Deuterium occurs in trace amounts naturally as deuterium gas, written symbolicaly 2H2, but most natural occurrence in the universe is bonded with a typical 1H atom, a gas called hydrogen deuteride (1H2H).
Deuterium behaves chemically similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other element. Bonds involving deuterium and tritium are somewhat stronger than the corresponding bonds in light hydrogen, and these differences are enough to make significant changes in biological reactions.
Anyways, the problem wasn't so much with deuterium, but with tritium contaminatin.
Deuterium is indeed wonderful stuff from a nuclear bomb maker's perspective, but by squirting tritium instead of deuterium into the Hohlraum at the moment of ignition, larger quantities of neutrons could be generated in order to boost the normal fission reaction (by a factor of five to 40). Such reaction could even blast neutrons into another tritium supply, and thereby cause a fusion reaction.
In simple terms, neutrons are the stuff of atom bombs. When they're liberated from their host atoms, they radiate outwards bombarding other atomic nuclei, causing them to fission and thereby release even more neutrons. Hydrogen isn't supposed to have any neutrons (albeit the deuterium hydrogen isotope does have one/I>), let alone the two that tritium contains.
The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium (the most abundant hydrogen isotope) contains no neutrons. It is a molecular gas (T2 or 3H2) at standard temperature and pressure. Tritium combines with oxygen to form a liquid called tritiated water T2O or partially tritiated THO.
31T ==> 32He+ + e - + ve
This reaction releases about 18.6 KeV of energy with the electron carrying an average kinetic energy of 6.5 keV, and the remaining energy being carried off undetectably by the electron antineutrino. As such, the low energy decay particles emitted creates a difficulty in detecting tritium labelled compounds except through the use of liquid scintillation counting.
The means of mass producing tritium are by placing Lithium-Aluminum into a nuclear reactor and allowing the thermal neutron flux to irradiate and transform the Li into tritium. By extracting the small faceted bubbles inside the metal, one can concentrate the tritium these bubbles contain. The Germans did this at the Greifswald plant.
Since that's a pretty high-tech and resource intensive process, the source of the tritium undoubtedly came from the former DDR nuclear program. Although the German nuclear plants were under international inspection, they did manage to circumvent some plutonium inspections, and there's no international controls on tritium at all. Concealing tritium production would be child's play (such as smuggled into the country via NiH batteries - virtually undetectable to scrutiny).
The most likely reason that DPRK's recent alleged nuclear test was probably a "fizzle", is that the bomb engineer was shot in the back of the head at 1m range prior explaining the proceedure for extraction of the tritium from the NiH batteries containing it. While the process is somewhat delicate, it is nevertheless pretty straightfoward: heating of the batteries would release the tritium (something any university student of nuclear science would be capable of performing).
However, since tritium is inherently unstable on a nuclear level it decays radioactively into 32He+. It has a half-life of about 12.3 years, and therefore, it would've been necessary to filter out the significant quantity of He-3 decay products in order to ensure pure tritium could be introduced into the bomb at the moment of ignition. Filtering the tritium through a thin block of palladium would've easily separated out the 3He from the tritium.
The fact of the matter is that the head of DPRK's bomb program was in fact an ex-DDR nuclear scientist, and while brilliant and meticulous to a fault, was the stereotypical arrogant, egotistical German and quite impertinent towards the Illustrious Leader of North Korea. Therefor, once the final assembly process had been completed, the mastermind had been quite simply neutralized. Besides, he knew too much about where the bodies where buried with respect to the international aspects of the DPRK (and others) nuclear program(s). However, he was snuffed prior to imparting this last bit of fairly critical imformation, and as such the bomb's operation depended upon hardly any worse material imaginable.
The net result was that the intensely neutron-starved-3He-poisoned-tritium trapped over 2/7th of all the high-energy neutrons emitted from the Primary in useless reactions. Albeit, while the following reaction did occur to some extent:
n + 3He ==> 3H + 1H + 0.764 MeV,
and some tritium was generated as a result, that process is strongly spin dependent, i.e., spin-polarized Helium-3 allows the transmission of neutrons having one spin component, while absorbing the other spin-component species of neutron. While 1/2 of the scavanged high-energy neutrons essentially are allowed a get-out-of-jail-free card, 50% of the remaining half are either converted into utterly worthlessly stable 4He, and so about 25% are then caught in the above reaction. In any event, even so tritium is created out of the 3He poison, no additional neutrons are generated by 2/7th of the neutrons emitted from the Primary. This is very fatally bad for any aspiring nuclear chain reaction. Very very very bad in fact. Most reactions of this type "fizzle", instead this one "foomped".
This should be a lesson to everybody: do not "off" your main science dweebs before (at the very least) the evil weapon has been proven proof in concept, and secondly, don't buy evil-havengod(sp?)-weapons supplies/components from has-been science-dweebs foreign nationals of has-been Soviet bloc countries that you're employing that you plan to snuff out before they come through. I think that pretty much sums it up.
I can't tell you how hearbroken I am 'bout all that.
