The critical obstacle for a nuclear weapon is not the warhead design but acquisition of special nuclear material (SNM), which is either Uranium-235 (U-235) or Plutonium-239 (Pu-239
Pakistan and India, with estimated combined numbers of 250 nuclear weapons (130 and 120 respectively)1 and roughly total amount 6.3 tons of highly enriched uranium (HEU-235) and 5.26 tons plutonium (Pu-239
) for military uses, remain on the verge of war.
The use of part length rods reduces the amount of fuel in the top of assembly, where neutron moderation is less effective and the build-up of Pu-239
is produced when U-238 nuclei absorb slow neutrons.
The core of a nuclear fission explosive device is either composed of high proportion of Pu-239
(which is a radioactive isotope of plutonium metal) or highly-enriched isotope of uranium i.e.
When the team determined that one isotope, Pu-239
, had fissionable properties that would make it usable in atomic weapons, Seaborg was recruited to join the Manhattan Project.
) is the fissile isotope in pits.
Experiments with rotating collimators cutting out pencil of alpha-particles at radioactive decay of Pu-239
evidence sharp anisotropy of space.
The total exposure dose rate of reference organisms resulting from ionising radiation of technogenic radionuclides in Lake Druksiai Insect larvae H-3, Pu-239
<1% Cs-137 40% Cs-134 1% C-14 2% Mn-54 4% Co-60 42% Sr-90 10% Vascular plant H-3, Pu-239
<1% Cs-137 40% Cs-134 1% C-14 2% Mn-54 4% Co-60 43% Sr-90 9% Crustacean H-3, Pu-239
<1% Cs-137 40% Cs-134 1% C-14 3% Mn-54 4% Co-60 41% Sr-90 1% Gastropod H-3, Pu-239
<1% Cs-137 38% Cs-134 1% C-14 4% Mn-54 4% Co-60 46% Sr-90 6% Note: Table made from pie chart.
According to Cosmos magazine: "Unlike U-235 and Pu-239
, no matter how much thorium you pack together, it will not start splitting atoms and blow up.
The type of plutonium in the bottle - known as Pu-239
- is a so-called alpha emitter.