ML13317A679
| ML13317A679 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/24/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Dietch R Southern California Edison Co |
| References | |
| LSO5-81-09-062, LSO5-81-9-62, NUDOCS 8110080625 | |
| Download: ML13317A679 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 September 24, 1981 Docket No. 50-206 LS05-81-09-062 DISTRIBUTION A
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NRC PDR Gray File
- LPDR, EMcKenna Mr. R. Dietch, Vice President TERA Nuclear Engineering and Operations NSIC Southern California Edison Company ORB#5 RF 2244 Walnut Grove Avenue DCrutchfield Post Office Box 800 SNowicki Rosemead, California 91770 HSmith
'OELD
Dear Mr. Dietch:
OE 3
OI&E (3)
SUBJECT:
SLIGHTLY CONTAMINATED-BEACH SAND - SAN ONOFRE UNIT 1 Your letter'dated July 16, 1981, requested approval to backfill a recently excavated pit that contained slightly contaminated sand at its bottom.
The contamination was discovered on May 10, 1981, during a routine survey on the beach west of the San Onofre:Nuclear Generating Station Unit 1 seawall.
The contaminated sand was uncovered during construction of the beach walkway project outside of the seawall.
We have evaluated the contamination levels existing at the bottom of the pit and have found that they do not pose a significant hazard to the public health and safety and, therefore, backfilling is acceptable. The conclusions of the enclosed evaluation were provided to your staff by telephone so that backfilling could proceed.
Sincerely, Original sigped y Dennia U.. frtchf9ie14 Dennis M. Crutchfield, Chief Operating Reactors Branch #5 Division of Licensing
Enclosure:
Evaluation cc w/enclosure:
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Mr. September 24, 1981 cc w/enclosure:
Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Orrick, Herrington & Sutcliffe 600 Montgomery Street San Francisco, California 94111 Harry B. Stoehr San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector/San Onofre NPS c/o U. S. NRC P. 0. Box 4329 San Clemente, California 92672 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 Mayor City of San Clemente San Clemente, California 92672 Chairman Board of Supervisors County of San Diego
-San Diego, California 92101 California Department of Health ATTN: Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814 U. S. Environmental Protection Agency Region IX Office ATTN: Regional Radiation Representative 215 Freemont Street San Francisco, California 94111
Enclosure EVALUATION OF CONTAMINATED BFACH SAND AT SAN ONOFRE INTRODUCTION By letter from Southern California Edison Company (SCEC) 1 to U.S.
NRC dated July 16, 1981, SCEC requested approval to backfill a recently excavated pit that contained slightly contaminated sand at.its bottom.
The pit was origin ally excavated to remove contaminated sand.
This enclosure proVides an eval uation of potential hazard to the public health and safety resulting from backfilling the pit and leaving the slightly contaminated sand at its bottom.
The sand removed from the pit with higher contamination levels has been trans ported to a waste disposal site.
We have evaluated the environmental consequences of this action on the basis of three different criteria and found in each case that it does not pose a hazard to the public health and safety.
We, therefore, recommend approving the backfilling action proposed by SCEC.
EVALUATION EPA Proposed Rule:
In the memorandum from K.P. Baskin to D.M. Crutchfield dated July 16, 1981, the average concentration of radiocesium-137 at the bottom of the pit was described as being less than 5.0 x 10-77 pCi/g.
In telephone communication between Mr.Yuhas (Region V inspector) and W. Pasciak, the staff was informed that radiocesium-137 was the only measurable radionuclide at the bottom of 2
the pit.
Current EPA proposed disposal standards for inactive uranium processing sites 3 stipulate environmental standards for cleanup of open lands.
They apply specif ieally to average concentrations of radium-226, a radionuclide significantly more hazardous than Cs-137, attributable to residual radioactive material from any designated processing site and are not to exceed 5 pCi/g.
-2 Since radium-226 is significantly more hazardous than Cs-137, and since the average levels of Cs-137 are about 10 times smaller than this limit for radium-226, this comparison suggests that the levels of Cs-137 at the bottom of the pit are not a significant hazard to the public health and safety.
Dose via Fish Consumption In the July 16, 1981 memorandum noted above, it is stated.that the total activity of Cs-137 in the sand at the bottom of the pit is about 50 to 200 micro-curies. A dose to humans can be estimated for the fish consumption pathway based on the-assumption that the cesium diffuses into the ocean water through-the ground.
On the basis that the entire 200 micro-curies of Cs-137 reaches the ocean and is mixed into an area of about 1/4 square mile by 30' deep, and an individual consumes 20 kg of fishes from this area, the individual would receive a dose of less than 1 mrem, or about 1% of annual natural background (methods described in Regulatory Guide 1.109 were used for this estimate').
A dose of 1 mrem is considered to be negligible as it is well below existing criteria for protection of the public from radiation doses, and suggests that the 1-vels of Cs-137 at the bottom of the pit are not a significant hazard to the public health and safety.
External Dose Rate In the July 16, 1981 memorandum noted above, it is stated that the exposure rate above the surface of the bottom of the pit is 5 micro-R.per hour. After the pit is backfilled, the dose rate on the beach surface above the pit loca tion will be negligible. Even if, however, the dose rate is the same on
-3 the beach surface as it is at the bottom of the pit, a person would have to spend 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> a day for 300 days a year to receive a dose of 12 mrad per year.
A dose of 12 mrad is about 12% of the natural background dose and within statistics of natural background fluctuation.
These low exposure rates expected after backfill is completed, suggest that these contaminants do not pose a significant public hazard.
CONCLUSION The potential hazards to the public health and safety from the slightly con taminated sand at the bottom of the pit have been evaluated and found to be negligible. Therefore, we conclude that backfilling the pit without removal of the slightly contaminated sand at its bottom is acceptable.
REFERENCES
- 1. Letter from Southern California Edison Co. to U.S. NRC dated July 16, 1981.
- 2. Telephone conversation between Mr. Uhas (NRC Inspector) and W. Pasciak (RAB staff) on July-29, 1981.
- 3.
EPA Proposed Rule for disposal standards for inactive uranium processing sites, 46 FR 2556-2563, January 9, 1981.
- 4. U.S. NRC Regulatory Guide 1.109 "Calculation of Annual Doses to Man From Routine Releases of Reactor Effluents for the Purpose of Evaluating Com pliance with 10 CFR Part 50, Appendix I, Rev. 1, Octo.ber 1977.