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The density of plutonium-238 at room temperature is about 19.8 g/cc. [3] The material will generate about 0.57 watts per gram of 238 Pu. [4] The bare sphere critical mass of metallic plutonium-238 is not precisely known, but its calculated range is between 9.04 and 10.07 kilograms. [5]
U-232 hazards, a result of its highly radioactive decay products such as thallium-208, are significant even at 5 parts per million. Implosion nuclear weapons require U-232 levels below 50 PPM (above which the U-233 is considered "low grade"; cf. "Standard weapon grade plutonium requires a Pu-240 content of no more than 6.5%."
For instance, 3.6 kg of plutonium-238 undergoes the same number of radioactive decays per second as 1 tonne of plutonium-239. Since the morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly the same, [55] plutonium-238 is around 275 times more toxic by weight than plutonium-239.
Reactor-grade plutonium. Reactor-grade plutonium (RGPu)[1][2] is the isotopic grade of plutonium that is found in spent nuclear fuel after the uranium-235 primary fuel that a nuclear power reactor uses has burnt up. The uranium-238 from which most of the plutonium isotopes derive by neutron capture is found along with the U-235 in the low ...
Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion, and its decay products are naturally found in some concentrated ores of uranium, [52] such as the natural nuclear fission reactor in Oklo, Gabon. [53]
It would have produced 140 watts of electricity using a quarter of the plutonium an RTG or MMRTG needs. [11] The two finished units had these expected specifications: [12] ≥14-year lifetime; Nominal power: 130 W; Mass: 32 kg (71 lb) System efficiency: ≈ 26%; Total mass of plutonium-238-dioxide: 1.2 kg (2.6 lb)
Plutonium-244 (244 Pu) is an isotope of plutonium that has a half-life of 80 million years. This is longer than any of the other isotopes of plutonium and longer than any other actinide isotope except for the three naturally abundant ones: uranium-235 (704 million years), uranium-238 (4.468 billion years), and thorium-232 (14.05 billion years).
The most stable are plutonium-244 with a half-life of 80.8 million years; plutonium-242 with a half-life of 373,300 years; and plutonium-239 with a half-life of 24,110 years; and plutonium-240 with a half-life of 6,560 years. This element also has eight meta states; all have half-lives of less than one second. The known isotopes of plutonium ...