"TENORM [technologically enhanced/concentrated naturally occurring radioactive material] contamination levels in equipment varied widely among types of equipment and geographic region. The geographic areas with the highest equipment readings were northern Texas and the gulf coast crescent from southern Louisiana and Mississippi to the Florida panhandle. Very low levels of TENORM were found in California, Utah, Wyoming, Colorado, and northern Kansas.
According to an API industry-wide survey, approximately 64 percent of the gas producing equipment and 57 percent of the oil production equipment showed radioactivity at or near background levels. TENORM radioactivity levels tend to be highest in water handling equipment. Average exposure levels for this equipment were between 30 to 40 micro Roentgens per hour (μR/hr), which is about 5 times background. Gas processing equipment with the highest levels include the reflux pumps, propane pumps and tanks, other pumps, and product lines. Average radiation levels for this equipment as between 30 to 70 μR/hr. Exposures from some oil production and gas processing equipment exceeded 1 mR/hr.
Gas plant processing equipment is generally contaminated on the surface by lead-210 (Pb-210). However, TENORM may also accumulate in gas plant equipment from radon (Rn-222) gas decay. Radon gas is highly mobile. It originates in underground formations and dissolves in the organic petroleum areas of the gas plant. It concentrates mainly in the more volatile propane and ethane fractions of the gas.
Gas plant scales differ from oil production scales, typically consisting of radon decay products which accumulate on the interior surfaces of plant equipment. Radon itself decays quickly, (its half-life is 3.8 days). As a result, the only radionuclides that affect disposal are the radon decay products polonium-210 (Po-210) and lead-210. Polonium-210 is an alpha emitter with a half-life of 140 days. Pb-210 is a weak beta and gamma emitter with a half-life of 22 years.
Disposal and Reuse: Past Practices: Recycling of Metals
Before the accumulation of TENORM in oil production equipment was recognized, contaminated materials were occasionally recycled for use in making steel products....
Disposal and Reuse: Current Practices -Recycling of Metals:
Now that the petroleum industry is aware of the potential for contamination, they take a number of precautions before recycling:
Loads of scrap metal are surveyed for hidden radioactive sources and TENORM.
Piping and equipment are cleaned before release for recycling at smelters.
Pollution control devices, such as filters and bubblers, are installed in smelter stacks to reduce airborne radiation releases.
Although much of the NORM-contaminated equipment is presently stored in controlled areas, some companies are now cleaning the equipment and proposing to store it at designated disposal sites.
http://www.epa.gov/rpdweb00/tenorm/oilandgas.html
No comments:
Post a Comment