Ok, so the prez is coming to Argonne Natl Lab today to see a show and tell about new anti-terrorist weapons. According to NPR, one that they’re scheduled to demonstrate is a portable neutron detector, helpful in finding small or hidden nuclear arms. I think I understand that neutrons may occasionally escape the fuel and the containing material, and presumably if detected, their presence can indicate a reactor someplace. (a premise fraught with assumptions and half-understandings, admittedly). So, my question is this: is it possible to detect these neutrons from a distance? Could a spy satellite detect neutron radiation from some source, thereby pointing to a potential nuclear fuel source? Or, would there be no difference between this radiation and that which normally comes from uranium mines, etc. ? Could we do weapons inspection in Iraq, eg, by remote sensing?
I think the emissions would probably adhere to the inverse square law, and thus become more and more difficult to detect with every increase in distance.
The Atomic Weapons Research Establishment at Aldermaston had, sometime in the early Eighties, a mobile radiation detector that could fit in the back of a truck, and discriminate to some extent between sources of radiation. It seems likely that someone’s improved on this technology in the intervening twenty years.
Supposedly, and this is according to a friend of mine who’s dad works for Oak Ridge, they do have satellite based nuclear detectors. What types of radiation they look for and how sensative they are, I don’t know. They also supposedly have a nuclear detector the size of a quarter. Again, no specs on sensativity. Considering the worries of some tin-pot dictator (or worse) getting hold of a nuke and using it, its no surprise that the US would be doing research on it. I imagine that a good portion of the “black budget” is devoted to such things.
CC
The U.S. employs space based nuclear detonation detection. This happens to be the secondary mission of the Global Positioning System satellites. To be able to detect nuclear weapons prior to detonation from space would be extremely expensive. Not likely to occur any time soon.
Beerfan
Neutron radiation would actually fall off quicker than the inverse square, since free neutrons are unstable and decay. Beta and alpha particles (electrons and helium nuclei) are stable, but they’ll lose energy with collisions with ordinary matter, and once they’ve slowed down, they’re no longer recognizable as “radiation”. Your best bet for detecting radioactive material from a distance is probably gamma rays (high-energy photons). I don’t know how effective this is, though.
… Heh. Yeah, but not much faster. The free neutron lifetime is about 15 minutes, which (even discounting relativistic corrections) is plenty of time to get to any Earth-orbiting satellites.
I still doubt that this is feasible, just because of noise from background radioactivity, but I don’t know enough about it to say.
I saw a recent article that stated that airborne detectors could locate radiation sources on the ground equivalent to an unshielded package of 100 thorium lantern mantles.
From what I understand, it’s easy to conceal and transport a small nuke if it’s unshielded, but to hide from detection requires quite a heavy mass of lead.