Passive actinide self-burner

Abstract

The invention relates to the confinement of an alloy formed of actinide transuranic radioactive wastes and beryllium metal within a neutron moderating and reflecting apparatus to cause accelerated destruction (burning) of the actinide wastes. Waste actinides, including plutonium, neptunium, americium, and curium, emit alpha particles by radioactive decay. The alpha particles are converted into neutrons by the beryllium through an alpha-neutron (alpha, n) reaction. The neutrons developed by the alpha, n reaction are moderated by a surrounding layer of graphite, which allows the slowed neutrons to cause additional fission or decay events within the waste actinide alloy. This process is passive because the alpha particles that initiate the actinide burning are an intrinsic physical property of the actinides. The burning or decay process is accelerated because neutrons that would ordinarily escape the confinement fixture (a Standard Source capsule) are reflected back into the actinide waste, transmuting them into heavier, less stable isotopes that decay more rapidly. The use of the moderator/reflector material allows the waste actinides to be destroyed in a 10,000-year repository period instead of requiring one million years to attain the same waste reduction by natural radioactive decay alone. Beryllium may also be used as a neutron moderator/reflector, but is not a cost effective choice for large scale use.