Fast neutron reaction data

F is the remaining fraction of 38Ar at temperature t °C. t is derived from 37At outgassing data because this isotope is artificially produced by a nuclear reaction between fast neutrons and Ca. 

For the reactor route, the saturation yield of Cu from the Zn(n,p) reaction at BOB is 4.14 0.37 GBq mg (112 10 pCi mg ) of Zn at position no. 5 in the High Flux Isotope Reactor (HFIR) hydraulic tube (reactor midplane). Production data and fast neutron fluxes available in irradiation facilities in HFIR and the High Flux Beam Reactor (HFBR, this reactor was permanently shut down in 1999) are summarized in Table 38.8. 

The nuclear reaction (b) is chiefly induced by thermal neutrons and shows a cross section of 6 10 cm (Maxwell spectrum, T=575 K). Reaction (c) on the other hand is induced by fast neutrons with an effective threshold energy of 2.4 MeV the cross section averaged over the flux of neutrons with energies beyond this threshold value amounts to 8.5 10 cm . Using this data and assuming a lithium concentration of 2 ppm (99.99% Li), which is held constant... 

Inelastic neutron scattering is used for the smdy of transmission or absorption neutron energy spectra, particularly the side-group motion in polymers. All data reported so far for polymers have been concerned with symmetric top molecules. Three spectrometries are available at present (1) slow neutron spectrometry, which studies slow neutron excitation functions with continuous-energy neutron sources (2) fast neutron spectrometry, which smdies the spectra of neutrons produced in nuclear reaction and (3) monoenergetic slow neutron spectrometry, which smdies the spectra of neutrons corresponding to the inelastic scattering from atoms in solids or fluids. 

The current situation on fast reactor calculations is that, while a combination of basic differential cross section data, adjusted by correlation methods, with two-dimensional transport or three-dimensional diffusion codes, can give reasonable agreement for quantities such as critical mass or relative reaction rates in central regions of an FBR core, more precise data are still required for accurate prediction of differential effects such as the Doppler and sodium void coefficients. These two effects, together with the influence of the delayed neutron parameters for a fast reactor, are most conveniently dealt with in the following section, which considers the dynamic behavior of the system. 

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