An Evaluation of the Radiation Health Physics Data Collected at a Commercial NORM Oilfield Waste Disposal Facility With Application to Field Production Facilities

Abstract

Abstract Regulations pertaining to naturally occurring radioactive materials (NORM) in oilfield wastes have now been promulgated in many of the major oil & gas producing states (AR, AL, LA, MS, NM, TX, etc ). This paper will evaluate the radiation exposure of workers and members of the general public to these wastes by looking at the radiation health physics data compiled at the largest NORM oilfield waste disposal facility in the country. This facility, owned by Newpark Environmental Services, has been in operation since October, 1994 In this paper, we will assume that the facility (operating under a typical worker protection plan) represents a worst case scenario for exposure to radiation when compared to oil & gas production facilities containing diffuse NORM. Monitoring methods used to determine both external and internal exposure will be described for both occupational doses (not to exceed 5000, millirem (mrem) per year) and doses to individual members of the public (not to exceed 100 mrem per year). Occupational monitoring included measurements of external dose using individual thermoluminescent dosimeters (TLDs), breathing zone air samples (BZA) to determine the potential intake to workers in conjunction with derived air concentration (DAC) limits, and urine bioassay samples to determine actual individual intakes in conjunction with annual limits of intake (ALI). Public monitoring included continuous external gamma monitoring using environmental TLDs at multiple locations around the facility, downwind boundary effluent air monitoring and passive radon monitoring. From these measurements, a total effective dose equivalent (TEDE) can be calculated and compared to the limits for occupational and public exposure. Though the data were analyzed over time in the paper, they can be summarized, since the opening of the facility through September 30, 1996 (24 months), as follows: The average annual TEDE for occupational dose is <5 mrem/year.The same calculation for public exposure is <25 mrem/year. The public dose is higher because 100% occupancy must be assumed, whereas workers exposure is based on actual time on the job. Through the end of 1996 (27 months), 129,999 barrels of NORM oilfield wastes were received with an average specific activity of 131 picoCuries per gram (pCi/g) for 226Ra and 708 pCi/g total activity (the range was 3-5,865 pCi/g 226Ra and 15-28,509 pCi/g total activity).