Double neutron capture

Lutetium-177 produced by neutron capture reactions Iodine-125 produced by neutron capture followed by Tungsten-188 produced by double neutron capture Tin-117m produced by neutron inelastic scattering Copper-67 produced by fast neutron-induced reactions... 

The long-lived (69.78 days) parent nuclide, W, is produced in a nuclear reactor by double neutron capture by highly enriched... 

More complex is the production of Pu-238 and californium-252. For Pu-238 there are two irradiation cycles the first starts with natural uranium but maximizes the neptunium-237 yield then the Np-237 is separated, converted into aluminum-clad oxide targets, and irradiated to Pu-238 in a second cycle. The total process requires double neutron capture. 

There are four modes of radioactive decay that are common and that are exhibited by the decay of naturally occurring radionucHdes. These four are a-decay, j3 -decay, electron capture and j3 -decay, and isomeric or y-decay. In the first three of these, the atom is changed from one chemical element to another in the fourth, the atom is unchanged. In addition, there are three modes of decay that occur almost exclusively in synthetic radionucHdes. These are spontaneous fission, delayed-proton emission, and delayed-neutron emission. Lasdy, there are two exotic, and very long-Hved, decay modes. These are cluster emission and double P-decay. In all of these processes, the energy, spin and parity, nucleon number, and lepton number are conserved. Methods of measuring the associated radiations are discussed in Reference 2 specific methods for y-rays are discussed in Reference 1. 

The principal nuclear reactions that take place when mixtures of U and U are used as fuel in a reactor are illustrated in Fig. 3.1. Fissile materials are double underlined, and their fission cross sections for 2200 m/s neutrons are given on upward-slanting arrows. Fertile materials are sin e underlined, and their capture cross sections for 2200 m/s neutrons are given on horizontal arrows. Beta-decay reactions with short enough half-lives to be important are shown by vertical arrows. 

Decay modes are a = alpha particle emission (B = negative beta emission p+ = positron emission EC = orbital electron capture IT = isomeric transition from upper to lower isomeric state n = neutron emission sf = spontaneous fission (B(B = double beta decay. Total disintegration energy in MeV units. 

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