Criticality safety evaluation of materials concerning pyroprocessing

Abstract

Criticality evaluation of materials concerning pyroprocessing has been performed employing Monte Carlo techniques. Fresh UO2 fuel and spent PWR fuel have been employed in an electroreducer and, according to the pyroprocessing material flow, their metallic products are also evaluated correspondingly. TRU and Pu metals are evaluated concerning the electrowinner products. Totally, 6 kinds of reflectors and 4 stuffing materials are introduced to simulate the complexity during the pyroprocessing. With the optimized water intrusion models, certain subcritical data have been determined: 33.6 kg for UO2 fuel in electroreducer, 617.5 kg for spent fuel in electroreducer, 613.6 kg for metallic spent fuel in electroreducer, and 40.0 kg for U in electrorefiner. The conservative cases for electrowinner indicate the subcritical masses of 6.8 kg for Pu and 7.9 kg for TRU. However, with regard to the dilution effect of Cd, the Pu mass needed to reach the subcriticality changes from 11.1 kg with 1.2 kg of Cd to 500.0 kg with 2000.0 kg of Cd. The TRU mass needed to reach subcriticality changes from 13.0 kg with 1.4 kg Cd to 714.0 kg with 2856.0 kg of Cd. TSUNAMI has been employed to clarify the contributions of each nuclide quantitatively. The data obtained would therefore be used in the conceptual design study of pyroprocessing facilities. © 2011 Atomic Energy Society of Japan.