Neutron irradiation
Making elements that barely exist in nature by feeding neutrons to ones that do — how plutonium is produced, and how everything past uranium is made at all.
Several elements cannot be mined at all, because there is essentially none of them to mine. Technetium has no stable isotope and no natural occurrence worth the name; plutonium exists in nature only in traces; americium, curium and californium do not occur naturally at all.
They are made. A nucleus that absorbs a neutron becomes a heavier isotope of the same element, and that isotope frequently decays by emitting an electron — which converts a neutron into a proton and moves the atom one place up the periodic table. Repeat, and uranium becomes plutonium, then americium, then curium, one capture at a time.
Processing
In a power reactor the process happens whether anybody wants it or not. Uranium-238 makes up most of the fuel, absorbs neutrons without fissioning, and becomes plutonium-239 — which is itself fissile, and supplies a meaningful fraction of the energy a reactor produces by the end of a fuel cycle. Recovering it means reprocessing spent fuel chemically, which is the step that makes the whole subject a proliferation question rather than an industrial one.
The heavier elements need deliberate effort. Each step up requires another capture before the previous product decays, so yield falls sharply with atomic number: americium and curium are produced in kilograms, californium in milligrams, and the elements past them in counts of individual atoms.
Technetium arrives by a different route entirely. It is a fission product rather than a capture product — a fragment of a split uranium nucleus — and is recovered from spent fuel in quantities far larger than any deliberate synthesis would give.
Economic significance
Almost none of this is a commodity. Americium is the exception most people own: a fraction of a gram in a domestic smoke detector, ionising the air in a small chamber so that smoke particles change the current across it.
The rest are instruments or problems. Californium-252 is a portable neutron source used to start reactors and to scan for explosives; technetium-99m is the workhorse of nuclear medicine, in tens of millions of scans a year; and plutonium is a fuel, a weapon and a waste-management liability depending entirely on who is holding it.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
produces
- Plutonium — element · from uranium-238 absorbing a neutron and decaying twice — produced in every power reactor whether or not anybody wants it, and recovered only by reprocessing spent fuel
- Americium — element · two further captures beyond plutonium, in kilogram quantities — and the only one of these most people own, as a fraction of a gram in a smoke detector
- Curium — element · another step up again, and the point at which yields start falling away sharply
- Californium — element · produced in milligrams, as a portable neutron source for starting reactors and scanning for explosives
- Technetium — element · not by capture but as a fission product — a fragment of a split uranium nucleus, recovered from spent fuel in quantities no deliberate synthesis would match
- Promethium — element · the same way, and the reason an element with no stable isotope is available at all
takes as input
- Uranium — element · uranium-238 is the feedstock for everything heavier: it absorbs neutrons without fissioning, which is what starts the sequence
Sources
- Material WorldOur own writing