Nuclear Waste…Why?•Recently nuclear power has entered many discussions asworld energy needs rise and oil reserves diminish.•Most opponents of nuclear power point to two mainarguments: meltdowns and nuclear waste.•Nuclear waste is any form of byproduct or end product thatreleases radioactivity.•How to safely dispose of nuclear waste is pivotal for thecontinued operation of nuclear power plants, safety of peopleliving around dump sites, and prevention of proliferation ofnuclear materials to non-nuclear states
Nuclear Fuel cycleMost nuclear waste comes from the byproducts of the nuclear fuelcycle. The cycle typically is split into three sections: front end,service period, and back end. There can be intermediate stagesthat include the reprocessing of nuclear waste elements.
Radioactive WasteWe will discuss - Low Level Radioactive Waste High Level Radioactive Waste Mining Tailings
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 ofthe fuel cycle.•Front end waste consists primarily of lowlevel alpha emission waste.•Service period waste typically includesLLW and ILW such as contaminated reactorhousings and waste from daily operation.•Back end waste normally is the mostradioactive and includes spent fuel rods andreactor 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/m3). – 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, Spent nuclear fuel in a cooling pond in North neptunium-237, Korea. plutonium-238 and americium-241are found in back end waste.
Low Level Radioactive WasteLow Level Radioactive waste consists of microcurie, millicurie and at times curie activity waste.(A Curie is a unit of nuclear transformations. 1 Curie is 3.7 x1010 transformations per second)
Waste Management (LLW) There are several options available for the disposal of LLW due to its lack of radioactivity. Waste Isolation Pilot Plant Map of WIPP Facility On-site disposal
Radioactive Waste Low level radioactive liquids are either: – Incinerated – Deep well injected (not as frequent anymore) – Solidified – Sewer Disposed (Regulations allow curie levels of some isotopes to be sewer disposed of if dilution is large enough)
Radioactive Waste Radioactive animal carcasses are either incinerated or buried onsite.
Radioactive Waste Small sealed sources are “Stabilized” in concrete and buried. Stabilized concrete is concrete that is certified to resist wear for a certain time period.
Radioactive Waste Low level contaminated solid wastes are buried. GSU has it’s solid waste “Supercompacted” at 30,000 psi to reduce the volume to be buried
Radioactive WasteMost low level wastes come from Governmentand Utilities. These consist of contaminatedsolids from nuclear reactor usage and weaponconstruction.
Radioactive Waste Colleges, research and medical applications account for less than 25% of the low level Radioactive wastes created
Radioactive Waste Class A low-level radioactive waste is the least hazardous, containing mostly short-lived radionuclides that will be reduced in radioactivity (decay) in a relatively short time. It contains only small amounts of radionuclides that take a relatively short time to decay. Class A waste will be disposed of in concrete canisters that will maintain their shape and strength for hundreds of years.
Radioactive Waste Class B low-level radioactive waste is more hazardous than Class A waste. Most of it comes from nuclear reactors. It must be in a stable form for disposal and will also be disposed of in concrete canisters. Stabilization can be accomplished by solidifying liquid waste, compacting solid waste, or placing the low-level radioactive waste in a container that will be stable for many years. Class B low- level radioactive waste makes up only a small percent of the waste volume generated; but along with Class C waste, it contains the largest portion of the total radioactivity.
Radioactive Waste Class C low-level radioactive waste is the most hazardous and must be handled accordingly. It also must be disposed of in a stable form.
Radioactive Waste The compact system was set up by NRC to have all states share in the responsibility of disposal of radioactive waste and to limit waste transport distance. Georgia is in the Southeast compact. Until 1992, all states within the SE compact (excluding Florida) would host a LLRW landfill on a 20-25 year revolving timetable.
Radioactive Waste Kentucky was the first (Maxie Flats), then South Carolina (Barnwell). In 1995, North Carolina was to open a site but the citizens protested and sued. The State legislature refused. North Carolina was then “kicked out” of the S.E. compact and left with no place to dispose of waste. Other States followed N.C.’s lead and refused This lead to the collapse of the traditional compact system and the
Radioactive WasteIn the past, many Universities andcompanies were allowed to bury theirradioactive wastes onsite. Some wereallowed to deep well inject liquidradioactive waste.
Radioactive Waste N.I.M.B.Y.NotInMyBackYard The true politics of Hazardous Waste
NIMBY: Not In My Back Yard Fear of radiation because they don’t understand it Concern that the waste facility will release long-term contamination Worry that property values will be reduced with construction of a waste facility Belief that power companies are the ones responsible for storing their own waste People don’t want dumped on by other peoples’ waste Belief that nuclear power should just go away and be replaced by other energy resources Environmental concerns
Waste Management (HLW) Most common utilized option are reactor pools and dry cask storage. Other Options for waste management include: – Deep Geologoical Storage – Transmutation Locations of storage sites for nuclear – Reuse waste in the U.S. – Launching it into space
High-Level Radioactive Waste High-Level Radioactive Waste is: the irradiated fuel from the cores of nuclear reactors, the liquid and sludge wastes that are left over after irradiated fuel has been reprocessed (a procedure used to extract uranium and plutonium), the solid that would result from efforts to solidify that liquid and sludge from reprocessing.
Radioactive WasteBecause there is currently no high level radioactive waste disposal facility, HLRW is held On-Site in water pools
Radioactive WasteOnce these Pools are full, Waste is transferred to casks which are also held on-site
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.
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 Yucca Mountain Site focusing on Yucca Mountain.
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
Yucca Mountain Yucca Mountain • Technically sound • 1,000’ below ground • Repository in block of solid rock • 1,000’ above water table • Remote location on Nevada Test Range It is better to have used nuclear fuel in one locationFor more information, http://www.ocrwm.doe.gov/ymp/index.shtml
Built for 300 years of retrieval10,000 years of storage
Waste Isolation Pilot Plant Opened March 26, 1999 Storage of transuranic waste leftover from research an production of nuclear weapons http://www.wipp.energy.gov/ http://www.radiochemistry.org/wipp_tour/index.html
Private Fuel Storage (Skull Valley, Utah) Temporary storage of spent nuclear fuel until Yucca Mountain is operational Goshute Indian Skull Valley Band 3-ft thick concrete storage pads http://www.privatefuelstorage.com/ http://www.kued.org/skullvalley/
Conclusions HLW is most dangerous byproduct of nuclear power. Borosilicate glass most common storage. Several venues being researched for the safe disposal of HLW.