Incineration Of Minor Actinides Research Articles

The GDT-based fusion neutron source as driver of a minor actinides burner

At present, accelerator driven systems seem to have a good chance to play an important role in a long-term sustainable utilization of fission reactor technology. Compared with reactors, such systems offer several advantages regarding the incineration of minor actinides. However, they demand intense neutron sources. The spallation neutron source is favoured for this purpose because of its high neutron emission intensity, which seems to be attainable. The Budker Institute of Nuclear Physics Novosibirsk is developing a 14 MeV fusion neutron source on the base of the gas dynamic trap (GDT), which is primarily destined for an irradiation facility for fusion material research. The potential of this neutron source as driver of a minor actinides burner was studied by means of neutron transport calculations and compared with a spallation source. To this end, a simple model of a burner was derived from an international numerical benchmark exercise that was conducted by the Nuclear Energy Agency of the OECD. The paper presents and discusses the main results of the study and draws the conclusion that both the source strength and the efficiency of the GDT-based neutron source must be substantially increased. Moreover, advices are derived, which show that by stretching the neutron production volume and by raising the electron temperature of the GDT plasma the desired improvements could be accomplished.

FUJI: A Comparative Irradiation Test with Pellet, Sphere-Pac, and Vipac Fuels

Particle fuels such as sphere-pac and vipac have been considered as promising fuel systems for fast reactors because of their inherent potential in remote operation, cost reduction, and incineration of minor actinides or low-decontaminated plutonium. The FUJI test addresses the questions of fabrication of mixed-oxide (MOX) particle fuels with high Pu content (20%) and its irradiation behavior during the start-up phase. Four kinds of fuel, i.e., MOX sphere-pac, MOX vipac, MOX pellet, and Np-MOX sphere-pac, have been and will be simultaneously irradiated under identical conditions in the High Flux Reactor in Petten, Netherlands. First results show that the particle fuel undergoes a substantial structure change already at the very beginning of the irradiation when the maximum power is reached. The changes in microstructure, i.e., the formation of a central void and the densification of fuel, decrease the fuel central temperature. Thus, the fast and strong restructuring helps to prevent central fuel melting at high power levels.

06/02007 Reprocessing of AHWR spent-fuel: challenges and strategies: Kant, S. International Journal of Nuclear Energy Science and Technology, 2005, 1, (2–3), 204–214

A fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel is given. The present cermet fuel consists of an oxide solid solution of Th and minor actinides and Mo-inert matrix. It has been proposed as a high-performance device that can enhance minor actinide incineration in a fast reactor cycle. It is used in an independent small sub-cycle, whereby dedicated cycle technologies are adopted. Two-step reprocessing process was proposed for the present cermet fuel; it consists of a pre-removal of Mo-inert matrix and an actinide recovery. A preliminary test for the pre-removal of Mo-inert matrix was carried out using a surrogate cermet fuel. Burnup characteristics of a fast reactor core loaded with the cermet fuel were investigated by using neutronic calculation codes. It was revealed that a heterogeneous composition of Mo-inert matrix in inner and outer cores may lead to an effective transmutation of minor actinides and a flattened power density. It was concluded that the present cermet fuel was potentially promising as a high-performance incineration device of minor actinides for fast reactors.

Contribution of Phénix to the Development of Transmutation Fuels and Targets in Sodium Fast Breeder Reactors

Studies focusing on different long-lived radioactive waste transmutation scenarios illustrate the relevance of fast breeder reactors (FBRs) vis-à-vis the incineration of minor actinides (MAs) and certain long-lived fission products.This research program evaluates fuels and targets for transmutation, relying mainly on irradiation data from Phénix to experimentally validate and demonstrate the technical feasibility of the envisaged concepts.As regards the homogeneous transmutation of MAs in fast reactors, Phénix clearly demonstrates the good behavior of MA-bearing oxide fuel, at least up to 6.4 at.% of burnup. Similar results on metallic MA-bearing fuels as well as technetium targets will be available very soon. Important knowledge on innovative composite fuels developed for the transmutation of MAs in fast reactors or in accelerator-driven reactors (accelerator-driven systems) is also gained. Inert matrices resistant to neutron and fission product damage have been selected. The role of the microstructure and irradiation conditions on the composite behavior under irradiation is explained.This program also highlights the possibilities of designing and fabricating transmutation targets, obtaining authorization to irradiate these targets in a power reactor—a series of stages to be accomplished in order to demonstrate the technical feasibility of incinerating MAs and technetium in FBRs.

Fast Burner Reactor Devoted to Minor Actinide Incineration

This study proposes a new fast reactor core concept dedicated to plutonium and minor actinide burning by transmutation. This core has a large power level of ~1500 MW(electric) favoring the economic aspect. To promote plutonium and minor actinide burning as much as possible, total suppression of 238U, which produces 239Pu by conversion, and large quantities of minor actinides in the core are desirable. Therefore, the 238U-free fuel is homogeneously mixed with a considerable quantity of minor actinides.From the safety point of view, both the Doppler effect and the coolant (sodium) void reactivity become less favorable in a 238U-free core. To preserve these two important safety parameters on an acceptable level, a hydrogenated moderator separated from the fuel and nuclides, such as W or 99Tc, is added to the core in the place of 238U. Tungsten and 99Tc have strong capture resonances at appropriate energies, and 99Tc itself is a long-lived fission product to be transmuted with profit.This core allows the achievement of a consumption rate of ~100 kg/TW(electric)·h of transuranic elements, ~70 kg/TW(electric)·h for plutonium (due to 238U suppression), and 30 to 35 kg/TW(electric)·h for minor actinides. In addition, ~14 kg/TW(electric)·h of 99Tc is destroyed when this element is present in the core (the initial loading of 99Tc is >4000 kg in the core).The activity of newly designed subassemblies has also been investigated in comparison to standard fast reactor subassemblies (neutron sources, decay heat, and gamma dose rate). Finally, a transmutation scenario involving pressurized water reactors and minor actinide-burning fast reactors has been studied to estimate the necessary proportion of burner reactors and the achievable radiotoxicity reduction with respect to a reference open cycle.

Inert matrix fuel for the utilisation of plutonium

Utilising fuel resources responsibly, reducing waste volume and emissions as well as conflict potentials within the international community (non-proliferation, energy demand) are among the principles for the judgment of sustainable development. Utilising and burning plutonium in a light water reactor has been shown to be feasible for the disposition of the large amount of excess plutonium produced in today's power reactors and resulting from the disarmament efforts of the super powers. With regard to material technology aspects, efforts have concentrated on the evaluation of fabrication feasibility and on the determination of the physicochemical properties of a single phase zirconium/erbium/plutonium oxide material stabilised as a cubic solution by yttrium for plutonium and minor actinide incineration and transmutation. Due to the absence of uranium as origin for plutonium build-up, such a nuclear fuel is called Inert Matrix Fuel. Irradiation testing with a dedicated experiment in the material test reactor in Halden, Norway, is underway within the framework of the OECD-Halden Reactor Project.

Possible use of accelerator driven subcritical reactors for minor actinides incineration

The possible interest of accelerator driven subcritical reactors for minor actinides incineration is examined. The physics of neutron multiplying systems is recalled. The differences between critical and subcritical reactors' control are described, with emphasis on the importance of the delayed neutrons fraction. The minor actinides fuel evolution is studied with the conclusion that fast neutron spectra are clearly more efficient then thermal neutron spectra. It is, also, shown that characteristic times for incineration should be in the order of 10 years. The number of minor actinides incinerators necessary for 60 PWRs is estimated to be about 6 with total thermal power of 9 GW. These reactors will, also, be able to transmute essentially all 99Tc and 129I produced by the 60 PWR. The excess electricity cost for MA incineration is estimated to be about 5%.

Minor Actinides Incineration by Loading Moderated Targets in Fast Reactor

The effect of hydrogen concentration and loaded mass of minor actinides (MAs) in the target on the core performance and MAs transmutation rate was analyzed in this paper. An optimum core was proposed which has 96 MAs target assemblies of which MAs fuel pins per assembly is 38 with the composition ratio U/MA/Zr/H of 1/4/10/50. This optimized core offers good core performance and can transmute MAs very effectively, the transmutation rate was about 67% (939 kg) and the incinerate (transmute by fission) rate was about 35% (489 kg) through 3 years of reactor operation. It is about 2–3 times larger than current transmutation method that MAs are loaded homogeneously in the PWR and fast reactor core.

Fast Reactor Core Concepts for Minor Actinide Transmutation Using Hydride Fuel Targets

Fast reactor core concepts are studied which reduce long-term radiotoxicity of nuclear waste by using minor actinides (MAs) in the form of zirconium-hydride fuel targets. A systematic parameter survey is carried out to investigate the fundamental characteristics of MA transmutation and the core safety parameters such as sodium void reactivity in a 1,000 MWe-class fast reactor core. Two core concepts are proposed, using 36 target assemblies, by adjusting the composition of hydride fuels. One is the MA burner core to transmute a large amount of MAs in a short time combined with Pu multi-recycling in fast reactors, whereby the MAs produced in about 13 LWRs can be transmuted every year with a 58% MA transmutation rate in discharged targets. The other is the MA once-through core to incinerate a small amount of MAs by fission, whereby the MAs produced in about 2 LWRs can be incinerated every year with a 64% MA incineration rate (a 93% transmutation rate) in discharged targets. This study shows these concepts have great potential to achieve good transmutation characteristics of MAs while providing the improved safety characteristics of a fast reactor core.

Minor actinides incineration by loading moderated targets in fast reactor

The effect of contained hydrogen and loaded mass of minor actinides (MAs) in the target on the core performance and MAs transmutation characteristic was analyzed. An optimum core was proposed which has MAs pin cells per assembly of 38 with the composition ratio U/MA/Zr/H of 1/4/10/50. This optimum core can offer good core characteristics and transmute MAs very effectively by about 67% (93kg) and incinerate (transmute by fission) MAs by about 35% (489kg) through 3 years of reactor operation. It is about 2–3 times larger than the current transmutation method which loads MAs homogeneously in the PWR and FR.

Minor Actinides Incineration by Loading Moderated Targets in Fast Reactor.

Minor Actinides Incineration by Loading Moderated Targets in Fast Reactor.

Source of thermonuclear neutrons based on gas dynamic trap: Status of conceptual design and alternative applications

The paper reviews some results of conceptual design of the 14 MeV D–T neutron source dedicated for fusion reactor materials and components testing. The source is based on use of the so called ‘gas dynamic trap’ (GDT) which was first proposed and studied at the Budker Institute of Nuclear Physics (Novosibirsk). The neutron flux in the test zone of the source makes up 2–2.5 MW m −2 under realistic assumptions on achievable plasma parameters and amounts of tritium circulating in the system. An alternative application of using the proposed neutron source as a basis of pilot facility for long-lived radioactive waste transmutation is studied. It is shown that incineration of minor actinides in the transmutator provides a drastic reduction of amount and activity of long-lived waste.