ML13330A347
| ML13330A347 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/16/1981 |
| From: | Baskin K Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8107210403 | |
| Download: ML13330A347 (3) | |
Text
Southern California Edison Company P. 0. Box 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 K. P. BASKIN July 16, 1981 TELEPHONE MANAGER OF NUCLEAR ENGINEERING, (213) 572-1401 SAFETY, AND LICENSING Director, Office of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5
)
Division of Licensing U. S. Nuclear Regulatory Commission o
Washington, D.C. 20555 A-v r L Lw Gentlemen:
JUL 20 1981w U.S. NUCLEAR REGULATORY
Subject:
Disposal of Contaminated Beach Sand" COMMISSION San Onofre Nuclear Generating Station Unit 1
/
During an NRC inspection conducted by Region V personne olt June 1-3, 1981, it was suggested that Southern California Edison (SCE) advise you of its intended action in connection with the continued excavation of low activity level in beach sand. Accordingly this letter provides notification of SCE's plans to cease excavation of beach sand contaminated with minimal levels of radioactivity and begin backfilling operations.
Contamination was discovered on May 10, 1981, during a routine survey on the beach west of the SONGS 1 seawall.
A Radiation level of 200 uR/hr was found on contact with an out of service drainline recently uncovered during excavation work associated with a proposed beach walkway along the Units 2 and 3.
seawall.
Radiation levels on the beach directly in front of the drainline ranged up to 90 uR/hr. Background levels on the beach from plant operation prior to the excavation were approximately 12 uR/hr.
The station yard drainline, which had been capped off and abandoned in place approximately 6 years ago, penetrated the Unit 1 seawall four feet below the present beach elevation.
Subsequently, sample analyses indicated that the sand removed from the drain line contained 3.9 E-4 uCi/g dry weight Cs-137, 3.4 E-5 uCi/g Cs-134, and 5.0 E-6 uCi/g Co-60. The highest concentrations observed in the beach sand were 2.5 E-4 uCi/g Cs-137, 1.2 E-5 uCi/g Cs-134, and 6.6 E-6 uCi/g Co-60. Normal background concentrations observed in control samples from the beach are approximately 6 E-8 uCi/g to 1.2 E-7 uCi/g Cs-137.
8107210403 810716V PDR ADOCK 05000206 P
D. M. Crutchfield, Chief
-2 Based on the above analyses the beach walkway project has been stopped and an extensive sampling and excavation program has been undertaken to define the extent to which the contamination has spread. SCE has been attempting to remove the contaminated material until background levels are reached. Excavation and removal of beach sand has occurred to a depth of 13 feet below the normal beach elevation and covers an area extending approxima ely 25 feet to the west, south, and north of the drainline. To date 21,600 ft of sand in 44 shipments has been disposed of at the U.S. Ecology burial site at Richland, Washington. The estimated cost for this sand disposal is approximately $835,000.
Presently, the highest concentrations of sand activity remaining in the excavation are less than 5.0 E-6 uCi/g Cs-137 while average concentrations are less than 5.0 E-7 uCi/g Cs-137. Assuming that background sand activity levels could be reached by excavating an additional 10 feet below the present pit depth, a new problem is encountered. Excavation of a twenty-three foot deep pit in the beach would require either installation of a new deep well point system or modification of the existing well point system to lower the local water table an additional 10 feet. An alternative is to develop a means of moving large volumes of liquified sand and drying the material prior to shipment to a burial site.
None of these alternatives is considered practical but the one offering the highest probability of success is the installation/modification of a well point system with an estimated cost of
$500,000.
Excavation to a depth 10 feet below the present pit elevation represents approximately 10,000 ft3 additional sand with a total activity ranging from 0.2 to 0.05 mCi.
Disposal of this material combined with the well point system represents an additional cost of $850,000 for 0.2 to 0.05 mCi of total activity. Continued disposal of such low activity material in burial sites of limited capacity is also a concern to SCE from an overall effective burial space utilization point of view.
Further, all dose rates measured three feet above the existing contaminated sand at the bottom of the excavation are less then 5uR/hr above background levels existing during routine plant operations. Backfill, using uncontaminated sand, will further reduce any direct radiation levels at the beach surface level.
After the excavated area is backfilled and the 2" thick asphalt beach walkway is completed, radiation levels on the beach are expected to be at normal background levels. Since no drinking water or ingestion pathway will exist to the public, no health hazard will result from ceasing removal of
D. M. Crutchfield, Chief
-3 additional beach sand at this time. Therefore, continued excavation of beach sand cannot be justified from a cost-benefit point of view. Consequently, SCE will terminate excavation work and begin backfilling.
The above information has previously been discussed with members of your staff. Should you disagree with this action, please notify me as soon as possible. If you require any further information on this subject, please contact me.
Very truly yours, cc: R. H. Engelken, Director, OIE, Region V L. F. Miller -
USNRC Resident Inspector