Neutronics analysis of a subcritical blanket system driven by a gas dynamic trap-based fusion neutron source for 99Mo production

Gamma-emitting radionuclide ^99mTc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECT) characteristics.However,the short half-life of ^99mTc (T_1/2=6 h)makes it di?cult to store or transport.Thus,the production of ^99mTc is tied to its parent radionuclide ⁹⁹Mo (T_1/2=66 h).The major production paths are based on accelerators and research reactors.Th...     

D-T中子源快中子照相准直屏蔽系统设计

减少散射中子对成像质量的影响是快中子照相的关键技术之一。本文采用MCNP程序完成了D-T中子源快中子照相准直屏蔽系统的设计,该设计具有很好的中子散射屏蔽效果,能够将实验室墙壁的散射中子数量降低一个量级,大大减少了成像的对比度失真;同时,能够增加约20%的中子源强,提高了成像速度。     

Simulation and experimental study of a random neutron analyzing system with （252）~Cf neutron source

Experiments were performed on a high-speed online random neutron analyzing system(HORNA system)with a 252Cf neutron source(up to 1 GHz sampling rate and 3 input data channel),to obtain time-and frequencydependent signatures which are sensitive to changes in the composition,fissile mass and configuration of the fissile assembly.The data were acquired by three high-speed synchronized acquisition cards at different detector angles,source-detector distances and block sizes.According to the relationship between 252Cf source and the ratio of power spectral density,Rpsd,all the signatures were calculated and analyzed using correlation and periodogram methods.Based on the results,the simulated autocorrelation functions were utilized for identifying different fissile mass with Elman neural network.The experimental results show that the Rpsd almost remains at constant amplitude in frequency range of 0-100 MHz,and is only related to the angle and source-detector distance.The trained Elman neural network is able to distinguish the characteristics of autocorrelation function and identify different fissile mass.The average identification rate reached 90% with high robustness.     

Supermirror neutron guide system for neutron resonance spin echo spectrometers at a pulsed neutron source

A neutron guide system for neutron resonance spin echo spectrometers has been constructed at BL06 of the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility. The spectrometers consist of two types of neutron spin echo instruments, a modulated intensity by zero effort instrument (MIEZE) and a neutron resonance spin echo instrument (NRSE), to cover a wide energy range for various sample environments. A neutron beam from the moderator is deflected by supermirror neutron guides, split, and separately guided into the MIEZE and NRSE. The characteristic wavelengths of the neutron guide tube for the MIEZE and NRSE are 2.9 and 4.9 Å, respectively. The cross sections of the exit of the MIEZE and NRSE guides are 15 mm × 50 mm and 30 mm × 50 mm, respectively. The neutronics and shielding design were optimized by using the heavy ion transport code system (PHITS), and the absolute average neutron fluxes at the exits of the MIEZE and NRSE guides are estimated to be 2.7 × 10⁸ and 6.9 × 10⁸ n/cm²/s/MW, respectively. The measured fluxes of the MIEZE and NRSE neutron guides are 0.56 and 0.95 times the calculated values, respectively.     

Simulation and optimization for a 30-MeV electron accelerator driven neutron source

A neutron source driven by electron accelerator is proposed in Shanghai Institute of Applied Physics (SINAP). The facility is planned for the study of nuclear data in Thorium-Uranium cycling system, and for material research. A detailed simulation of the neutron source is performed for the program to get the neutron generation maximum economically. Several parameters of the facility, which affect the neutron yield and the neutron escape from outer surface of the target, are analyzed respectively. Besides, the yielding neutron spectrum and the escaping neutron angular distribution are calculated and discussed.     

Effects of neutron spectrum and external neutron source on neutron multiplication parameters in accelerator-driven system

The neutron multiplication parameters: neutron multiplication M, subcritical multiplication factor k_s, external source efficiency φ^*, play an important role for numerical assessment and reactor power evaluation of an accelerator-driven system (ADS). Those parameters can be evaluated by using the measured reaction rate distribution in the subcritical system. In this study, the experimental verification of this methodology is performed in various ADS cores; with high-energy (100 MeV) proton–tungsten source in hard and soft neutron spectra cores and 14 MeV D–T neutron source in soft spectrum core. The comparison between measured and calculated multiplication parameters reveals a maximum relative difference in the range of 6.6–13.7% that is attributed to the calculation nuclear libraries uncertainty and accuracy for energies higher than 20 MeV and also dependent on the reaction rate distribution position and count rates. The effects of different core neutron spectra and external neutron sources on the neutron multiplication parameters are discussed.     

Resolution analysis of thermal neutron radiography based on accelerator-driven compact neutron source

Owing to the immobility of traditional reactors and spallation neutron sources, the demand for compact thermal neutron radiography(CTNR) based on accelerator neutron sources has rapidly increased in industrial applications. Recently, thermal neutron radiography experiments based on a D-T neutron generator performed by Hefei Institutes of Physical Science indicated a significant resolution deviation between the experimental results and the values calculated using the traditional resolution model....     

~(241)Am-Be源在煤中所形成中子场的参数拟合

研究了7种煤中主要元素对241Am-Be中子源在煤中形成中子场的影响,给出了描述中子场中快中子和热中子数量变化曲线的经验公式和拟合参数。     

Computational characteristics of a neutron source based on the CERN colliding-beams accelerator

The computational characteristics of a pulsed source of thermal neutrons, which can be implented on the basis of the collidng-beams accelerator under construction at CERN, are presented. The calculations were performed at the All-Russia Reserach Institute of Experimental Physics (Sarov) using two Monte Carlo programs: the GEANT-3 program developed at CERN and our own program S-95. The neutron source is assumed to be a cylindrical tungsten target with an internal neutron moderator made of zirconium hydride bombarded by protons from a colliding-beam accelerator. The maximum power of the source is estimated on the basis of the results of calculations of the dynamical stresses in tungsten. To decrease the negative impact of mechanical stresses, recommendations are formulated dividing the target efficiently into individual elements. __________ Translated from Atomnaya énergiya, Vol. 100, No. 2, pp. 117–125, February, 2006.     

基于D-D中子源的硼中子俘获治疗慢化体设计

为了探讨利用D-D中子源评估硼中子俘获治疗(Boron Neutron Capture Therapy,BNCT)中子通量探测器性能的可能性,本文利用蒙特卡罗模拟程序MCNP5(Monte Carlo N Particle Transport Code, version 5)设计了基于D-D中子源的BNCT慢化体,并最终给出了一种"5 cm聚乙烯(Polyethylene,PE)+24 cm氟化钛(TiF3)+22 cm氟化镁(MgF2)"的组合作为慢化层、20 cm的镍(Ni)作为反射层以及0.03 cm的镉(Cd)作为热中子吸收层的慢化体设计方案。模拟计算结果表明:D-D中子源经设计的慢化体慢化后形成的中子场可以用于BNCT中子通量探测器性能的实验测试。     

中子源识别芥子气毒剂弹的蒙特卡罗模拟

日本战败后遗弃的化学武器不断造成伤人事件的发生。在这些事件中，因接触者无识别能力而造成重大损失，其中又以芥子气毒剂伤人事件最多和最为严重。芥子气毒剂弹由于埋藏时间较长，锈蚀、泄露比较严重，已经无法从外观上与普通炮弹进行识别，传统的化学试剂识别方法对人员容易造成伤害。研究了非接触性的外中子源诱发γ谱识别方法，模拟计算了外中子源对芥子气毒剂弹照射后的γ谱。根据γ谱上Cl、S和Fe等关键核素的特征射线，便可完成对毒剂弹的识别。     

Feasibility of a multi-purpose demonstration neutron source based on a compact superconducting spherical tokamak

Tokamak neutron sources would allow near term applications of fusion such as fusion–fission hybrid reactors, elimination of nuclear wastes, production of radio-isotopes for nuclear medicine, material testing and tritium production. The generation of neutrons with fusion plasmas does not require energetic efficiency; thus, nowadays tokamak technologies would be sufficient for such purposes. This paper presents some key technical details of a compact (～1.8 m³ of plasma) superconducting spherical tokamak neutron source (STNS), which aims to demonstrate the capabilities of such a device for the different possible applications already mentioned. The T-11 transport model was implemented in ASTRA for 1.5 D simulations of heat and particle transport in the STNS core plasma. According to the model predictions, total neutron production rates of the order of ～10¹⁵ s^?1 and ～10¹³ s^?1 can be achieved with deuterium/tritium and deuterium/deuterium respectively, with 9 MW of heating power, 1.4 T of toroidal magnetic field and 1.5 MA of plasma current. Engineering estimates indicate that such scenario could be maintained during ～20 s and repeated every ～5 min. The viability of most of tokamak neutron source applications could be demonstrated with a few of these cycles and around ～100 cycles would be required in the worst cases.     

Conditions for effective utilization of the electronuclear blanket system as a neutron source

The efficiency of an intermediate-energy electronuclear setup with a blanket as an alternative source of neutrons is discussed on the basis of experience in designing the electronuclear neutron generator at the Institute of Theoretical and Experimental Physics. A classification of electronuclear setups is introduced. The factors determining the efficiency of the driver-target-multiplying blanket scheme at low and intermediate driver energies are examined. To obtain high neutron fluxes, the possibility of compensating an inadequate driver current by decreasing the subcriticality store is examined and the conditions for realizing such a possibility while preserving the fundamental requirement of nuclear safety are formulated. The concept of the criterion of dynamical safety, in contrast to the criterion of static safety ordinarily assumed for subcritical systems, is introduced. A program of precision investigations for studying operating regimes of a blanket under conditions of a low store of subcriticality is formulated on the basis of the criterion of dynamical safety. The results of an implementation of this program are important for the assessment of the technological possibility and desirability of replacing research reactors with subcritical setups based on an accelerator. 2 figures, 6 references. State Science Center of the Russian Federation-Institute of Theoretical and Experimental Physics. Translated from Atomnaya énergiya, Vol. 87, No. 4, pp. 255–262, October, 1999.     

冷中子源中氢系统的纵深防御设计

反应堆冷中子源装置的安全性包括核安全、辐射安全和氢安全,其中氢安全是最复杂的一方面.冷中子源氢系统一般采取纵深防御的安全设计方法,即通过多重屏障的技术措施尽可能杜绝氢和空气(氧气)直接接触的可能性.本文详细描述了一座建设中的反应堆冷中子源氢系统的纵深防御安全设计特点,这种安全设计可以确保冷中子源的氢安全性.