High level waste
Encyclopedia
High level waste is a type of nuclear waste created by the reprocessing of spent nuclear fuel. It exists in two main forms:
Liquid high level waste is typically held temporarily in underground tanks pending vitrification. Most of the high level waste created by the Manhattan project
and the weapons programs of the cold war
exists in this form because funding for further processing was typically not part of the original weapons programs. Both spent nuclear fuel and vitrified waste are considered as suitable forms for long term disposal, after a period of temporary storage in the case of spent nuclear fuel.
HLW contains many of the fission products and transuranic elements generated in the reactor core
and is the type of nuclear waste with the highest activity. HLW accounts for over 95% of the total radioactivity produced in the nuclear power process. In other words, while most nuclear waste is low-level and intermediate-level waste, such as protective clothing and equipment that have been contaminated with radiation, the majority of the radioactivity produced from the nuclear power generation process becomes high-level waste.
In the US, HLW from reprocessing of spent fuel from electrical power stations amounts to less than 1% of the total volume of US HLW; the rest is defense related. Some other countries, particularly France, reprocess commercial spent fuel.
High level waste is very radioactive and, therefore, requires special shielding during handling and transport. It also needs cooling, because it generates a great deal of heat. Most of the heat, for the first several hundred years, is from the medium-lived fission products cesium-137 and strontium-90
.
A typical large nuclear reactor produces 25–30 tons of spent fuel
per year. If the fuel were reprocessed
and vitrified, the waste volume would be only about three cubic meters per year, but the decay heat
would be almost the same.
It is generally accepted that the final waste will be disposed of in a deep geological repository
, and many countries have developed plans for such a site, including France
, Japan
, and the United States
(see also High-level radioactive waste management
).
Spent (used) reactor fuel.
Waste materials from reprocessing.
s and in dry cask storage
facilities.
In 1997, in the 20 countries which account for most of the world's nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilized. With annual additions of about 12,000 tonnes, issues for final disposal are not urgent.
The status of disposal plans in various countries is described in the article High-level radioactive waste management
.
- First and second cycle raffinateRaffinateRaffinating something is a technique used in metallurgy to remove impurities from liquid material. There are many different kinds of raffination, for example you can use vacuum to extract hydrogen from metals....
and other waste streams created by nuclear reprocessingNuclear reprocessingNuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
.
- Waste formed by vitrification of liquid high level waste.
Liquid high level waste is typically held temporarily in underground tanks pending vitrification. Most of the high level waste created by the Manhattan project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...
and the weapons programs of the cold war
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
exists in this form because funding for further processing was typically not part of the original weapons programs. Both spent nuclear fuel and vitrified waste are considered as suitable forms for long term disposal, after a period of temporary storage in the case of spent nuclear fuel.
HLW contains many of the fission products and transuranic elements generated in the reactor core
Nuclear reactor core
A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place.- Description :...
and is the type of nuclear waste with the highest activity. HLW accounts for over 95% of the total radioactivity produced in the nuclear power process. In other words, while most nuclear waste is low-level and intermediate-level waste, such as protective clothing and equipment that have been contaminated with radiation, the majority of the radioactivity produced from the nuclear power generation process becomes high-level waste.
In the US, HLW from reprocessing of spent fuel from electrical power stations amounts to less than 1% of the total volume of US HLW; the rest is defense related. Some other countries, particularly France, reprocess commercial spent fuel.
High level waste is very radioactive and, therefore, requires special shielding during handling and transport. It also needs cooling, because it generates a great deal of heat. Most of the heat, for the first several hundred years, is from the medium-lived fission products cesium-137 and strontium-90
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
.
A typical large nuclear reactor produces 25–30 tons of spent fuel
Spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...
per year. If the fuel were reprocessed
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
and vitrified, the waste volume would be only about three cubic meters per year, but the decay heat
Decay heat
Decay heat is the heat released as a result of radioactive decay. This is when the radiation interacts with materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms.-Natural occurrence:...
would be almost the same.
It is generally accepted that the final waste will be disposed of in a deep geological repository
Deep geological repository
A deep geological repository is a nuclear waste repository excavated deep within a stable geologic environment...
, and many countries have developed plans for such a site, including France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
(see also High-level radioactive waste management
High-level radioactive waste management
High-level radioactive waste management concerns management and disposal of highly radioactive materials created during production of nuclear power and nuclear warheads. The technical issues in accomplishing this are daunting, due to the extremely long periods radioactive wastes remain deadly to...
).
Definitions
High-level waste is the highly radioactive waste material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations; and other highly radioactive material that is determined, consistent with existing law, to require permanent isolation.Spent (used) reactor fuel.
- Spent nuclear fuelSpent nuclear fuelSpent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor...
is used fuel from a reactor that is no longer efficient in creating electricity, because its fission process has slowed due to a build-up of reaction poisonsNuclear poisonA neutron poison is a substance with a large neutron absorption cross-section in applications, such as nuclear reactors. In such applications, absorbing neutrons is normally an undesirable effect...
. However, it is still thermallyDecay heatDecay heat is the heat released as a result of radioactive decay. This is when the radiation interacts with materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms.-Natural occurrence:...
hot, highly radioactive, and potentially harmful.
Waste materials from reprocessing.
- Materials for nuclear weaponNuclear weaponA nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
s are acquired by reprocessingNuclear reprocessingNuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
spent nuclear fuel from breeder reactorBreeder reactorA breeder reactor is a nuclear reactor capable of generating more fissile material than it consumes because its neutron economy is high enough to breed fissile from fertile material like uranium-238 or thorium-232. Breeders were at first considered superior because of their superior fuel economy...
s. Reprocessing is a method of chemically treating spent fuel to separate out uraniumUraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and plutoniumPlutoniumPlutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
. The byproduct of reprocessing is a highly radioactive sludgeSludgeSludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. It can also refer to the settled suspension obtained from conventional drinking water treatment, and numerous other industrial processes...
residue.
Disposing of high-level wastes
High-level radioactive waste is stored temporarily in spent fuel poolSpent fuel pool
Spent fuel pools are storage pools for spent fuel from nuclear reactors. They are typically 40 or more feet deep, with the bottom 14 feet equipped with storage racks designed to hold fuel assemblies removed from the reactor. A reactor's pool is specially designed for the reactor in which the...
s and in dry cask storage
Dry cask storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in the spent fuel pool for at least one year.. These casks are typically steel cylinders that are either welded or bolted closed. When inside, the fuel rods are surrounded...
facilities.
In 1997, in the 20 countries which account for most of the world's nuclear power generation, spent fuel storage capacity at the reactors was 148,000 tonnes, with 59% of this utilized. Away-from-reactor storage capacity was 78,000 tonnes, with 44% utilized. With annual additions of about 12,000 tonnes, issues for final disposal are not urgent.
The status of disposal plans in various countries is described in the article High-level radioactive waste management
High-level radioactive waste management
High-level radioactive waste management concerns management and disposal of highly radioactive materials created during production of nuclear power and nuclear warheads. The technical issues in accomplishing this are daunting, due to the extremely long periods radioactive wastes remain deadly to...
.
External links
See also
- Radioactive wasteRadioactive wasteRadioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
- low level wasteLow level wasteLow-Level Waste is a term used to describe nuclear waste that does not fit into the categorical definitions for high-level waste , spent nuclear fuel , transuranic waste , or certain byproduct materials known as 11e wastes, such as uranium mill tailings...
- transuranic wasteTransuranic wasteTransuranic waste is, as stated by U.S. regulations and independent of state or origin, waste which has been contaminated with alpha emitting transuranic radionuclides possessing half-lives greater than 20 years and in concentrations greater than 100 nCi/g .Elements having atomic numbers greater...
- mixed wasteMixed waste (radioactive/hazardous)According to the United States Environmental Protection Agency, mixed waste is a waste type defined as follows; "MW contains both hazardous waste and radioactive waste . It is jointly regulated by NRC or NRC's Agreement States and EPA or EPA's RCRA Authorized States...