Radioactive materials are widely used in our society. They are used in food irradiation, generating electrical energy, medical treatment and diagnosis. They are also by products of certain mining operations. The large amounts of radioactive wastes resulting from these activities create a potential for exposure of the population to levels of radiation that are well above naturally occurring levels.
Waste containing the by - products of nuclear reaction is called nuclear waste
. Radioactive waste is defined as the waste generated from nuclear reactors, fission or fusion products.
Radioactive wastes are highly toxic by-products produced in nuclear fuel processing plants, nuclear weapons industries and medicines. The radioactive waste can be solid, liquid or gaseous.
The radioactive waste
contains radioactive material in varying quantity which can have adverse effects. It remains active for thousands of years , therefore, it has to be treated before releasing, so that it doesn’t pose any threat to the environment. For example, nuclear spent fuel contain Np -237 which has a half-life of million years and Pu-239 which has a half-life of 24000 years.Management of radioactive waste done in following ways.
- Concentrate method.
- Dilute and disperse.
- Delay and decay method.
The high level radioactive waste can be processed in the following steps. First the radioactive waste is held for some time in borosilicate glasses. It is stored for some time with continuous check, making it ready for ultimate disposal. The treated radioactive waste is then disposed.
The discharge of radioactive wastes into air and water causes radioactive pollution. Radioactive waste pollution is caused by mainly four human activities. The following activities are responsible for it.
Radioactive waste is generated by nuclear power plants.
- Usage of radioactive isotopes in medical, research applications and industrial sector.
- Radioactive materials used in nuclear power plants.
- Production of usable radioactive substances through mining and processing of available ores.
- Usage of radioactive materials in nuclear weapons.
1. Nuclear power plants
Nuclear power plants produce three different types of radioactive wastes.
2. Nuclear weapons
- Fission products. The fission products mainly emit beta and gamma rays and alpha particles. The examples are: - U- 234, Np - 237, Pu- 238, Am -241.
- Liquid and gaseous wastes from fuel elements. This is basically alpha emitting waste and mainly contains decay products. For example, U- 235 is generated as by product.
- Low – level radioactive liquid wastes
Nuclear weapons industries, their testing in air and leakage in underground nuclear detonations etc give rise to radioactive fallout. This has far reaching effects on mankind. Some of the radioactive waste examples are:
3. Medical Radioactive wastes
- Uranium and plutonium are used in nuclear weapons but it is often contaminated by trace quantities of Pu - 240, Pu- 241 and Pu- 238.
- Nuclear weapons waste contains radioactive isotopes which emit gamma and beta rays. For example, Pu – 239.
Radioactive wastes from the medical processes and medicines beta and gamma radiating radioactive isotopes. Some of the examples are as below:
4. Radioactive wastes from industries
- I - 131 is used for treating thyroid cancer and has a half-life of 8 days.
- Co -60 is specially used in radiotherapy. It has a half-life of 5.3 years.
- Cs- 137 is also used in radiotherapy, has a half-life of 30 years
- Y – 90 has a half-life of 2.7 days and is used in the treatment of lymphoma.
Radioactive waste from industries contains beta, alpha and gamma emitters. Some of the examples are as below:
Nuclear radioactive waste is generated from different sources and is classified into different categories.
- Radium and its decay products from oil and gas industries.
- Radioactive waste in the form of coal ash.
- Waste from water treatment solids
- Waste form the phosphate processing units.
- Uranium tailings. These are the waste generated during the rough processing of uranium ore. These also contain lead and arsenic and are mainly found in the mining sites.
- Low level waste. Waste generated from industries and nuclear fuel cycle. These wastes in general do not possess any radioactivity. These are materials contaminated with radioactive substances or become exposed to nuclear radiations.
- Intermediate level waste. Intermediate level waste includes used reactor components such as fuel tank, filters etc. These are more toxic than low level radioactive waste and have to be treated before disposing.
- High level waste. This waste is generally comprised of fission products and transuranic elements produced in the nuclear reactor.
- Transuranic waste. It is composed of transuranic elements for example, plutonium, americium, neptunium etc. These are basically produced during recycling of used fuel and in the nuclear weapon industries.