Presented By

RENJINI CHANDRAN

The nuclear wastes are radio- active substances which are released from atomic reactors of nuclear power stations. When these substances are released into water , air or earth as a result of human activity either by accident or by intention is called nuclear hazards or nuclear waste.

Nuclear weapon testing

Nuclear fuel being used in atomic reactor

Accidental release of nuclear material from nuclear power plants

Nuclear waste is segregated into several classifications.

Low Level Radioactive Waste

Intermediate –Level Waste

High Level Radioactive Waste

Low level radio active waste(LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. Low-level wastes include paper, rags, tools, clothing, filters, and other materials which contain small amounts of mostly short-lived radioactivity. Low level radio active waste normally contain small amount of radioactivity dispersed in large volume of material

Intermediate-level waste (ILW) contains higher amounts of radioactivity Intermediate-level wastes includes resins, chemical sludge and metal nuclear fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. As a general rule, short-lived waste is buried in shallow repositories, while long-lived waste (from fuel and fuel reprocessing) is deposited in geological repository.

(HLW) is produced by nuclear reactors. After a nuclear fuel rod serves one fuel cycle and is removed from the core, it is considered HLW. Fuel rods contain fission products and transuranic elements generated in the reactor core. Spent fuel is highly radioactive and often hot.

HLW accounts for over 95 percent of the total radioactivity produced in the process of nuclear electricity generation. The amount of HLW worldwide is currently increasing by about 12,000 metric tons every year, which is the equivalent to about 100 double-decker buses.

Nuclear waste management are two long-lived fission products, which dominate spent fuel radioactivity after a few thousand years. Nuclear waste requires sophisticated treatment and management to successfully isolate it from interacting with the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving storage, disposal or transformation of the waste into a non-toxic form. Governments around the world are considering a range of waste management and disposal options, though there has been limited progress toward long-term waste management solutions.

Long term above ground storage, not implemented.

Disposal in outer space, not implemented.

Deep borehole disposal, not implemented.

Rock-melting, not implemented.

Disposal at subduction zones, not implemented.

Ocean disposal, done by the, the United Kingdom, Switzerland,& many other countries

Sub seabed disposal, not implemented, not permitted by international agreements.

Disposal in ice sheets.

Direct injection

Vitrification

Long-term storage of radioactive waste requires the stabilization of the waste into a form which will neither react nor degrade for extended periods of time. One way to do this is through vitrification. Currently at Sellafield the high-level waste is mixed with sugar and then calcined. Calcination involves passing the waste through a heated, rotating tube. The purposes of calcination are to evaporate the water from the waste, and de-nitrate the fission products to assist the stability of the glass produced.

It is common for medium active wastes in the nuclear industry to be treated with ion exchange or other means to concentrate the radioactivity into a small volume. The much less radioactive bulk (after treatment) is often then discharged. For instance, it is possible to use a ferric hydroxide to remove radioactive metals from aqueous mixtures.

Above-ground disposal

Dry cask storage typically involves taking waste from a spent fuel pool and sealing it in a steel cylinder, which is placed in a concrete cylinder which acts as a radiation shield. It is a relatively inexpensive method which can be done at a central facility or adjacent to the source reactor. The waste can be easily retrieved for reprocessing

Ocean disposal

From 1946 through 1993, thirteen countries (fourteen, if the USSR and Russia are considered separately) used ocean disposal or ocean dumping as a method to dispose of nuclear/radioactive waste. The waste materials included both liquids and solids housed in various containers, as well as reactor vessels, with and without spent or damaged nuclear fuel. Since 1993, ocean disposal has been banned by international treaties.

Deep borehole disposal is the concept of disposing of high-level radioactive waste from nuclear reactors in extremely deep boreholes. Deep borehole disposal seeks to place the waste as much as 5 kilometres (3.1 mi) beneath the surface of the Earth and relies primarily on the immense natural geological barrier to confine the waste safely and permanently so that it should never pose a threat to the environment.

Another option is to find applications for the isotopes in nuclear waste so as to re-use them.

Space disposal is attractive because it removes nuclear waste from the planet. It has significant disadvantages, such as the potential for catastrophic failure of a launch vehicle, which could spread radioactive material into the atmosphere and around the world.