ML20028A427
| ML20028A427 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 11/16/1982 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20028A426 | List: |
| References | |
| NUDOCS 8211220137 | |
| Download: ML20028A427 (3) | |
Text
ESTIMATION OF TOTAL BODY GAMMA RADIATION DOSE TO AN INDIVIDUAL FROM rec 0CATED CONTAMINATED S0Il AT OYSTER CREEK
===1.
Background===
By letter dated October 27, 1982, GPU Nuclear staff proposes to remove from a radiation controlled area 17,000 cubic feet of soil contaminated with varying levels of Co-60, Cs-137, Cs-134 and Mn-54 (See Attachment I of the letter) and bury it in another area outside the radiation controlled area, but within the site boundary, in trenches with a minimum cover of six (6) inches of clean soil.
The letter also stated that GPU Nuclear may pave this area with asphalt in the near future. The licensee provides'the justification for their work in their attachment II to the letter.
2.
Evaluation (a) Direct gamma radiation doses sc-The direct gamma radiation doses to the total body of an individual were estimated for several different occupancy conditions using Regulatory
. Guide 1.109 methods and the data and information provided in licensee's letter and attachments.
The occupancy conditions considered are (1) continuous occupancy of a person on the central portion of the surface of the six (6) inches of cican soil for a whole year (extremely conservative and highly unlikely).
(ii) occupancy for 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> per year by an employee on the surface of the soil.
A conservative assumption is made in the staff calculations that the gamma ray source term consisted of a uniformly contaminated ground plane six (6) inches beneath the clean soil surface and that all the radioactivity in the relocated soil was uniformly distributed on the contaminated ground plane.
The staff also assumed that the effective gamma radiation energy is about 1 MeV.
Actually the gamma ray energies range from about 0.7 to 1.3 MeV.
8211220137 821116
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. The staff's calculations were based upon average concentrations of 5 pCi/g Co-60 and 3 pCi/g Cs-137.
A shielding factor of 0.18 was determined based upon data
- on attenuation of dose rates due to 1 MeV gamma radiation by the six (6) inch layer of covering soil. Staff estimates indicate that a person continuously occupying this location will receive a total body dose of 60 mrom per year.
For a worker who spends only 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> a year on the clean soil surface the total body dose is reduced to 14 mrem /yr.
If the licensee paved this area with asphalt, and if the asphalt is about six (6) inches thick, the total body dose to a worker will further be reduced by a factor of about six (6) to less than 3 mrem per ye.r.
For a member of the public who infrequently visits the
'"# 0yster Creek facility and who spends much less time at this location than a worker, the total body dose will be proportionately lower.
3.
Conclusion These estimated doses are negligibly small from the standpoint of occupational exposure limits and acceptably small from the standpoint of non-occupational exposure limits.
They are close to or within the dose design objectives of -
10 CFR Part 50, Appendix I for controlling radioactive effluents from light-water l
l cooled reactors and are fiithin nominal spatial ~and temporal variations in annual natural background exposure. Based on these conservative esticates of the total body doses due to direct gamma radiation to different types of individuals,
- " Shielding Characteristics of Air, Soil, Water, Wood and Other Common Materials, Vol. 2.
Attenuation of Gamma Rays and Neutrons" by David Spielberg, WKNL-89 (Vol. 2), March 25,1957.
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2 1 the staff concludes that gama radiation from the contaminated soil buried inder about six (6) inches of clean soil will not affect the health and safety of the public or personnel at this site and therefore the licensee's plan is approved.
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