# Nuclear power/Thorium

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."
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".
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".

## Fuel cycles

"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."
    $\mathrm {n} +_{\ 90}^{232}\mathrm {Th} \rightarrow_{\ 90}^{233}\mathrm {Th} {\xrightarrow {\beta ^{-}}}_{\ 91}^{233}\mathrm {Pa} {\xrightarrow {\beta ^{-}}}_{\ 92}^{233}\mathrm {U}$
    $\mathrm {n} +_{\ 90}^{232}\mathrm {Th} \rightarrow_{\ 90}^{233}\mathrm {Th} {\xrightarrow {\beta ^{-}}}_{\ 91}^{233}\mathrm {Pa} {\xrightarrow {\beta ^{-}}}_{\ 92}^{233}\mathrm {U} +\mathrm {n} \rightarrow_{\ 92}^{232}\mathrm {U} +2\mathrm {n}$
    $\mathrm {n} +_{\ 90}^{232}\mathrm {Th} \rightarrow_{\ 90}^{233}\mathrm {Th} {\xrightarrow {\beta ^{-}}}_{\ 91}^{233}\mathrm {Pa} +\mathrm {n} \rightarrow_{\ 91}^{232}\mathrm {Pa} +2\mathrm {n} {\xrightarrow {\beta ^{-}}}_{\ 92}^{232}\mathrm {U}$
    $\mathrm {n} +_{\ 90}^{232}\mathrm {Th} \rightarrow_{\ 90}^{231}\mathrm {Th} +2\mathrm {n} {\xrightarrow {\beta ^{-}}}_{\ 91}^{231}\mathrm {Pa} +\mathrm {n} \rightarrow_{\ 91}^{232}\mathrm {Pa} {\xrightarrow {\beta ^{-}}}_{\ 92}^{232}\mathrm {U}$
    $_{\ 92}^{232}\mathrm {U} {\xrightarrow {\ \alpha \ }}_{\ 90}^{228}\mathrm {Th} \ \mathrm {(68.9\ years)}$
    $_{\ 90}^{228}\mathrm {Th} {\xrightarrow {\ \alpha \ }}_{\ 88}^{224}\mathrm {Ra} \ \mathrm {(1.9\ year)}$
    $_{\ 88}^{224}\mathrm {Ra} {\xrightarrow {\ \alpha \ }}_{\ 86}^{220}\mathrm {Rn} \ \mathrm {(3.6\ day,\ 0.24\ MeV)}$
    $_{\ 86}^{220}\mathrm {Rn} {\xrightarrow {\ \alpha \ }}_{\ 84}^{216}\mathrm {Po} \ \mathrm {(55\ s,\ 0.54\ MeV)}$
    $_{\ 84}^{216}\mathrm {Po} {\xrightarrow {\ \alpha \ }}_{\ 82}^{212}\mathrm {Pb} \ \mathrm {(0.15\ s)}$
    $_{\ 82}^{212}\mathrm {Pb} {\xrightarrow {\beta ^{-}\ }}_{\ 83}^{212}\mathrm {Bi} \ \mathrm {(10.64\ h)}$
    $_{\ 83}^{212}\mathrm {Bi} {\xrightarrow {\ \alpha \ }}_{\ 81}^{208}\mathrm {Tl} \ \mathrm {(61\ m,\ 0.78\ MeV)}$
    $_{\ 81}^{208}\mathrm {Tl} {\xrightarrow {\beta ^{-}\ }}_{\ 82}^{208}\mathrm {Pb} \ \mathrm {(3\ m,\ 2.6\ MeV)}$
Transmutations in the thorium fuel cycle :
| $^{231}$Th | ← | $^{232}$Th | → | $^{233}$Th | | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) | (White actinides: t$_½$<27d) |
| $^{231}$Pa | → | $^{232}$Pa | ← | $^{233}$Pa | → | $^{234}$Pa | | (Colored : t$_½$>68y) | (Colored : t$_½$>68y) | (Colored : t$_½$>68y) | (Colored : t$_½$>68y) | (Colored : t$_½$>68y) |
| $^{231}$U | ← | $^{232}$U | ↔ | $^{233}$U | ↔ | $^{234}$U | ↔ | $^{235}$U | ↔ | $^{236}$U | → | $^{237}$U |
| (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | (Fission products with t$_½$<90y or t$_½$>200ky) | | $^{237}$Np |

## Thorium-fueled reactors

| Name | Country | Reactor type | Power | Fuel | Operation period |
| AVR | Germany | HTGR, experimental (pebble bed reactor) | 015000 15 MW(e) | Th+$^{235}$U Driver fuel, coated fuel particles, oxide & dicarbides | 1967–1988 |
| THTR-300 | Germany | HTGR, power (pebble type) | 300000 300 MW(e) | Th+$^{235}$U, Driver fuel, coated fuel particles, oxide & dicarbides | 1985–1989 |
| Lingen | Germany | BWR irradiation-testing | 060000 60 MW(e) | Test fuel (Th,Pu)O$_2$ pellets | 1968-1973 |
| Dragon (OECD-Euratom) | UK (also Sweden, Norway & Switzerland) | HTGR, Experimental (pin-in-block design) | 020000 20 MWt | Th+$^{235}$U Driver fuel, coated fuel particles, oxide & dicarbides | 1966–1973 |
| Peach Bottom | USA | HTGR, Experimental (prismatic block) | 040000 40 MW(e) | Th+$^{235}$U Driver fuel, coated fuel particles, oxide & dicarbides | 1966–1972 |
| Fort St Vrain | USA | HTGR, Power (prismatic block) | 330000 330 MW(e) | Th+$^{235}$U |
| MSRE ORNL | USA | MSR | 007500 7.5 MWt | $^{233}$U molten fluorides | 1964–1969 |
| BORAX-IV & Elk River Station | USA | BWR (pin assemblies) | 002400 2.4 MW(e); 24 MW(e) | Th+$^{235}$U Driver fuel oxide pellets | 1963 - 1968 |
| Shippingport | USA | LWBR, PWR, (pin assemblies) | 100000 100 MW(e) | Th+$^{233}$U Driver fuel, oxide pellets | 1977–1982 |
| Indian Point 1 | USA | LWBR, PWR, (pin assemblies) | 285000 285 MW(e) | Th+$^{233}$U 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+$^{235}$U, 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+$^{233}$U Driver fuel, ‘J’ rod of Th & ThO$_2$, ‘J’ rod of ThO$_2$ | 1960-2010 (CIRUS); others in operation |
| KAPS 1 &2; KGS 1 & 2; RAPS 2, 3 & 4 | India | PHWR, (pin assemblies) | 220000 220 MW(e) | ThO$_2$ 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 | ThO$_2$ blanket | 1985; in operation |

## India

"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."
"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."

## Thorcon

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