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.     

Thermal-hydraulic analysis of LBE spallation target for accelerator-driven systems

In an accelerator-driven subcritical system (ADS), a high-performance spallation neutron source is used to feed the subcritical reactor. Neutron generation depends on the proton beam intensity. If the beam intensity is increased by a given factor, the number of generated neutrons will increase. The mechanism yielding a high rate of neutron production per energy is the spallation process, and this mechanism produces a very high-energy deposition in the spallation target material. Producing a high rate of neutrons is accompanied by creation of problems of decay heat cooling and radiological protection. As a first step in designing a full-scale industrial ADS, a small-scale experimental ADS, which is similar to the European experimental ADS (XADS) is analysed. The analysis presented in this paper is based on lead–bismuth eutectic (LBE) cooled XADS-type experimental reactors, designed during the European experimental (PDS-XADS) project. Computational fluid dynamics analysis has been carried out for the spallation target. Steady state behaviour and shear stress transport turbulence model with the automatic wall treatment were applied in the present analysis.     

The design simulation of the superconducting section in the ADS injector Ⅱ

The high-current superconducting proton linac is being studied for the accelerator-driven system (ADS) project undertaken by the Chinese Academy of Sciences. The injector Ⅱ will be operated at 162.5 MHz, and the proton out from the RFQ with an energy of 2.5 MeV will be accelerated to 10 MeV by two cryo-modules, which are composed of eight superconducting half wave resonance cavities and nine solenoids. In this paper, the design and beam simulation of the superconducting section of the injector Ⅱ, the acceptance calculation and a stability analysis are presented.     

ADS瞬态分析中的概率论-确定论耦合方法

针对加速器驱动次临界系统(ADS)瞬态问题,采用预估校正改进准静态方法(PCQS)处理时空中子动力学方程中的时间自变量,采用蒙特卡罗方法处理相应的空间-角度-能量自变量,重点解决了低次临界度下模拟计算不稳定的问题,验证了TWGIL-Seed-Blanket动力学基准问题和小型模拟ADS问题,得到瞬态过程的功率变化结果,与基于其他方法的程序比较,经初步验证取得了较好结果,证明了该耦合方法可行。     

质子入射散裂产物理论研究方法探讨

简要介绍了几种关于中高能质子入射引起散裂反应产物理论计算的方法,以及这些方法的最新发展.比较了这些方法在理论计算中的特点,指出经典外推方法有局限性,量子分子动力学方法和改进后的M C方法的计算结果与实验数据有较好的符合,但是计算量大,而且量子分子动力学方法在与宏观输运理论连接上存在不少的困难.半经验计算方法已经取得了初步的成果,需要根据新的实验结果来对其进行发展. The analysis on spallation product of proton-induced reaction with intermediate energy has important applications, such as astrophysics, biophysics, spallation neutron source, and accelerator-driven system (ADS) etc. In recent year, some theoretical models have been developed to investigate this reaction processes. At present work, we introduce the extrapolated classic theory, the quantum molecule dynamic (QMD) plus statistical decay and fission models, the method of Mento-Carlo and Smiempirical method for...     

Determining the Fast Neutron Flux Density and Transmutation Level Measurements in ADS by the Use of a Threshold Nuclear Reaction

Determining the Fast Neutron Flux Density and Transmutation Level Measurements in the ADS by the use of a Threshold Nuclear Reaction. The aim of the project was determining the fast neutron flux density by using data from the Quinta experiment (E+T RAW collaboration). The experimental assembly based on natural uranium was irradiated by a 660 MeV proton beam. To gain the knowledge about the neutron flux inside the experimental assembly, nuclear threshold reactions of (n, xn) type were used. The level of isotopes production are measured by the activation method using a gamma radiation HPGe detector. This paper describes the Quinta assembly, experimental results, calibration procedure and average high energy neutron calculation based on yttrium (Y-89) isotopes production. In the future, results and conclusions from an experiment like this could be useful to design accelerator-driven subcritical systems (ADS) or other 4th generation fast reactors. The investigation has been performed at the Laboratory of High Energy Physics, JINR.     

Beam experiments with a non-intercepting beam induced f luorescence profile monitor for the ADS LINAC

An accelerator-driven subcritical system(ADS) project was launched in China in 2011, aiming to design and build an ADS demonstration facility with the capability of more than 1000 MW thermal power. The driver linac is defined to be a 10 m A current of high energy protons at 1.5 Ge V in continuous wave operation mode. To meet the extremely high power and intense beam accelerator requirements, non-interceptive monitors for the beam transverse profile are required for this proton linac. Taking advantage of the residual gas as active material, the Beam Induced Fluorescence(BIF) monitor exploits gas-excited fluorescence in the visible spectrum region for transverse profile measurements. The advantages of this non-intercepting method are that nothing is installed in the vacuum pipe,component design is compact and there is no need for expensive signal processing electronics. Beam experiments have been performed under constant beam conditions. The helium spectrum has been verified with different optical filters, showing that a proper optical band-pass filter covering 400–500 nm is necessary for fluorescence experiments with helium. By changing gas pressure, it is shown that gas pressure is proportional to the signal amplitude but has no influence on detected profile width. Finally, a comparison experiment between the BIF monitor and a wire scanner shows that the detected profile width results of both methods agree well.     

Prospects for transmutation of nuclear waste and associated proton-accelerator technology

While a considerable and world-wide growth of the nuclear share in the global energy mix is desirable for many reasons, a major concern or objection is the long-term burden that is constituted by the radiotoxic waste from the spent fuel. The concept of Partitioning & Transmutation, a scientific and technological answer, is therefore of high interest. Its deployment may use dedicated “Transmuter” or “Burner” reactors, using a fast neutron spectrum. For the transmutation of waste with a large content (up to 50%) of (very long-lived) Minor Actinides, a sub-critical reactor, using an external neutron source is a solution of high interest. It is constituted by coupling a proton accelerator, a spallation target and a subcritical core. This promising new technology is named ADS, for accelerator-driven system. The present paper aims at an introduction into the field in order to focus, in its later part, on the development of the required accelerator technology.     

Neutron cross-sections above 20 MeV for design and modeling of accelerator driven systems

One of the outstanding new developments in the field of partitioning and transmutation (P&T) concerns accelerator-driven systems (ADS) which consist of a combination of a high-power, high-energy accelerator, a spallation target for neutron production and a sub-critical reactor core. The development of the commercial critical reactors of today motivated a large effort on nuclear data up to about 20 MeV, and presently several million data points can be found in various data libraries. At higher energies, data are scarce or even non-existent. With the development of nuclear techniques based on neutrons at higher energies, nowadays there is a need also for higher-energy nuclear data. To provide alternative to this lack of data, a wide program on neutron-induced data related to ADS for P&T is running at the 20–180 MeV neutron beam facility at ‘The Svedberg Laboratory’ (TSL), Uppsala. The programme encompasses studies of elastic scattering, inelastic neutron production, i.e., (n, xn′) reactions, light-ion production, fission and production of heavy residues. Recent results are presented and future program of development is outlined.      

The physics of accelerator driven sub-critical reactors

In recent years, there has been an increasing worldwide interest in accelerator driven systems (ADS) due to their perceived superior safety characteristics and their potential for burning actinides and long-lived fission products. Indian interest in ADS has an additional dimension, which is related to our planned large-scale thorium utilization for future nuclear energy generation. The physics of ADS is quite different from that of critical reactors. As such, physics studies on ADS reactors are necessary for gaining an understanding of these systems. Development of theoretical tools and experimental facilities for studying the physics of ADS reactors constitute important aspect of the ADS development program at BARC. This includes computer codes for burnup studies based on transport theory and Monte Carlo methods, codes for studying the kinetics of ADS and sub-critical facilities driven by 14 MeV neutron generators for ADS experiments and development of sub-criticality measurement methods. The paper discusses the physics issues specific to ADS reactors and presents the status of the reactor physics program and some of the ADS concepts under study.      

加速器驱动次临界系统中堆外中子注量率监测方法（英文）

在加速器驱动的次临界（ADS）系统中,次临界反应堆的功率控制是通过控制束流强度来实现。监测堆外中子注量率,不仅提供了反应堆功率指示,也为反应堆保护系统在启动和运行阶段提供了重要的监测信息,因此,堆外中子注量率的监测在ADS系统的控制与保护中起着非常重要的作用。采用3套裂变室和3套非补偿电离室来监测ADS堆外中子注量率。由于裂变室有脉冲、电流和均方电压3种操作模式,1套裂变室可以监测源量程、中间量程和功率量程等宽范围的反应堆功率。所以,使用的监测方法有3个优点,即:增加了监测通道的冗余度,提高了保护系统的可靠性,以及能提供更多的轴向功率分布信息。由于这些中子探测器对中子能谱很敏感,提出了一种有效的校准方法,即先用一个标准的中子源校准这些中子探测器,然后再将中子注量率除以一个修正因素。基于Geant4仿真结果显示,所提取的裂变室和非补偿电离室的修正因素分别为5和42。In an accelerator driven sub-critical (ADS) system, power control in sub-critical reactor is achieved through the control of the beam current. Excore neutron flux monitoring in an ADS system, not only provides indication of reactor power, but also provides important inputs to reactor protection system during startup and power operation, and thus plays a very important role in the control and protection of ADS system. This paper presents the excore neutron flux monitoring method which uses three fission chambers (FCs) and three uncompensated ion chambers (UICs). With three operation modes, pulse mode, current mode, and mean square voltage mode, an FC can monitor reactor power over a wide range from the source range to the intermediate and power ranges. The proposed monitoring method increases the redundancy of independent monitoring channels, improves the reliability of the protection system, and provides more information on axial power distribution. Since these neutron detectors are sensitive to the neutron energy spectrum, we propose an effective calibration method to provide the exact value of neutron flux, i.e., these neutron detectors are calibrated with a standardized neutron source, and then, a correction factor is added in the calibration by comparing the neutron energy spectrum of the neutron source with that in ADS system. Based on Geant4 simulation, the correction factors of 5 and 42 are extracted for FCs and UICs, respectively.     

Development of ADS virtual accelerator based on XAL

XAL is a high level accelerator application framework that was originally developed by the Spallation Neutron Source(SNS), Oak Ridge National Laboratory. It has an advanced design concept and has been adopted by many international accelerator laboratories. Adopting XAL for ADS is a key subject in the long term. This paper will present the modifications to the original XAL applications for ADS. The work includes a proper relational database schema modification in order to better suit the requirements of ADS configuration data, redesigning and re-implementing db2 xal application, and modifying the virtual accelerator application. In addition, the new device types and new device attributes for ADS online modeling purpose are also described here.     

Antioxidant systems in supporting environmental and programmed adaptations to low temperatures

Hetero and endothermic adaptive responses arising as a result of natural responses to environmental cues include antioxidant systems that support adaptations to environmental low temperatures in the broadest sense. These temperatures induce phase changes in energy production and consequently changes in the concentration of reactive oxygen species (ROS). The latter may lead to oxidative stress and the impairment of cellular homeostasis and antioxidant defence systems (ADS) scavenge the ROS so generated. In endotherms the ADS responds to oxidative pressure during acute cold stress conditions, this response is tissue specific and does not extend to prevent other oxidative damage. The early acute phase of cold exposure is accompanied by a significant depletion in redox equivalents. Under such conditions it is questionable if ADS has the capacity to neutralize elevated levels of ROS since there is also an increased energy demand and enhanced ATP consumption. Prolonged exposure to cold leads to ADS adaptation. Hibernators and freeze-tolerant species elevate their ADS before hibernation or freezing in order to prepare for and cope with re-awakening. The involvement of ROS and the role of the ADS in organisms subjected to low temperatures are features intercalated into physiological mechanisms of homestasis. The exact mechanisms for ADS regulation have not been fully defined and are the subject of many ongoing intriguing scientific investigations.     

Heavy density liquid metal spallation target studies for indian ADS programme

Department of Atomic Energy, India has taken up the development of ADS in view of many attractive features like inherent safety, capability to transmute large quantities of nuclear waste, better utilization of thorium etc. A roadmap has been finalized for the development of ADS. One of the key components of the ADS is the spallation target. Considering the neutron yield, thermal-hydraulics and radiation damage issues, we are proposing to develop spallation target based on heavy density liquid metals like lead and lead-bismuth-eutectic (LBE). Both window and windowless target configurations are presently being studied. In view of the various advantages we are also studying liquid metal flow circulation based on gas lift mechanism. An R&D programme has been initiated to address various physics and technology issues of ADS target. Under this programme, mercury and LBE experimental facilities are presently being set up. Along with these facilities, computational tools related to spallation physics (FLUKA) and CFD are being developed, and the existing ones are utilized to design the entire target loop as well as sub-systems. In this presentation the details of these activities are presented.      

Relative roles of acetic acid, dodecyl sulfate and benzotriazole in chemical mechanical and electrochemical mechanical planarization of copper

The efficiency of chemical mechanical or electrochemical mechanical planarization (CMP or ECMP) carried out in the fabrication of integrated circuits is largely governed by the functional chemicals used in these processes. In this work, we study the individual and combined chemical and electrochemical effects of a selected set of such chemicals that can potentially support both CMP and ECMP of copper. These chemicals include acetic acid (HAc) as a complexing agent, H2O2 as an oxidizer, and ammonium dodecyl sulfate (ADS) as a dissolution inhibitor. Surface passivating effects of ADS under both CMP (open circuit) and ECMP (voltage activated) conditions are compared with those of a standard dissolution inhibitor for Cu, benzotriazole (BTAH), and the combined effects of a BTAH-ADS mixture also are explored. The experiments are performed in the absence of mechanical polishing using static and rotating Cu disc electrodes, and electro-dissolution of Cu for ECMP is activated using a voltage pulse modulation technique. A mechanism of surface reactions is proposed to describe the relative roles of HAc, H2O2, ADS and BTAH as electrolyte components for CMP and ECMP of Cu.     

Three-dimensional free view reconstruction in axially distributed image sensing

In this Letter, we propose a three-dimensional(3D) free view reconstruction technique in axially distributed image sensing(ADS). In typical integral imaging, free view reconstructed images can be obtained by tilting all elemental images or tilting the reconstruction plane due to large lateral perspectives for 3D objects. In conventional ADS, the reconstructed images at only a front view can be generated since the sensor is moved along with its optical axis so that it has small lateral perspectives for 3D objects. However, the reconstructed 3D images at any viewing point may be obtained because the virtual viewing camera may capture these slightly different perspectives for 3D objects. Therefore, in this Letter, we employ the virtual viewing camera to visualize the 3D images at the arbitrary viewing point. To support our proposed method, we show the experimental results.     

Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

In this paper, we study a monitoring method for neutron flux for the spallation target used in an accelerator driven sub-critical(ADS) system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique,i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 Me V-proton beam with Geant 4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber(FC), by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.     

Research into accelerator driven systems using particle track detectors

In the interaction of relativistic protons with heavy and extended targets such as lead, large number of neutrons is produced in the course of the so-called spallation process. These neutrons can be used to drive a sub-critical nuclear assembly for energy generation and/or for the transmutation of the long-lived nuclear waste isotopes to environmentally safer nuclear species. Such nuclear assemblies are referred to as accelerator driven systems (ADS).

Knowledge of the neutron yield in the spallation process and an understanding of the behaviour of these neutrons in the desired sub-critical assembly are the most important and determining factors in the design and operation of these systems. Many parameters related to the neutronics of an ADS can be studied qualitatively as well as quantitatively using solid-state nuclear track detectors (SSNTD). In some circumstances SSNTDs provide the best and the most logical detector option for these investigations.

In this paper applications of the SSNTDs into research related to ADS are discussed and some experimental and theoretical results presented.     

Influence of laser treatment on the adsorption interaction of cadmium sulfide films with oxygen

During interaction of pulsed laser radiation with the surface of polycrystalline cadmium sulfide films an enrichment of sulfur vacancies near the surface was previously observed. In this paper, the adsorption-desorption sensitivity (ADS) of the cadmium sulfide film to oxygen was determined by the temperature dependence of the dark current. In this case, the sulfur vacancies serve as adsorption centers. The presence of surface and volume components of ADS was detected. Here the surface portion of ADS remains essentially unchanged, but the volume component grows with increase in the radiation dose.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 82–85, March, 1990.     

Study on the HOMs coupler design of spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of high power proton linac for an Accelerator Driven Sub-critical System (ADS).Considering that the High Order Modes (HOMs)in the superconducting cavity have far reaching influence on power dissipation and beam stability,the analysis of HOMs of the spoke cavity is needed.In this paper,we put emphasis on the analysis of HOMs of the spoke cavity and the HOMs coupler design.