Accelerator-driven Subcritical System Research Articles

Numerical Prediction of Fluid Flow and Heat Transfer in the Target System of an Axisymmetric Accelerator-Driven Subcritical System

Thermal hydraulics related to the design of the spallation target module of an accelerator-driven subcritical system (ADSS) was investigated numerically using a streamline upwind Petrov-Galerkin (SUPG) finite element (FE) method. A large amount of heat is deposited on the window and in the target during the course of nuclear reaction between the proton beam and the molten lead-bismuth eutectic (LBE) target. Simulations were carried out to predict the characteristics of the flow and temperature fields in the target module with a funnel-shaped flow guide and spherical bottom of the container. The beam window was kept under various thermal conditions. The analysis was extended to the case of heat generation in the LBE. The principal purpose of the analysis was to trace the temperature distribution on the beam window and in the LBE. In the case of turbulent flows, the number of recirculation regions is decreased and the maximum heat transfer was found to take place downstream of the stagnation zone on the window.

Application of nuclear energy for environmentally friendly hydrogen generation

It is universally admitted that hydrogen is one of the best energy media and its demand will increase greatly in the near future. However, little hydrogen exists naturally, so that how to generate hydrogen without bringing forth much CO 2 will be very important research subject. Hydrogen generation from water using nuclear energy is one of the solutions for this problem. Especially, the high temperature gas cooled reactor (HTGR) has a possibility to generate hydrogen economically compared with other types of nuclear reactors. As for long-lived radioactive waste to be generated by nuclear reactors, it is expected to significantly reduce its burden to the human environment by applying transmutation technologies. This report describes the feature of the hydrogen generation with HTGR and the development of the accelerator-driven subcritical system to reduce radioactive waste ongoing at JAEA.

A dc arc plasma torch as a tailored heat source for thermohydraulic simulation of proton beam–target interaction in ADSS

Currently, research on accelerator driven subcritical systems (ADSS) is gaining significance due to their high safety levels and extremely attractive potential in terms of both thorium utilization and nuclear waste transmutation. While high energy and high current proton beams are being built worldwide, intensive efforts are being undertaken in parallel towards the development of complex lead bismuth eutectic target systems. The major focus is directed towards understanding of the material compatibility and detailed thermohydraulic simulation of the liquid metal flow. The requisite heat flux is being deposited using innovative and easily controllable heat sources. This paper presents an experimental and simulation study to explore the potential of using dc arc plasma torches as a tailored heat source for thermohydraulic simulation of proton beam–target interaction in such systems.

A SUPG–finite element study of an ADSS

Analysis of fluid flow and heat transfer characteristics in the spallation zone of an accelerator driven sub-critical system (ADSS) plays a crucial role in its design. In this study, a numerical investigation of a window based ADSS is carried out using streamline upwind Petrov–Galerkin (SUPG)–finite element (FE) method. The time-dependent governing equations for conservation of mass, momentum and energy together with turbulent kinetic energy and its dissipation rate are solved. Simulations have been carried out to predict the flow and temperature distribution in the spallation region. At the first place, laminar regime of the flow is considered. Subsequently, the analysis is extended for the turbulent flows. The Reynolds number of interest is varied over a specified range.

Space-Time Correction for Reactivity Determination in Source-Driven Subcritical Systems

The presence of a localized spallation source in an accelerator-driven subcritical system leads to significant spatial variations in the power distribution and invalidates the simple point-kinetics approach. To eliminate higher-harmonics contamination in the detector response and to account properly for spatial and spectral effects in reactivity determination, a method directly combining measurements with numerical simulations of the experimental data is developed through a quasi-static formulation. The method provides space-time correction to a variety of traditional point-kinetics techniques and determines the reactivity essentially independent of the detector position, as long as sufficiently accurate information on the reactor configuration is provided. In the current work, the space-time corrections are derived for two well-known point-kinetics methods: area-ratio technique and α-method. Numerical simulations performed with the FX2-TH diffusion theory code along with a space-time analysis of MUSE-4 pulsed source experimental data illustrate the applicability of the proposed methods for the determination of significant subcriticality levels in fast and thermal reactor systems.

NSRP-16, Radiation Transport : Experiments, Computations and Theory, Workshop on Physics of Accelerator Driven Sub-Critical System (ADS) for Energy and Transmutation

NSRP-16, Radiation Transport : Experiments, Computations and Theory, Workshop on Physics of Accelerator Driven Sub-Critical System (ADS) for Energy and Transmutation

Properties of the Feynman-α method applied to accelerator-driven subcritical systems

A Monte Carlo study of the Feynman-method with a simple code simulating the multiplication chain, confined to pertinent time-dependent phenomena has been done. The significance of its key parameters (detector efficiency and dead time, k-source and spallation neutrons multiplicities, required number of fissions etc.) has been discussed. It has been demonstrated that this method can be insensitive to properties of the zones surrounding the core, whereas is strongly affected by the detector dead time. In turn, the influence of harmonics in the neutron field and of the dispersion of spallation neutrons has proven much less pronounced.

Properties of the feynman-α method applied to accelerator-driven subcritical systems

Properties of the feynman-α method applied to accelerator-driven subcritical systems

Investigation on turbulent heat transfer to lead–bismuth eutectic flows in circular tubes for nuclear applications

Since many years, the Forschungszentrum Karlsruhe has been working on the research and development of an accelerator driven sub-critical system (ADS) cooled by lead–bismuth eutectic (LBE). Although various numerical tools for thermal hydraulics have been established at the Forschungszentrum Karlsruhe, reliably validated physical models related to turbulent heat transfer in LBE flows are still missing. Especially, physical models on heat transfer and turbulent Prandtl number have to be re-evaluated in LBE conditions to improve the reliability of numerical tools. In the present paper, review and assessment of the existing physical models are made. Computational fluid dynamics (CFD) analysis is carried out for circular tube geometries. Based on the assessment of the existing models and the CFD results achieved, recommendations are made on correlations of heat transfer and turbulent Prandtl number for numerical applications to LBE flows.

Nitrides as a nuclear fuel option

Nitrides have been proposed to be a suitable material for fast neutronic systems from beginning of the development of nuclear fuel. Starting with the production of uranium nitride and sesquinitrides up to mixed plutonium uranium nitrides, today's developments are inert nitride matrix materials to burn plutonium or to transmute long-lived actinides in accelerator-driven sub-critical systems (ADS) or fast reactors (FR). Several authors proposed zirconium nitride as possible inert matrix material for this reason. Mixed zirconium nitrides can be fabricated by carbothermal nitridation of the oxides in a narrow temperature window. Obtaining high quality material with low carbon and oxygen content is still the major challenge. Producing mixed nitride fuels by special shaping methods, as for example direct coagulation casting or freeze drying, in comparison to conventional powder compaction enables to use this material in special shapes to optimize burn up.The history of nitride fuels at PSI will be shown up to today's CONFIRM project, dealing with plutonium zirconium nitride fuels.

Corrosion resistance study of argon implanted and ion-beam-mixed 316 SS

The objective of the present work is to study and develop a suitable structural material for the Accelerator Driven Subcritical System (ADSS), which can withstand extreme conditions of irradiation in corrosive environment. Effects of radiation damage on corrosion resistance are evaluated and a possible solution is attempted by adding alloying elements such as Al or Si. Aqueous corrosion studies were carried out in 0.5 N H 2SO 4 solution on 316 SS, Ar + implanted 316 SS, Al ion-beam-mixed 316 SS and Si ion-beam-mixed 316 SS. At a low dose 30 keV Ar + implantation, the martensitic phase transformation was observed in 316 SS. Corrosion potential reduced to very low negative values after Ar + implantation, indicating the reduction in corrosion resistance. As the dose was increased further, the corrosion resistance marginally improved. This correlates with the reduction in martensitic phase, as observed using glancing angle X-ray diffraction (GXRD). Si ion-beam-mixed 316 SS displayed good corrosion resistance with higher corrosion potential, higher pitting potential and large passive region, whereas Al ion-beam-mixed 316 SS displayed no passive region but had a higher corrosion potential.

On the Neutron Kinetics and Control of Accelerator-Driven Systems

This work addresses fundamental aspects of the time- and space-dependent behavior of an Accelerator-Driven Subcritical Core System (ADS) and presents a paradigm ADS neutron kinetics model that is solved exactly. Thus, this paradigm model can serve for benchmarking two- and/or three-dimensional computational tools. Furthermore, this work also proposes a global optimal control theory framework for the operation and control of an ADS. This framework encompasses conceptually the time- and space-dependent behavior of the ADS coupled neutron kinetics/thermal-hydraulic balance equations and aims at the optimal control of ADS operational objectives, which would include minimization of local flux disturbances, load and source following, etc. Importantly, this new conceptual framework makes no use of a “fictitious ADS steady state” and yields the correct and complete (i.e., including sources) adjoint equations, without leaving any room for ambiguities. Thus, this new conceptual framework provides a natural basis for developing new computational methods and corresponding verification experiments specifically tailored for the control and operation of ADS.

Theory and Analysis of the Feynman-Alpha Method for Deterministically and Randomly Pulsed Neutron Sources

In future planned accelerator-driven subcritical systems, as well as in some recent related experiments, the neutron source to be used will be a pulsed accelerator. For such cases the application of the Feynman-alpha method for measuring the reactivity is not straightforward. The dependence of the Feynman Y(T) curve (variance-to-mean minus unity) on the measurement time T will show quasi-periodic ripples, corresponding to the periodicity of the source intensity. Correspondingly, the analytical solution will become much more complicated. One can perform such a pulsed Feynman-alpha measurement in two different ways: either by synchronizing the start of each measurement block with the pulses (“deterministic pulsing”) or by not synchronizing (“random pulsing”). The variance-to-mean has been derived analytically for both cases and reported briefly in previous publications. However, two different methods were used and the two cases were reported separately. In this paper we give a unified treatment and a comparative analysis of the two cases. It is found that the stochastic pulsing leads to an analytic solution that is much simpler than that for the deterministic case, and the relationship between the pulsed and continuous source is much more straightforward than in the deterministic case. However, the amplitude of the ripples, constituting a deviation of the pulsed Feynman Y curve from the smooth curve corresponding to the traditional constant source case, is much larger for the stochastic pulsing than for the deterministic one. The reasons for this are also analyzed in the paper. The results are in agreement with recent measurements, made by other groups in the European Community-supported project MUSE.

U-Pb accelerator-driven sub-critical systems research at the proton beam of the JINR NUCLOTRON

AbstractNeutron spectra, yields and energies of particles generated by a uranium electro-nuclear set-up which is now used in Dubna for transmutation research of various isotopes with a proton beam of an energy of 1–2 GeV, were analyzed by means of mathematical modelling based on the Monte Carlo code CASCADE. The influence of space dispersion on the proton beam and its possible deviation from the center of a lead target is investigated. It is shown that the polyethylene radiation shielding that is being used now, does not protect the measuring room from neutrons and γ-rays.

Transmutation: Towards Solving Problem of Spent Nuclear Fuel

An Accelerator Driven Subcritical System (ADS) is a promising, new concept for transmutation of long-lived isotopes originating from spent nuclear fuel. In the mainstream of research is the proton accelerator-driven ADS, however, on smaller scale an electron accelerator-driven machine could be an alternative. Using international codes we started to investigate the reactor physical aspects of such a device. In our paper we present the results of the first step of the modelling: the target optimization.

04/00234 Transmutations of nuclear waste in accelerator-driven subcritical systems: Taczanowski, S. Applied Energy, 2003, 75, (1–2), 97–117

04/00234 Transmutations of nuclear waste in accelerator-driven subcritical systems: Taczanowski, S. Applied Energy, 2003, 75, (1–2), 97–117

Radiation safety in the Russian atomic power industry

Of all the radioactive wastes known in nuclear power industry and engineering, long-lived actinides and fission products from spent nuclear fuel are the most hazardous. One way to reduce their radiation hazard is to resort to nuclear transmutation, which can be performed either in reactors of various types or in accelerator-driven subcritical systems, whose nuclear safety is superior to that of conventional reactors. Fundamentally resolving the problem of the destruction of long-lived radioactive wastes is likely to stimulate progress in the development of the nuclear power industry.

Zirconium nitride as inert matrix for fast systems

Zirconium nitride has been proposed as inert matrix material to burn plutonium or to transmute long-lived actinides in accelerator-driven sub-critical systems or fast reactors. In combination with the possibility to fabricate specially shaped fuel pellets, e.g. barrel with a hole, an innovative fuel would be designed to reach higher burnup.The current project aims to use the direct coagulation casting process to shape mixed plutonium zirconium nitride annular pellets. As a backup option the conventional powder-pressing route is used to produce standard pellets. Gibbs energy calculations were used to optimise the thermal treatment of carborthermic reduction to yield mixed nitride powders. The status quo of the powder and pellet production as well as the first analytical results are presented in the following.

Transmutations of nuclear waste in accelerator-driven subcritical systems

The physical preconditionings of transmutations are analysed. It has been suggested that one of the most viable incineration concepts is a symbiotic nuclear-energy system, consisting of a transmuter and a number of co-operating light-water reactors (LWRs). Closing of the fuel cycle is not easily achievable, since the minor actinides (MAs), unavoidably then produced in significant quantities, show disadvantageous safety properties (positive void reactivity coefficients). Accelerator-driven subcritical systems (ADSSs), distinct by their remoteness from super prompt criticality, have been attracting more and more attention. The superiority of subcritical ones is shown by comparing their behaviours in the case of a rapid reactivity insertion that brings no risk, in contrast to the fast critical ones. Finally, research problems and difficulties are mentioned. Any form of closed fuel cycle cannot avoid dealing with large quantities of radioactive materials. Yet, a definitive elimination of actinides, with the use of the enormous released energy, is worth this price. Summarising, the concept of nuclear transmutations in accelerator-driven subcritical systems significantly heightens the safety of nuclear-power systems.

Accelerator-driven sub-critical reactor system (ADS) for nuclear energy generation

In this talk we present an overview of accelerator-driven sub-critical reactor systems (ADS), and bring out their attractive features for the elimination of troublesome long-lived components of the spent fuel, as well as for nuclear energy generation utilizing thorium as fuel. In India, there is an interest in the programmes of development of high-energy and high-current accelerators due to the potential of ADS in utilizing the vast resources of thorium in the country for nuclear power generation. The accelerator related activities planned in this direction will be outlined.