Fission-neutron irradiation, effects

Studies of the effect of neutron irradiation are divided into three groups slow or thermal neutrons, fission products and reactor neutrons. The slow neutrons are obtained from a radioactive source or high energy neutrons that are produced by deuterium bombardment of a beryllium target in a cyclotron and slowed down passing thru a thick paraffin wax block. The fission products in one case are produced when a desired sample is mixed or coated with uranium oxide and subsequently irradiated with slow neutrons. The capture of neutrons by U23S leads... 

Fig 25 The Effects of Gamma-Ray 235U Fission Spectrum Neutron, and Combined Gamma-Ray and Neutron Irradiation on Whole Crystals of Ammonium Perchlorate Thermally Decomposed at 227° (Ref 224)... 

Effects of Radiation. LA exposed to gamma radiation by Warren et al and by Kosen-wasser, as reported in Ref 139, exhibited post-irradiation gas evolution as measured by vac stab test appar. Bowden Singh (Ref 135) irradiated Pb, Ag and Cd azides with electrons, neutrons, fission prods and x rays. All azides were exploded by an intense 75-kv electron scream. Thermal neutron irradiation did affect the subsequent decompn of Li and Pb azides. Muraour Ercaud (Ref 129) also subjected LA to a neutron flux. Raney (Ref 158) reported that a total flux of 7.5 10 ... 

We consider here the effects produced by electrons with energy smaller than a few hundred electron volts. We have seen that these electrons carry away more than 80% of the total energy dissipated by the various types of radiation, with the exception of fast neutrons in the presence of heavy element targets. Let us remember that these electrons are obtained (1) by gamma and beta irradiation, after a great number of successive processes, (2) by proton, deuton, and alpha irradiations, after a small number of successive processes, and (3) directly by fission fragment irradiations. 

More accurate data on the effect of liquid helium temperature neutron irradiation (fission and 14 MeV) on Jc of commercially important composite superconductors (primarily NbTi, but also NbaSn and VsGa). 

The effect of neutron irradiation on metals is mainly to increase the yield and the ultimate strength and to reduce the toughness. Helium or fission gas production within the metal matrix leads to changes in material properties and also to swelling. Swelling is particularly important in reactor control devices made of boron compounds. 

Major issues of radiation effects on V-aUoys are radiation embrittlement at relatively low temperature, and irradiation creep at intermediate temperature. Void swelling is known to be quite small if the alloy contains Ti. He embrittlement is a key issue determining the high-temperature operation limit in fusion neutron environments where 5—10 appm He are produced by transmutation during the irradiation to 1 dpa. However this may be a minor issue for fission neutron environments where the production rate is much lower because the cross-section of He-producing reactions is small when the neutron energy is below 10 MeV. 

The comment as to the plutonium from the PIPPA would not be suitable for weapon manufacture might need some explanation. It was not, as the note maintains, because of the greater heat at which these piles would operate , but the effects of more intense and longer neutron irradiation. Some isotopes of plutonium are more suited to atomic weapons than others. The isotope produced from uranium 238 hy neutron absorption is plutonium 239. If the plutonium 239 is struck hy a further neutron, it will either fission or it will absorb the neutron to become plutonium 240. 27% of the neutron collisions result in the formation of the Pu isotope. 

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