Prototype studies on the forward MWDC tracking array of the external target experiment at HIRFL-CSR

A prototype of the forward tracking array consisting of three multiwire drift chambers (MWDC) for the external target experiment (CEE) at the Heavy Ion Research Facility at the Lanzhou -Cooling Storage Ring (HIRFL-CSR) has been assembled and tested using cosmic rays. The signals from the anode wires are amplified and fed to a Flash-ADC to deliver the drift time and charge integration. The performances of the array prototype are investigated under various high voltages. For the tracking performances, after the space-time relation (STR) calibration and the detector displacement correction, the standard deviation of 223 μm of the residue is obtained. The performances of the forward MWDCs tracking array meets the requirements of CEE in design.     

Monte Carlo studies on the burnup measurement for the high temperature gas cooling reactor

Online fuel pebble burnup measurement in a future high temperature gas cooling reactor is proposed for implementation through a high purity germanium (HPGe) gamma spectrometer. By using KORIGEN software and MCNP Monte Carlo simulations,the single pebble gamma radiations to be recorded in the detector are simulated under different irradiation histories. A specially developed algorithm is applied to analyze the generated spectra to reconstruct the gamma activity of the ¹³⁷Cs monitoring nuclide. It is demonstrated that by taking into account the intense interfering peaks,the ¹³⁷Cs activity in the spent pebbles can be derived with a standard deviation of 3.0%(1σ). The results support the feasibility of utilizing the HPGe spectrometry in the online determination of the pebble burnup in future modular pebble bed reactors.     

多物理耦合计算中动态输运问题高效蒙特卡罗模拟方法

多物理耦合计算在众多领域都有重要应用.如果其包含粒子输运过程,用蒙特卡罗方法模拟粒子输运常占据大部分的计算时间,因此多物理耦合计算中动态输运问题的高效蒙特卡罗模拟方法意义重大,其不可避免地依赖于大规模并行.基于动态输运问题的特点,本文提出了两种新方法:一是针对输运燃耗耦合计算的新型计数规约算法;二是动态输运计算样本数自适应算法.两种算法都能在保持计算结果基本不变的前提下使计算时间大幅减少,从而提高了效率.     

神光III主机上球腔辐射场实验的三维数值模拟与分析

2015年在神光Ⅲ激光装置上开展了两孔球腔物理实验.利用三维隐式蒙特卡罗数值模拟程序模拟两孔球腔中的辐射输运问题,研究辐射场分布及其动态演化过程.数值模拟结果大多数与实验结果符合较好,但局部位置存在明显差异.分析了产生差异的可能原因,提出解决措施及未来发展方向.综合数值模拟结果及其与实验结果的对比可知,三维隐式蒙特卡罗数值模拟程序具备较好的黑腔三维辐射输运数值模拟能力.     

HTR-PM中燃耗测量方法研究和测量系统原型研制

作为球床模块式反应堆中燃料元件循环的重要组成部分,燃耗测量系统必须对连续排出堆芯的燃料球进行非破坏性在线测量,以确定是作为乏燃料球退出循环,还是将其返回堆芯。137Cs的活度和燃耗值存在很好的单调对应关系,因此在高温气冷堆(HTR-PM)核电站示范工程中将利用高纯锗探测器测量燃料球中137Cs的活度,进而根据燃耗计算曲线确定其燃耗值。通过实验以及基于Geant4的蒙特卡罗全模拟,利用效率传递方法准确得到了系统刻度的修正因子。同时发展了快速自动的谱寻峰和峰面积分析程序用于双源实验和MCNP模拟的γ谱分析,结果表明,尽管有干扰峰的影响,该系统预计对137Cs的活度测量相对不确定度依然可以控制在3.0%以内。在以上工作基础上成功研制并测试了一套全尺寸的燃耗测量系统原型。     

Conditioning the γ spectrometer for activity measurement at very high background

The application of a high purity Germanium(HPGe) γ spectrometer in determining the fuel element burnup in a future reactor is studied.The HPGe detector is exposed by a 60Co source with varying irradiation rate from 10×103s-1 to 150×103s-1 to simulate the input counting rate in real reactor environment.A137 Cs and a152 Eu source are positioned at given distances to generate a certain event rate in the detector with the former being proposed as a labeling nuclide to measure the burnup of a fuel element.It is shown that both the energy resolution slightly increasing with the irradiation rate and the passthrough rate at high irradiation level match the requirement of the real application.The influence of the background is studied in the different parameter sets used in the specially developed procedure of background subtraction.It is demonstrated that with the typical input irradiation rate and 137Cs intensity relevant to a deep burnup situation,the precision of the 137Cs counting rate in the current experiment is consistently below 2.8%,indicating a promising feasibility of utilizing an HPGe detector in the burnup measurement in future bed-like reactors.