Radioactive Material

Radiation and radioactive materials are the link between a device or process as a source and the living being to be protected from hazard.

From: Nuclear Energy (Seventh Edition) , 2015

Radioactive materials

K. Kovler , in Toxicity of Building Materials, 2012

8.1.1 Radiation basics

Radioactivity is a process by which certain naturally occurring or artificial nuclides undergo spontaneous decay releasing a new energy. This decay process is accompanied by the emission of one or more types of radiation, ionizing or non-ionizing, and/or particles. This decay, or loss of energy, results in an atom of one type, called the parent nuclide, transforming to an atom of a different type, named the daughter nuclide. The SI derived unit of radioactivity is the becquerel (symbol Bq), which is defined as the activity of a quantity of radioactive material in which one nucleus decays per second; in other words, Bq is equivalent to s −1.

Ionizing radiation is electromagnetic (in the form of waves with a wavelength of 100   nm or less, i.e. a frequency of 3   ×   10−   15  Hz or more) or corpuscular radiation that has sufficient energy to ionize certain atoms of the matter in its path by stripping electrons from them. This process can be direct (as with alpha particles) or indirect (gamma rays and neutrons).

Gamma radiation composed of high-energy photons, which are weakly ionizing but have high penetrating power (more than the X-ray photons used in radiodiagnosis), can travel through hundreds of meters of air. Thick concrete shielding or lead helps to protect personnel. Gamma radiation is primarily responsible for external exposure. As far as internal radiation exposure hazard is concerned, the high penetrating power means that the energy released by gamma rays and taken up by a small volume of tissue is comparatively small. Hence the harm to the organ is also smaller. Therefore, the internal radiation exposure hazard caused by gamma rays is not as severe as that induced by other types of radiation (alpha and beta).

Alpha radiation consists of 4He nuclei and has low penetrating power. Its path in biological tissues is no longer than a few tens of micrometers. This radiation is strongly ionizing, i.e. it easily strips electrons from the atoms in the matter it travels through, because the particles shed all their energy over a short distance. Alpha emitters are primarily responsible for internal exposure, which includes inhalation, ingestion and skin contact.

Beta radiation is made up of electrons and has moderate penetrating power. Hence, exposure to beta particles presents greater external irradiation hazard and less internal radiation hazard than exposure to alpha particles. However, as the external irradiation brought by beta particles is mostly confined to the epidermis and outer skin tissue, such external irradiation hazard is not too severe.

Exposures are not limited to the intake of large amounts at one time (acute exposure). Chronic exposure may arise from an accumulation of small amounts of radioactive materials over a long period of time.

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Produced Water Treating Systems

Maurice Stewart , Ken Arnold , in Emulsions and Oil Treating Equipment, 2009

3.3.11 Naturally Occurring Radioactive Materials (NORM)

NORM can be transported to the surface in produced water and can be found in production wastes, equipment, and solids at production facilities. At offshore locations, dissolved NORM are discharged along with produced water. Because of concern over human exposure to environmental radiation, oil-field NORM have received regulatory attention and managing waste has become a significant cost factor for the industry.

Oil-field NORM result from the presence of uranium and thorium in hydrocarbon bearing formations. Many oil and gas bearing formations contain shales that have higher than average concentrations of uranium and thorium. These elements occur in chemical forms that are not water-soluble under reservoir conditions (U238 and Th232). U238 and Th232 decay into different isotopes of radium (Ra236 and Ra228). These radium isotopes further decay into the radioactive gas called radon (Rn232). Both radium and radon are soluble in formation water under reservoir conditions and can be transported to the surface along with oil, gas, and produced water.

Once produced water leaves the reservoir, decreases in temperature and pressure can lead to the precipitation of NORM scale and particulates in production equipment, where it can accumulate as hard scales, sludge, or tank bottoms. Radon in produced fluids partitions into the gas phase during primary separation and enters the gas processing stream. Radon's boiling point is between that of ethane and propane, and radon is concentrated in the natural gas liquids fraction (this is generally a problem only in a gas plant fractionation section). Accumulated NORM containing solids are periodically cleaned out of vessels during maintenance and must be disposed of in a controlled fashion. Some equipment items cannot be readily decontaminated and are subject to special handling procedures. NORM that remain in solution are disposed of by whatever process is used to dispose of the produced water.

Radium and its decay products, including radon, may be found in any equipment that comes into contact with the produced water. Radium is often associated with barium scales since radium and barium are in the same chemical family. Radon and its decay products may be found in any equipment that comes into contact with natural gas or natural gas liquids.

Oil-field NORM are an environmental concern because of the potential for human exposure to ionizing radiation. The radium and radium decay products in oil-field NORM present a hazard only if taken into the body by ingestion or inhalation. The external radiation from equipment or waste containing NORM is almost never a significant concern. The discharge of radium in produced water is of concern because it may accumulate in seafood consumed by humans. Since no established safe level exists for the intake of radium, any consumption of radium in food is of potential concern. However, for the case of radium discharged in produced water, risk assessment studies show that consumption of fish caught near produced water outfalls will not pose an unacceptable human health risk, even in the worst cases.

Regulations governing NORM focus on equipment and wastes containing NORM rather than produced water. Regulations generally specify a limit on the external radiation level from wastes or equipment above which the material must be treated as NORM and cannot be released for unrestricted use without prior decontamination. Regulations also specify the maximum acceptable radium concentration in wastes and soils for unrestricted release or disposal. Existing regulations do not limit the radium concentration in offshore produced water discharges. Operators in the U.S. Gulf of Mexico are required to measure and report the radium concentrations of their effluents to the EPA.

NORM accumulations in production equipment can be controlled in some situations but cannot be eliminated entirely. Since NORM are incorporated in scale and other precipitates, reduced NORM accumulation is a benefit of a properly managed scale control program. NORM cannot be made nonradioactive. Consequently, the emphasis in NORM waste management is on identification, control, and volume reduction. NORM site remediation activities are directed at reducing the potential for human exposure to hazardous amounts of radioactive material.

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Evacuation and decontamination in response to the Fukushima nuclear power plant accident

Y. Hatamura , in The 2011 Fukushima Nuclear Power Plant Accident, 2015

5.8.1 Radioactive material cannot be erased

Radioactive materials released from the Fukushima nuclear reactor floated in the air as a radioactive plume, like an invisible cloud. The wind carried the radioactive materials far and wide. As time passed, they started to fall on the ground and on leaves.

If rain falls from above the radioactive plume, clusters of radioactive material and lumps of water (raindrops) collide, and raindrops that have captured radioactive material fall on the earth (i.e., soil grains and surfaces of leaves). Areas highly contaminated by rain with radioactive material are called "hot spots." This is shown in Figure 5.12.

Figure 5.12. Mechanism of vaporized cesium falling as raindrops.

Figure 5.13 shows a sketch of what the residents of the village of Iitate, one of the hot spots, felt and thought about. The sketch is based on comments from them. The comments were "Invisible clouds of radioactivity came from the other side of the southeast hills and the 'radioactivity' fell on and got stuck to our rice patties, produce fields, houses, and forests."

Figure 5.13. Cloud of radioactivity that reached Hiso area of Iitate-mura (sketch by Hatamura based on comments from local residents).

Some of the fallen radioactive materials were washed away with the rainwater. That is why higher radiation was measured in rain gutters, water ditches, and naturally formed rain channels. Radioactive material that was not washed away, on the other hand, stuck to soil particles, leaves, and roof shingles and stayed there even after the water evaporated. Radioactive material molecules that got stuck to other object surfaces cannot be washed away even with brushes. Figure 5.14 shows the mechanism.

Figure 5.14. Small particles with the size of atoms cannot be removed by physical means.

It is a natural desire to remove the radioactive material that spread out from the nuclear plant. Unlike chemically disinfecting poison with neutralizers, we do not have processes for erasing radioactivity.

The accident released several types of radioactive material, and the one that matters the most in terms of decontamination is cesium 137 with a half-life of 30 years. Cesium 131, that can accumulate in the thyroid gland, has a half-life of 8 days, and it quickly changes into a non-radioactive material called xenon. Cesium 134 has a half-life of 2 years, and so 2 years after the accident, about half of it had changed into barium 134. Cesium 137 emits radiation to turn into nonradioactive barium 137. The amount of radiation with cesium 137 reduces to half the original in 30 years, a quarter in 60 years, an eighth in 90 years, and about one-tenth in 100 years. We can only count on decay of radioactivity in dealing with released radioactive material.

Under these conditions, the best practice is to acknowledge the existence of radioactive materials, take measures to minimize their impact on humans, and wait for time to pass so the radioactivity decays.

The central and local government agencies are currently working on plans to gather the soil and leaves contaminated with radioactive material and store them at designated places. The motivation is to ease people's anxiety in living close to radioactive material without thinking about the amount of radiation. If we, however, open our eyes to reality, such measures are likely to fail. This is because areas that are named for storage and others in the route of transportation are refusing to take those roles.

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Introduction to the packaging, transport and storage of radioactive materials

K.B. Sorenson , in Safe and Secure Transport and Storage of Radioactive Materials, 2015

1.1 Introduction

Radioactive material, by its nature, embodies radiological, chemical, and physical attributes that can be particularly hazardous to human health and the environment. However, the benefits of commercial, industrial, and medical uses for nuclear and radioactive material are significant. Implementing the correct balance of the beneficial uses of radioactive material, the resultant positive impacts on society, and the inherent dangers of using this material is a constantly evolving process that is played out in individual communities, regions, and countries around the world. It is also a process that is being played out between the public, industry, regulator, and international oversight organizations, such as the International Atomic Energy Agency. Acceptance of beneficial use is not uniform around the world or across applications. For example, medical uses tend to be more generally accepted than other types of use. Industrial uses tend to be less visible to the public and do, therefore, tend to be less controversial. Generation of electric power using nuclear energy, and the associated benefits and costs of the entire commercial nuclear fuel cycle, is one area that generates much controversy in some countries, while generating little controversy in other countries.

This book covers a rather narrow operational section of radioactive materials applications. That is, it discusses the packaging, transport, and storage of radioactive materials specifically. It will not cover operational aspects associated with resultant beneficial use.

By its nature, radioactive material has properties that can make it dangerous for long periods of time after its beneficial use is finished. Additionally, some uses (e.g., nuclear power generation) will produce radioactive spent fuel that is more dangerous than when it was put in the reactor. Because of these characteristics, there is a broad range of technical knowledge, operational experience, and regulatory oversight that goes into the packaging, transport, and storage of radioactive materials. This book covers these operational aspects in sufficient detail to provide the reader with a broad understanding of all the factors that support these important operational aspects of using radioactive materials.

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Nuclear Power Plants, Decommissioning of

Rebekah Harty Krieg , ... Michael T. Masnik , in Encyclopedia of Energy, 2004

4.7 Radiological

Radioactive materials are present in the reactor and in the support facilities after operations cease and the fuel has been removed from the reactor core. Exposure to these radioactive materials during decommissioning may have consequences for workers. Members of the public may also potentially be exposed to radioactive materials that are released to the environment during the decommissioning process. To date, doses from occupational exposures to individual workers during decommissioning activities at nuclear power facilities in the United States are similar to, or lower than, the doses experienced by workers in operating facilities. In addition, these doses have been below the regulatory limits. Off-site exposures, which could affect members of the public, during periods of major decommissioning have not differed substantially from those experienced during normal operations, which are also below the regulatory limits.

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Radiation protection by shielding in packages for radioactive materials

H. Issard , in Safe and Secure Transport and Storage of Radioactive Materials, 2015

Abstract

Radioactive materials emit radiation, which can be from different types—particularly gamma or neutron radiations, which are penetrant radiations. Systems to transport or store radioactive material include a shielding material, which is interposed between the source of radiation and persons or environment, in order to absorb radiation and thereby reduce radiation exposure. After explaining the regulatory dose rate limits, this chapter presents the basis of shielding design and safety analysis, some typical shielding materials used by the industry, and the methods used to justify shielding performance in the long term in the case of extended storage periods.

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Health and Safety, Legal Requirements and Insurance

J.F. Cameron , C.G. Clayton , in Radioisotope Instruments, 1971

Absorption

Radioactive material may penetrate the skin by diffusion through the skin barrier or via cuts and wounds. Once absorbed they may subsequently disperse in the blood-stream. Organic solvents in particular are potentially hazardous as they can easily penetrate the skin. In general, however, the skin forms an efficient barrier against contamination.

Cuts and wounds can allow active materials direct access into the blood-stream. If a cut or a wound occurs in a potentially contaminated area then it should be washed immediately and mild bleeding should be stimulated. All cuts and wounds must be covered with a suitable dressing before undertaking any work with radioactive materials.

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Assessment of radiation pollution from nuclear power plants

Jibran Iqbal , ... Evan K. Paleologos , in Pollution Assessment for Sustainable Practices in Applied Sciences and Engineering, 2021

20.11 How dangerous is nuclear radiation?

Radioactive material can be detrimental from a distance and in that sense it differs from toxins that require absorption or inhalation to cause damage. In fact, chemical toxins must enter our body to cause chemical changes that damage cells and biological processes, while radioactive materials release energy particles that can travel distances. The effects of radionuclides would be the result of the spread of radioisotopes on land, in the air and in water, and the subsequent absorption or inhalation of these isotopes. In general, radioisotope concentrations have been reported to be too low for soil, water, or air to cause a significant direct radiation dose to a person nearby. However, when radioactive isotopes are swallowed or inhaled and then spend a lot of time in the body, they cause harmful effects that the public fears. However, in this respect, radioactive materials are no different than other toxins. In fact, they need to be inhaled or ingested to have effect.

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Radionuclide Releases into the Environment

Pavel P. Povinec , ... Michio Aoyama , in Fukushima Accident, 2013

Abstract

Radioactive materials were released to the environment from the Fukushima Dai-ichi Nuclear Power Plant as a result of reactor accidents caused by a total loss of electric power (black out) after the Tohoku earthquake and tsunami on 11 March 2011. Radioactive materials were emitted into the atmosphere and transferred to the land and ocean through wet and dry deposition. In addition, highly contaminated fresh and seawater was directly released to the ocean. It is estimated that 2.6% of 131I (159   PBq) from the nuclear reactors inventories was released to the atmosphere, while for 137Cs this number was lower, 2.2% (15.3   PBq). Thirty two percent of 131I (1940   PBq) was dissolved in the stagnant water, while 20% of 137Cs (141   PBq) was dissolved in the stagnant water in turbine buildings and surrounding areas. It is estimated that 0.5% of 137Cs (3.6   PBq) was released directly to the ocean.

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Naturally Occurring Radionuclides

M.I. Ojovan , W.E. Lee , in An Introduction to Nuclear Waste Immobilisation, 2005

5.1 NORM and TENORM

Naturally occurring radioactive materials (NORM) are part of the Earth. The majority of radionuclides in NORM (principally radium and radon) arise from uranium and thorium decay. Radon exposure in homes can be high, particularly those built on Rn-containing rocks such as in SW England and the Peak District in Derbyshire as the gas continuously accumulates and may achieve potentially dangerous concentrations. Human activities and technological processes such as fossil fuel burning, mineral extraction and fertiliser application often increase concentrations of radionuclides in the NORM. Industrial practices involving natural resources often concentrate radionuclides to a degree that may pose a risk to humans and the environment. Materials that contain natural radionuclides, whose levels are concentrated due to technological operations, are termed technologically enhanced naturally occurring radioactive materials (TENORM). TENORM are, in many cases, large-volume, low-activity waste streams produced by industries such as mineral mining, ore beneficiation, phosphate fertiliser manufacture, water treatment and purification, paper and pulp manufacture, oil and gas production, scrap metal recycling and waste incineration. The level of individual exposure from NORM is usually trivial. However, TENORM in some cases can be dangerous and classified as radioactive waste.

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