Accelerator-driven Subcritical Reactor Research Articles

Actinide evolution and equilibrium in fast thorium reactors

The development of accelerator-driven sub-critical reactors operating with pure and enriched thorium fuel mixtures has been heralded as delivering a new era in sustainable nuclear power production. Many benefits have been claimed for these systems, particularly with respect to their ability to consume existing plutonium stockpiles and their inability to breed additional plutonium. This paper examines the operation of fast thorium reactors using a lumped model that can demonstrate to first-order accuracy the principles of actinide evolution and equilibrium and allow the identification of trends within the nuclide transformations. The fundamental mechanisms that affect nuclide evolution are demonstrated and the freedoms and constraints bounding this process are shown. Fast reactors operating with a 100% thorium fuel source are shown to generate plutonium and to offer no advantage over enriched thorium fuel in terms of actinide generation in longer-term operation.

China Spallation Neutron Source - an overview of application prospects

The China Spallation Neutron Source (CSNS) is an accelerator-based multidisciplinary user facility to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an H− linear accelerator, a rapid cycling synchrotron accelerating the beam to 1.6 GeV, a solid-tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. Construction of the CSNS project will lay the foundation of a leading national research center based on advanced proton-accelerator technology, pulsed neutron-scattering technology, and related programs including muon, fast neutron, and proton applications as well as medical therapy and accelerator-driven subcritical reactor (ADS) applications to serve China's strategic needs in scientific research and technological innovation for the next 30 plus years.

China Spallation Neutron Source: Design, R&D, and outlook

The China Spallation Neutron Source (CSNS) is an accelerator based multidiscipline user facility planned to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an negative hydrogen linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV energy, a solid tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user's facility with upgrade potential at a fraction of “world standard” cost. We report the status, design, R&D, and upgrade outlook including applications using spallation neutron, muon, fast neutron, and proton, as well as related programs including medical therapy and accelerator-driven sub-critical reactor (ADS) programs for nuclear waste transmutation.

Thermal and mechanical properties of uranium nitride prepared by SPS technique

Nitride fuel is a promising nuclear fuel in fast breeder reactor (FBR) or accelerator-driven subcritical reactor (ADSR) system. In this study, high-density UN pellets were prepared by Spark plasma sintering (SPS) technique. The sample density strongly depended on the sintering temperature and pressure, and the pellets with 90% of theoretical density were easily obtained with low sintering temperature and short sintering time without any milling process. The grain size and pore size were much smaller compared with those for samples prepared by conventional sintering process. Despite of the small grain size, the thermal conductivity remains the high value. The SPS process permits easy densification of nitrides without any deterioration of thermal and mechanical properties, considered to be suitable as a preparation method of nitride fuels.

Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly

A series of preliminary experiments on an accelerator-driven subcritical reactor (ADSR) with 14 MeV neutrons were conducted at Kyoto University Critical Assembly (KUCA) with the prospect of establishing a new neutron source for research. A critical assembly of a solid-moderated and -reflected core was combined with a Cockcroft-Walton-type accelerator. A neutron shield and a beam duct were installed in the reflector region for directing as large a number as possible of the high-energy 14MeV neutrons generated by deuteron-tritium (D-T) reactions to the fuel region, since the tritium target is located outside the core. And then, neutrons (14MeV) were injected into a subcritical system through a polyethylene reflector. The objectives of this paper are to investigate the neutron design accuracy of the ADSR with 14MeV neutrons and to examine experimentally the neutronic properties of the ADSR with 14MeV neutrons at KUCA. The reaction rate distribution and the neutron spectrum were measured by the foil activation method for investigating the neutronic properties of the ADSR with 14 MeV neutrons. The eigenvalue and fixed-source calculations were executed using a continuous-energy Monte Carlo calculation code MCNP-4C3 with ENDF/B-VI.2 for the subcriticality and the reaction rate distribution, respectively; the unfolding calculation was done using the SAND-II code coupled with JENDL Activation Cross Section File 96 for the neutron spectrum. The values of the calculated subcriticality and the reaction rate distribution were in good agreement with those of the experiments. The results of the experiments and the calculations demonstrated that the installation of the neutron shield and the beam duct was experimentally valid and that the MCNP-4C3 calculations were accurately carried out for analyzing the neutronic properties of the ADSR with 14MeV neutrons at KUCA.

Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly

Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly

Analytical investigation and experimental application of the source modulation technique to measure ρ/ βeff

In recent years great interest has been displayed, worldwide, for Accelerator Driven Sub-critical reactors (ADS) to incinerate the minor actinides generated by existing energy-producing reactors. In sub-critical systems, the effective neutron multiplication factor is lower than 1.0 and the neutrons otherwise required to maintain the chain reaction can be put to other uses, in particular, the destruction of nuclear wastes such as minor actinides (MA). One of the major advantages of such ADS systems is that it can be operated with very high MA content without jeopardizing the overall safety due to a small effective delayed neutron fraction, a small Doppler temperature coefficient and possibly also a large void coefficient depending on the chosen coolant. This enhanced safety, however, requires at all time a sufficient sub-criticality margin. Reliable reactivity monitoring techniques are hence required to achieve this goal. The MUSE-4 program is a series of low power experiments carried out at the CEA-Cadarache MASURCA facility to investigate the various methods leading to the measurement of the reactivity level and associated kinetic parameters such as the effective delayed neutron fraction. The aim of this paper is to present the results obtained with a method which directly gives the ratio, for a sub-critical assembly, between the reactivity ρ and the effective delayed neutron fraction β eff. By combining these results to those obtained with the k p-method for the prompt neutron multiplication coefficient, we have access to the parameters which govern the prompt and the slow kinetics of a sub-critical assembly. These parameters can be obtained without reference to any calibration measurement in critical configuration. It opens the way to the control of larger sub-critical demonstrators that are operating with fuels which cannot be used in critical reactor, and, thanks to sub-criticality, which are characterized by a deterministic safety.

Concept of an accelerator-driven subcritical research reactor within the TESLA accelerator installation

Study of a small accelerator-driven subcritical research reactor in the Vinča Institute of Nuclear Sciences was initiated in 1999. The idea was to extract a beam of medium-energy protons or deuterons from the TESLA accelerator installation, and to transport and inject it into the reactor. The reactor core was to be composed of the highly enriched uranium fuel elements. The reactor was designated as ADSRR-H. Since the use of this type of fuel elements was not recommended any more, the study of a small accelerator-driven subcritical research reactor employing the low-enriched uranium fuel elements began in 2004. The reactor was designated as ADSRR-L. We compare here the results of the initial computer simulations of ADSRR-H and ADSRR-L. The results have confirmed that our concept could be the basis for designing and construction of a low neutron flux model of the proposed accelerator-driven subcritical power reactor to be moderated and cooled by lead. Our objective is to study the physics and technologies necessary to design and construct ADSRR-L. The reactor would be used for development of nuclear techniques and technologies, and for basic and applied research in neutron physics, metrology, radiation protection and radiobiology.

Application of variance-to-mean technique to subcriticality monitoring for accelerator-driven subcritical reactor

To investigate the applicability of the Feynman- (or variance-to-mean) and Rossi-α techniques to subcriticality monitoring of the future accelerator-driven subcritical reactor (ADSR), a series of experiments was performed at the Kyoto University Critical Assembly (KUCA). To simulate the pulse mode operation of the ADSR, a D-T pulsed neutron generator was employed. As a result, it was observed that the α-values measured by these techniques clearly depended on the subcriticality, ranging from $0.65 to $2.72. Furthermore, through measurements in transient states that were realised by operating control rods, it was found that one can detect subcriticality changes in quasi-real-time.

Study on neutronics design of accelerator driven subcritical reactor as future neutron source, part 1: static characteristics

In this paper, a basic neutronics design for a future neutron source in Kyoto University Research Reactor Institute (KURRI) is presented. The neutron source is a final goal of so-called “Neutron Factory” project which is anticipated to be realized as an accelerator driven subcritical reactor (ADSR). To generate spallation neutrons, high-energy protons are injected into a target element installed at the center of the core. Spallation neutrons are multiplied in the subcritical reactor to be used as a neutron source for various research fields. The conceptual design was carried out on the basis of the current research reactor KUR in KURRI and was focused on examining its feasibility as a neutron source, for example, the neutron intensity, spectrum, neutron/gamma-ray flux ratio. The impact of the subcriticality, injected proton energy and target material on the performance of neutron source was examined through a kind of sensitivity studies. Furthermore, the power distribution inside the core was extensively investigated since a higher peaking factor in the ADSR may cause a problem in the heat removal and may restrict the usable neutron intensity. Calculations were carried out using the MCNPX code. Calculated results were compared with those of the KUR and the basic feasibility of the ADSR as a neutron source was confirmed.

Study on neutronics design of accelerator driven subcritical reactor as future neutron source, part 2: kinetic characteristics

In this paper, kinetic behavior of the accelerator driven subcritical reactor (ADSR) is investigated through the neutronics calculation in relation with a future plan of neutron source in Kyoto University Research Reactor Institute (KURRI). This neutron source is a hybrid system of the spallation neutron source and the subcritical reactor where the generated neutrons by spallation reactions are multiplied in the subcritical reactor. Kinetic behavior is important in the neutron source for research purpose since the pulse operation of accelerator can provide pulsed neutrons. Kinetic characteristic of this neutron source is examined by using the MCNPX code with taking advantage of the time-dependent tally capability. High-energy protons (500 MeV) are assumed to be injection particles, meanwhile 14 MeV neutrons are also considered to make a comparison. From the calculation results, time-dependent behavior of neutron flux in the ADSR was revealed. The results will provide basis for further investigation on the thermal-hydraulics and mechanical stress analysis of the ADSR. The calculated results also indicate that the kinetic behavior of neutron source is almost similar regardless of either 500 MeV protons or 14 MeV neutrons injection. Therefore, the basic experiments of ADSR can be carried out using the Kyoto University Critical Assembly (KUCA), where there is only the 14 MeV neutron source. The experimental data obtained in KUCA will be useful for verification of nuclear design method of the ADSR. However, to confirm the detailed neutronics characteristics of ADSR experimentally, a high-energy proton accelerator will be highly desirable.

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.

Basic study on neutronics of future neutron source based on accelerator driven subcritical reactor concept in Kyoto University Research Reactor Institute (KURRI)

A basic study on the nuclear characteristics in the accelerator driven subcritical reactor (ADSR) was performed through a series of neutronics design calculations and reactor physics experiments. Calculations were executed mainly by the MCNPX code, and experiments were performed at the Kyoto University Critical Assembly (KUCA). Some nuclear features of the research reactor type ADSR were revealed through the present study. The following facts were found: 1) Further studies are necessary concerning the nuclear data in the high energy region and the generated neutrons through the spallation reactions especially by the light nuclei and the lower energy protons. 2) The adjustment of subcriticality by the control rod significantly affects the reactor power of ADSR because of the distortion in the neutron flux distribution caused by the control rod insertion. 3) An accurate calculation is essential to evaluate the neutron multiplication in the ADSR. 4) The neutronics behavior after a pulse injection can be approximately simulated by the calculation.

A few comments based on Nuclear Physics

The workshop and symposium on “Accelerator-Driven Sub-Critical Reactor System and Nuclear Physics” were held in March 2000 at KEK (Tsukuba) and in October 2000 at Niigata University during the Autumn Meeting of the Japan Physical Society. This was the first joint meeting between the Japanese nuclear physics community members and the Japanese Atomic Energy Society members. About 150 participants working in various fields, such as nuclear physics, reactor physics, reactor engineering, and nuclear power plants in industries discussed the problems related to the nuclear transmutation. Young students also participated in the meetings. Based on the comments in these meetings and on my personal research experience on nuclear physics at university I would like to make a few comments in considering the energy problem in the 21 st century.

Spectrum shaping of accelerator-based neutron beams for BNCT

We describe Monte Carlo simulations of three facilities for the production of epithermal neutrons for Boron Neutron Capture Therapy (BNCT) and examine general aspects and problems of designing the spectrum-shaping assemblies to be used with these neutron sources. The first facility is based on an accelerator-driven low-power subcritical reactor, operating as a neutron amplifier. The other two facilities have no amplifier and rely entirely on their primary sources, a D-T fusion reaction device and a conventional 2.5 MeV proton accelerator with a Li target, respectively.

Isotopic yields and kinetic energies of primary residues in 1 A GeV 208Pb+p reactions

The production of primary residual nuclei in the reaction 1 A GeV 208Pb on proton has been studied by measuring isotopic distributions for all elements from titanium ( Z=22) to lead ( Z=82). Kinematical properties of the residues were also determined and used to disentangle the relevant reaction mechanisms, spallation (projectile fragmentation) and fission. The fragment separator FRS at GSI, Darmstadt, was used to separate and identify the reaction products. The measured production cross sections are highly relevant for the design of accelerator-driven subcritical reactors and for the planning of future radioactive-beam facilities.

Design and corrosion study of a closed spallation target module of an accelerator-driven system (ADS)

At the Forschungszentrum Karlsruhe (FZK) the characteristics of an accelerator-driven subcritical reactor system (ADS) are critically evaluated, mainly with respect to the potential of transmutation of minor actinides and long-lived fission products, to the feasibility and to safety aspects. The work is concentrating on system design, neutronics, thermalhydraulics, safety, materials and corrosion. This article describes the FZK approach to design a closed 4 MW(th) spallation target module with a solid beam window and eutectic lead–bismuth (Pb–Bi) as spallation material and cooling fluid, which is going to be implemented in the FZK three-beam concept of an ADS. This multi-beam concept shows significant improvements towards single-beam concepts from the literature with respect to power distribution in the subcritical blanket and thermal loads of heat removal from the beam window and the spallation region. For some selected martensitic and austenitic steels, corrosion tests in static lead are performed to examine their suitability as structural or window materials. Alloying aluminum into the surface layer by high-power electron beam treatment, corrosion can be reduced to nearly zero. One prerequisite to minimize corrosion is a proper oxygen control system (OCS) via the gas-phase to set the oxygen concentration in the liquid Pb–Bi. The dynamic behaviour of this oxygen control system is described. Finally, the KArlsruhe Lead LAboratory (KALLA) is introduced, the objectives of which are technological, thermal-hydraulic and corrosion investigations into the beam window, the spallation target module and the primary system of an ADS.

Feasibility of a Small Accelerator Driven Subcritical Reactor for BNCT Applications

A feasibility study for an epithermal neutron source constituted by an accelerator-driven subcritical core coupled with an epithermal column is presented. With a core multiplication constant k≤0.985, the proposed facility, equipped with two Li-target, 2.5 MeV, 10 mA accelerator units, appears to be able to fulfil, still keeping a high degree of nuclear safety, the main requirements for BNCT applications as regards the flux level at beam port as well as the neutron spectrum purity.

Accelerator driven subcritical system as a future neutron source in Kyoto University Research Reactor Institute (KURRI) —Basic study on neutron multiplication in the accelerator driven subcritical reactor—

A basic study on the nuclear characteristics in the accelerator driven subcritical reactor (ADSR) was performed through a series of neutronics calculations in view of a future neutron source in Kyoto University Research Reactor Institute (KURRI) for the joint use program among researchers of Japanese universities. In this series of calculations, it was assumed that three kinds of monoenergetic neutrons were isotropically generated at the center of spherical and homogeneous cores with different moderator-to-fuel volume ratios in order to examine the spectrum mismatching effect between injected neutrons and fission neutrons born in the subcritical core. The results of calculations clearly showed the spectrum mismatching effect on the neutron multiplication in the ADSR.

00/00195 Theory of neutron noise induced by source fluctuations in accelerator-driven subcritical reactors

00/00195 Theory of neutron noise induced by source fluctuations in accelerator-driven subcritical reactors