Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM)

http://www.colorado.gov/cs/Satellite/CDPHE-WQ/CBON/1251597783648

Radioactivity is naturally present throughout the environment, including drinking water supplies. For many systems, radionuclides are present only in trace amounts but are being removed inadvertently through conventional treatment methods. In some instances, the source water levels are above health standards for drinking water and must be removed to reduce public health risks.

Once these radionuclides have been removed from the drinking water, they become concentrated in the water treatment residuals and must be handled appropriately to reduce further risk to the public, workers, or the environment. These residuals are classified as Technologically Enhanced Naturally Occurring Radioactive Material (TENORM).

Regulation of TENORM in drinking water treatment residuals is not clearly spelled out in Federal or State regulations and has been dealt with on a case-by-case basis. The Department realizes that this approach is vague and inefficient for the regulated community; therefore, the Department has undertaken the task of developing policy and guidance to streamline this process.

Stakeholder input from industry professionals and the public are a critical piece of developing this policy and guidance. The following web pages are intended to provide background information, updates on project status, and access to the draft policy and guidance document and previous stakeholder work.

http://www.epa.gov/radiation/tenorm/about.html

TENORM is produced when radionuclides that occur naturally in ores, soils, water, or other natural materials are concentrated or exposed to the environment by activities, such as uranium mining or sewage treament.

Radioactive materials can be classified under two broad headings:

man-made
naturally occurring radioactive materials (NORM).

Man-made radionuclides are produced by splitting atoms in nuclear reactors or by bombarding atoms with subatomic particles in accelerators, nuclear reactors, and other devices. Examples of man-made radionuclides include cobalt-60, strontium-90, and cesium-137. Radionuclides in Naturally-Occurring Radioactive Material (NORM)include primordial radionuclides that are naturally present in the rocks and minerals of the earth’s crust and cosmogenic radionuclides produced by interactions of cosmic nucleons with target atoms in the atmosphere and in the earth. Example of cosmogenic radionuclides include carbon-14 and tritium (hydrogen-3). Materials containing cosmogenic radionuclides also fall under the definition of NORM but natural concentrations of nuclides generated by cosmic nucleons are small and present minimal risks.

NORM consists primarily of material containing potassium-40 and isotopes belonging to the primordial series. The principal primordial radionuclides are isotopes of heavy elements belonging to the radioactive series headed by the three long-lived isotopes uranium-238 (uranium series), uranium-235 (actinium series), and thorium-232 (thorium series). All three of these series have numerous radionuclides in their decay chains before reaching a stable end point, lead. At background concentrations, the naturally occurring radionuclides in the uranium, actinium, and thorium series contribute about one-half of the natural background external radiation, and over 80 percent of the background including radon, to which all humans are continuously exposed.

The principal radionuclide of concern in NORM is radium-226, a member of the uranium series, which is present in natural soils in concentrations of about 1 pico Curie per gram (Ci/g). However, NORM radioisotopes may be present in different materials in varying concentrations, and some NORM wastes may have radium-226 concentrations that are much higher than 1 pCi/g, and may be as high as hundreds of thousands of pCi/g.

The ultimate sources of the primordial radionuclides in the environment are the earth’s crust and its underlying mantle. Selective movement of some materials from the mantle to the crust, usually resulting from fluid movement driven by temperature differences, has caused a heterogeneous organization of the chemical elements in the crust. Redistribution has also occurred as a result of weathering, sedimentation, and chemical interactions in the crust. As a consequence of these processes, potassium-40 and the uranium and thorium series nuclides have tended to concentrate in certain minerals and certain geologic formations. For example, uranium in significantly elevated concentrations is associated with phosphate ores in three major locations in the U.S.: southeastern Idaho and parts of neighboring states, central Florida, and central Tennessee and northern Alabama. Radionuclides from the uranium and thorium series are also associated in widely varying proportions in the crude oil and brine extracted from underground petroleum reservoirs.

NORM wastes are the radioactive residues from the extraction, treatment, and purification of minerals, petroleum products, or other substances obtained from parent materials that may contain elevated concentrations of primordial radionuclides. They also include any radioactive material made more accessible by the actions of man. Each year, hundreds of millions of metric tons of NORM waste are generated from a wide variety of processes, ranging from uranium and phosphate mining to municipal drinking water treatment. Processes that produce NORM wastes analyzed in this study include uranium mining, phosphate and elemental phosphorus production, phosphate fertilizer production, coal ash generation, oil and gas production, drinking water treatment, metal mining and processing, and geothermal energy production. Primordial radionuclides present in the parent materials can become concentrated in the wastes during mining and beneficiation, mineral processing, oil and gas extraction, or various other processes. This results in radionuclide concentrations in NORM wastes that are often orders of magnitude higher than in the parent materials.

The exposure to individuals from NORM wastes occurs in three main ways. The first is associated with the normal onsite disposal of the waste in piles or stacks. This type of disposal can lead to groundwater contamination and to airborne releases of radioactive particulates and radon. The second is from the improper use and/or disposal of these wastes, such as for soil conditioning or fill dirt around homes. This can lead to build-up of radon gas in homes, direct exposure to individuals located nearby, contamination of soil and the crops growing in that soil, and groundwater contamination. The third way is the reuse of NORM-contaminated materials, such as in concrete aggregate, which could lead to increased radiation risks to members of the public in a variety of ways.

Advertisements