANTLING AND DECOMMISSIONING ACTIVITIES'FOR THE UNIVERSITY OF OKLAHOMA AGN211P NUCLEAR' REACTOR FACILITY DOCKET NO. 50-112 1.0- BACKGROUND A dismantling and decommissioning plan for the University of l Oklahoma AGN211P nuclear reactor facility was submitted to the USNRC on 25 Oct 88. Additional requested information was sub-mitted on 9 March 1989. On 5 June 1989 the USNRC Office of Nu-clear Reactor Regulation issued an order authorizing dismantling and disposition of component parts for facility license No. R-53, in accordance with the above mentioned plan, as supplemented.
The fuel for this facility had previously been transferred to a l Department.of Energy facility. The Ra-Be start-up source was transferred to a shielding container and is being stored by the University Radiation Safety Office awaiting DOE determination of a suitable repository for these type sources. The remaining ac-tivities to be conducted consisted of dismantling and' disposal of components and a radiation survey to confirm that radiation and surface' contamination levels in the facility area satisfy the values specified in the dismantling plan and in the commission's guidance.
2.0 DESCRIPTION
OF FACILITIES The reactor complex consisted of the following major areas:
- 1. the control panel
- 2. the tank assembly
- 3. the east pit
- 4. the west pit The control panel contained operator controls and was lo-cated on ground level approximately 10 feet north of the tank assembly. The tank assembly contained the fuel and control mechanisms for achieving criticality. The tank is approximately 96 inches deep and 36 x 59 inches in cross sectional area. Dur-
v . . . . .
Page 2 of 8 ing operation distilled water was maintained in the tank to a level within 9 inches of the top. Grid plates located in the bottom of the tank served as positioning guides for fuel rods and graphite reflectors loaded into the reactor.
Fuel rod assemblies were 5 19.9% enriched uranium oxide in a polyethylene matrix positioned between graphite and lead end caps. Fuel assemblies at one time were repainted annually with an epoxy paint. However this procedure was abandoned when it was detenmined that the fuel cell integrity was intact but that ele-ments in the paint scrapings showed activation products. Fuel elements were added to or removed from the core by means of a manually operated grasping tool. A Radium-Beryllium start up source was also kept in the pool.
Control rods consisted of two safety rods, one coarse con-trol rod and one fine control rod. A rod drive assembly located above the pool served to raise and lower the control rods via in-put from the control panel.
The cast pit contained a honeycomb assembly for storage of fuel rods when not in the reactor. The honeycomb was designed so that the distance between fuel rods precluded criticality even should the pit be flooded. No other reactor material was kept in this pit, although it was also used for storage of shielded high level sources (e.g. calibration sources) utilized in the Univer-sity's Broad License program.
The west pit provided access to the core for irradiations.
A one inch diameter pipe (glory hole) provided access to the center of the core and was used for reactivity experiments and I activation of samples. Two four-inch pipes allowed access to either side of the core for irradiations. Also located in the west pit was an ion exchange resin and pump for the circulating j pool water.
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c Page 3 of 8 Radiation monitors included a water monitor on the recircu-lation loop, an air monitor directly above the pool, and an area monitor on the ceiling directly above the pool. Dosimeters were required of all personnel in the facility, and three environmen-tal dosimeters were placed in rooms on the second floor. The room directly above the core was a storage closet. Whenever the reactor was in operation, this room was locked and the only key was kept at the reactor console to preclude accidental entry.
One of the environmental dosimeters was located in this room.
The closest occupied office to this storage facility was also monitored with an environmental dosimeter. In addition, surveys were conducted during operation to assure that radiation levels,in unrestricted areas were within the limits specified in 10CFR20.105. The third environmental dosimeter served as a control and was located in a second floor office at the distant location.
Any samples for activation were encapsulated prior to insertion in the glory hole. Irradiated samples were surveyed prior to removal from the pit and then transferred to the counting facility. When no longer needed, radioactive samples were disposed of via the low level waste system of the University Radiation Safety Office.
3.0 DISMANTLING AND DISPOSAL ACTIVITIES Radiation surveys were conducted with instruments calibrated by the University Radiation Safety Office (e.g. survey meters).
Measurements requiring absolute activity (dpm) determination were conducted using calibration standards approximating the geometry I of the measured sample (e.g. scintillation counting, proportional and G-M counting). All results were kept in a bound note book and entries were dated and signed by the personnel performing the operations.
Page 4 of 8 The three empty honeycomb assemblies from the east pit were surveyed with a GM detector for residual activity. One tube showed an activity level of approximately twice background. The tube was inverted over absorbent paper, and dirt, paint chips etc. removed. These contents were determined to be the source of activity. A followup survey of the cleaned tube indicated a background level. All tubes were similarly treated and any con-tents checked for activity. All these assemblies have been re-tained for release after NRC confirmation.
The bridge assembly above the pool was disassembled sufficiently to allow removal of the control rods. Each rod was surveyed at its surface as it was being removed. Safety rods #1 and #2 and the coarse control rod were at background level. The blade of the fine control rod yielded a survey reading of 4mR/Hr at the surface and 0.1 mR/Hr at one meter. The fine control 1
I blade was removed from the rod drive holder which was determined to be at background level. Gamma spectrometry of this blade indicated the activity to be due to co-60 activation products.
l The blade was segregated and will be disposed of as low level waste by the University Radiation Safety Office.
Water samples were removed from a location at approximately one half the depth of the pool. One sample of approximately 15 cc was analyzed for 60 minutes for gamma activity on a Canberra l GeLi Detector calibrated for an energy range of 0-2 MeV (2048 channels). The background count rate was 325 1 2 cpm and the l sample rate was 323 2 cpm with no energy peaks discernible other than those of natural background, e.g. K-40, U-daughters.
l l
Another water sample of 0.5 cc volume was placed in 5 cc of Scintiverse (U$ Fisher) Liquid Scintillation Solvent and counted for 100 minutes in a Beckman L55801 Liquid Scintillation Counter (H-3 efficiency = 67%, C-14 efficiency = 97%). Count rates were 53.7 i 0.7 cpm for a 0.5 cc tap water sample and 53.4 1 0.7 cpm L___________________
l Page 5 of 8 for the pool water sample. The water was removed from the tank by means of a submersible pump via a hose directly into a floor drain connecting to the sewer system. Because of the presence of the grid plate in the bottom of the pool, a small volume of water l remained in the bottom.
The reactor superstructure was disassembled and all parts separated. G-M survey of each component showed no activity above background on any bridge assembly components. Similarly the gre hite reflector rods and ionization detectors were removed from the pool with G-M surveys indicating background levels on all. All components and parts have been retained for release after NRC confirmation. After removal of the grid plates from the bottom of the pool, the effluent (water and some solids) remaining in the bottom of the pool was tested for radioactivity.
Assay results indicated no activity other than background.
The major components from the west pit are the ion exchange resin bed and the glory hole and irradiation port tubes. The ion exchange resin bed was removed from the water circulation loop and an approximately 500 cc sample of water syphoned from the i bed. A sample of 100 cc of this water was analyzed for gamma activity on a 3" NaI detector calibrated for 0-1800 kev. The background count rate was 517 i 3 cpm and the sample count rate was 463 i 3 cpm with no peaks other than those of natural back-ground. A 0.5 cc sample of the ion exchange water was assayed for beta activity by the previously described liquid scintilla-tion counting method. The background for a tap water sample was 52.0 1 2 cpm and the count rate for the test sample was 50.7 1 2 cpm. A sample was saved for NRC confirmation and the remainder ;
of the water was disposed of directly to the sanitary sewer. I Water flow in the ion exchanger was from bottom to top. Two resin samples were taken, one from the top and one from the bottom. The top sample showed no activity above background. The
Page 6 of 8 sample from the bottom indicated the presence of Cs-137 via gamma spectrometry. A quantitative measurement was made by placing a Cs-137 standard in the approximately geometric center of an equal weight of clean resin and determining the efficiency of the GeLi
~ for Cs-137 in this configuration. Using this approximation it was determined that the specific activity of the resin was ap-proximately 1.34 pCi/g and the total activity in the resin ap-9 proximately 940 pCi. The resin will be disposed of as low level waste by the University Radiation Safety Office.
The tubes from the glory hole and irt.tdiation ports were re-moved after the water was removed from the tank. A G-M survey of the external surfaces of these tubes indicated no activity above background. Swabs rubbed on the inside of each tube and counted for activity were also background level.
The console was disconnected from the power source and all components of it were disconnected from cabling. All individual components were surveyed for radiation with a G-M meter. No ac-tivity above background was detected. Reusable components such as power sources and recorders have been retained for other uses at the University. Nonusable components such as the frame work for the console were scrapped. In accordance with the NRC au-thorizing order all components have not been disposed of to one person or organization.
4.0 RADIATION SURVEY OF DISMANTLED FACILITY Following dismantling / disassembly of all components and removal of water from the tank, a contamination survey of the permanent facility was conducted.
- .~ l l
l l l Page 7 of 8 I Surface Contamination Swipe Tests l The tank and pits walls and floors were marked off in one meter grids. A smear sample of approximately 100 square centi-
)
meters was taken from each one square meter of the grid system to indicate removable contamination. Smear samples were assayed for removable alpha activity by 10 minute counts in an NMC model PC-3A proportional counter with an efficiency of 37.5% for the alpha radiation of a Th-230 standard. None of the smear samples exceeded the alpha plateau background. Beta-gamma analysis was performed by 10 minute counting under a Johnson PPA-2 probe con-necting to a Ludlem Model 2200 scaler / timer. This configuration had an efficiency of 11.7% for a Tc-99 standard. The only sample statistically exceeding background was from one location on the floor of the east pit. The area was cleaned and a subsequent smear wipe assay indicated a background level. All these smear samples have been retained for NRC inspection.
nR/Hr Survey A G-M survey was made of the surfaces of the pits and tank walls and floor using the same grid locations as for the surface contamination swipe tests. To measure the microRoentgen per hour rate, an Eberline HP260 probe was used in conjunction with an Eberline PRS-1 meter in the cpm mode. For calibration, a Cs-137 Reference [DuPont-NEN Cesium-137 Reference Source Model No: NES-131S Lot No: NES-1315-022688 1.1 nCi ON 2-26-88] was used to correlate cpm with a nR/Hr exposure. Using a gamma constant of 3.3 R
- cm 2. h ~1
- mci -1 and decaying the source to the test date (8-2-89) yields an exposure rate of 35 nR/Hr at 10 cm from this source. Using inverse square law, the 4R/Hr exposure rate was calculated for 4 points and the mean net cpm for 2 one-minute counts was determined. Linear Regression Analysis was used to determine the mathematical solution to the nR/Hr dose for a given cpm.
Page 8 of 8 The following data were used for calibration:
Exposure rate at 10 cm = 35 nR/Hr Average background one-minute counts [44,32) = 38 Source to Detector Exposure Rate One-Minute Mean " net" Distance (cm) 4R/Hr Counts (dupl) One-Min. Counts 5 140 1170, 1121 1108 10 35 414, 398 368 15 15 185, 198 154 20 9 125, 121 85 Linear Regression Equation for exposure:
nR/Hr = -6.065 + .013 * [ net one-minute counts)
Correlation coefficient (R) = 0.997 Note: using the above, a 5 kR/Hr count rate is equivalent to a ne,t one-minute count of 85. l This calibrated GM survey probe was positioned one meter from each grid square and counts accumulated for one minute. Back-grounds were measured at floor level above each pit / tank. Back-ground counts ranged from 43-54 for a one minute accumulation.
The survey measurements ranged from 29 to 63 [9 counts in excess of background). These measurements indicate no levels exist which exceed 5 kR/Hr above natural background. All individual data are on file for NRC inspection. l Additional Tests One additional radiation measurement (not specified in the decommissioning plan) was conducted. A Nuclear Associates digital radon monitor with data logger was placed in the reactor room for a monitoring period of 45 days. The average measured 24-hour interval concentration for this period was 1.6 pCi/L with a range of 0.9 to 2.8 pCi/L.
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