Passive actinide self-burner
First Claim
1. An apparatus for the confinement of long-life waste actinide and beryllium mixture in a capsule placed within a neutron moderator material to accelerate the destruction or transmutation of the waste actinide to the stable nonradioactive states of the waste actinide decay series, and said capsule being a double shell, stainless steel vessel containing the waste actinide having a length of about 2.0 inches and a diameter of about 0.75 inches.
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Accused Products
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.
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Citations
16 Claims
- 1. An apparatus for the confinement of long-life waste actinide and beryllium mixture in a capsule placed within a neutron moderator material to accelerate the destruction or transmutation of the waste actinide to the stable nonradioactive states of the waste actinide decay series, and said capsule being a double shell, stainless steel vessel containing the waste actinide having a length of about 2.0 inches and a diameter of about 0.75 inches.
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15. A preferred method of making an apparatus for passively accelerating the rate of radioactive decay of waste actinides, the method including the steps of
a. mixing a powder form of waste actinide and beryllium in an atomic weight ratio of 1: - 13 to form a uniform first mixture;
b. loading the mixture into a beryllium oxide crucible and subsequently heating the mixture to 1375°
F., under vacuum, to achieve a molten alloy;c. shaping the molten alloy in a suitable die forming an ingot; d. loading the ingot into a double shell capsule and closing the inner and outer capsules by welding, inspecting and testing wells to verify sealing; e. preparing a graphite disk to accept sealed capsules by encasing the bottom and sides of the graphite in stainless steel or aluminum, creating wells within the graphite, also lined with stainless steel or aluminum, to form a graphite assembly; f. loading sealed capsules in the wells of the graphite assembly, using crumpled aluminum or similar material as necessary to provide axial support or to improve heat transfer from the capsules to the graphite disk housing; and g. closing the graphite assembly by installing and welding in place a top closure plate.
- 13 to form a uniform first mixture;
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16. An apparatus comprising long-life waste actinide and beryllium mixture in a capsule placed within a neutron moderator, reflector material incorporated into said capsule, said mixture comprising alpha particle radiation emitted in natural decay which undergoes a subcritical nuclear reaction with adjacent beryllium thereby releasing a fast neutron which is subsequently slowed down or thermalized, and said neutron being retained within the apparatus by said reflector material such that it is available to cause transmutation of other waste actinides within the apparatus and thereby accelerate the destruction or transmutation of the waste actinide to the stable nonradioactive states of the waste actinide decay series.
Specification