Neutron attenuation in the laser ducts of an inertial-confinement fusion reactor

This report deals with the problem of neutron streaming through the laser beam ducts of an inertial confinement fusion power plant. The neutron flux through these ducts must be attenuated by a factor of 1012 to meet radiological safety limits. The problem is dealt with by using mirrors to bend the path of the laser beam while cutting off a line of sight path for neutrons. The Monte Carlo Code MCNP was used to analyze the two mirror SOLASE design, which only attenuated the neutron flux by a factor of 103. The Westinghouse design, initially assuming four mirrors, attenuated the neutron flux by 104 per mirror bend, and hence only three mirror bends were needed. Further studies also revealed that the large length/diameter ratio of the ducts and the thinner mirror design were crucial to the large attenuation. It may also be possible to develop a two mirror system, at 106 attenuation per mirror bend, utilizing improvements such as point cross overs, a second flux trap, and acute column-to-column angles. Further studies are needed to check this possibility