Uranium-233 is a
fissileIn nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
isotope of uraniumUranium is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The average atomic mass of natural uranium is 238.02891 u...
, bred from Thorium as part of the
thorium fuel cycleThe thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
. It has been used in a few
nuclear reactorA nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s and has been proposed for much wider use as a
nuclear fuelNuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
. It has a
half-lifeHalf-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 160,000 years.
Uranium-233 is produced by the
neutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
irradiationIrradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to...
of thorium-232. When thorium-232 absorbs a neutron, it becomes thorium-233, which has a half-life of only 22 minutes. Thorium-233 decays into
protactiniumProtactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume...
-233 through
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. Protactinium-233 has a half-life of 27 days and beta decays into uranium-233; some proposed
molten salt reactorA molten salt reactor is a type of nuclear fission reactor in which the primary coolant, or even the fuel itself is a molten salt mixture...
designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur.
233U usually fissions on neutron absorption but sometimes retains the neutron, becoming
uranium-234, although the proportion of nonfissions is smaller than for the other common fission fuels,
uranium-235- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
and
plutonium-239Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
, as well as
plutonium-241Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like Pu-239 but unlike 240Pu, 241Pu is fissile, with a neutron absorption cross section about 1/3 greater than 239Pu, and a similar probability of fissioning on neutron absorption, around 73%. In the non-fission...
. It is slightly smaller at all neutron energies.
Fissile material
In 1946 the public first became informed of U-233 bred from Thorium as "a third available source of nuclear energy and atom bombs" (in addition to U-235 and Pu-239), following a
United NationsThe United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
report and a speech by
Glenn T. SeaborgGlenn Theodore Seaborg was an American scientist who won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements, and developed the actinide concept, which led to the current arrangement of the...
.
The United States produced, over the course of the cold war, approximately 2 metric tons of uranium-233, in varying levels of chemical and isotopic purity. These were produced at the
Hanford SiteThe Hanford Site is a mostly decommissioned nuclear production complex on the Columbia River in the U.S. state of Washington, operated by the United States federal government. The site has been known by many names, including Hanford Works, Hanford Engineer Works or HEW, Hanford Nuclear Reservation...
and
Savannah River SiteThe Savannah River Site is a nuclear reservation in the United States in the state of South Carolina, located on land in Aiken, Allendale and Barnwell Counties adjacent to the Savannah River, southeast of Augusta, Georgia. The site was built during the 1950s to refine nuclear materials for...
in reactors that were designed for the production of
plutonium-239Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...
. Historical production costs, estimated from the costs of plutonium production, were $2-4 million / kg. There are few reactors remaining in the world with significant capabilities to produce more uranium-233.
Nuclear fuel
Breeding uranium-233 from thorium feedstock is the long-term strategy of the
nuclear power program of IndiaNuclear power is the fourth-largest source of electricity in India after thermal, hydroelectric and renewable sources of electricity. As of 2010, India has 20 nuclear reactors in operation in six nuclear power plants, generating 4,780 MW while seven other reactors are under construction and...
, which has substantial thorium reserves. Breeding can be done in either fast reactors or
thermal reactorA thermal reactor is a nuclear reactor that uses slow or thermal neutrons. Most power reactors are of this type. These type of reactors use a neutron moderator to slow neutrons until they approach the average kinetic energy of the surrounding particles, that is, to reduce the speed of the neutrons...
s, unlike uranium-based
fuel cycleThe nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in...
s which require the superior
neutron economyNeutron economy is defined as the ratio of an adjoint weighted average of the excess neutron production divided by an adjoint weighted average of the fission production....
of a fast reactor in order to
breed plutonium, that is to produce more fissile material than is consumed.
Flibe EnergyFlibe Energy is a company that intends to design, construct and operate small modular reactors based on liquid fluoride thorium reactor technology.-Corporation:...
is a company that intends to develop small modular reactors based on liquid fluoride thorium reactor (LFTR) technology.
Energy released
The fission of one atom of U-233 generates 197.9
MeVIn physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
= 3.171 × 10
−11 J, i.e. 19.09 TJ/
molThe mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
= 81.95 TJ/kg.
| Source | Average energy released
(MeV) |
| Instantaneously released energy |
|
| Kinetic energy of fission fragments |
168.2 |
| Kinetic energy of prompt neutrons |
4.9 |
| Energy carried by prompt γ-rays |
7.7 |
| Energy from decaying fission products |
|
| Energy of β−-particles |
5.2 |
| Energy of anti-neutrinos |
6.9 |
| Energy of delayed γ-rays |
5.0 |
| Sum |
197.9 |
| Energy released when those prompt neutrons which don't (re)produce fission are captured |
9.1 |
| Energy converted into heat in an operating thermal nuclear reactor |
200.1 |
Weapon material
While it is possible to use uranium-233 as the fission fuel of a
nuclear 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...
, this has been done only occasionally. The United States first tested U-233 as part of a bomb core (with plutonium) in
Operation TeapotOperation Teapot was a series of fourteen nuclear test explosions conducted at the Nevada Test Site in the first half of 1955.During shot "Wasp", ground forces took part in Exercise Desert Rock VI which included an armored task force "Razor" moving to within 900 meters of ground zero, under the...
in 1955.
Uranium-233 compares roughly to plutonium-239: its radioactivity is only one seventh (159,200 years half-life versus 24,100 years), but its bare critical mass is 60% higher (16 kg versus 10 kg), and its spontaneous fission rate is twenty times higher (6×10E−9 versus 3×10E−10) — but since the radioactivity is lower, the neutron density is only three times higher. A nuclear explosive device based on uranium-233 is therefore more of a technical challenge than with plutonium, but the technological level involved is roughly the same. The main difference is the co-presence of uranium-232 which makes uranium-233 very dangerous to work on, and quite easy to detect.
U-232 impurity
Production of
233U (through the irradiation of Thorium-232) invariably produces small amounts of uranium-232 as an impurity, because of parasitic (n,2n) reactions on Uranium-233 itself, or on Protactinium-233:
- 232Th (n,γ) 233Th (β−) 233Pa (β−) 233U (n,2n) 232U
- 232Th (n,γ) 233Th (β−) 233Pa (n,2n) 232Pa (β−) 232U
The
decay chainIn nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
of
232U quickly yields strong gamma radiation emitters:
- 232U (α, 72 years)
- 228Th (α, 1.9 year)
- 224Ra (α, 3.6 day, 0.24 MeV)
- 220Rn (α, 55 s, 0.54 MeV)
- 216Po (α, 0.15 s)
- 212Pb (β−, 10.64 h)
- 212Bi (α, 61 s, 0.78 MeV)
- 208Tl (β−, 3 m, 2.6 MeV)
- 208Pb (stable)
This makes manual handling in a glove box with only light shielding (as commonly done with
plutoniumPlutonium 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...
) too hazardous, (except possibly in a short period immediately following chemical separation of the uranium from thorium-228,
radiumRadium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
-224,
radonRadon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...
-220, and
poloniumPolonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Skłodowska-Curie and Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for...
) and instead requiring remote manipulation for fuel fabrication.
Further information
Thorium, from which U-233 is bred, is roughly three times more common than uranium.
The decay chain of
233U itself is in the neptunium series.
Uses for uranium-233 include low-mass nuclear reactors for space travel applications, use as an isotopic tracer, use in nuclear weapons and nuclear weapon research, investigation of the
thorium fuel cycleThe thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
and the production of medical isotopes actinium-225 and bismuth-213. The radioisotope
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
-213 is a decay product of uranium-233; it has promise for the treatment of certain types of
cancerCancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, including
acute myeloid leukemiaAcute myeloid leukemia , also known as acute myelogenous leukemia, is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute...
and cancers of the
pancreasThe pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
,
kidneyThe kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s and other
organsIn biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
.