An effective way to manage minor actinides is to transmute them in nuclear systems. However, due to a lack of experimental data, which has meant an absence of precision in MA nuclear data, it remains difficult to establish a detailed design of transmutation systems with reliable accuracy and the capacity to precisely predict the composition of spent fuel. OECD (2015), Review of Integral Experiments for Minor Actinide Management, Nuclear Science, OECD Publishing, Paris.
The necessity of managing minor actinides (MA), such as neptunium, americium and curium in the spent fuel, becomes more important when mixed oxide (MOX) fuel is used on a large scale in power reactors, both light-water reactors and fast reactors, as more MA will be accumulated in the spent fuel. One way to manage MA is to transmute them in nuclear reactors, such as light-water reactors, fast reactors and accelerator-driven subcritical systems.
The transmutation of MA is, however, not straightforward, as the loading of MA generally affects physics parameters, such as coolant void, Doppler, and burn-up reactivities. In addition, the accuracy of MA nuclear data is not sufficient for the detailed design of transmutation systems and for precise prediction of the composition of the spent fuel, because of a lack of measured MA data. Nuclear data of the major actinides, such as U-235, U-238 and Pu-239, are based on a vast number of differential and integral experiments, using accelerators, critical facilities and experimental reactors. Integral experiments on MA are much more difficult because of material handling restrictions at facilities, the difficulty of sample preparation and the necessity to improve measurement techniques to reduce the influence of background radiation. Moreover, most facilities for nuclear data measurements and validation are getting old.
The Nuclear Science Committee (NSC) had therefore decided to establish an expert group to critically review integral experiments for validating MA nuclear data, to recommend additional integral experiments needed for validating MA nuclear data and to investigate the possibility of establishing an international framework to facilitate integral experiments for MA management.
The expert group worked closely with the Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS) [WPRS includes the Expert Group on Minor Actinide Burning in Thermal Reactors (MA-ThR), and the International Reactor Physics Benchmark Experiments (IRPhE) Project], the Working Party on Scientific Issues of the Fuel Cycle (WPFC) [the taskforces on comparative study on homogeneous and heterogeneous recycle of TRU and on potential benefits of advanced fuel cycles with partitioning and transmutation, etc.] and the Working Party on International Nuclear Data Evaluation Co-operation (WPEC) [the subgroup on meeting nuclear data needs for advanced reactors (SG31) and the combined use of integral experiments and covariance data (SG33)].
The objectives of the expert group were to:
The expert group works in co-ordination with Working Party on Scientific Issues of Reactor Systems (WPRS) [including the IRPhE Project], Working Party on Scientific Issues of the Fuel Cycle (WPFC) and Working Party on International Nuclear Data Evaluation Co-operation (WPEC) [in particular with WPEC subgroup (SG39) and WPEC subgroup 40 (SG40 CIELO Pilot Project)].
The NEA's nuclear data evaluation co-operation activities involve the following evaluation projects: ENDF (United States), JENDL (Japan), ROSFOND/BROND (Russia), JEFF (other Data Bank member countries) and CENDL (China) in close co-operation with the Nuclear Data Section of the International Atomic Energy Agency (IAEA).
The Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS) studies the reactor physics, fuel performance, and radiation transport and shielding in present and future nuclear power systems.