Arbalest Arbalest The arbalest (also arblast) was a late variation of the crossbow coming into use in Europe during the 12th century. A large weapon, the arbalest had a steel prod ("bow"). Since the arbalest was much larger than earlier crossbows, and because of the greater tensile strength of steel, it had a greater force. However, the greater draw weight was offset by the smaller powerstroke, which limited its potential in fully transferring the energy into the crossbow bolt. The strongest windlass-pulled arbalests could have up to 22 kN (5000 lbf) of force and be accurate up to 100 m. A
Pit (nuclear weapon) risk of predetonation and fizzle. Weapon-grade plutonium therefore has plutonium-240 content limited to less than 7%. Supergrade plutonium has less than 4% of the 240 isotope, and is used in systems where the radioactivity is a concern, e.g. in the US Navy weapons which have to share confined spaces on ships and submarines with the crews. Plutonium-241, commonly comprising about 0.5% of weapon-grade plutonium, decays to americium-241, which is a powerful gamma radiation emitter. After several years, americium builds up in the plutonium metal, leading to increased gamma activity that poses occupational hazard for workers. Americium should therefore be separated,