Fast neutron reactors thermal conductivity

BeO is tapped for nuclear reactor service because of its lefiactoriness, high thermal conductivity and abUity to moderate (slow down) fast neutrons. The thermal neutrons that result are more efficient in causing fusion of Nuclear iudustry uses for berylha include reflectors and the matrix material for fuel elements. When mixed with suitable unclear poisons, BeO may be a new candidate for shielding and control rod assembly apphcations. 

Sodium is used as a heat-transfer medium in primary and secondary cooling loops of Hquid-metal fast-breeder power reactors (5,155—157). Low neutron cross section, short half-life of the radioisotopes produced, low corrosiveness, low density, low viscosity, low melting point, high boiling point, high thermal conductivity, and low pressure make sodium systems attractive for this appHcation (40). 

Pulsed Reactor Irradiation In the KIWI—TNT test of the NERVA program, BlkPdr was the only igniter tested in a pulse environment (Ref 192). In a M msec pulse, the max dose the BlkPdr was exposed to was 3.0 x 1014 n/cm2 fast neutrons, 1.1 x 101S n/cm2 thermal neutrons and 1.5 x 107 R gamma. On the various tests conducted no adverse effects were evident... 

Major applications for BeO ceramics include microwave tube parts substrates and mounting platforms for power transistors crucibles for melting uranium, thorium, and beryllium and numerous uses in the nuclear reactor industry because of beryllia s high thermal conductivity and ability to moderate fast neutrons. 

Preliminary reactor core concepts have been proposed at various institutions. Among them, the concept with mixed neutron spectrum proposed by SJTU [95,96] has achieved the special attention of Chinese researchers. The mixed spectrum SCWR core combines the merits of both thermal and fast spectra as far as possible. The basic idea is to divide the reactor core into two zones with different neutron spectra. In the outer zone, the neutron energy spectrum is similar to that of PWRs. To assess the performance of the reactor core, a coupled neutron-physics and thermal-hydraulics analysis was conducted [96]. 

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