I have posted about nuclear weapons and nuclear disarmament before. One of the problems with disarmament is the question of verifying that a nation has actually reduced their nuclear stockpile. While direct inspections are one method, you have to trust that the nation being inspected does not have a hidden stash of warheads or weapons grade nuclear materials tucked away somewhere. This is especially relevant when we are talking about the situation in Iran. Iran swears that it has no interest in developing a nuclear bomb while Israel swears that that is exactly what Iran is doing.
Neutrinos are "electrically neutral, weakly interacting elementary subatomic particles with half-integer spin." They are generated by nuclear processes such as those taking place in the Sun and in nuclear reactors. Neutrinos travel at the speed of light and are not affected by electromagnetism or the strong nuclear force. Because they are "weakly interactive," they easily pass through normal matter as if it were not there. About sixty five billion solar neutrinos pass through each square centimeter of the Earth perpendicular to the Sun each second. Neutrinos have related antimatter particles called antineutrinos.
Antineutrinos are very similar to neutrinos but they have the opposite spin. The antineutrino spectra of uranium 235, plutonium 239 and plutonium 241 were determined in the 1980s. However, the absence of a spectra for uranium-238 made it difficult to get an accurate reading of nuclear fuel in a reactor core. Physicists at Technische Universität München have now found the antineutrino spectra for uranium 238 which provides the mission information needed for analysis of antineutrino emissions from a nuclear reactor core.
A group of scientists at Virginia Tech are currently exploring the possibility that antineutrinos could be used to detect the mix of nuclear materials in a reactor core because they are generated by nuclear reactions and cannot be blocked by any type of shielding. A measurement of antineutrinos emitted from a nuclear reactor building could indicate the amount of plutonium inside the reactor.
Neutrino detectors have been built that are roughly one cubic meter in size. The researchers say that minor modifications of current neutrino detectors would allow a complete antineutrino detection system to be packaged into a twenty foot shipping container. Such a detection system could be shipped to the Iranian reactor at Arak to monitor compliance with international agreements. The Arak reactor is ideal for creating plutonium which is a prime material for construction nuclear warheads. The detection system that the researchers envision would even be able indicate the enrichment level of the fuel in the reactor. It would also be able to differentiate between antineutrinos emitted by isotopes of uranium from isotopes of plutonium. The system they envision should be able to function within about thirty feet of a nuclear reactor core. There is no other system in existence that would allow for such close monitoring of reactor fuels.
The existence of a reliable, compact and cost effective system for detecting antineutrino emissions remotely from a nuclear reactor core will assist the International Atomic Energy Agency in its work on verifying compliance with non-proliferation agreements.
LENS neutrino detector model:
