ML20059C115
| ML20059C115 | |
| Person / Time | |
|---|---|
| Site: | 05000356, University of Illinois |
| Issue date: | 10/04/1993 |
| From: | Hang D, Holm R, Bradley Jones ILLINOIS, UNIV. OF, URBANA, IL |
| To: | NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| References | |
| NUDOCS 9311010019 | |
| Download: ML20059C115 (4) | |
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University Of Illinois Department of College of Engineering 98-/ 9/ -
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214 Nudear Engineering 217 333-2295 Laboratory 217 333-2906 fax 103 South Goodwin Avenue Urbana,IL 61801-2984 October 4,1993 Docket Nos. 50-15I/50-356 fo - / N TO: Executive Director for Operations g
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U. S. Nuclear Regulatory Commission Washington, D. C. 20555 SUllJECT: Application for prior authorization to operate up to an annual dose limit for an individual member of the public of 0.5 rem (5 mSv) pursuant to 10 CFR 20.1301 (c) for the University ofIllinois Nuclear Reactor Laboratory.
Gentlemen:
10 CFR 20 Subpart D - Radiation Dose Limits for Individual Members of the Public states, at 20.1301 (c) that, "A licensee or license applicant may apply for prior NRC authorization to operate up to an annual dose limit for an individual member of the public of 0.5 rem (5 mSv)." The Nuclear Reactor Lab at the University ofIllinois has been in operation since August 16,1960 and has complied with the 0.5 rem limit at all times. The imposition of a new limit of 0.1 rem, afler 33 years of operation, places a significant burden on our ability to operate and remain in compliance with the regulation. Ilecause the facility was designed and built to comply with the 0.5 rem limit there are cenain areas at our Site Iloundary that have recorded annual doses greater than 0.1 rem but less than 0.5 rem. In addition, the publication of the proposed revision to Part 20 in the Federal Register included the following statements in Section XVII. Standards for Individuals in the General Public; 0.1-rem (1 mSv) Per Year Reference Level. " Dose limits are intended to apply to real doses to persons actually exposed" and " It is emphasized that the reference levels are not limits for pennitted dose, but rather define actions required to be taken by the licensee at specific exposure levels." Pursuant to the requirements in 20.301 (c) (1), (2), and (3) we have made every reasonable effort to reduce the annual dose at the Site lloundary but will be unable to comply with the 0.1 rem limit without incurring significant expense or cunailing operations. These effons are outlined i
below. We respectfully request that you rule favorably on this application.
20.301 (c) The licensee or license applicant shallinclude the followinginfonnation in this application:
(I) Demonstration of the need for and the expected duration ofoperations in excess o_Qhe limit in_garagrapk(_a) oOhis section:
IMCKGROUND in October 1987 a program of Environmental Monitoring of the area in the near vicinity of the Nuclear Reactor Lab utilizing Thermoluminescent Dosimeters (TLDs) was implemented. 'Ihe purpose was to demonstrate that there was no impact on the local ensironment from the only efIluent released by our lab, gaseous Ar-41.
In January 1990, afler discovery of a significantly higher dose rate on the Reactor Iluilding South Wall (on top of the Mechanical Equipment Room Roof) during a routine survey of the Site Iloundary in support of Reactor Pulsing for Nuclear Pumped Laser Research,4 TLDs were added to the monitoring locations. The purpose was to get a better assessment of the integrated dose at the Site Iloundary because of the impending imposition of a [
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- F -/ W lower limit in the revised 10 CFR 20 (from 500 to 100 mrem / Year). With the exception of the fenced area aroun'd the Cooling Towers, the Site Boundary is the Reactor Building Walls. Therefore, these 4 TLDs were allixed directly to the West, Nonh, and East Walls, at chest height for the average person; and on the South Wall, at that height if that person was standing on the Mechanical Equipment Room Roof. In addition, the locations were chosen to be in the direct line of a beam pon on the West Nonh, and East Walls; and on the South Wall in line with suspected streaming from both the 1RIGA and LOPRA cores through the Bulk Shielding Tank.
The results of these first 4 Site Boundary TLDs were not encouraging with readings ofbackground,55,85, and 105 mrem for the first quarter of 1991. Fortunately, the 4 locations closed out 1991 with doses ofbackground, 80,130, and 250 respectively. In 1992 these locations closed out the year at 10,90,170, and 390 (Attachment).
Ilowever, the founh location with doses of 250 and 390 is in an inaccessible area and is in line with the streaming from the reactors through the 11ulk Shielding Tank discussed in item b) below. 'Ihe projected dose for this location in 1993 is 220 mrem. All doses assume a subtraction of100 mrem for natural background.
After the first quarter 1991 results were received 12 more monitoring locations were added at the Site Boundary to more fully assess the scope of the p oblem. In 1992 we began efTorts to estab'ish the source ofexposure for the areas with the higher readings and took steps to reduce this exposure in keeping with the ALARA concept.
l The exposure reduction effons are summarized as follows:
a) The storage cage in the lower level of the Reactor Building is locked because it contains Nuclear Fuel.
Ilowever, over the past 30 years it was also used as a radioactive waste dump for materials with high dose rates.
In the summer of 1992 we cleaned out the storage cage, inventoried the items we retumed to it, and posted that inventory on the door. The criteria for whether an item belonged in the cage was revised to include security and not radiation dose rate consideration. The high dose rate items were placed in beam catchers on the lower level pending isotopic identification, activity determination, and ultimately disposal as radioactive waste. The beam catchers are ideally suited for this purpose using concrete and burial underground as natural shielding.
Remedial Action: The TLDs monitoring this corner of the building showed doses of 210 mrem for 1992 afler subtracting 100 mrem for natural background. For the first quarter of 1993 these badges read 40 & 60 mRent Multiplying by four and subtracting 100 mrem for background the projected doses for 1993 at this location are 60 & 140 mrem. Ilowever, a 40 mrem /hr flight tube was found in the overhead in the vicinity of the badge that recorded the 60 mrem reading for the first quarter and was removed to a beam catcher for disposal as waste. In all likelihood this reading should be low enough for the subsequent 3 quarters to bring this portion of the building under the 100 mrem limit.
b) IttvestigatimLof the_ apparent streaming through the Bulk Shielding Tank that created the highest badge reading, in the center of the South Wall on top of the mechanical equipment room, revealed that the source was both N-16 gamma radiation directly through the biological shield on the middle level of the TRIGA reactor and reflection of N-16 and fission gammas from the LOPRA reactor. Tims fission gammas from the LOPRA reactor were contributing to the high badge reading because past practice was not to remove the LOPRA core to a retracted storage position when not in operation. The dose recorded at this location in 1992 was 390 mrem and the projected value for 1993 is 220 mrem, with 100 mrem subtracted from both due to natural background.
'lhis would be a reduction of 45% if the projection holds.
Remedi.al Action: Approximately 13 tons of shielding were installed on the middle level of the biological shield and reduced the dose rate from N-16 to one third of the befbre shielding measurements. This shielding has also contributed to a reduction in dose rates in the control room area and at the North and East Building Walls.
l'unhermore, the operations staffhas now adopted a policy of retracting the LOPRA core to the storage position when not in use. In addition, the water level in both the LOPRA and TRIGA cores has been maintained at a level 2
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, approximately 6" higher than past practice reducing dose rates over each pool by about a third.
c) Beam Pon Streaming from open beam port experiments and panially ineffective shielding in the East
'throughport was determined to be the cause of the elevated readings on the center of the East Wall. The dose recorded in this location for 1992 was 170 mrem and the projected dose for 1993 is 40 mrem, with 100 mrem subtracted for natural background. This represents a possible reduction of 75% if the projection holds.
Remedial Action: Approximately 3 tons of shielding was added to the Blockhouse Wall at the east end raising it to a height within the building which is higher than that of any person standing on the ground next to the building at the east exterior wall. In addition, it has become policy to place a mobile beam catcher in front of the East
'Ihroughport, when it is not needed elsewhere, reducing the dose in the general area of the Blockhouse interior by about a third.
d) Elevated doses on the Nonh Wall are not really a problem because the fenced in area around the Cooling Towers renders this region inaccessible. Funhermore, the additional shielding of the N-16 gamma on the middle level of the biological shield has brought the 1993 projected dose for this location to 100 mrem with background subtracted and this is within the fenced area.
l Retnedial_ Action: No funher action required.
e) Transfer all Radwaste to the Campus Ilealth Physics Section for disposal. This process is underway.
1 Remedial Action: No further action required.
Demonstration of Need i
As one can easily see from the above sununary we have taken reasonable measures to reduce the Site Boundary dose to AIARA. Nevertheless, there remains the distinct possibility that one or more of the monitored locations will record a dose in excess of 100 mrem for 1994 and beyond. Because this potential exists it could become necessary for reactor operations to be cunailed to comply with the 0.1-rem / Year limit if this application is not reviewed favorably and the exemption granted. This would severely impact the mission of the nuclear reactor i
laboratory to provide opponunities for teaching, research and community ser ice in all areas of science and engineering represented on the campus that may benefit from ready access to a reactor, and to provide similar senices on a regional and national basis.
Expected duration of operations in excess of the limit The life of the facility.
(2) The licenseqigogram to assess and control dose within the 0.5 rem (5 mSv) annuallimit; Progranuo assess. dose Site Boundary dose will continue to be monitored with TLDs. A method to establish the correct value for subtraction of natural background radiation for this geographical area is currently under evaluation but is expected to be approximately 0.1 rem. This value will be deducted from the dose values recorded by the TLDs monitoring the Site Houndary. Furthennore, it is imponant to remember that the recorded doses noted above are "not real doses to persons actually exposed." Since our Site Boundary is essentially the walls of the Reactor l
Building and the building is surrounded by parking lots and grassy unoccupied areas it is highly unlikely that an individual member of the general public could receive a dose remotely close to the 0.1 rem limit by passing by 3
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1 our facilit'y. The TLDs monitoring the nearest nonnally occupied space, an ofIice facility, have not shown any recordable dose above the natural background.
hogdm_{o control dose in keeping with the requirements of the revised Part 20 a formal and documented Radiation Protection and AIARA program will be implemented on January 1,1994. These programs are cmrently being drafted and will include measures to maintain the Site Boundary dose A' ARA in the same fashion we have outlined above.
Those measures resulted in a significant reduction for 1992 and further reductions are expected at the close of q
1993.
1 (3)1heyrocedures to be followed to maintain the dose as low as is reasonably achievable.
Compliance with the Radiation Protection and ALARA programs will ensure that the annual dose is maintained AIARA.
Respectfully, W
Richard L llolm Reactor Supenisor Q'
Dan F. Ilang 9
Interim Director, Nuclear Reactor Laboratory i
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,9 l Y f l / / l Q7 A : A. P ^ O ll' rclay G. Jones //
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Ilead, Department of Nuclear Engineering Mak/mak Attachment ec: Regional Administrator, LJSNRC, Region Ill M. Kaczor P. Shafer.
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