Naturally occurring radioactive material

From Wikipedia, the free encyclopedia

Naturally occurring radioactive material (NORM) is encountered in oil and gas exploration, development and production operations. NORM originates in subsurface formations, which may contain radioactive materials such as Uranium and Thorium and their daughter products, Radium 226, Radium 228 and Radon 222.

Contents 1 Origin and characteristics 2 Hazards 3 Regulation 4 References

[edit] Origin and characteristics

Oil and gas NORM are created in the production process, when produced fluids from reservoirs carrying Barium sulfates up to the surface. 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 and Radium sulfates to precipitate out of solution and form scale on the inside, or on occasion, the outside of the tubulars. Using production tubulars in the production process that are NORM contaminated does not cause a health hazard if the scale is inside the tubulars. Concentrations of the radium 226 and 228 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 flaking to occur in turbulars. 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.

[edit] Hazards

The hazards associated with NORM are inhalation and ingestion routes of entry. Therefore, outside layers of protective personal clothing are not necessary precautions, except for hazards other than NORM exposure. 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 cancer from NORM exposure and decide to attack the employer for monetary repercussion.

Radium radionuclides emit alpha and beta particles as well as gamma rays. The radiation emitted from a Radium 226 atom is 96% alpha particle and 4% gamma ray. The alpha particle is the most dangerous particle associated with NORM. Alpha particles are large, similar in size and structure to a helium atom; containing two neutrons and two protons. Alpha particles travel short distances in air, of only 2-3 centimeters and cannot penetrate through a dead layer of skin on the human body. However, alpha particles are "bone seekers" do 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 1620 years, and will remain in the body for the lifetime of the human; a significant length of time to cause damage.

Alpha particles are also tissue destroyers inside the body by entering into chemical bonds with Oxygen. The list of combinations of alpha particles and Oxygen include, but are not limited to, hydrogen peroxide, alcohol and the breaking of H2O bonds causing more reactions. The damage caused by alpha particles could be potentially unstoppable. The gamma rays emitted from Radium 226, accounting for 4% of the radiation are in non-hazardous concentrations and are naturally not harmful to humans. Gamma rays are highly penetrating and pass through metals, so Geiger counters with a scintillation probe are used to measure gamma ray exposures when monitoring for NORM.

Radium 228 emits 100% beta particles, which are also a concern for human health through inhalation and ingestion. Beta particles are similar in size to an electron and travel farther than alpha particles in air. Beta particles can breach a thin sheet of paper, but are still prevented by a dead layer of skin on humans.

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 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 2000 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 2000 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.

[edit] Regulation

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 and has never developed NORM regulations. Therefore, this responsibility befalls the states. Since no government entity has implemented regulations, then states may choose the stringency or lax of the regulations. There are currently 17 states where NORM is known to exist.

[edit] References

• Cooley, Geri. "A Brief Overview of Oil and Gas NORM in Texas". Banking on the Permian Basin: Plays, Field Studies, and Techniques. 2004 West Texas Geological Society Fall Symposium, October 27-29, 2004, p 249-253.