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Plutonium-238 (238 Pu or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years.. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units.
Plutonium-238 has a half-life of 87.74 years. [128] It emits a large amount of thermal energy with low levels of both gamma rays/photons and neutrons. [129] Being an alpha emitter, it combines high energy radiation with low penetration and thereby requires minimal shielding. A sheet of paper can be used to shield against the alpha particles ...
Plutonium-238 has a half-life of 87.74 years [12] and emits alpha particles. Pure 238 Pu for radioisotope thermoelectric generators that power some spacecraft is produced by neutron capture on neptunium-237 but plutonium from spent nuclear fuel can contain as much as a few percent 238 Pu, originating from 237 Np, alpha decay of 242 Cm, or (n,2n ...
The plutonium-239 (or the fissile uranium-235) fissile cross-section is much smaller in a fast spectrum than in a thermal spectrum, as is the ratio between the 239 Pu/ 235 U fission cross-section and the 238 U absorption cross-section.
238 Pu has become the most widely used fuel for RTGs, in the form of plutonium(IV) oxide (PuO 2). [37] However, plutonium(IV) oxide containing a natural abundance of oxygen emits neutrons at the rate of roughly 2.3 × 10 3 n/sec/g of plutonium-238. This emission rate is relatively high compared to the neutron emission rate of plutonium-238 metal.
The energy source for each device was a rod of plutonium-238 providing a thermal power of approximately 1250 W. [23] This fuel capsule, containing 3.8 kilograms (8.4 lb) of plutonium-238 in oxide form (44,500 Ci or 1.65 PBq), was carried to the Moon in a separate fuel cask attached to the side of the Lunar Module. The fuel cask provided thermal ...
GPHSs are fueled with plutonium-238 dioxide. Each module has a temperature of over 600 degrees Celsius [citation needed] and delivers 250 watts at the time of manufacture. . They measure 9.8 cm wide x 9.4 cm deep x 5.4 cm high and weigh no more than 1.44 kg
Diagram of a radioisotope heater unit. A radioisotope heater unit (RHU) is a small device that provides heat through radioactive decay. [1] They are similar to tiny radioisotope thermoelectric generators (RTG) and normally provide about one watt of heat each, derived from the decay of a few grams of plutonium-238—although other radioactive isotopes could be used.