Naturally Occurring Radioactive Materials (NORM)
Naturally occurring radioactive materials (NORM) such as uranium, radium, and radon are dissolved in very low concentrations during normal reactions between water and rock or soil.
Many oil-field waters are particularly rich in chloride, and this enhances the solubility of other elements including the radioactive element radium.
Some of this saline, radium-bearing water is unavoidably brought to the Earth’s surface with the oil and must be separated and then disposed, usually by return to depth in an injection well. At some oil-field sites the pipes and tanks that handle large volumes of this "produced water" can become coated with scale deposits that contain radium.
Radiumbearing scale is the type of "diffuse NORM waste" that occurs in the oil industry. Radium accumulation in oil-field equipment in the United States first became apparent in the 1980’s when scrap metal dealers began to routinely detect unacceptable levels of radioactivity in shipments of oil-field pipe. Since that time the oil and gas industry has sought to better define the extent of the oilfield NORM problem, and to develop techniques for the prediction, prevention, remediation, and disposal of oil-field NORM.
Barium sulfate scale can be radioactive by incorporating Radium.
Radioactive lead can deposit along with other scales as well.
What are the Different Types of Radioactivity?
The three most common types of radiation are alpha particles, beta particles, and gamma rays.
Alpha particle emission
Alpha particles (α) are highly charged, have a large mass compared to other radioactive particles, and consist of two protons and two neutrons. They are emitted from the nucleus of an unstable atom. The size and charge of alpha particles limits their penetration to very short distances. Most alpha particles are stopped by a few centimeters of air, a sheet of paper, or the outer (dead) layer of skin on our bodies. Though their size and energy make them potentially one of the more dangerous radioactive particles, they are easily blocked and usually not of much concern unless the material that emits them is ingested or inhaled.
Beta particle emission
Beta particles (β) are the equivalent of energetic electrons and have significantly less mass and half the electrical charge of alpha particles. Because they are not as highly charged, beta particles do not have as many interactions with other particles. Therefore, they travel further before giving up all their energy and coming to rest. Beta particles have a limited penetrating ability. Their typical range in air is up to about 10 feet. In human tissue, beta particles can travel only a centimeter or so at most, so they are primarily of concern to eyes and skin as well as being an internal hazard if the material that emits them is ingested.
Gamma ray emissions
Gamma (γ), or x ray, radiation is made of photons, which travel at the speed of light and have no electrical charge or mass. As a result, they are less likely to interact with anything, giving them very high penetrating power and allowing them to travel great distances through different materials. Due to its high penetrating power, gamma radiation can result in radiation exposure to the whole body rather than a small area of tissue near the source.
Once formed, barite is a very insoluble mineral. One liter of water at the Earth’s surface dissolves only 0.0025 grams of barite. Efficient removal of barite deposits from oil-field equipment requires special chemicals or vigorous mechanical methods. The process of barite removal and disposal is complicated by the need to minimize radiation dose to workers and the general public.
Radiation exposure pathways include external gamma radiation (major), ingestion (minor), and inhalation of particulates and radon gas (major). Currently most oilfield NORM waste is stored at production sites awaiting disposal in specially designated and permitted landfills, disposal wells, or injection wells. Surface spreading and dilution of low-level NORM waste (fig. 4) is a past practice that is now disallowed by most States with NORM regulations.
Barite scale is the most likely host of elevated radium in these soils. The extreme insolubility of barite under natural conditions limits the rate of release of radium to water and suggests that dispersal of radium will be dominated by physical transport of barite particles.