PARAMETERS OF HIGH FLUX TESTING REACTORS

An investigation of thermal fixed-fuel reactors using a cylindrical annulus design with a central experimental facility results in calculated total neutron fluxes, in a gray absorber simulated experiment within the central experimental facility (radius 10 to 15 cm), of 4to 5 x 10/sup 15/n/cm/sup 2/ sec with D/sub 2/O as coolant, moderator and reflector at an operating power of 400 to 500 Mw. Total neutron fluxes of about one-half these could be obtained using H/sub 2/O as coolant., moderator and reflector at a power cost of 300 to 400 Mw. Reducing the fuel concentration results in significantly higher total fluxes but with prohibitively high operating powers. Obtainable fluxes in thc simulated experiments have proved to be inversely proportional to the radius of the experimental facility and the wall thickness of the experiment. It is found that thermal fixed-fuel reactors have a built-in upper limit for mean thermal neutron core flux depending upon the two parameters of allowable percentage fuel burnup and minimum allowable cycle time. For the particular case of 40% burnup and 6 day cycle time, the mean value for the time averaged thermal core flux is 1.7 x hat a limit exists with circulating fuel reactors with themore » parameters being allowable operating power and critical mass. (auth)« less