Monte Carlo optimization of an epithermal neutron flux monitor for BNCT

An epithermal neutron (0.5 eV < E_n < 10 keV) flux monitor developed for boron neutron capture therapy (BNCT) was optimized by Monte Carlo simulations. Based on this optimization study, the optimization results for each component of the epithermal neutron flux monitor were obtained. The simulation results indicated that the epithermal neutron flux monitor with optimal configuration was more efficiently applicable to precisely measure the epithermal neutron fluxes of BNCT neutron sources.     

A digital wide range neutron flux measuring system for HL-2A

To achieve wide-range, high-integration, and real-time performance on the neutron flux measurement on the HL-2A tokamak, a digital neutron flux measuring(DNFM) system based on the peripheral component interconnection(PCI) e Xtension for Instrumentation express(PXIe) bus was designed.This system comprises a charge-sensitive preamplifier and a field programmable gate array(FPGA)-based main electronics plug-in. The DNFM totally covers source-range and intermediate-range neutron flux measurements, and increases system integration by a large margin through joining the pulse-counting mode and Campbell mode. Meanwhile, the neutron flux estimation method based on pulse piling proportions is able to choose and switch measuring modes in accordance with current flux, and this ensures the accuracy of measurements when the neutron flux changes suddenly. It has been demonstrated by simulated signals that the DNFM enhances the full-scale measuring range up to 1.9?×?10~8cm~(-2)s~(-1), with relative error below 6.1%. The DNFM has been verified to provide a high temporal sensitivity at 10 ms time intervals on a single fission chamber on HL-2A.     

用钴活化法测定反应堆中热中子积分通量

本文叙述了用钴活化法测定高通量堆中热中子积分通量的方法。测得的热中子积分通量值与计算值作了比较。本法适于测定在高通量堆中长期辐照的较高热中子积分通量。     

HT-7超导托卡马克上聚变中子产额和中子注量率分布计算

利用所编制的三维托卡马克中子计算程序,计算了HT-7装置上中子产额随等离子体中心离子温度与密度的变化.同时计算了中子注量率及其在空间不同位置与方位角的分布特性.考虑了离子温度与密度分布的形状因子不同所带来的误差.计算结果为中子诊断和中子辐射防护等提供了依据.     

零功率反应堆内中子通量相对分布实时测量

在堆物理实验中,经常需要进行堆内中子通量相对分布的测量,以便获得有关的参数,如全堆平均热中子通量及功率不利因子、控制棒对中子通量分布的影响等等。为了要获得这些数据,有时不得不进行几千个测点的测量,才能求得结果。以往一般都采用经典的活化法。这种方法的最大缺点是测量工作量大,花费的人力多,不能很快地得到所需要的结果。为此,我们利用一种微型的中子探头,配以适当的电子仪器和机械设备,在轻水零功率反应堆内进     

Dynamic linear calibration method for a wide range neutron flux monitor system in ITER

As a key part of the diagnosis system in the International Thermonuclear Experimental Reactor(ITER),the neutron flux monitor(NFM),which measures the neutron intensity of the fusion reaction,is a Counting-Campbelling system with a large dynamic counting range.A dynamic linear calibration method is proposed in this paper to solve the problem of cross-over between the different counting and Campbelling channels,and improve the accuracy of the cross-calibration for long-term operation.The experimental results show that the NFM system with the dynamic linear calibration system can obtain the neutron flux of the fusion reactor in real time and realize the seamless measurement area connection between the two channels.     

反应堆中子注量率谱的谱参数法解

按照费米年龄理论,提出包含6个待定参数的数学表达式来描述反应堆堆内空间某点完整的中子注量率谱,并由此使用非线性规划可变容差法建立了新的解谱方法和相应解谱程序SNAIL。对于热中子反应堆内部的中子注量率谱,根据测量的反应率数据计算得到的整个能区中子注量率谱结果很满意,与NEUSPAC解谱程序解得的中子注量率谱符合得很好。对于中能中子场和快中子反应堆,在未使用可裂变材料探测器情况下,计算结果与文献公布的结果基本符合。     

Design of an epi-thermal neutron flux intensity monitor with GaN wafer for boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a promising cancer therapy. Epi-thermal neutron (0.5 eV < E_n < 10 keV) flux intensity is one of the basic characteristics for modern BNCT. In this work, based on the ⁷¹Ga(n,γ)⁷²Ga reaction, a new simple monitor with gallium nitride (GaN) wafer as activation material was designed by Monte Carlo simulations to precisely measure the absolute integral flux intensity of epi-thermal neutrons especially for practical BNCT. In the monitor, a GaN wafer was positioned in the center of a polyethylene sphere as neutron moderator covered with cadmium (Cd) layer as thermal neutron absorber outside. The simulation results and related analysis indicated that the epi-thermal neutron flux intensity could be precisely measured by the presently designed monitor.     

Development of a data acquisition and control system for the International Thermonuclear Experimental Reactor neutron flux monitor

To satisfy high-precision, wide-range, and real-time neutron flux measurement requirements by the International Thermonuclear Experimental Reactor(ITER), a data acquisition and control system based on fission chamber detectors and fast controller technology, has been developed for neutron flux monitor in ITER Equatorial Port #7. The signal processing units which are based on a field programmable gate array and the PXI Express platform are designed to realize the neutron flux measurement with 1 ms time resolution and a fast response less than 0.2 ms,together with real-time timestamps provided by a timing board. The application of the widerange algorithm allows the system to measure up to 10~(10) cps with a relative error of less than 5%.Furthermore, the system is managed and controlled by a software based on the Experimental Physics and Industrial Control System, compliant with COntrol, Data Access and Communication architecture.     

移动式堆芯中子注量率测量系统概述

堆芯中子注量率测量系统是压水堆核电站核测量系统的主要组成部分,用于测量反应堆堆芯的中子注量率水平,从而提供反应堆的功率分布情况。文章介绍了中核（北京）核仪器厂国产化的移动式堆芯中子注量率测量系统,并对测量系统的概况、系统组成、工作原理及功能等进行了描述。     

加速器中子源的中子注量测量方法

在用静电加速器中子源标定探测器的中子灵敏度实验中,采用“BF3长计数管 定标器”系统过渡,用^197Au中子活化分析方法达到了对中子注量在线、绝对监测的目的。这种方法给出与加速器束流不同角度、不同距离处的中子注量。介绍了这种中子注量测量方法。     

能谱变化对239Pu裂变室测量快中子注量的影响

热中子和共振区的中子在快中子临界装置中所占的份额很小,但是由于其相对大的截面,在慢化物存在的情况下,热中子和共振中子份额的微小变化,对^239Pu裂变室测量中子注量的结果影响很大。通过测量^239Pu裂变电离室在包镉和包硼、周围有无慢化物等情况下的反应率,Au、In活化片的镉比,S活化片在能谱变化下与^239。Pu的反应率比等,分析了快中子临界装置中热中子和共振区中子的分布,讨论了中子能谱变化对^239Pu裂变室测量快中子注量的影响及解决办法。     

软件仿真核电站堆芯核测量系统的设计与实现

针对堆芯核测量系统设计制造周期长、关键机械设备采购难、控制系统调试困难等问题,设计了仿真堆芯核测量系统。基于RSView32的仿真测量系统仿真电气设备和机械设备的功能,并配备了测量系统的状态监控界面。本文介绍了仿真测量系统的原理和实现方法。通过仿真测量系统与真实控制软件的联调试验,证实在系统设计过程中,仿真测量系统完全可以代替电气和机械设备,辅助测量系统的控制程序进行调试运行。该仿真测量系统的使用可显著减少机械磨损,缩短控制系统的调试周期。     

Real-time wide-range neutron flux monitor for thorium-based molten salt reactor

A novel full-digital real-time neutron flux monitor(NFM) has been developed for thorium-based molten salt reactor(TMSR).The system is based on the highspeed,parallel,and pipeline processing of the field programmable gate array as well as the high-stability controller area network platform.A measurement range of 10~8 counts per second is achieved with a single fission chamber by utilizing the normalization of the count and Campbell algorithms.With the advantages of using the measurement range,system integrity,and real-time performance,digital NFM has been tested in the Xi'an pulsed reactor fission experiments and was found to exhibit superior experimental performance.     

靶件内中子注量率分布计算方法研究

选择ANISN作为实验靶件内中子注量率分布计算的程序，编制辅助程序输入混合材料截面。计算得到延时水箱附近的中子注量率，与测量数据作对比。计算得到靶片自屏因子，并与2000年实验数据对比。确认计算方法可行后，计算得到实验靶件内热中子注量率分布数据。     

Design study of neutron flux intensity monitor between ten and several hundred keV for BNCT

Based on the activation method using ⁷¹Ga(n,γ)⁷²Ga reaction, two spherical monitors with gallium nitride (GaN) wafers as activation material were designed by Monte Carlo simulations to precisely measure the absolute integral neutron flux intensity between ten and several hundred keV. The two monitors are almost the same in shape and have an absorber/moderator/absorber/GaN arrangement from outside to inside. The differences between the two monitors are the kind of materials, the thicknesses of the absorbers and the diameter of the moderator. By making difference of the sensitivities between these two monitors, the contributions of thermal, epithermal and very high energy fast neutrons were removed completely, and constant monitor sensitivity to neutrons between ten and several hundred keV was extracted. The simulation results and related analysis indicated that the absolute integral neutron flux intensity between ten and several hundred keV could be precisely measured by the presently designed two monitors.     

Optimization of moderator assembly for neutron flux measurement: experimental and theoretical approaches

A moderator of paraffin wax assembly has been demonstrated where its thickness can be optimized to thermalize fast neutrons. The assembly is used for measuring fast neutron flux of a neutron probe at different neutron energies, using BF03(U10and 200) and3He(U0.500)neutron detectors. The paraffin wax thickness was optimized at 6 cm for the neutron probe which contains an Am–Be neutron source. The experimental data are compared with Monte Carlo simulation results using MCNP5 version 1.4. Neutron flux comparison and neutron activation techniques are used for measuring neutron flux of the neutron probe to validate the optimum paraffin moderator thickness in the assembly. The neutron fluxes are measured at(1.17 ± 0.09) 9 105 and(1.19 ± 0.1) 9 105n/s, being in agreement with the simulated values. The moderator assembly can easily be utilized for essential requirements of neutron flux measurements.     

多时空通道中子注量率密度数据采集系统方案设计

介绍了用在加速器驱动核能系统(ADS)次临界原理验证装置上的微机化多时空通道中子注量率密度数据采集系统设计方案．该数据采集系统用于采集多个空间位置的中子注量率密度水平随时间变化的数据。     

The study of aeroball system for measuring 3D neutron flux distribution in reactor core

Aeroball system is attractive in several aspects because it can easily transport the map of neutron flux distribution to be measured from incore to outside of a reactor vessel.However,before the aeroball system is put to practical use in the heating reactor.there are four topics that have to be further studied.They are the stability of the activated positions,enhancement of signal/noise(S/N)ratio,distributed control and data-acquisition system and on-lin nbeutron flux distribution reconstruction.Besides describing the rasons for them,this paper gives out the theory,concept and solution about the first two topics and it is helptul to give the possibility to enhance the reactor-power.