What is NORM Waste?
Referenced documents
A significant portion of the following information has been extracted from USGS Fact Sheet FS-142-99; Naturally Occurring Radioactive Materials (NORM) in Produced Water and Oil-Field Equipment—An Issue for the Energy Industry and EPA Facts about Radium.
Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) comprise environmentally sourced materials, such as industrial wastes, or by-products having radioactive elements, such as uranium, thorium and potassium and their decay products, such as radium and radon.
Natural radioactive elements are present in very low concentrations in the earth's crust, and are brought to the surface by oil and gas exploration or mining, and by natural processes like radon gas leakage to the atmosphere or dissolution into ground water. An example of TENORM is coal ash produced from coal burning in power plants.
Oil-field NORM
Oil and gas TENORM-NORM is created when produced reservoir fluids carry sulfates to the earth’s surface. Barium, calcium and strontium sulfates are larger compounds, and smaller atoms, such as radium-226 and radium-228, fit into compound empty spaces and are carried in the produced fluids. As produced fluids reach the surface, temperature and pressure changes cause barium, calcium, strontium and radium compounds to precipitate out of solution and form scale on the inside, or the outside of tubulars and/or casing. Concentrations of radium 226 and 228 and decay products such as lead-210 also form sludges in oilfield pits, tanks and lagoons. Radon gas in the natural gas streams concentrate as NORM in gas processing activities.
Radon decays to lead-210, then to bismuth-210, polonium-210 and stabilizes with lead-206. Radon decay elements occur as a shiny film on the inner surface of inlet lines, treating units, pumps and valves associated with propylene, ethane and propane processing systems.
NORM characteristics vary depending on the nature of the waste. NORM may be created in a crystalline form, which is brittle and thin, and can cause flaking to occur in tubulars. NORM formed in carbonate matrix can have a density of 3.5 grams/cubic centimeter and must be noted when packing for transportation. NORM scales may be white or a brown solid, or thick sludge to solid, dry flaky substances.
Cutting and reaming oilfield pipe, removing solids from tanks and pits, and refurbishing gas processing equipment expose employees to particles containing increased levels of emitting radionuclides that pose serious health risks if inhaled or ingested.
“Deposits of oil are found in 30 States, but the vast majority (86 percent) of onshore oil production is concentrated in Texas, Oklahoma, Louisiana, Wyoming, California, Kansas, and New Mexico (fig. 1A).
In 1989 the American Petroleum Institute sponsored a preliminary nationwide reconnaissance of measurable radioactivity at the exterior surfaces of oil-field equipment (Otto, 1989). The results of this nonstatistical sampling indicated that gamma-ray radiation levels exceeded natural background radiation levels at 42 percent of the sites. Radiation levels greater than five times the median background of all sites were found at approximately 10 percent of the sites. Most of the sites with markedly higher radioactivity were concentrated in specific geographical areas, such as the Gulf Coast, northeast Texas, southeast Illinois, and south-central Kansas (fig. 1B). Additional surveys by some State agencies identified radioactive oil-field equipment in northern Michigan and eastern Kentucky. Pipe, casing, fittings, and tanks that have an extended history of contact with produced water are more likely to contain radioactive deposits than other parts of the plumbing system at oil-field production.”
Abundance of Radium in Oil-Field NORM
Measurement of total radioactivity with a hand-held radiation detection instrument permits rapid assessment of a site for NORM contamination, but site cleanup criteria and waste disposal options are based on actual concentrations of radium isotopes. Some specialized field instruments permit rapid estimates of the concentration of radium isotopes, but such estimates require confirmation by careful laboratory analysis of selected subsets of samples. Radium concentrations are generally reported as picocuries/gram (pCi/g) of solid material or picocuries/liter (pCi/L) of water or air. A picocurie equals 2.22 disintegrations-per-minute (dpm).
Figure 3A illustrates the distribution of total radium concentration ( 226 Ra and 228 Ra) in barrels of oil-field NORM waste stored in Louisiana in 1992 (Wascom, 1994). The maximum radium concentration in this waste and in most reported oil-field scale from the U.S. is several thousand pCi/g, although very small quantities of scale have been reported with as much as 400,000 pCi/g of radium.
For comparison, most natural soils and rocks contain approximately 0.5–5 pCi/g of total radium. A uranium ore sample containing 1 weight percent uranium has approximately 3,300 pCi/g of 226 Ra. Most of the radium in older oil-field scale is 226 Ra, because the shorter lived 228 Ra decays with a half-life of 5.8 years.
Figure 3B illustrates the distribution of dissolved 226 Ra concentration in 215 samples of produced water from seven major oil-producing areas (Fisher, 1998). Radium tends to be more abundant in the more saline and chloride-rich varieties of these produced waters. The maximum concentration of dissolved 226 Ra in this limited data set is several thousand pCi/L, but concentrations above 10,000 pCi/L have been reported in the U.S. Produced water also contains dissolved 228 Ra, which is typically one-half to twice the concentration of 226 Ra. For comparison, the U.S. EPA maximum contaminant level for drinking water is 5 pCi/L for total dissolved radium.
REGULATION OF OIL FIELD NORM
“There currently exist no Federal regulations that specifically address the handling and disposal of oil-field NORM wastes. States that have enacted specific NORM regulations include some important oil producers such as Texas, Louisiana, New Mexico, and Mississippi. New NORM regulations or modifications to general radiation protection statutes are under consideration in other major oil-producing states such as California, Kansas, and Oklahoma. Standards for cleanup of radium-contaminated soils that typically appear in enacted or proposed NORM regulations call for an average concentration of less than 5 pCi/g in the upper 15 cm (centimeters) of soil and an average of less than 15 pCi/g in deeper increments of 15 cm. Some States allow an average of as much as 30 pCi/g of radium in the upper 15 cm of soil. For oil-field equipment, typical standards for release for other uses or for recycling require that radioactivity at the surface should not exceed some low multiple of natural background radioactivity.”
CITATIONS, REFERENCES
American Petroleum Institute, 1992, Bulletin on management of naturally occurring radioactive materials (NORM) in oil & gas production: American Petroleum Institute, Washington, D.C., API Bulletin E2, 45 p.
Fisher, R.S., 1998, Geologic and geochemical controls on naturally occurring radioactive materials (NORM) in produced water from oil, gas, and geothermal operations: Environmental Geosciences, v. 5, no. 3, p. 139–150.
Mast, R.F., Root, D.H., Williams, L.P., Beeman, W.R., and Barnett, D.L., 1998, Areas of historical oil and gas exploration and production in the conterminous
United States: U.S. Geological Survey Geologic Investigations Series I-2582. Scale 1: 3,750,000.
Otto, G.H., 1989, A national survey of naturally occurring radioactive materials (NORM) in petroleum producing and gas processing facilities: American Petroleum Institute, Dallas, Texas, 265 p.
Raloff, Janet, 1991, NORM—The new hot wastes: Science News, v. 140,p. 264–267.
Smith, K.P., Blunt, D.L., Williams, G.P., and Tebes, C.L., 1996, Radiological dose assessment related to management of naturally occurring radioactive materials generated by the petroleum industry: Argonne, Ill., Argonne National Laboratory, Publication ANL/EAD-2, 65 p.
Wascom, C.D., 1994, NORM disposal options in the State of Louisiana: Proceedings of the 1994 Rocky Mountain Symposium on Environmental Issues in Oil and Gas Operations, Colorado School of Mines, Golden, Colo., 10 p.