Abstract
JAERI has carried out R&D on transmutation of long-lived nuclides with a special emphasis placed on accelerator-driven systems (ADS) under the Japanese OMEGA Program. The ADS is designed to be introduced as a dedicated transmutation system into the second stratum of a double-strata nuclear fuel cycle concept. Early ADS concepts employed sodium coolant and solid tungsten target. A chloride molten-salt system and a molten-alloy system were investigated as advanced options to pursue the possibility of taking full advantages of liquid fuel systems. The current reference ADS design employs eutectic lead-bismuth as spallation target material and coolant. The fuel for the subcritical core is minor-actinide mononitride. The system consists of a 1.5-GeV, 14-mA proton accelerator and an 800-MWt subcritical core with an effective neutron multiplication factor of 0.95. The design incorporates salient features that the coolant inventory is large due to the tank-type configuration, the temperature rise through the core is relatively low, and the power conversion is operated on a saturated steam turbine cycle. These features help mitigate the problems of plant transient during beam interruptions. ADS related R&D is underway in various fields such as scenario study, lead-bismuth technology development, nitride fuel and fuel cycle technology development, nuclear data development, and high-intensity accelerator development. Construction of ADS experimental facilities is planned under the JAERI-KEK Joint Project of a high-power proton accelerator.
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