Nuclear power/Thorium

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Thorium-based fuels are appropriate both for pressurized-water reactors (top) and for high-temperature gas reactors (bottom). Credit: Barbara Aulicino.

Nuclear power is a phrase that refers to the use of a nuclear reactor as a provider of electrical power for commercial, public, or defense purposes.

Thorium is a fissionable element that can be used in a nuclear reactor.

"The use of thorium in power reactors has been considered since the birth of nuclear energy in the 1950s, in large part because thorium is considerably more abundant than uranium in the Earth's crust."[1]

Pressurized-water reactors such as diagrammed at the top right in the image on the right "use ordinary water to transfer heat from the core and to slow the neutrons generated in the fission reactions".[1]

High-temperature gas reactors, on the bottom of the image on the right, "use a gas such as helium to transfer heat and solid graphite to slow the neutrons".[1]

Fuel cycles[edit | edit source]

"Unfortunately, thorium atoms cannot themselves be easily induced to split—the basic requirement of a fission reactor. But when a quantity of thorium-232 (the common isotope of that element) is placed within a nuclear reactor, it readily absorbs neutrons and transforms into uranium-233, which, like the uranium-235 typically used for generating nuclear power, supports fission chain reactions. Thorium is thus said to be "fertile" rather than fissile."[1]

Transmutations in the thorium fuel cycle
230Th 231Th 232Th 233Th (White actinides: t½<27d)
231Pa 232Pa 233Pa 234Pa (Colored : t½>68y)
231U 232U 233U 234U 235U 236U 237U
(Fission products with t½<90y or t½>200ky) 237Np

Thorium-fueled reactors[edit | edit source]

Name Country Reactor type Power Fuel Operation period
AVR Germany HTGR, experimental (pebble bed reactor) 015000 15 MW(e) Th+235U Driver fuel, coated fuel particles, oxide & dicarbides 1967–1988
THTR-300 Germany HTGR, power (pebble type) 300000 300 MW(e) Th+235U, Driver fuel, coated fuel particles, oxide & dicarbides 1985–1989
Lingen Germany BWR irradiation-testing 060000 60 MW(e) Test fuel (Th,Pu)O2 pellets 1968-1973
Dragon (OECD-Euratom) UK (also Sweden, Norway & Switzerland) HTGR, Experimental (pin-in-block design) 020000 20 MWt Th+235U Driver fuel, coated fuel particles, oxide & dicarbides 1966–1973
Peach Bottom USA HTGR, Experimental (prismatic block) 040000 40 MW(e) Th+235U Driver fuel, coated fuel particles, oxide & dicarbides 1966–1972
Fort St Vrain USA HTGR, Power (prismatic block) 330000 330 MW(e) Th+235U
MSRE ORNL USA MSR 007500 7.5 MWt 233U molten fluorides 1964–1969
BORAX-IV & Elk River Station USA BWR (pin assemblies) 002400 2.4 MW(e); 24 MW(e) Th+235U Driver fuel oxide pellets 1963 - 1968
Shippingport USA LWBR, PWR, (pin assemblies) 100000 100 MW(e) Th+233U Driver fuel, oxide pellets 1977–1982
Indian Point 1 USA LWBR, PWR, (pin assemblies) 285000 285 MW(e) Th+233U Driver fuel, oxide pellets 1962–1980
SUSPOP/KSTR KEMA Netherlands Aqueous homogenous suspension (pin assemblies) 001000 1 MWt Th+HEU, oxide pellets 1974–1977
NRX & NRU Canada MTR (pin assemblies) 020000 20MW; 200MW (see) Th+235U, Test Fuel 1947 (NRX) + 1957 (NRU); Irradiation–testing of few fuel elements
CIRUS; DHRUVA; & KAMINI India MTR thermal 040000 40 MWt; 100 MWt; 30 kWt (low power, research) Al+233U Driver fuel, ‘J’ rod of Th & ThO2, ‘J’ rod of ThO2 1960-2010 (CIRUS); others in operation
KAPS 1 &2; KGS 1 & 2; RAPS 2, 3 & 4 India PHWR, (pin assemblies) 220000 220 MW(e) ThO2 pellets (for neutron flux flattening of initial core after start-up) 1980 (RAPS 2) +; continuing in all new PHWRs
FBTR India LMFBR, (pin assemblies) 040000 40 MWt ThO2 blanket 1985; in operation

India[edit | edit source]

"One country that has maintained interest is India, which began fueling some of its power reactors in the mid-1990s with bundles containing thorium. Although one of the reasons for employing thorium was simply to even out the distribution of power within the cores of these reactors, Indian engineers also took the opportunity to test how well thorium could function as a fuel source. The positive results they obtained motivated their current plans to use thorium-based fuels in more advanced reactors now under construction."[1]

"India's attraction to thorium-based fuels stems, in part, from its large indigenous supply. (With estimated thorium reserves of some 290,000 tons, it ranks second only to Australia.) But that nation's pursuit of thorium, which helps bring it independence from overseas uranium sources, came about for a reason that has nothing to do with its balance of trade: India uses some of its reactors to make plutonium for atomic bombs. Thus India refuses to be constrained by the provisions that commercial uranium suppliers in countries such as Canada require: They demand that purchasers of their ore allow enough oversight to ensure that the fuel (or the plutonium spawned from it) is not used for nuclear weapons."[1]

Thorcon[edit | edit source]

The subpage (linked in the subject header) covers a commercial thorium reactor effort.

See also[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Mujid Kazimi (September-October 2003). "Thorium Fuel for Nuclear Energy". American Scientist 91 (5): 408. doi:10.1511/2003.5.408. http://www.americanscientist.org/issues/id.884,y.2003,no.5,page.2/postComment.aspx. Retrieved 2015-07-16.