Arbalest skilled arbalestier (arbalester) could loose two bolts per minute. The term "arbalest" is sometimes used interchangeably with "crossbow". "Arbalest" is a Medieval French word originating from the Roman name ' (from ' 'bow' + " 'missile-throwing engine'), which was then used for crossbows, although originally used for types of artillery. Modern French uses the word ", which is linguistically one step further from the stem (disappearance of the "s" phoneme in the last syllable, before "t"). The word applies to both crossbow and arbalest (the latter may be referred to as a "heavy crossbow", but an actual heavy crossbow may
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,