[Spaceships] Orion space drive: launch from underwater?

[lwcamp]

Originally Posted by Fred Brackin

Nope, If being hit by neutrons does not make a substance radioactive (and this is quite common) they you can't call it a radioactive contaminant.

Radiatioactivity isn't like being tainted by Original Sin.

Tungsten contains five stable isotopes: W-180, W-182, W-183, W-184, and W-186. Neutron capture by W-180 leaves you with W-181, with a 121 day half life (and which normally decays via electron capture to stable Ta-181, so it will only give off x-rays and thus is not that bad). Neutron capture on W-182 and W-183 just gives you another stable iostope of tungsten. Neutron capture by W-184 gives W-185, with a 75 day half-life that beta decays to stable Re-185. Neutron capture by W-186 gives W-187, with a half-life of 1 day which beta decays to stable Re-187. So neutron bombardment of tungsten will give rise to some residual activity. A more complete analysis would look at neutron capture cross sections and the energy spectrum of neutrons within the tungsten shell.

Brett didn't specify what form of fusion is being used, but D-T fusion produces neutrons with 14 MeV of energy - this is really quite energetic and can lead to various nuclear spallation processes as well, such as having the neutron knocking off another neutron or proton or alpha particle. These can make make other radioactive particles, which can be the head end of a decay chain of several isotopes before you reach something stable.

Lead will be similar in general scope to tungsten, although different in the particulars.

Luke