Plutonium 238

Plutonium-238 oxide pellet glowing from its own heat

Plutonium-238 (also known as Pu-238 or ²³⁸Pu) is a radioactive isotope of plutonium that has a half-life of 87.7 years.

Plutonium-238 is a very powerful alpha emitter. This makes the plutonium-238 isotope suitable for usage in radioisotope thermoelectric generators (RTGs) and radioisotope heater units.

One gram of ²³⁸Pu corresponds to 1/238 moles, which is 2.53×10²¹ plutonium atoms. Considering its half-life t_1/2 = 87.7 years, its activity is

${\displaystyle A=\lambda N={\frac {\ln 2}{t_{1/2}}}N=634\,{\mbox{GBq}}}$.

It is the number of ²³⁸Pu decays per second. Each of the emitted alpha particles has kinetic energy 5.593 MeV or 8.96×10⁻¹³J which is quickly converted to heat when the particle decelerates in the material. Therefore each gram of ²³⁸Pu spontaneously generates 0.568 W of heat.

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