Accelerator Driven Subcritical Reactor System Research Articles

Effects of Pb and Bi on mechanical properties and fracture modes of bcc iron symmetrical tilt grain boundaries

The internal structural material T91 in the accelerator driven subcritical reactor system (ADS) has encountered the challenge of liquid metal embrittlement caused by Pb and Bi. Therefore, it is of utmost importance to gain a comprehensive understanding of their embrittlement mechanism. The effects of Pb and Bi on the surface energy of surfaces and separation work and fracture toughness of grain boundaries in body center cubic (BCC) Fe are examined using first-principles calculation. Pb and Bi atoms reduce the surface energy and grain boundary cohesion strength of BCC Fe, with a more significant decrease in surface energy. Meanwhile, the segregation of Pb and Bi in the grain boundary reduces the fracture toughness of the grain boundary. By comparing different surface energy and separation work, it is found that BCC pure Fe is more prone to intergranular fracture, while the presence of Pb and Bi causes cleavage fracture. This elucidates the low-temperature fracture mode of BCC-Fe and reveals the potential mechanism of brittle cleavage fracture caused by Pb and Bi in BCC-Fe. The derived results are discussed in terms of electronic structure and show good agreement with experimental results in the literature, ultimately contributing to a thorough understanding of the intrinsic mechanism of liquid metal embrittlement of T91 steel.

Design, development and characterization of tunable Permanent Magnet Quadrupole for Drift Tube Linac

Bhabha Atomic Research Centre, Trombay is developing LEHIPA (Low Energy High Intensity Proton Accelerator) as pre-injector for 1 GeV proton accelerator for proposed ADSS (Accelerator Driven Sub-critical reactor System). LEHIPA is 20 MeV, 30 mA room temperature accelerator and consists of RFQ (Radio Frequency Quadrupole) and DTL (Drift Tube Linac) as major accelerating structures. The RF (Radio Frequency) design of DT (Drift Tube) of DTL aimed at maximizing the shunt impedance; this demands the size (transverse) of DTs to be minimal. The width of the DT is governed by the β of the particle and trade-off between transit time factor and effective accelerating voltage in the DT gap. The availability of limited volume in DTs for housing magnetic quadrupole has motivated the use of permanent magnets for generating the quadrupole field, as they have high magnetic energy density when compared to conventional electromagnets. With usage of permanent magnets, joule heating is eliminated, this helps in limiting the heat load. DTL has copious microwave heat with heat flux as large as 10 W/cm2 at certain locations. The beam dynamics requires uniformity of integral magnetic field gradient of PMQ (Permanent Magnet Quadrupole) to be better than ±0.5% with nominal value of 2.05 T. Further the drift tubes which houses these PMQs have microwave heat generation on outer surface which ranges from 5 kW to 8 kW depending on the size of the DT. This heat is required to be removed, not doing so would result in resonant frequency detuning in DTL cavity and enhanced temperature would deteriorate the strength of permanent magnets of the PMQ, thereby compromising their focal length. The drift tube has hydraulic circuit for microwave heat removal. This paper describes the magnetic design of the PMQ using Sm2Co17 rare earth permanent magnets. Paper discusses the magnetic design for optimizing integral magnetic field gradient (integral Gdl) uniformity. A novel magnetic field tuning technique is used for tuning the integral magnetic field gradient to required value. Comprehensive magnetic tuning and characterization scheme is presented which relates the measured magnetic moment of the permanent magnets, un-tuned integral Gdl and pole length to the required integral Gdl. Based on this scheme thirty six PMQ embedded drift tubes have been developed. Paper also details the results of characterization of twenty PMQs which forms part of 10 MeV to 15 MeV DTL. The scheme used for tuning integral magnetic field gradient is universal and can be implemented in similar permanent magnets quadrupoles and other permanent magnet based systems.

Verification of a HC-PK-CFD coupled program based a benchmark on beam trip transients for XADS reactor

It is important to employ multi-physics coupling strategy in thermal-hydraulics/safety analysis of nuclear reactors. In general, it is based on couplings of system codes with neutron dynamics codes, which is incompetent to cope with multi-dimensional thermal-hydraulics/safety problems involved in liquid metal cooled pool-type reactors. To cope with it, Computational Fluid Dynamics tools are good choices which have attracted considerable attentions in reactor simulation these years. In order to apply a commercial CFD program in thermal-hydraulics/safety analyses, the research on couplings of Point Kinetics (PK) model and a fuel pin Heat Conduction (HC) model to the commercial CFD platform FLUENT abbreviated as HC-PK-CFD is performed in this study. Verifications are performed by the benchmark simulation on beam interruption transients for an accelerator-driven sub-critical reactor system. It is demonstrated that the results simulated by HC-PK-CFD agrees well with the ones by other ten multi-physics coupling codes participating in this benchmark.

Development and validation of depletion code system IMPC-Burnup for ADS

Depletion calculation is important for studying the transmutation efficiency of minor actinides and long-life fission products in accelerator-driven subcritical reactor system (ADS). Herein the Python language is used to develop a burnup code system called IMPC-Burnup by coupling FLUKA, OpenMC, and ORIGEN2. The program is preliminarily verified by OECD-NEA pin cell and IAEA-ADS benchmarking by comparison with experimental values and calculated results from other studies. Moreover, the physics design scheme of the CIADS subcritical core is utilized to test the feasibility of IMPC-Burnup program in the burnup calculation of ADS system. Reference results are given by the COUPLE3.0 program. The results of IMPC-Burnup show good agreement with those of COUPLE3.0. In addition, since the upper limit of the neutron transport energy for OpenMC is 20 MeV, neutrons with energies greater than 20 MeV in the CIADS subcritical core cannot be transported; thus, an equivalent flux method has been proposed to consider neutrons above 20 MeV in the OpenMC transport calculation. The results are compared to those that do not include neutrons greater than 20 MeV. The conclusion is that the accuracy of the actinide nuclide mass in the burnup calculation is improved when the equivalent flux method is used. Therefore, the IMPC-Burnup code is suitable for burnup analysis of the ADS system.

Multiplication characteristics of a gas-cooled ADS with fast-thermal coupling configuration

Abstract The Accelerator Driven Subcritical Reactor System (ADS) is developed to transmute the nuclear wastes. Nevertheless, just like the traditional reactors, the ADS is faced with the problem of how to remove the decay heat efficiently. In order to solve the problem, a design of helium-cooled ADS with tungsten target is presented in this paper, and the multiplication characteristics of it are researched. The design of the subcritical core is based on the scheme of high temperature gas-cooled reactor, and to improve the ability of transmutation, the subcritical core is divided into two regions, which form up the fast-thermal coupling configuration. The parameters of fuel arrangement, position of target, height of active core, and height of top/bottom reflector are optimized to achieve the good physical and thermal performance. In the process of optimization, the influences of these parameters on the characteristics of the core are investigated through numerical experiments simulated by the MCNP6 code. The results indicate that the K eff and the K s may differ considerably for the gas-cooled ADS with fast-thermal coupling configuration. Moreover, we find that even with the same K eff , the K s of the subcritical core is different for similar schemes.

The research on the characteristics of target and core in a gas-cooled ADS with passive safety

The Accelerator Driven Subcritical Reactor System (ADS) has a strong ability to transmute minor actinides (MAs) and it has inherent safety because of its subcritical core. However, the removal of decay heat is a major problem for the ADS and the design of spallation target is still a difficulty. Therefore, this paper presents a design of gas-cooled ADS with passive safety to attain the good performance of removing decay heat and transmutation.For the design of the target, the helium-cooled tungsten target is decided to adopt, and it is modelled into the cone structure to strengthen the convective heat transfer. A series of numerical experiments have been made to determine the optimal parameters of the target using the MCNP and CFX code. In the design of core, the subcritical core is divided into fast neutron region which the MAO2 is placed in and thermal neutron region which the UO2 is placed in to improve the performance of the transmutation. Two methods are proposed in this paper for the thermal-hydraulic calculation in the steady-state analysis, and the results show its good thermal performance.

Thermal-Hydraulic Model and Program Development for Helium-Cooled Accelerator-Driven System

The accelerator-driven subcritical reactor system (ADS) is a kind of nuclear reactor which can burn minor actinide waste products produced from conventional reactors with inherent safety features. In this paper, the thermal-hydraulic model and a corresponding program for a 10 MW helium-cooled experimental ADS are presented. Through the analysis of the heat transfer mechanism in ADS, the thermal-hydraulic model of ADS was built, in which the solid domain is simulated with three-dimensional heat conduction model and the fluid domain is simulated with the one-dimensional quasi-static model. In order to analyze the transient characteristics of ADS with cooling system, a RELAP5–TRCAP coupling model for the cooling system was established, in which the decay heat of the target and core is considered. The results of steady condition and transients demonstrate the effectiveness of the transient model.

Accident analysis of tungsten target coupled with ADS core

The Accelerator Driven Subcritical Reactor System (ADS) is a kind of nuclear reactor which can burn minor actinide waste produced from conventional reactors with inherent safety features. Because of the characteristics of a sub-critical reaction process, the fission chain reaction is maintained by additional neutrons generated by protons in spallation target. This paper presents a concept design and the accident analysis of helium gas-cooled tungsten target for 10 MW helium-cooled experimental ADS.The thermal-hydraulic model of the target coupling with core was built, in which the solid domain was simulated with three-dimensional heat conduction model and the fluid domain was simulated with one-dimensional quasi-static model. In order to analyze the transient characteristics of the target with cooling system, a RELAP5-TRCAP coupling model for cooling system was established, in which the decay heat of the target and core was considered. The simulated results indicate that the peak temperature in the target is lower than the limiting value under the rated operation state and during four typical transient with actuation of the safety system.

Thermal Analysis of Spent Nuclear Fuels Repository

In the first part, Pressurized Water Reactor (PWR), Very High-Temperature Reactor (VHTR) and Accelerator-Driven Subcritical Reactor System (ADS) spent fuels (SF) were evaluated to the thermal of the spent fuel pool (SFP) without an external cooling system. The goal is to compare the water boiling time of the pool storing different types of spent nuclear fuels. This study used the software Ansys Workbench 16.2 - student version. For the VHTR, two types of fuel were analyzed: (Th,TRU)O2 and UO2. This part of the studies were performed for wet storage condition using a single type of SF and decay heat values at times t=0 and t=10 years after the reactor discharge. The Ansys CFX module was used and the results show that the time that water takes to reach the boiling point varies from 2.4 minutes for the case of VHTR-(Th,TRU)O2 SF at time t=0 year after reactor discharge until 32.4 hours for the case of PWR SF at time t=10 years after the discharge reactor.The second part of this work consists of modeling a geological repository. Firstly, the temperature evaluation of the spent fuel from a PWR was analyzed. A PWR canister was simulated using the Ansys transient thermal module. Then the temperature of canister could be computed during the time spent on a portion of a geological repository. The mean temperature on the canister surface increased during the first nine years, reaching a plateau at 35.5°C between the tenth and twentieth years after the geological disposal. The idea is to extend this study for the other systems analyzed in the first part. The idea is to include in the study, the spent fuels from VHTR and ADS and to compare the canister behavior using different spent fuels.

Thermal–hydraulic modeling and transient analysis of helium-cooled tungsten target coupled with ADS core

The Accelerator Driven Subcritical Reactor System (ADS) is a kind of nuclear reactor which can burn minor actinide waste produced from conventional reactors with inherent safety features. This paper presents a concept design of helium gas-cooled tungsten target for 10MW helium-cooled experimental ADS.In the design scheme, the tungsten spallation target was modeled into the honeycomb structure. The thermal–hydraulic model of the target coupling with core was built, in which the solid domain was simulated with three-dimensional heat conduction model and the fluid domain was simulated with one-dimensional quasi-static model. The target was modeled with fine meshes. The core was modeled roughly as the boundary condition of the target. In order to analyze the transient characteristics of the target with cooling system, a RELAP5–TRCAP coupling model for cooling system was established, in which the decay heat of the target and core was considered. The simulated results indicate that the peak temperature in the target is lower than the limiting value under the rated operation state and during the Loss of Flow Accident (LOFA) transient with actuation of the safety system.

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.

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.

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.