In the late 19th century, physicists identified three kinds of nuclear radiation. One could be stopped easily by a sheet of paper; they named it alpha, for the first letter of Greek alphabet. The second would pass through paper, but could be stopped by a sheet of metal. It got named beta. The last could only be stopped by a thick chunk of metal, so it got the name gamma (the third Greek letter).

Eventually, alpha radiation was identified as helium nuclei (2 protons + 2 neutrons). Beta radiation is either an electron or positron (antimatter electron). Gamma rays are high energy photons.

Originally, beta decay was believed to be neutron –> proton + electron, but the nucleus behaved very strangely. Although it spits out a beta particle at a pretty good speed, the parent nucleus does not recoil. It would be like firing a loaded pistol and not feeling the kick. In 1930, physicist Wolfgang Pauli proposed there was another, unseen particle involved in the decay process, which was “stealing” the missing energy and momentum. It also had to be electrically neutral (to conserve charge), so in 1934 Enrico Fermi, the Italian physicist who later played a key role in the Manhattan Project, called the hypothetical particle the “neutrino” for “little neutral one.”

Neutrinos are slippery little fellas, and can zip through the earth as if it were made of air. They were not detected until 1959.

What happens is that U238 absorbs a neutron & so becomes U239. However, U239 is unstable & quickly goes through 2 beta decays which convert 2 neutrons to 2 protons & you end up with Pu239.

Dave –
My intent was not to counteract the fearmongering in the MSM, but to try to explain why the nuclear powers are worried by Iran crashing the party. Reading over my own post, though, I agree with you that I could have spent more time explaining the “we just want electricity” side of the story, since I do bring up the issue. My personal feeling is that Iran just wants electrical power, because you can’t modernize a country without it.

Jim & Dave (as opposed to Sam & Dave) –
So I am going to rework the piece to reflect your suggestion, in a few days. I need a refresher on nuclear reactor design first.

On a slightly different issue, I’ve been amused by the eclipse-driven press reports about our former arch-enemy, Libya. Ghaddafi has brought fresh water into the coastal cities, retired his sabre and looks like he wants to be Europe’s best buddy. So who’s to say Iran can’t follow suit?

(a) Various European countries get a non-neglible fraction of their electrical power from nuclear power, so it is not unreasonable for Iran to wish for nuclear power as it continues to develop and support the increasingly large population of Iran. And lets not forget the US lobbied hard in the 70′s (back when the Shah ruled undemonocratically with Western support) for Iran to start a nuclear power program. Its not like they suddenly said “lets go nuclear” after all.

(b) Plutonium production is a better indication of an A-bomb program in the making, and you need to breed that in a reactor by bombarding U-238 with neutrons in a nuclear reactor (which you mention). But that only works well in certain types of reactor. The Iranians are building a pressurized light water reactor, which no-one has ever (?) used to breed Plutonium for weapons – there are much easier ways to breed Pu and everyone whi has made nuclear weapons has used those easier ways. This doesn’t prove the Iranians don’t want weapons (and why shouldn’t they want them, or be allowed to have them? Vastly more dangerous countries have them already), but it adds weight to the argument that they are genuinely interested in nuclear power for electricity.

As neutrons are slowed the chance of a neutron causing a U235 fission increases faster than the chance of the neutron getting absorbed by U238. So to get a nuclear fission reaction you can use highly enriched uranium ie: mostly U235 & no moderator, or you can use a moderator such as water to slow the neutrons & need only a few % U235, or even with an even better moderator, heavy water, use natural uranium 0.7% U235. Look up CANDU for more detail on the option of no enrichment.