Minor Actinide Recycling Research Articles

A Thermoelectric-Conversion Power Supply System Using a Strontium Heat Source of High-Level Radioactive Nuclear Waste

A thermoelectric-conversion power supply system with radioactive strontium in high-level radioactive waste has been proposed. A combination of Alkali Metal Thermo-Electric Conversion (AMTEC) and a strontium fluoride heat source can provide a compact and long-lived power supply system. A heat source design with strontium fluoride pin bundles with Hastelloy cladding and intermediate copper has been proposed. This design has taken heat transportation into consideration, and, in this regard, the feasibility has been confirmed by a three-dimensional thermal analysis using Star-CD code. This power supply system with an electric output of 1MW can be arranged in a space of 50m2 and approximately 1.1m height and can be operated for 15 years without refueling. This compact and long-lived power supply is suitable for powering sources for remote places and middle-sized ships. From the viewpoint of geological disposal of high-level waste, the proposed power supply system provides a financial base for strontiumcesium partitioning. That is, a combination of minor-actinide recycling and strontium-cesium partitioning can eliminate a large part of decay heat in high-level waste and thus can save much space for geological disposal.

ECRIX-H experiment: Synthesis of post-irradiation examinations and simulations

The purpose of the ECRIX-H experiment is to study the behaviour of a composite ceramic target made of AmO 1.62 microdispersed in an MgO matrix irradiated for 318 EFPD in the Phenix sodium-cooled fast reactor (SFR), in a specific carrier sub-assembly equipped with annular blocks of CaH x acting as a neutron moderator. Results indicate that magnesia-based inert matrix targets display satisfactory behaviour and moderate swelling under irradiation, even for significant quantities of helium produced and a high burn-up. On this basis, the design of transmutation fuel pins for recycling of minor actinides (MA) in accelerator-driven systems (ADS) or in fast neutron reactors (FR) could be optimised so as to increase their performance level (initial MA content, burn-up, etc.). The measured Am fission rate (25 at.%) was found to be lower than that predicted by neutronic simulations probably due to the inaccuracies linked to the complexity of neutron modelling and the uncertainties on nuclear data related to moderated neutron spectrum. In addition, as most of the initial Am transmuted into Pu under irradiation, a PuO x -type phase was created within the initial AmO 1.62 particles, leading to the incomplete dissolution of the irradiated targets under standard reprocessing conditions. This issue will have to be considered and investigated in greater detail for all transmutation fuels and targets devoted to the multi-recycling of MA.

Impact of the Core Minor Actinide Content on Fast Reactor Reactivity Coefficients

A major challenge for future fast reactors could be the recycling of minor actinides (MAs) in the core fuel in order to minimize waste and to meet both the sustainability objective and the reduction in the burden of geological disposal. Although the prevailing issues will be found in the development and validation of the appropriate fuels, the presence of MAs in the core can deteriorate the core reactivity coefficients. However, in this paper, we will show that there is no well-defined physical limit to the amount of MAs in the core fuel, and that a careful physics analysis can indicate the most appropriate measures that reduce the MA impact on the reactivity coefficients, and in particular, for Na-cooled reactors, on the Na void reactivity coefficient.

State of the Art of Pyroprocessing Technology in Japan

Abstract Minor actinide recycling in a fuel cycle is a potential technology to minimize the environmental radioactivity burden in waste disposal in the fast reactor era after 2050. Pyroprocessing technology with metal electrorefining expects that no additional process is required to separate minor actinides and short- cooled fuels can be treated due to no-use of organic solvent that degrades by radiation. Pyroprocessing has been explored for metal fuel cycle and nitride fuel cycle in Japan. Metal fuel fast reactor, which can achieve a high breeding ratio over 1.3, and its fuel cycle is a compact system by integrating pyroprocessing. Oxide fuel can be also treated by converting to metals by reduction. Separation of transuranium elements from high level liquid waste originating from aqueous reprocessing has been challenged. Verification of the process and development of an engineering scale device are the current interests for study. In addition, irradiation study of metal fuel with minor actinides currently much advances from the point of fundamental investigation. Accelerator-driven system (ADS) for transmutation of minor actinides is integrated with pyroprocessing for recycling system. The denitriding at anode and azotizing at cathode together with electrorefining have been fundamentally studied by use of plutonium.

Study on actinides burner cores in fast reactors

Feasibility studies have been performed to develop core concepts in an LMFBR which can burn minor actinide(MA) effectively in consideration of fuel cycle technology. The homogeneous loading of MA and rare earth(RE) has no serious penalties to the reactor core performances, provided that the amount of MA and RE in the fuel is less than 5 and 10wt%, respectively. The MA recycling in LMFBRs is feasible from neutronic and thermal-hydraulic points of view.