[en] The Los Alamos accelerator transmutation of waste (ATW) concept uses an accelerator to produce a beam of protons or deuterons that strike a spallation target. This interaction generates tens of neutrons per incident particle, resulting in an intense neutron source from the target. Material to be irradiated is located in a blanket region that surrounds the target. In this region, source neutrons are moderated to thermal energies to enhance their probability of capture and multiplied via the fission of transuranic waste. The ATW target blanket is a complex nuclear system, and performance depends strongly on the integrated performance of the target, blanket, and separations subsystems