Even though current fission type nuclear bombs either use plutonium-239 or uranium-235, can neptunium be used as a viable substitute in a similar fission type bomb?
By: Ringo Bones
Most nuclear weapons systems - i.e. fission type nuclear bombs / atomic bombs / fission type bombs that trigger thermonuclear weapons systems – in existence either use plutonium-239 or uranium-235 as the active component in order for it to explode thousands of times more powerful than the same weight and volume of chemical high explosive. But, is it possible to use neptunium – a transuranic element – instead of either plutonium or uranium in a fission type bomb?
Strangely enough, the neptunium bomb or neptunium fission-type nuclear device was first proposed in Nazi-era Germany by the cosmogonist and physicist Baron Carl Friedrich von Weizsäcker in a secret report dated July 17, 1940. Just a few months before, neptunium was just been discovered by Glenn T. Seaborg and its most stable isotope, neptunium-239, was later produced by Edwin M. McMillan and Philip H. Abelson at the University of California in Berkeley, when they bombarded uranium with neutrons.
Even though it was Seaborg and team who were credited in the discovery of neptunium, it was Dr. Enrico Fermi who attempted to manufacture element number 93 – or neptunium – by bombarding uranium-238 with neutrons and observing the electrons emitted after neutron capture producing neptunium-239. The chemical properties of neptunium and plutonium were investigated on a tracer scale several years before these transuranic elements were isolated in visible amounts from the uranium-graphite atomic pile. The development of the atomic bomb was materially expedited by the preliminary knowledge of the chemical properties of the radioactive isotopes of neptunium-239 and plutonium-238.
Ever since the fission nuclear power facilities went online several years after World War II that also serve as a valuable source of nuclear weapons grade / fissile material like plutonium-239, these plants also produce large quantities of neptunium-237 with a half-life of 2.2 million years as a by-product of plutonium-239 production. By contrast, plutonium-239 popularly used in fission type nuclear weapons systems and initiator of thermonuclear weapons systems, only has a half-life of 24,360 years. For all intents and purposes, neptunium is considered as radioactive waste in the production of weapons-grade plutonium. Neptunium in trace amounts is found in nature as a result of low-level spontaneous transmutation reactions in uranium ores, brought about by neutrons which are present, usually fro the naturally occurring fission of uranium.
Prior to 9/11 and the then growing “popularity” of the threat of dirty bombs, the common wisdom adopted by the world’s nuclear energy regulatory groups like the International Atomic Energy Commission or IAEA is that, having been stripped of its weapons-grade uranium and plutonium, waste from spent nuclear reactor fuel assemblies poses only the problem of finding a safe means of long-term storage. However, waste from spent nuclear reactor fuel assemblies are still pregnant with elements like neptunium which, despite their never having been used in World War II era deployed nuclear weapons systems by America, are every bit as fissionable as their better-known transuranic elements like plutonium-239 and uranium-235.
Thus, by defining the problem exclusively in terms of fissionable uranium and plutonium – i.e. plutonium-239 and uranium-235 – the historical basis of all past bombs – the IAEA has inadvertently opened the door to a very curious future. As far as I know in our post-9/11 world, there are no controls yet for neptunium, tons of which still languish in radioactive waste repositories around the world. Those repositories are intended to keep us humans safe from radiation, rather than the radioactive waste safe from persons bent on mining it for fissionable elements – elements like neptunium that were originally rejected for weapons use simply because they were uncompetitive – i.e. makes for a bulkier fission type nuclear bomb, harder and costlier to chemically purify, etc. – in comparison to plutonium-239 and uranium-235, not because they will not do the job.