ML20235Q381

Forwards Experiment 2, Continued Analysis of Activation Products in Reactor Structure (Thermal Column), as Second Step in Planning Pocess for Decommissioning.Univ Proposes to Unload Graphite from Thermal Column to Make Survey

ML20235Q381
Person / Time
Site:	05000148
Issue date:	09/23/1987
From:	Rosson H KANSAS, UNIV. OF, LAWRENCE, KS
To:	Alexander Adams Office of Nuclear Reactor Regulation
References
NUDOCS 8710070578
Download: ML20235Q381 (3)

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THE UNIVERSITY OF KANSAS LAWRENCE, KANSAS 66045-2223

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~g,@d' DEPARTMENT OF CHEMICAL AND PETROLEUM ENGINEERING YaNNs September 23, 1987 Mr. Alexander Adams, Jr.

Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Re License R-78, Docket 50-148

Dear A1:

As the second step in our planning process for decommissioning, we would like to obtain better information about the activation products within the thermal column and thermal column structure. We propose to unload the graphite from the thermal column and make a survey to estimate residual activity.

Enclosed is a written procedure and hazards analysis. We seek your approval.

Sincerely, Harold F. Rosson i Reactor Director i Enclosure Copy: Nuclear Reactor Committee  !

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J EXPERIMENT #2 Continued Analysis of Activation Products in the Reactor Structure (Thennal Column)

The purpose of the; proposed experiment is to continue to determine the types and quantities (if possible) of activation products in the shielding structure of the former reactor.

We have checked the radiation levels in the beam port (previously.

approved experiment) . With plugs removed, no rpdiation fields could be measured at the beam port entrance (approximately ,

0.003 mR/hr). However, the inner plugs have activation products in the metal screws set in the plugs.

Spectra indicate this activity to be Co 60. Highest dose rates six ' inches from the screws was 1.8 mR/hr for an approximate estimate of 0.030 mci of activity. Only one beam port has been examined. No removable activity was found on the plugs or screws. The spectra obtained in the tank also correspond to Co 60 spectra. Based on these findings, we believe that most of the activity may be in the framework which supports the thermal column. We now propose an experiment to determine the validity of our assumption and to determine more accurately the bulk of activity which will need to be handled so that an appropriate decommissioning plan can be submitted at a later date.

Specifically, we propose to remove the graphite from the thermal column and to store the graphite and the beam plugs within the storage tank in the reactor bay or in the reactor tank itself. We would then evaluate, as well as we can, the location, source and type of induced activity remaining. (Note:

Our desire to store the plugs with the graphite is to remove the contributions they would make to our next evaluation.)

Hazard Analysis & Procedure I. Removal and storage of beam port plugs. Renoval will proceed as specified in the previously approved procedure. Beam plugs will be re-inserted if the dose rate at the entrance of any beam port or at the accessible portion (top) of the storage area is greater than 0.01 mR/hr from that source.

II. Removal of graphite frca thermal column. Since the maximum dose rate inside the tank is 30 mR/hr, we do not expect dose rates appreciably higher than that in the thermal column area. However, dose rates always will be measured frun a protected area as the thermal colum is opened and as the graphite stringers are removed. If dose rates greater than 50 mR/hr at i foot are observed, further removal would be terminated.

i Standard protective gear (lab coats, gloves arri drop cloths) will be used '

in handling the graphite. Wipe tests will be made of the graphite and evaluated as they are removed. Graphite will be placed on drop cloths on pallets and will be directly monitored for activity in addition to the wipe tests. Only personnel performing the experiments will be in the room. i No one will be allowed to position themselves in front of the open j thermal column except for those engaged in the removal process. If necessary, time limits will be placed on the time spent in the thermal column. ALARA

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i will be considered to be achieved if total exposures are kept below 0.2 person-rems. Re-evaluation of procedures will be accomplished if this 1 arbitrary limit is approached. Self reading dosimeters will be worn in addition to film badges.

Drop clothes will be monitored. If contrary to our expectations, contamination is found, they will be disposed of in our radioactive waste. >

Spectra wjl1 be obtained as needed.

After our evaluation and removal of the graphite, the thermal column door will be closed and locked. Reconis will be made of the relocking. They will also be closed and locked at the end of a given day's procedure.

We would also lilw to store the " pipes" which Icd to the control rods in i one of the two tanks as well. They currently are lying across the top rails of the reactor structure, { j I

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