Abstract
The effectiveness of the external neutron source has been evaluated in terms of its multiplication in subcritical reactors. Mathematical formulas for the source neutron multiplication are reviewed and their implications are addressed. In order to identify dependency of the spallation neutron multiplication on the core design features, numerical experiments are performed with a Monte Carlo code for an accelerator-driven system, HYPER (HYbrid Power Extraction Reactor). For various core conditions, the actual source multiplication factors are compared with the conventional critical mode expectation. Sensitivity of the multiplication factor to the radial power distribution is investigated to find an optimum radial power distribution from the point of the spallation neutron multiplication. Also, impacts of neutron absorbers on the source multiplication are considered in this work. In addition, the efficiency of external spallation neutrons is evaluated for proton target designs.
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