基于微型电离室的高浓度氚在线测量关键问题研究

Tritium is the main fuel for fusion reactor, and more than 100 kg tritium will be handled in DT recycling system. It will be a great challenge to deal with such amount of tritium, including the complex processing techniques and high concentration tritium up to pure level. Therefore, it is of great importance to measure tritium in line during the process, which is essential to provide information for both process control and tritium safety. We intend to develop a kind of micro ionization chamber, which can be connected to tritium process system directly and give tritium concentration in line immediately. Based on the basic interaction theory of beta rays and gas in ionization chamber, theoretical calculations and Monte Carlo simulations are employed to calculate the energy deposition in ionization chambers quantitatively. The relationship between output signal and tritium concentration in ionization chamber will be established according to the calculations. With the established energy deposition theory, implantable micro ionization chamber for tritium in-line measurements is designed. In addition, experiments will also be performed to obtain the effect of gas pressure, gas composition, and tritium concentration on the output signal of ionization chamber. It is predicted that the key issues about the micro ionization chamber for tritium measurements in high level will be solved with the results obtained above, which will provide important techniques for fast, in-line measurements of tritium in DT recycling system for fusion reactor.

氚是聚变堆主要燃料，聚变堆DT燃料循环系统中氚处理量将高达100kg以上。处理如此大规模的氚必将面临复杂的处理工艺、高达纯氚级的氚浓度，这对处理工艺的控制、氚安全均是极大挑战。因此，在线测量工艺系统中各个环节氚浓度，对DT燃料循环系统中氚工艺控制、氚安全操作均具有重要意义。本项目拟通过研究可植入工艺系统的流气式微型测氚电离室，实现工艺系统中高浓度氚的快速、在线测量。从氚的β射线与电离室内介质相互作用理论出发，通过建模计算和蒙卡模拟结合的方式建立电离室内能量沉积的定量计算方法，获得不同条件下输出信号与电离室内氚浓度之间的关系；通过电离室结构材料选取及表面处理技术研究降低记忆效应；在理论基础上设计植入式微型电离室并开展实验研究，探明不同压力、载气气氛、氚浓度下电离室的响应规律。该技术成果预期解决微型电离室测量高浓度氚的关键技术问题，为聚变堆DT燃料循环系统中氚的快速、在线测量提供技术支撑。

针对聚变堆DT燃料循环系统中高浓度氚，按照申请书中规划的内容开展研究工作。基于理论建模和蒙卡模拟的方法建立了氚的β射线在电离室内能量沉积的定量计算方法；从材料吸氚特性、电离室结构两方面出发，设计了高浓度氚情况下低记忆效应电离室；并自主搭建了电离室测量实验系统，并在系统上从理论和实验上研究了不同载气成分及压力对微型电离室输出信号的影响。