ML20133B783

Safety Evaluation Re Util 850208 SER Concerning Reactor Bldg Decontamination & Dose Reduction Activities.Licensee Efforts in Continuing Decontamination & Dose Reduction Activities Meet Programmatic ALARA Goals

ML20133B783
Person / Time
Site:	Three Mile Island
Issue date:	09/25/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20133B768	List: ML20133B765 ML20133B783
References
NUDOCS 8510070109
Download: ML20133B783 (6)

Text

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ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION , '

REACTOR BUILDING DECONTAMINATION AND DOSE REDUCTION A. Introduction .

On February 8, 1985, GPU Nuclear Corporation (GPUNC) submitted to the staff, for review, a Safety Evaluation Report (SER) for the Reactor Building (RB)

Decontamination and Dose Reduction Activities. On March'25, 1985, GPUNC submitted Supplement 1 to the SER. The GPUNC SER assesses the safety aspects of the scheduled RB decontamination and dose reduction activities for 1985 and the first quarter of 1986. On July 26, 1985, the staff met -.

with the licensee to discuss the subject SER. On August 7, 1985, GPUNC submitted to the staff a letter attaching the additional information J requested by the staff at the July 26, 1985 meeting.

1 B. Discussion .

The subject SER is an update of earlier safety evaluations from GPUNC

' (Radiological and Safety Evaluation of Ongoing ont'ainment Building, Decontamination and Dose Reduction Activities for TMI-2 Recovery, submitted by GPUNC on September 23, 1982 and revised on September 29,1983). The l

criteria for planned decontamination activities remain the same as

( discussed in the earlier safety evaluations, i.e., decontamination and dose i

reduction activities must either exhibit a net positive man-rem savings or i be designated as a desired cleanup. endpoint. Since the 1985 projected man-hour estimate indicates that the reactor disassembfy an'd defueling (RD&D) activities will represent the largest expe'nditure of in-containment man-hours, the 1985 - 1986 reactor building decontamination effort will be concentrated in those areas where the greatest reduction in RD&D 8510070109 850925 DR ADOCK 0 % gO

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It is also recognized that to occupational exposure can be realized.

achieve the greatest ALARA effectiveness, these decontamination and do reduction activities should be performed as early in the RD&D activity.as permitted by other constraints such as resources and scheduling.

C. Planned Dose Reduction Activities Areas in the reactor building where large amounts of man-rem exposure are estimated for work associated with RD&D are candidates These. areas are prioritized for decontami_

and dose reduction activities.

nation based on estimation of achieving the greatest net man-rem saving _

Based on current radiological characterization during RD&D activities.

information, GPU'NC has identified several sources for planned dose re-

-i duction activities. Those major sources are: ,

Reactor Building (RB) Air Coolers - The RB air coolers contribbte (1)

' about 50 mrem /hr to the adjacent area on e' leva' tion 305' and the f Shielding of the air coolers is planned hatch area on elevation 347'.

Shielding does to significantly reduce the dose rate contribution.

not preclude future decontamination and/or dismantlement. ' ,

Floors - Floor contamination contributes.to general area dose.. In

' (2) past, the licensee has successfully reduced surface contaminati

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levels and general area dose rates on elevation 34'7'.by'scabbling.

Scabbling on the 305' elevation by the enclo' sed stairwell and .

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- - - - - - , - -.-.--,,---,,,.m+ g-,,,--- t v-~ w e* e- g e e, , s---, , , , . , - + + - t+--- ,- ris, w + + w- + = - ,- __.

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equipment hatch has recently been completed. Scabbling in combination with shielding of the floor hatch will reduce the transit dose to the RD&D workers and improve the access to the 282' elevation for robotic work. .

(3) The open stairwell exhibits high dose rates contribu' ting to transit exposure of the workers. Reshielding of the open stairwell at the 305' elevation is being evalua'ted.' In addition to lowering the -

transit dose, reshielding may be. advantageous in providing access to the basement level for robotic characterization of the area below the reactor coolant drain tank vent line.

(4) The overhead contamination at the 305' elevation results in a'n exposure field of 200 mR/hr just below the overheads. Characterization data for the contamination deposited between cables, cable insulatibn and other surfaces is being obtained. .

(5) The 305' elevation floor hatch area dose rate is about 150 mR/hr following shielding emplacement. This source contributes'to worker exposure during lifting activities to the 282' and 347' elevations and further shielding of decontamination may be warranted.

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l (6) The D-ring internals and walkways are major source's of contamination contributing to worker dose during RD&D and 'ex-vessel fuel character-ization activities in the D-rings. The licensee plans to evaluate l

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J man-rem expenditure and potential savings prior to implementing dose reduction activities such as water flushing. .

(7) Contamination at several areas such as the refueling canal, the ,

internals indexing fixture (IIF) platform, the main fuel handling bridge, cable trays and the seal table contributes t'o the general area dose during RD&D activities. The licensee is evaluating dose reduction techniques for these ardas in view of the large number of projected man-hours for RD&D. .

The dose reduction techniques (i.e., shielding, scabbling, flushing with water, steam and vacuum cleaning and the application of strippable-coatings) are methods the licensee has employed since the beginnin'g of the

. dose reduction program in 1982. This decontamination. experience is an important element in the licensee's planning of future dose reduction

- activities in order to optimize effectiveness, positive man-rem savings, resource utilization and scheduling. The licensee has committed to review and plan all dose reduction activities so as to provide a work environment for the RD&D effort that is consistent with the ALARA concept,'thereby maintaining the overall cleanup activity occupational dose ALARA. -

D. Occupational Exposure i The total occupational exposure for dose reduction activities in support of the RD&D effort is estirated to be 1.ess than 200 'wan-rem. This estimate.is 1

likely to be conservative based on past experience. Because of the l

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improved environment in the reactor building, many factors such as the decreased airborne contamination. levels (such that respirators are not necessary in many instances), and the completion of the Reactor Building Chilled Water System (to decrease the ambient temperatures) will likely, result in improvements in worker efficiency. The conservative man-rem estimate is well within the estimated worker exposure for' decontamination activities in the Supplement I to the Programmatic Environmental Impact Statement (NUREG-0683).

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E. Offsite Radiological Doses .

Decontamination activities in the reactor building will not significantly increase the airborne particulate activity in the reactor building. In fact, over the long term, airborne particulate activity should dec'rease as surface decontamination activities progress. ' Water flushing will be per-formed using processed accident generated water which contains tritium.

= Based on past experience, the licensee estimates th'at the average airborne tritium level in the building atmosphere will increase by a factor of four over the present average concentration during the time when flushing is taking place. The calculated airborne tritium release to the e'nvironment is estimated to be about 45,Ci per year. The dose to the maximum exposed offsite individual due to airborne release pathways is estimated to.be less than 0.2 mrem (whole body) per year . Th'is is well within the offsite dose limits in Appendix B, Section 2.1 of the THI-2 Technical Specifications.

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F. Conclusion and 50.59 Evaluation Based on the above discussion, the staff concludes that the licensee's.

planned effort in continuing the decontamination and dose reduction activ-ities in the reactor building to support RD&D efforts will result in ,

overall man-rem savings and meet the programatic ALARA goal. The staff also concludes that, based on the criteria of 10 CFR 50.5'9, the planned activity is not an unreviewed safety issue. The planned activity will not increase the probability of occurrence'or the consequences of an accident or malfunction of equipment important-to-safety previously evaluated. It does not create the possibility for an accident or malfunction of a different type than any evaluated previously or reduce the margin of safety.

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