Accelerator-driven Reactor Research Articles

Distribution of Neutrons from The Reaction (p, n) on the Liquid Lead Target in The Accelerator Driven System Reactor

This paper presents results of calculating energy distribution, angular distribution, neutron yield, the double-differential cross-section of the neutron as a proton beam, which produced from the accelerator, spallation on the liquid lead, thus providing the basis for the distribution of the target, calculating fuel … for the accelerator-driven reactor system reactor. These results have shown that the produced neutron energy spectrum extends from thermal neutrons to fast neutrons, which have concentrated in 1MeV to 3MeV. These neutrons are produced at angles of 0° to 10° and turn decreased to the larger angles. This shows that neutrons tend to be produced forward in the direction of the incoming protons.

Optimization of breeding properties of the spallation neutron source target for ADS

One of the main components of an ADS (accelerator-driven reactor systems) is the spallation target, generating neutrons for power plant. Neutrons are generated due in spallation reactions induced on heavy nuclei by accelerator beam of high-energy protons with subsequent multiplication of neutrons in the cascade process of interactions of secondary intermediate-energy particles with target nuclei, subcritical core and blanket.On average, from 20 (for Hg and Pb targets) to 50 (for U target) neutrons are produced per 1-GeV proton in spallation reactions in the target containing nuclei of heavy elements (for example, Hg, Ta, W, U,).Heavy elements such as lead, bismuth, mercury, tantalum, and tungsten are considered as suitable materials for the targets. Lead-bismuth eutectic targets are successfully developed.It is demonstrated in the present paper that there exist optimal size of the target material allowing obtaining for the given incident particle energy maximum number of “spallation” neutrons. Results of calculations of energy spectrum of neutrons generated in the proton interactions with heavy targets for the energy range of incident protons from 0.8 to 1.4GeV.Implemented analysis of variation of neutron generation rate for cylindrical target with 10cm diameter and length from 1 to 120cm at impinging proton energies from 0.8 to 1.4GeV allowed calculating optimal target dimensions consisting of heavy nuclei for the nuclear power installations under design.Optimization of dimensions of neutron generating targets consisting of natural natBi, natHg, natPb и natW isotopes was implemented.

토륨 핵연료 주기 기술동향

토륨은 우라늄에 비해 풍부한 자원으로서의 가치와 핵분열 물질인 U233을 증식하고, 장주기 액티나이드 핵종 발생이 감소하는 특성으로 인해 원자력 연구개발 초기부터 우라늄 주기와 함께 주요 연구대상이었다. 하지만 토륨은 자체적으로 핵분열이 불가능하므로 에너지원으로 활용하기 위해서는 별도의 외부 중성자원이 필요하고, 토륨 주기 과정에서 고방사성 물질이 발생하며, 효과적인 증식을 위해서는 긴 시간의 중성자 조사가 필요했다. 이에 따른 기술적 어려움과 연구개발 필요성의 감소로 1970년대 중반 이후 토륨 관련 연구가 거의 중단되었다. 하지만 1990-2000년대에 에너지 자원에 대한 사회적 시각 변화와 외부 중성자 공급원으로 이용하는 가속기 구동 원자로의 출현으로 과거 토륨주기의 단점으로 지목되었던 성질들이 오히려 핵확산 저항성과 감시성을 높이고, 가속기 구동 원자로의 미임계 운전 특성에 의한 원자력 안전성 증대라는 장점으로 부각되어 토륨에 관한 연구가 세계적으로 활발히 추진되고 있다. 본 연구에서는 토륨주기의 장단점을 우라늄주기와 비교, 분석하고 가속기 구동형 원자로를 이용한 토륨 연구의 기술 현황을 분석한다. The production of nuclear energy from thorium which is non-fissile material was a main issue until the middle of 1970's, because of the thorium's abundance as energy resources, its capability of breeding fissile material U233, and the reduction of long-lived actinides. However, to use thorium as nuclear fuel, some obstacles such as the necessities of external neutron source and long-term neutron irradiation for effective breeding, and the production of high radioactive isotopes in the course of thorium breeding cycle should be overcome. The difficulties to resolve these cons of thorium cycle became the reason of interruption of the related researches in the middle of 1970's. But in the 21st century, the change of societal perspective regarding nuclear energy and the appearance of accelerator-driven nuclear reactor shift those cons into pros and rehabilitate the study of thorium. The high activity of thorium cycle turned out to be a good option as higher resistance and easier detectibility of nuclear proliferation and the employment of subcritical accelerator-driven reactor as external neutron sources is considered to enhance the nuclear safety. In this study we compare the thorium cycle with the currently-used uranium cycle and analyze the technical status and perspective of thorium researches which use accelerator-driven reactors.

Conceptual design of a gas-cooled accelerator-driven reactor with very fast spectrum

A new reactor configuration is proposed under the requirements of providing a high value of breeding ratio and very high safety standards in all conditions, particularly in severe accidents. This double objective conveys the need of very fast neutron spectrum and the use of fuels with a relatively high content of transuranium nuclei, particularly plutonium isotopes. These facts define a narrow design window where a solution must be found to the safety problems created by the lack of Doppler effect and by a strong reduction in the percentage of delayed neutrons. The operational range in safe conditions almost vanishes, because of the lack of negative feedback mechanism and the very small reactivity margin before arriving to prompt-criticality. In order to improve operation conditions, the reactor is kept subcritical, and power level is kept constant with the help of an external source of neutrons, generated by spallations induced by accelerated protons. Main innovations are found in the fuel configuration, because the fuel is embodied into small disks with suitable cladding and different diameters, and the disks are fixed to a geometrical structure forming a virtual spherical surface or cage. The reactor core is therefore a pebble bed, but the pebbles are not actual pebbles, as already said, although they can be evacuated from the core by letting them fall down into a core catcher where subcriticality and decay heat cooling are guaranteed.

Kinetics of the Migration and Clustering of Extrinsic Gas in bcc Metals

Abstract We study the mechanisms by which gas atoms such as helium and hydrogen diffuse and interact with other defects in bcc metals and investigate the effect of these mechanisms on the nucleation of embryonic gas bubbles. Large quantities of helium and hydrogen are produced due to spallation and transmutation in structural materials in fusion and accelerator-driven reactors. The long time evolution of the extrinsic gas atoms and their accumulation at vacancies is studied using a kinetic Monte Carlo algorithm that is parameterized by the migration energies of the point defect entities. First-order reaction kinetics are observed when gas clusters with vacancies. If gas-gas clustering is allowed, mixed-order diffusion limited kinetics are observed. When dissociation of gas from clusters is allowed, gas-vacancy clusters survive to steady state while gas-gas clusters dissolve. We obtain cluster size distributions and reaction rate constants that can be used to quantify microstructural evolution of the irradiated metal.

Research Project on Accelerator-driven Subcritical System Using FFAG Accelerator and Kyoto University Critical Assembly

The Research Reactor Institute of Kyoto University started the KART (Kumatori Accelerator-driven Reactor Test facility) project in fiscal year 2002 under the Contract with the Ministry of Education, Culture, Sports, Science and Technology of Japan. The purpose of this research project is to demonstrate the basic feasibility of accelerator-driven system (ADS), studying the effect of incident neutron energy on the effective multiplication factor in a subcritical nuclear fuel system. For this purpose, a variable-energy FFAG (Fixed Field Alternating Gradient) accelerator complex is constructed and coupled with the Kyoto University Critical Assembly (KUCA). This paper presents the present status of the project and some of the results from the task performed up to Fiscal Year 2005.

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.

Reactivity determination in accelerator driven reactors using reactor noise analysis

Feynman-alpha and Rossi-alpha methods are used in traditional nuclear reactors to determine the subcritical reactivity of a system. The methods are based on the measurement of the mean value, variance and the covariance of detector counts for different measurement times. Such methods attracted renewed attention recently with the advent of the so-called accelerator driven reactors (ADS) proposed some time ago. The ADS systems, intended to be used either in energy generation or transuranium transmutation, will use a subcritical core with a strong spallation source. A spallation source has statistical properties that are different from those traditionally used by radioactive sources. In such reactors the monitoring of the subcritical reactivity is very important, and a statistical method, such as the Feynman-alpha method, is capable of resolving this problem.

The role of the accelerator in energy: (Recent development of an accelerator-drive systems (ADS))

I describe the recent development of an accelerator-driven reactor for producing energy, and for transmuting minor actinides and long-lived fission products. To run these reactors in a slightly subcritical condition rather than at deep criticality, the proton accelerator can be a low-powered cyclotron which requires only a small building and site; hence, the cost of generating electricity by this system becomes inexpensive. To get a higher beam current for a circular accelerator, a fixed field alternating gradient (FFAG) synchrotron can be used for driving the subcritical reactor without jeopardizing the reduction of the shock wave created by manipulating the pulsed-mode operation. The induction FFAG is discussed. To reduce the energy costs of transmuting long-lived fission products (LLFPs) such as Tc-99, and I-129, I reconsider the old concept of depositing of them into outer space by not rocket but by an ions thruster.

Long-lived radioactive waste transmutation and the role of accelerator driven (hybrid) systems

Partitioning and transmutation strategies are studied in several countries within the framework of R&D programs devoted to the management of high-level radioactive wastes. One option is to use accelerator-driven reactors in order to transmute Pu and minor actinides and/or long-lived fission products. Conceptual studies underway in France and Japan are illustrated in the present paper. Some basic ideas of a reactor park capable of stabilizing production and consumption of Pu and minor actinides, which could reduce significantly the potential source of radiotoxicity in a geological repository, are worked out.

Design of a supersonic wind shutter device for an accelerator-driven reactor system

The design of a supersonic wind shutter for the proton line of high-current accelerator is considered. The proposed device enables to avoid using a membrane separating vacuum proton line from cooling liquid of reactor system.