ML20087A077
| ML20087A077 | |
| Person / Time | |
|---|---|
| Site: | U.S. Geological Survey |
| Issue date: | 12/30/1991 |
| From: | Danni Smith INTERIOR, DEPT. OF, GEOLOGICAL SURVEY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9201080160 | |
| Download: ML20087A077 (4) | |
Text
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" d. United States Department of the Interior Iwam_J gu.
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i GEOLOGICAL SURVEY sumusumammum DOX 25046 M.S.
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"a DENVER FEDERAL CENTER DENVER, COI.ORADO 80225 IN 8INY RtFik 10-BRANCH OF GEOCHEMISTRY December 30, 1991 Docket No. 50-274 License No. R-113 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555-Dear Sirst SUBJEC
" PLY TO A NOTICE OF VIOLATION This letter is an amendment to our responso dated November 26, 1991, to your Notice of Violation dated October 30, 1991.
This amendment is to the response for the first violation in the referenced notice.
We agree that Experimont 0-13 could contain an amount of Ar-41 that would cause greater than 3% MPC in the reactor room, llowever, routine operation at full power since initial reactor operation in 1969 results in Ar-41 levels from 100% to 200% MPC. Thus, the 3%
MPC value of llazards Summary Report Section 8.2.1 has been incorrect and violated since initial facility operation.
The error results largely from the use of data from a facility with a reactor room of much larger air volumo.
This error was not discovered during the compliance inspection of June, 1991, but was identified by our staff in July, 1991, We have submitted-revised 1
analyses for the Ar-41 hazard produced in the facility and those analyses were accepted by NRR in October, 1991.
We submitted a revised section 8.2.1 of the Hazards Summary Report to NRR on November 13, 1991.
During the Ar-41 hazard analysis review by NRR, it was pointed out to our staff that the 10 CFR 20 Appendix B value for Ar-41 is not applicable to our facility because the argon cloud is not a semispherical, infinite cloud as assumed in the Appendix.
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8-2' inse'rtion of a fuel element into the core while the reactor is operating at a steady-state power that the maximum reactivity that could be introduced in a single action would be $1.13.
Since step additions of reactivity greater than this value are made on a routine basis when the reactor is pulsed, the addition of one fuel element (or even two or three) into the critical reactor core would present no hazard.
8.2.
PRODUCTION AND RELEASE OF RADIOACTIVE GASCH 8.2.1.
Exnerimental Facilities In the TRIGA Mark I reactor installation, the pneumatic transfer tube, and the rotary specimen rack contain air.
In addition, the main reactor room is of course also filled with air that is in contact with the reactor pool. Of the radioisotopes produced in these air cavities, argon-41 is the most significant with respect to hazards and nitrogen-16 is considerably less significant.
At prolonged 1000-kw operation with no air exchange, the argon-41 activity in the pneumatic' transfer tube is 4 mci', and in the rotary specimen rack it is 860 mci.
A measurabic argon-41
,. release from the rotary specimen rack and reactor pool water occurs during normal 1000-kw operation.
The release of argon-41 from the reactor pool water is discussed in Section 8.2.2.
Release of argon-41 into the reactor room is evaluated by representing the room as a 'temisphere of 550 cm radius.
This I
results in a whole body dose from argon-41 that is a factor of 33 less then the dose received by an infinite radius hemispherical cloud, as assumed in 10 CFR 20 Appendix B. Therefore, the values of i
Appendix B do not directly correspond to the radiological hazard presented by the argon-41. dispersed in the reactor room.
Ope.ational data shows that a typical argon-41 concentration in the reactor room during 1000-kw operation is '4.35 x 10 6 uCi/ml.
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A_ typical stay time in this envi annent of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> per week would give a whole body dose of abou' 16.5 mrem per calendar quarter, Therefore, if a person remair 4 in the reactor room for 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per week under the same conditj ns, a quarterly whole body dose of about 82.5 mrem would result.
..ese doses are well within the limitations of 10 CFR 20.
Routine
.leeses of argon-41 from reactor operation do not present r, signi' tcant radiological hazard to the staf f.
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g_3 Accidental flooding of an air-filled experimental cavity could release larger quantities of argon-41 into the reactor roca..
Flooding of the rotary specimen rack could result in the acute release of 860 mci into the reactor room instantaneously.
If the room ventilation system is operating normally, this activity will remain in the room for about 12 minutes.
The maximum argon-41 concentration in the room would be 2.46 x 10 uC1/ml, assuming 4
uniform mixing.
Using the finite hemisphere cloud approximaticn, this discharge of 860 mci into the reactor room would give a whole body dose of about 17.9 mrem to a person positioned in the center of the room.
Comparing this accident with the release of 10 Ci of cobalt-60 equivalent activity disc.
'ed in Section 8.3, an accidental release of 10 Ci of argon-41 would give a whole body doce of about 208 mrem.
All of these doces are well below the occ"cational limits of 10 CFR 20.
The routine exposure of personnel in unrestricted areas from argon-41 releases is evaluated by assuming a pc son is standing next to the reactor building wall, at a distance of 8 meters from the release point.
An annual release of 25 Ci of argor: 41 would give a whole body dose of less than 17 mrem per year to a person near the building wall.
The acute release of 3 Ci c argon-41 would give a whole body dose of about 2 mrom to a person standing near the reactor building wall.
l In summary, the argon-41 produced in the reactb2 cavities is not a sigt.ificant hazard to operating personnel or the general public.
I 8.2.2 Roiease__of Arnon-41 from Reactor Water Aargon-41 activity in the reactor pool water results from irradiation of the air dissolved in the water.
The following calculations were performed to evaluate the rate of argon-41 escaping from the reactor pool water into the reactor room.
The calculations show that the argon-41 decays while in the water, and most of the radiation is safely absorbed in the water.
The changes in argon-41 concentration in the reactor, in the pool water external to the reactor, and in the air of the reactor room are given by dN V
=V3N a
-N (v 4 V 304l + A4l 4l g+N2 D' g) 3 3
Our revised Section B.2.1 corrects this error by removing references to MPC values.
Futuro experimental evaluations for Ar-41 hazard will be evaluated against the revised hazard analysis.
Sinccroly,,
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David D. Smith Reactor Administrator
Enclosure:
Rovised Section 8.2.1 of llazards Summary Report Copy to:
U.S. 14uclear Regulatory Commission Regional Administrator 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 Tim DeBoy, USGS r, "
Subscribed and affirmed before me this 7e'Eday of December, 1991.
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