Fusion-driven Subcritical System Research Articles

Neutronic Analysis for Feasibility of Fusion-Driven Subcritical System with Constant Fusion Power by Online Feeding of Molten Salt Fuel

To enhance the practical application of a fusion-driven subcritical reactor, a system with constant fusion power by online feeding of molten salt fuel was designed. The system satisfies multiple purposes including waste transmutation, tritium breeding (TB), and energy multiplication (EM) through constant fusion power. All neutronic calculations were performed by SERPENT2.1.29 with the ENDF/B-VII.0 neutron cross-section library in order to simulate the online-feeding process.A constant k-eff is maintained by the amount of the feeding being larger than the amount of the removed fission products. However, system performance is significantly improved by just reducting the reactivity swing with the feeding. Compared to a once-through cycle (OTC), the performance of TB and EM is significantly improved as the feeding rate increases. However, there is no deep burning effect like the OTC for waste transmutation.The performance of waste transmutation is changed in the feeding scenarios. For the scenario with a high plutonium ratio, transmutation with plutonium is increased. On the other hand, for the feeding scenario with a high minor actinide ratio, transuranic waste is burned. However, the transmutation performance is degraded due to a low fission-to-capture ratio.

Preliminary sustainable and economic analysis of nuclear fuel cycle with subcritical system

Summary Nuclear power is attractive for helping carbon reduction and energy restructuring, but the low utilization of nuclear resource and technical problems on reprocessing are key issues for further nuclear development. Subcritical system might be a potential way to solve these problems, which include fusion-driven subcritical system and accelerator-driven subcritical system. Especially the new subcritical system conception spent fuel burner could be used for waste transmutation, nuclear fuel breeding, and energy production. In this contribution, 2 nuclear fuel cycle scenarios with subcritical system for spent fuel burning and pressurized water reactor were assessed with the performances of sustainability of resources, environmental impacts, and economy. The results showed that the advanced fuel cycle based on subcritical system is an attractive option for the long-term development of nuclear power in China.

Neutronics analysis of minor actinides transmutation in a fusion-driven subcritical system

The minor actinides (MAs) transmutation in a fusion-driven subcritical system is analyzed in this paper. The subcritical reactor is driven by a tokamak D-T fusion device with relatively easily achieved plasma parameters and tokamak technologies. The MAs discharged from the light water reactor (LWR) are loaded in transmutation zone. Sodium is used as the coolant. The mass percentage of the reprocessed plutonium (Pu) in the fuel is raised from 0 to 48% and stepped by 12% to determine its effect on the MAs transmutation. The lesser the Pu is loaded, the larger the MAs transmutation rate is, but the smaller the energy multiplication factor is. The neutronics analysis of two loading patterns is performed and compared. The loading pattern where the mass percentage of Pu in two regions is 15% and 32.9% respectively is conducive to the improvement of the transmutation fraction within the limits of burn-up. The final transmutation fraction of MAs can reach 17.8% after five years of irradiation. The multiple recycling is investigated. The transmutation fraction of MAs can reach about 61.8% after six times of recycling, and goes up to about 86.5% after 25.

Preliminary analysis of liquid LiPb MHD flow and pressure drop in DWT blanket of FDS-I

The dual-cooled waste transmutation (DWT) blanket of FDS-I (fusion-driven subcritical system) has been proposed to transmute long-lived nuclear waste, to breed nuclear fuels such as tritium and plutonium and to generate energy. The special magnetohydrodynamics (MHD) problems of liquid metal LiPb coolant in the DWT blanket are caused by the “banana shape” blanket module. The MHD effects of liquid metal LiPb fluid have been analysed and simulated by using computation fluid dynamics (CFD) software FLUENT added MHD user subroutine. The velocity profile and pressure distribution of LiPb flow in bend channels have been presented. The effect of wall conductance ratio of wall, including electrically insulting coating, electrically insulated flow channel insert (FCI) and electrically conducting wall, on flow velocity is analyzed.

A fusion-driven subcritical system concept based on viable technologies

A fusion-driven hybrid subcritical system (FDS) concept has been designed and proposed as spent fuel burner based on viable technologies. The plasma fusion driver can be designed based on relatively easily achieved plasma parameters extrapolated from the successful operation of existing fusion experimental devices such as the EAST tokamak in China and other tokamaks in the world, and the subcritical fission blanket can be designed based on the well-developed technologies of fission power plants. The simulation calculations and performance analyses of plasma physics, neutronics, thermal-hydraulics, thermomechanics and safety have shown that the proposed concept can meet the requirements of tritium self-sufficiency and sufficient energy gain as well as effective burning of nuclear waste from fission power plants and efficient breeding of nuclear fuel to feed fission power plants.

Economic assessment of fusion and fusion-driven subcritical systems based on internalization of external costs and benefits

A complete economic assessment of fusion and fusion-driven subcritical system (FDS) systems should include the internalities and externalities, which reflect the costs/benefits of economy, environment and safety. A method of internalization of external costs and benefits, which are quantified by a tax levied on the environmental pollution of energy production, is presented. Based on the methodology, cost–benefit models of FDS are constructed. The economic performances of FDS-I (a typical design of FDS) has been calculated and compared with those of pure fusion energy systems. The impacts of the characteristic parameters of FDS-I on economy have been studied. The results have been specified to give recommendations for the improvement of the design.

ICONE15-10138 PRELIMINARY ANALYSIS OF TYPICAL TRANSIENTS IN FUSION DRIVEN SUBCRITICAL SYSTEM (FDS-I)

The potential safety characteristic is expected as one of the advantages of fusion-driven subcritical system (FDS-I) for the transmutation and incineration of nuclear waste compared with the critical reactor. Transients of the FDS-I may occur due to the perturbation of external neutron source, the failure of functional device, and the occurrence of the uncontrolled event. As typical transient scenarios, the following cases were analyzed: unprotected plasma overpower (UPOP), unprotected loss of flow (ULOF), unprotected transient overpower (UTOP). The transient analyses for the FDS-I were performed with a coupled two-dimensional thermal-hydraulics and neutronics transient analysis code NTC2D. The negative feedback of reactivity is the interesting safety feature of FDS-I as temperature increase, due to the fuel form of the circulating particle. The present simulation results showed that the current FDS-I design has a resistance against severe transient scenarios.

Optimization of Positions and Currents of Tokamak Poloidal Field Coils Using Genetic Algorithms

Plasma equilibrium geometry has a great influence on the confinement and magnetohydrodynamic stability in tokamaks. The poloidal field (PF) system of a tokamak should be optimized to support the prescribed plasma equilibrium geometry. In this paper, a genetic algorithm-based method is applied to solve the optimization of the positions and currents of tokamak PF coils. To achieve this goal, we first describe the free-boundary code EQT. Based on the EQT code, a genetic algorithm-based method is introduced to the optimization. We apply this new method to the PF system design of the fusion-driven subcritical system and plasma equilibrium geometry optimization of the Experimental Advanced Superconducting Tokamak (EAST). The results indicate that the optimization of the plasma equilibrium geometry can be improved by using this method.

Conceptual design activities of FDS series fusion power plants in China

A series of fusion power plants (named FDS series) have been designed and assessed for the examination of the feasibility and the safety, environmental and economical potential of fusion with emphasizing the blanket design optimization on neutronics, thermal-hydraulics, electro-magnetics, material, structural performance analyses in China. Four concepts have been developing, which are the fusion-driven subcritical system (FDS-I) with the goal of transmutation of the long-lived nuclear wastes and breeding of fissile nuclear fuels, the fusion power reactor (FDS-II) with the goal of electricity generation, the fusion-based hydrogen production reactor (FDS-III) and the spherical tokamak-based compact reactor (FDS-ST). Four types of blankets, including the He/LiPb dual-cooled high level waste transmutation (DWT) blanket, the He single-cooled LiPb tritium breeder (SLL) blanket and the He/LiPb dual-cooled (DLL) blanket, the high temperature liquid LiPb (HTL) blanket, and Test Blanket Modules (TBMs) and the testing strategy have been studied. R&D status on materials, design and analysis tools are also presented.

Conceptual design of the fusion-driven subcritical system FDS-I

The fusion-driven subcritical system (named FDS-I) was previously proposed as an intermediate step toward the final application of fusion energy. A conceptual design of the FDS-I is presented, which consists of the fusion neutron driver with relatively easy-achieved plasma parameters, and the He-gas/liquid lithium–lead Dual-cooled subcritical Waste Transmutation (DWT) blanket used to transmute long-lived radioactive wastes and to generate energy on the basis of self-sustainable fission and fusion fuel cycle. An overview of the FDS-I is given and the specifications of the design analysis are summarized.

Neutronics safety analysis in severe transients of the dual-cooled waste transmutation blanket for the FDS-I

The conceptual design of the fusion-driven subcritical system FDS-I with the multifunctional subcritical dual-cooled waste transmutation (DWT) blanket proposed as a middle step toward the final application of fusion energy was presented previously. Safety is a key concern for the innovative conceptual system. The potential safety characteristic is expected as one of the advantages of FDS-I for the transmutation and incineration of nuclear waste compared with the critical reactor. With the intent of evaluating the inherent and passive safety features of FDS-I, the reactivity coefficients (e.g. the coolant density/void effect and the Doppler feedback), which are similar to those in critical reactors, and the kinetics quantities (e.g. neutron generation time and β eff), which are influenced by the external neutron source of the source-driven system, are calculated and analyzed. In addition, the specific transient scenarios for FDS-I, which show the effects of the source power perturbation on the safety parameters, is presented.

Analysis on fuel cycle schemes in the dual-cooled waste transmutation blanket for the FDS-I

The fusion-driven subcritical system (FDS-I) which consists of the fusion neutron driver with feasible and easy-achieved plasma parameters and the multifunctional subcritical blanket (DWT) was proposed as an intermediate step toward the final application of fusion energy. In this contribution, fuel configuration and chemical form to be adopted in the FDS-I and possible fuel cycle schemes are clarified and analyzed based on the general survey. The influences of initial fuel loadings on the fuel cycle parameters are presented. Optimal analysis on the in-pile operation length is discussed and some recommendations are given to guide the design of optimized fuel cycle scheme on the basis of comprehensively considering the balance of the spent fuel loadings and the transmutation capacity.

Preliminary transient thermal analysis for safety of the dual-cooled waste transmutation blanket for the FDS-I

The dual-cooled waste transmutation (DWT) blanket is one of the key components of the fusion-driven subcritical system (FDS-I). Because of the large energy gain, the heat removal in accidents remains a major safety concern. In this contribution, several representative transients such as unprotected loss of flow accident in helium gas and LiPb (ULOFA), protected loss of flow accident in helium gas and LiPb (LOFA) and loss of power accident (LOPA) are calculated and analyzed. The blanket will not melt until several hours if the plasma core is shut down in time when the accidents occur. It has enough time to start additional action to keep the system safety. The results show that passive solution to shut down the plasma shall be given due to the little scale of responding time. Also, the results show an effective active heat removal solution such as liquid metal (LM) drain system and emergency blanket cooling system is needed.

Probabilistic safety assessment of the dual-cooled waste transmutation blanket for the FDS-I

The subcritical dual-cooled waste transmutation (DWT) blanket is one of the key components of fusion-driven subcritical system (FDS-I). The probabilistic safety assessment (PSA) can provide valuable information on safety characteristics of FDS-I to give recommendations for the optimization of the blanket concepts and the improvement of the design. Event tree method has been adopted to probabilistically analyze the safety of the DWT blanket for FDS-I using the home-developed PSA code RiskA. The blanket melting frequency has been calculated and compared with the core melting frequencies of PWRs and a fast reactor. Sensitivity analysis of the safety systems has been performed. The results show that the current preliminary design of the FDS-I is very attractive in safety.

Preliminary leakage reliability analysis of DFLL-TBM based on a combinational approach

Dual-functional lithium lead-test blanket module (DFLL-TBM) is designed to demonstrate and validate related technologies for the high-power density liquid metal blanket of fusion commercial demo reactors (e.g. FDS-II) and the He/LiPb dual-cooled multi-functional blanket of a fusion-driven sub-critical system (i.e. FDS-I). It is important to assess the reliability of DFLL-TBM due to its complexity. A new approach is proposed by combining the probabilistic fracture mechanics (PFM) method and the probabilistic safety assessment (PSA) method. A reliability analysis code for blanket modules is developed. One of the failure modes of DFLL-TBM, leakage failure, is analyzed as an example to demonstrate the capability of the combinational approach. Some key aspects that affect the leakage reliability of DFLL-TBM are identified.

05/00471 Monte Carlo importance sampling optimization for system reliability applications: Campioni, L. and Vestrucci, P. Annals of Nuclear Energy, 2004, 31, (9), 1005–1025

Reduced activation ferritic/martensitic steels (RAFM steels) are presently considered as the primary structural materials for a demonstration (DEMO) fusion plant and the first fusion power reactors because of their attractive properties. Studies on various properties of China low activation martensitic steel (CLAM) are underway. The activation level of CLAM steel was calculated with the widely used inventory code FISPACT with the latest data library FENDL/A-2 based on the first wall (FW) neutron spectrum of the fusion-driven subcritical system (FDS) from the Monte Carlo transport code MCNP/4C calculation with FENDL-2 data library. The results were compared with the activation levels of other RAFM steels, such as EUROFER97, F82H, JLF-1 and 9Cr–2WVTa etc., under the same irradiation conditions. Furthermore, the dominant nuclides to γ-ray dose rate of CLAM steel were analyzed. The required control levels of impurities in CLAM steel will soon be implemented based on the hands-on and remote recycling dose rate limits.

Activation Characteristics of Fuel Breeding BlanketModule in Fusion Driven Subcritical System

Shortage of energy resources and production of long-livedradioactivity wastes from fission reactors are among the main problemswhich will be faced in the world in the near future. The conceptualdesign of a fusion driven subcritical system (FDS) is underway inInstitute of Plasma Physics, Chinese Academy of Sciences. There arealternative designs for multi-functional blanket modules of the FDS,such as fuel breeding blanket module (FBB) to produce fuels for fissionreactors, tritium breeding blanket module to produce the fuel, i.e.tritium, for fusion reactor and waste transmutation blanket module to try topermanently dispose of long-lived radioactivity wastes from fissionreactors, etc. Activation of the fuel breeding blanket of the fusiondriven subcritical system (FDS-FBB) by D-T fusion neutrons from the plasma and fissionneutrons from the hybrid blanket are calculated and analysed under theneutron wall loading 0.5 MW/m2 and neutron fluence15 MW.yr/m2. The neutron spectrum is calculated with theworldwide-used transport code MCNP/4C and activation calculations arecarried out with the well known European inventory code FISPACT/99 with thelatest released IAEA Fusion Evaluated Nuclear Data Library FENDL-2.0and the ENDF/B-V uranium evaluated data. Induced radioactivities, doserates and afterheats, etc, for different components of the FDS-FBB arecompared and analysed.

Study of irradiation effects in China low activation martensitic steel CLAM

Reduced activation ferritic/martensitic steels (RAFM steels) are presently considered as the primary structural materials for a demonstration (DEMO) fusion plant and the first fusion power reactors because of their attractive properties. Studies on various properties of China low activation martensitic steel (CLAM) are underway. The activation level of CLAM steel was calculated with the widely used inventory code FISPACT with the latest data library FENDL/A-2 based on the first wall (FW) neutron spectrum of the fusion-driven subcritical system (FDS) from the Monte Carlo transport code MCNP/4C calculation with FENDL-2 data library. The results were compared with the activation levels of other RAFM steels, such as EUROFER97, F82H, JLF-1 and 9Cr–2WVTa etc., under the same irradiation conditions. Furthermore, the dominant nuclides to γ-ray dose rate of CLAM steel were analyzed. The required control levels of impurities in CLAM steel will soon be implemented based on the hands-on and remote recycling dose rate limits.

Influence of blanket structural materials on liquid metal Pb–17Li flow in the FDS

The Dual-cooled Waste Transmutation Blanket design of the Fusion-Driven Sub-critical System is a dual-cooled liquid metal Pb–17Li and He system with Chinese Low Activation Martensitic steel structure. The effects of the structural material on liquid metal MHD flow, including pressure drop and heat transfer, are presented. The influences of the wall conductance of the duct wall on the MHD pressure drop have been analysed and estimated. The pressure drop is too large to be accepted when Pb–17Li coolant flows in these ducts without insulating coating. This can be improved by using Al 2O 3 electrically insulating coating, while heat transfer must also be cautiously considered.

Preliminary Analysis of Advanced Equilibrium Configuration for the Fusion-Driven Subcritical System

The Fusion-Driven Subcritical System (FDS) is a subcritical nuclear energy system drived by fusion neutron source. In this paper, an advanced plasma configuration for FDS system has been proposed, which aims at high beta, high bootstrap current and good confinement. A fixed-boundary equilibrium code has been used to obtain ideal equilibrium configuration. In order to determine the feasibility of FDS operation, a two-dimensional time-dependent free boundary simulation code has been adopted to simulate time-scale evolution of plasma current profile and boundary position. By analyses, the Reversed Shear mode as the most attractive one has been recommended for the FDS equilibrium configuration design.