Naturally occurring radioactive material
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (August 2011)|
Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) consist of materials, usually industrial wastes or by-products enriched with radioactive elements found in the environment, such as uranium, thorium and potassium and any of their decay products, such as radium and radon. These natural radioactive elements are present in very low concentrations in earth's crust and are brought to the surface through human activities such as oil and gas exploration or mining and through natural processes like leakage of radon gas to the atmosphere or through dissolution in ground water. Another example of TENORM is coal ash produced from coal burning in power plants. If radioactivity is much higher than background level, handling TENORM may cause problems in many industries and transportation.
NORM in oil and gas exploration
Oil and gas TENORM and/or NORM is created in the production process, when produced fluids from reservoirs carry sulfates up to the surface of the Earth's crust. Some states, such as North Dakota, uses the term "diffuse NORM". Barium, calcium and strontium sulfates are larger compounds, and the smaller atoms, such as radium 226 and radium 228, can fit into the empty spaces of the compound and be carried through the produced fluids. As the fluids approach the surface, changes in the temperature and pressure cause the barium, calcium, strontium and radium sulfates to precipitate out of solution and form scale on the inside, or on occasion, the outside of the tubulars and/or casing. The use of tubulars in the production process that are NORM contaminated does not cause a health hazard if the scale is inside the tubulars and the tubulars remain downhole. Enhanced concentrations of the radium 226 and 228 and the daughter products such as lead-210 may also occur in sludge that accumulates 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 centimeters 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 may expose employees to particles containing increased levels of alpha emitting radionuclides that could pose health risks if inhaled or ingested.
The hazards associated with NORM are inhalation and ingestion routes of entry as well as external exposure where there has been a significant accumulation of scales. Respirators may be necessary in dry processes, where NORM scales and dust become air borne and have a significant chance to enter the body.
The hazardous elements found in NORM are radium 226, 228 and radon 222 and also daughter products from these radionuclides. The elements are referred to as "bone seekers" which when inside the body migrate to the bone tissue and concentrate. This exposure can cause bone cancers and other bone abnormalities. The concentration of radium and other daughter products build over time, with several years of excessive exposures. Therefore, from a liability standpoint an employee that has not had respiratory protection over several years could develop bone or other cancers from NORM exposure and decide to seek compensation such as medical expenses and lost wages from the oil company which generated the TENORM and the employer.
Radium radionuclides emit alpha and beta particles as well as gamma rays. The radiation emitted from a radium 226 atom is 96% alpha particles and 4% gamma rays. The alpha particle is not the most dangerous particle associated with NORM. Alpha particles are helium nuclei. Alpha particles travel short distances in air, of only 2–3 cm, and cannot penetrate through a dead layer of skin on the human body. However, some radium alpha particle emitters are "bone seekers" due to radium possessing a high affinity for chloride ions. In the case that radium atoms are not expelled from the body, they concentrate in areas where chloride ions are prevalent, such as bone tissue. The half-life for radium 226 is approximately 1,620 years, and will remain in the body for the lifetime of the human — a significant length of time to cause damage.
Beta particles are high energy electrons or positrons. They are in the middle of the scale in terms of ionizing potential and penetrating power, being stopped by a few millimeters of plastic. This radiation is a small portion of the total emitted during radium 266 decay. Radium 228 emits beta particles, and is also a concern for human health through inhalation and ingestion. Beta particles are electrons or positrons and can travel farther than alpha particles in air.
The gamma rays emitted from radium 226, accounting for 4% of the radiation, are harmful to humans with sufficient exposure. Gamma rays are highly penetrating and some can pass through metals, so Geiger counters or a scintillation probe are used to measure gamma ray exposures when monitoring for NORM.
Alpha and beta particles are harmful once inside the body. Breathing NORM contaminates from dusts should be prevented by wearing respirators with particulate filters. In the case of properly trained occupational NORM workers, air monitoring and analysis may be necessary. These measurements, ALI and DAC, are calculated values based on the dose an average employee working 2,000 hours a year may be exposed to. The current legal limit exposure in the United States is 1 ALI, or 5 rems. A rem, or Roentgen Equivalent Man, is a measurement of absorption of radiation on parts of the body over an extended period of time. A DAC is a concentration of alpha and beta particles that an average working employee is exposed to for 2,000 hours of light work. If an employee is exposed to over 10% of an ALI, 500 mREM, then the employee's dose must be documented under instructions with federal and state regulations.
NORM is not federally regulated in the United States. The Nuclear Regulatory Commission (NRC) has jurisdiction over a relatively narrow spectrum of radiation, and the Environmental Protection Agency (EPA) has jurisdiction over NORM. Since no federal entity has implemented NORM regulations, NORM is variably regulated by the states.
In the UK regulation is via the Environmental Permitting (England and Wales)Regulations 2010.
This defines two types of NORM activity:
- Type 1 NORM industrial activity means:
(a)the production and use of thorium, or thorium compounds, and the production of products where thorium is deliberately added; or
(b)the production and use of uranium or uranium compounds, and the production of products where uranium is deliberately added
- Type 2 NORM industrial activity means:
(a)the extraction, production and use of rare earth elements and rare earth element alloys;
(b)the mining and processing of ores other than uranium ore;
(c)the production of oil and gas;
(d)the removal and management of radioactive scales and precipitates from equipment associated with industrial activities;
(e)any industrial activity utilising phosphate ore;
(f)the manufacture of titanium dioxide pigments;
(g)the extraction and refining of zircon and manufacture of zirconium compounds;
(h)the production of tin, copper, aluminium, zinc, lead and iron and steel;
(i)any activity related to coal mine de-watering plants;
(j)china clay extraction;
(k)water treatment associated with provision of drinking water;
(l)The remediation of contamination from any type 1 NORM industrial activity or any of the activities listed above.
An activity which involves the processing of radionuclides of natural terrestrial or cosmic origin for their radioactive, fissile or fertile properties is not a type 1 NORM industrial activity or a type 2 NORM industrial activity.
- Background radiation, ionizing radiation constantly present in the natural environment of the Earth
- Environmental radioactivity
- North Dakota Department of Health
- NORM Technology Connection, Interstate Oil and Gas Compact Commission
- Radiation Quick Reference Guide, Domestic Nuclear Detection Office
- Naturally Occurring Radioactive Materials from the World Nuclear Association
- UK guidance on Radioactive Substances Regulation For the Environmental Permitting (England and Wales) Regulations 2010:Defra