ML20245G193

Clarifies Data for Radiation Levels Provided in . Remaining Areas Need Only Be Designated as Radiation Areas. Revised Data for Radiation Levels & Shield Door Evaluation Encl

ML20245G193
Person / Time
Site:	Idaho State University
Issue date:	04/14/1989
From:	Adam Wilson IDAHO STATE UNIV., POCATELLO, ID
To:	Michaels T Office of Nuclear Reactor Regulation
References
NUDOCS 8905030091
Download: ML20245G193 (4)

Text

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J' G vs Idaho State University Pocatello, Idaho 83209-0009 College' of Engineering Box 8060 (208) 236-2902 Apri1 14, 1989 L

l Mr. Theodore Michaels Standardization and Special~

Projects Branch Division of Licensing U.S. Nuclear. Regulatory Commission Washington, D.C. 20555 REF: Docket No. 50-284

Dear Mr. Michaels:

I am supplying the clarification needed for my previous letter of February 15, 1989.

The data for the' radiation levels provided as an enclosure with the February 15 letter were all taken with the reactor operating at a power level-of five (5) watts and with the shield doors on top of the reactor closed. The graphite thermal column was in place during the measurements since that is the column which is used with-the neutron radiography experiment. I have provided a revised copy of the enclosure with the power level indicated above the table of dose rates. I would appreciate it if you would substitute this diagram and table for the one sent on February 15.

In order to predict what the dose rates would be in the various locations at ten (10) watts, the values in the table were simply doubled. It is apparent that the dose rate would exceed 100 mrem /hr only in those areas already designated as high radiation areas. . Therefore, the remaining areas need only be designated as radiation areas which is consistent with our present practice.

i We have subsequently made measurements in the high radiation area j on toplof the reactor to evaluate the effect of the movable shield doors over the thermal column area. These readings were taken when the reactor was at a power level of five tenths (0.5) watts with the graphite thermal column in place. Readings were taken with the shield doors open and with them closed *. assess the value of the doors. Readings are shown on the seconk enclo-sure sheet entitled " Shield Door Evaluation."

8905030091 890414 PDR ADOCK 05000284; pM P PNU.'

ISU is An EqualOpportunity Employer ll L __2______________ _

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l Mr. Theodore Michaels i April 14, 1989 J Page 2 l I

It is apparent that closing the shield doors reduces the radia-  !

tion levels in the high radiation area on top of the reactor sig- l nificantly. Even more important, however, is the reduction in dose rate within the rest of the laboratory. Since the dose rates in these areas are quite low when the reactor is operating at 0.5 watts, it is difficult to get accurate data for the actual reductions. The bottom line on the Shield Door Evaluation table shows values at the console and should be typical of the rest of the lab. The shield doors reduca the radiation level by approxi-mately a factor of two. This reduction is felt to be signifi-cant at a power level of 5.0 watts and is part of our ALARA pro-gram to reduce exposure.

If you have further questions regarding our request for changes l in the Technical Specifications, please let me know.

Sincerely,

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Albert E. Wilson i Reactor Administrator AEW:lk -

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SHIELD DOOR EVALUATION NOTE: 'The following radings were taken with the reactor at a

' power level of 0.5 watts and with the graphite. thermal column in place. Whole body, (WB), readings were taken one meter above the surface indicated. Contact, (C), readings were taken with meter placed on surface indicated. All readings are in mrem /hr. ,

Doors Open Doors Closed Location of Reading Gamma Neutron Gamna Neutron i

Top of Stairs (WB) 2.5 1.0 0.7 0.3 Walkway So. of Doors (WB) 10.0 5.0 1.8 1.0 Above Thermal Column (WB) 22.0 16.0 2.0 1.0 i Top of Thermal Col. (C) 85.0 140.0 -- --

On shield doors (C) - -

14.0 7.0 Operator Position * (WB) 0.3 0.2 0.1 0.1 l

• All readings except operator position are in the designated high radiation area. Operator position is the normal operator loca-

. tion at the operating console.

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