Slashdot Mirror
The Controversy of a Potential Hafnium Bomb
deglr6328 writes "Physics Today has a report detailing the surprisingly heated controversy surrounding the usually sober science of nuclear isomers (the Washington Post has run a less scientifically rigorous version). Since the 70's it has been known that the specific "m2" isomer of Hafnium-178 has an extraordinarily long half life of 31 years (nuclear isomers usually have half-lives on orders of pico or nanoseconds) and on decaying, emits high energy gamma rays at ~2.5 Mev. The prospect of energy storage and rapid release in Hf-178 for the puropse of creating large energy stores, bombs and even exotic gamma ray lasers did not escape the interest of Reagan era Star Wars researchers and was seriously studied for a time during SDI's heyday, but was eventually abandoned after being considered unfeasible. Then, in 1999, Carl Collins at the Univ. of Texas Center for Quantum Electronics reported inducing energy release from Hf-178 by bombarding a sample with X-rays (from a dental machine no less). Immediately, comments about the article were submitted, pointing out inconsistencies with basic nuclear theory and the controversy has only grown since then, with claims and counter-claims of flawed experimental design, incompetence and irrational theories in feuds reminiscent of the cold fusion debacle of the late 80's. It's seeming more unlikely as the arguments drag on, but if a Hafnium bomb could be built, it is thought that a golf ball sized chunk could produce the energy equivalent of 10 tons of conventional explosives."
Find out here!
Who modded this up? Obviously no one who understood the physics of the story. So let's explain.
The process described is neither fission nor fusion. Instead, it's analogous to how a light bulb works.
(What? Yes, a light bulb. Bear with me.)
In a lightbulb, you add energy to a fillament. The electrons (mostly) in the fillament are placed into excited states by the energy, then very quickly release the energy in the form of photons (visible light) and fall from the excited state into a ground state.
A similar thing can be done to particles other than electrons -- such as neutrons. In most cases, the neutrons fall from the excited state very quickly and release photons (gamma rays and the like).
In hafnium, however, the excited state of the neutrons is metastable -- which is just a fancy way of saying they stay excited for a long time between when they're excited and when they release photons.
If a way could be developed to induce the grounding, then hafnium could be used to store large amounts of energy in the metastable state, and then induced to release it all at once, resulting in much larger discharges than ordinary chemical reactions can store/release.
It doesn't yield energy; at best you get from the grounding the energy you put in to get the neutrons excited. It isn't fission, and it isn't fusion; not what we typically call a "nuclear" reaction. However, it is a beyond-chemical-bond-capacity energy release based on the nucleus.
Oh, and by the way, there are middlish-weight elements that are unstable, and thus can provide nuclear energy through ordinary radioactive decay. The classic example is Technetium, number 43 on the Periodic Table, atomic mass 98.