Nucular Waste A Technical Analysis Ian Baird 51208

Nucular Waste A Technical Analysis Ian Baird 5/12/08

Nuclear Waste…Why? • Recently nuclear power has entered many discussions as world energy needs rise and oil reserves diminish. • Most opponents of nuclear power point to two main arguments: meltdowns and nuclear waste. • Nuclear waste is any form of byproduct or end product that releases radioactivity. • How to safely dispose of nuclear waste is pivotal for the continued operation of nuclear power plants, safety of people living around dump sites, and prevention of proliferation of nuclear materials to non-nuclear states.

Nuclear Fuel Cycle Most nuclear waste comes from the byproducts of the nuclear fuel cycle. The cycle typically is split into three sections: front end, service period, and back end. There can be intermediate stages that include the reprocessing of nuclear waste elements.

Nuclear Fuel Cycle (Cont. )

Classifications • Nuclear waste is segregated into several classifications. • Low level waste is not dangerous but sometimes requires shielding during handling. • Intermediate level waste typically is chemical sludge and other products from reactors. • High level waste consists of fissionable elements from reactor cores and transuranic wastes. • Transuranic waste is any waste with transuranic alpha emitting radionuclides that have half-lives longer than 20 years.

Low Level Waste LLW • Low level waste is any waste that could be from a high activity area. • 90% volume of waste • It does not necessarily carry any radioactivity. • Split into four catagories: A, B, C, and GTCC.

Intermediate Level Waste ILW • Intermediate level waste requires shielding when being handled. • 7% volume of waste • Dependent on the amount of activity it can be buried in shallow repositories. • Not recognized in the United States.

High Level Waste HLW • High level waste has a large amount of radioactive activity and is thermally hot. • 3% volume of waste • 95% of radioactivity • Current levels of HLW are increasing about 12, 000 metric tons per year. • Most HLW consists of Pu-238, 239, 240, 241, 242, Np-237, U-236

Transuranic Waste TRUW • Transuranic waste consists of all waste that has radionuclides above uranium. • TRUWs typically have longer half-lives than other forms of waste. • Typically a byproduct of weapons manufacturing. • Only recognized in the United States.

Creation of Nuclear Waste • Nuclear waste is generated at all points of the fuel cycle. • Front end waste consists primarily of low level alpha emission waste. • Service period waste typically includes LLW and ILW such as contaminated reactor housings and waste from daily operation. • Back end waste normally is the most radioactive and includes spent fuel rods and reactor cores.

Front End Waste • Front end waste consists mostly of LLW and ILW. • The primary front end waste is depleted uranium and radium. – DU has several uses due to its high density (19, 050 kg/m 3). – Mix with uranium to form reactor fuel

Service Period Waste • Consists of mostly ILW. • Mostly waste produced at the plant during normal operation. • Spent fuel rods are the most dangerous waste produced during the service period.

Back End Waste • Nuclear waste developed during the back end of the fuel cycle is the most dangerous and includes most of the HLW produced. • Most back end waste emits both gamma and beta particles. • Also uranium-234, neptunium-237, plutonium 238 and americium-241 are found in back end waste. Spent nuclear fuel in a cooling pond in North Korea.

Waste Management (LLW) • There are several options available for the disposal of LLW due to its lack of radioactivity. • Waste Isolation Pilot Plant • On-site disposal Map of WIPP Facility

Treatment (LLW) • • • Filtration Ion Exchange Evaporation Incineration Compaction Solidification Typical LLW treatment facility.

Waste Management (HLW) • Most common utilized option are reactor pools and dry cask storage. • Other Options for waste management include: – Deep Geologoical Storage – Transmutation – Reuse – Launching it into space Locations of storage sites for nuclear waste in the U. S.

Treatment • Most common initial treatment of waste is vitrification. – Waste is first mixed with sugar and then passed through a heated tube to de-nitrite the material. – This material is then fed into a furnace and mixed with glass. – The molten glass mixture is poured into steel cylinders and welded shut.

Treatment (Cont. ) • Mid level active waste is commonly treated with ion exchange • Process reduces the bulk volume of radioactive material. • Typically, mixed with concrete for a solid storage form.

Treatment (Cont. ) • Synroc is a new method for storing nuclear waste developed in 1978 by Ted Ringwood. • Attempts to hold radioactive material in a crystalline matrix. • Currently in use for military waste management at Savannah River Site. • Can hold 50%-70% volume of waste.

Deep Geological Repository • Most common method for handling nuclear waste. • Typically kept separate from actual plants and buried far below ground. • First used in 1999 in the US. • Current research is focusing on Yucca Mountain Site

Transmutation of Nuclear Waste • • Reduces transuranic waste. Integral Fast Reactor Banned 1977 -1981 (U. S. ) MOX Fuel – Behaves as low-enriched uranium • Research now in subcritical reactors. • Fusion also being researched.

Reuse of Nuclear Waste • Research is being performed to find uses for nuclear waste. • Caesium-137 and strontium-90 already used in industrial applications. • Some waste can be used for radioisotope thermoelectric generators (RTGs). • Overall can reduce total HLW but not eliminate it.

Launch it into Space • Near infinite storage space • Completely removes waste from biosphere • Technical risks and problems • Political entanglements

Conclusions • HLW is most dangerous byproduct of nuclear power. • Borosilicate glass most common storage. • Several venues being researched for the safe disposal of HLW.