Fertile material

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Speed of transmutation varies greatly by nuclide, and percentages are relative to total transmutation and decay. After removal of fuel from reactor, decay will predominate for shorter-lived isotopes such as ²³⁸Pu, ²⁴¹Pu, ^242–244Cm; but ^245–248Cm are all long-lived.

Fertile material is a material that, although not fissile itself, can be converted into a fissile material by neutron absorption.

Naturally occurring fertile materials

Naturally occurring fertile materials that can be converted into a fissile material by irradiation in a reactor include:

• thorium-232 which converts into uranium-233
• uranium-234 which converts into uranium-235
• uranium-238 which converts into plutonium-239

Artificial isotopes formed in the reactor which can be converted into fissile material by one neutron capture include:

• plutonium-238 which converts into plutonium-239
• plutonium-240 which converts into plutonium-241

Some other

need more than one neutron capture before arriving at an isotope which is both fissile and long-lived enough to probably be able to capture another neutron and fission instead of decaying.

• plutonium-242 to americium-243 to curium-244 to curium-245
• uranium-236 to neptunium-237 to plutonium-238 to plutonium-239
• americium-241 to curium-242 to curium-243 (or, more likely, curium-242 decays to plutonium-238, which also requires one additional neutron to reach a fissile nuclide)

Since these require a total of 3 or 4 thermal neutrons to eventually fission, and a thermal neutron fission generates only about 2 to 3 neutrons, these nuclides represent a net loss of neutrons. A

, those nuclides may require fewer neutrons to achieve fission, as well as producing more neutrons when they do fission. However, there is also the chance of (n,2n) or even (n,3n) "knockout" reactions (an incident fast neutron hits a nucleus and more than one neutron leaves) with fast neutrons which are not possible with thermal neutrons.

Fissile materials from fertile materials

A

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Applications

Proposed applications for fertile material includes a space-based facility for the manufacture of fissile material for

as used in the current enrichment technology.

References