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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.
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 .
The isotope produces 0.57 watts of thermal power per gram of 238 Pu. [5] Soviet missions have used other isotopes, such as the polonium-210 heat source used in the Lunokhod lunar rovers. [6] [7] With a half-life of 138.376 days, polonium-210 produces more thermal power per unit mass, but is suitable only for shorter duration missions.
The pits of the first nuclear weapons were solid, with an urchin neutron initiator in their center. The Gadget and Fat Man used pits made of 6.2 kg of solid hot pressed plutonium-gallium alloy (at 400 °C and 200 MPa in steel dies – 750 °F and 29,000 psi) half-spheres of 9.2 cm (3.6 in) diameter, with a 2.5 cm (1 in) internal cavity for the initiator.
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
Nuclear weapon design. Appearance. The first nuclear explosive devices provided the basic building blocks of future weapons. Pictured is the Gadget device being prepared for the Trinity nuclear test. Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package [ 1 ] of a nuclear weapon to detonate.
Integral fast reactor. The integral fast reactor (IFR), originally the advanced liquid-metal reactor (ALMR), is a design for a nuclear reactor using fast neutrons and no neutron moderator (a "fast" reactor). IFRs can breed more fuel and are distinguished by a nuclear fuel cycle that uses reprocessing via electrorefining at the reactor site.
talk. edit. Plutonium (94 Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being plutonium-238 in 1940.