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SPR-IIIM, A new design for improved performance and reliability coupled with reduced maintenance and personnel dose

Philbin, J.S.; Schmidt, T.R.; Tucker, C.W.

This report discusses the Sandia Pulse Reactor-IIIM (SPR-IIIM) is a modernized, improved version of the SPR-III burst reactor. Fast burst reactors are bare metal reactors that have very short neutron lifetimes (10--20 nanos) and pulse widths (50--100 {mu}s full width half maximum). The Sandia National Laboratories SPR reactors have been used to produce bursts of fast neutrons to simulate certain hostile weapon environments. Generations of weapon-related electronic components and subsystems have been tested for radiation vulnerability and hardness at the SPR Facility. The reactor consists of two right circular hollow cylinder core halves separated by about 3.5 inches when the reactor is shutdown (scrammed). To operate, the movable lower core half (safety block) is driven vertically upward until it makes contact with the stationary upper core half. Final reactivity is added by four external reflector elements, three are nickel control elements and one is an aluminum pulse element. The reflector elements travel up and down just beyond the outer diameter of the cylindrical reactor core and conform to the curvature of the outer vertical surface. The ``pulse`` element adds reactivity at a rate of $10/s. Experiments can be placed in the central cavity (usable space is 7.5-in. OD by 14.5-in. height). The integrated dose in the central cavity is 6{times}10{sup 14} n/cm{sup 2} on a nominal size burst (300{degrees}C{Delta}T). The dose at the closest approach outside the reactor is 1{times}10{sup 14} n/cm{sup 2}. The unmoderated neutron spectrum peaks at {approximately}350 keV.