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Promoting this video and sending it back into the queue for one more try; last queued Tuesday, June 19th, 2012 8:26am PDT - promote requested by pumkinandstorm.

To continue this lesson, it is important to note that most bomb technology doesn't use enriched uranium alone. The other key material compound is plutonium. For all intents and purposes, all plutonium is man made (with only traces of 244 found in nature, of which is completely unsuitable for weapons..Pu244). Plutonium is usually needed in a bomb because of its much lower critical mass. This lower mass makes bomb fabrication easier, but that creation of plutonium is by no means trivial.

You need huge facilities, dedicated to the sole purpose of uranium exposure. Like the video mentions, normal uranium is mostly U238, this junk gains value in the creation of plutonium. Weapons grade plutonium is a special isotope of plutonium, Pu239. This need is very specific, the different isotopes of Pu can have so very serious implications for bombs. Lets go over them as we as we go over how uranium is exposed to make this very special isotope

First, we start off with U238...the fuel stock. This isotope is bombarded with neutrons. These neutrons are occasionally absorbed by the uranium, turning it into U239. U239 is highly unstable, and quickly decays (in 23.45 minutes) to neptunium 239. This will in turn, decay into Pu239 (in about 2.3 days). Sounds easy, right? Not exactly, neutron absorption isn't something you can control with ease. What I mean is, there is little to stop our Neptunium or Plutonium from absorbing neutrons any more or less than the Uranium (in fact, their absorption cross sections are typically much larger...they are more hungry of neutrons than uranium in other words). When this undesired absorption happens, the neptunium and plutonium eventually becomes Pu240...and that is a big problem.

Plutonium Pu240 is HIGHLY undesirable in a bomb. Pu240 is a medium lived isotope of Plutonium, meaning it decays pretty quick, but it is HOW it decays that is the problem. Pu240 often decays by spontaneous fission. Having spontaneous fission in your fission bomb is just as undesirable as it sounds. Firstly, all even number isotopes are poor fission candidates, so for every even number isotope in your bomb, that lowers the bombs over all yield (because they prefer to fission themselves, and for very little return energy). This is further complicated by high densities of Pu240 causing your bomb to prematurely detonate, ya...bad news. The levels of Pu240 represent yet another challenge in the level of heat they generate from their rather quick decay, though, considering the previous 2 issues, this one is less problematic, though still troublesome. And lastly, there is nothing stopping our Pu240 from absorbing yet another neutron causing yet another isotope of plutonium to arises, namely Pu241.

Pu241, being an odd numbered isotope heavier than lead makes it a rather good subject to undergo fission. It doesn't have the same set of problems as Pu241, but it rapidly decays (14 years) into Americium 241, which is not fissile, and has a halflife of 432 years. These factors add large amounts of heat to the bomb, and reduce overall yield, as well as detract from critical mass.

The solution for this is a very low tech, time consuming, laborious process with produces tons of waste and very little plutonium. One has to expose small blocks of uranium to neutrons under a very brief window. The brief window decreases the chances of undesired neutron absorption and negates much (but not all!) of the heavier forms of plutonium being created. After exposure, they are left to decay, then after a few months, are chemically processed to remove any plutonium and other undesirables (this is also very very hard, and I won't even go into how this is done), then re-exposed. This yields gram(s) at a time. To make a weapons, you need 10 killos, at least...for one bomb...if everything went great. This means you need HUGE facilities, HUGE staff, and HUGE uranium resources. Your facility would be obvious and serve no other purpose, use tons of energy, and pile up radioactive waste of the kind no one wants, heavier than uranium wastes...the worse of the worst. No such facility could exist alongside some traditional uranium facility and not be noticed, period, end of story, done.

We haven't even covered bomb making problems, of which killed some of our top minds in our own bomb program. A set of incidents revolving around a specific bomb type, after taking 2 lives, was dubbed the Demon core. These are the reasons over half the budget of the DOD gets soaked up in nuclear weapons, and we haven't even covered some of the more important aspects (like delivery systems, one simply doesn't walk into Mordor). Nuclear weapons are hugely expensive, hugely conspicuous, require massive facilities and require a level of sophistication that is completely absent from the training of reactor nuclear scientists.

Reactor research and materials are orders of magnitude different from weapons grade materials and research. No bomb in history has EVER been made from reactor grade plutonium because the levels of Pu240 and Pu241 (and we haven't even covered Pu238!) are blisteringly high, way to high for weapons. Isotopic separation for Pu would be even more costly than uranium because of their mass similarities (compared to U235 and U238) and need a different set of enrichment facilities specially tailored to plutonium enrichment, of which all the people who knew something about that are Russian and American, and most likely dead or work classified to the highest degree.

The problem of nuclear weapons via reactor development is all a game to ratchet up the fear machine to get a particular end. It isn't a technical problem, it is a political problem. In the end, though, emerging technology could make enrichment easier anyway, so many of the issues I mentioned might eventually fall to the wayside (not within the next 10 years I imagine; for interested parties, google laser enrichment...coming to a world near you, but not exactly tomorrow, it's awesome stuff though). Eventually, the US is going to have to get used to the idea of more and more nations owning the bomb...but that issue is completely unrelated to reactor design and research. Reactors and nuclear weapons share about as much in common as cars and space shuttles...trying to link them as a dual proliferation argument is a political game and doesn't map on to them technologically.



I should note that I am not yet a nuclear engineer, but I did stay at a holiday inn express.

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Boosting this quality contribution up in the Hot Listing - declared quality by GeeSussFreeK.

The facility required to make a nuclear bomb is ALMOST as complex as my latest farm in minecraft.