Abstract: In pebble-bed high temperature gas-cooled reactor, the detection and number counting of the spent fuel pebbles discharged from the reactor core are the crucial part for fuel monitoring. To meet the requirement by IAEA for nuclear security of pebble-bed high temperature gas-cooled reactor, a new detection scheme based on a principle independent of the existent eddy current detection should be developed for fuel distinguishing and counting in the fuel handling system’s pipeline. Based on γ measurement, a novel detection scheme was proposed, a prototype of the detector was designed, and its function was examined when the reactor was in steady-state operation. With the radionuclides’ data from the reactor HTR-10, through Monte Carlo simulation and analysis for the process when pebbles of various velocities and burnups passing through the detecting area, the reliability of the scheme for the distinguishing and counting for single fuel pebble was verified. Meanwhile, the feasibility of this scheme to detect the pebble flow was preliminarily proved. The result provides the designing foundation for scheme’s improvement and device production in the future.

Key words: pebble-bed high temperature gas-cooled reactor, scintillator, γ measurement, Monte Carlo simulation, fuel monitoring

摘要： 在球床式高温气冷堆中，对排出堆芯的乏燃料球的探测和数量统计是燃料监测的重要内容。按国际原子能机构针对球床式高温气冷堆核安保的要求，对于燃料装卸系统管道内的燃料监测应开发一种独立于现有涡流检测原理的新监测方案。本文提出了一种基于γ测量原理的新探测方案，设计了探测器构型，对其在堆稳态运行时的探测功能进行验证。结合球床式高温气冷堆HTR-10的燃料球放射性核素数据，及对不同球速不同燃耗的燃料球经过探测区域过程的蒙特卡罗模拟分析，验证了此方案对单个燃料球鉴别和计数的可靠性，同时证明了该方案对于燃料球球流探测的可行性，为今后该探测方案的完善和实际装置的制作提供了设计基础。

关键词: 球床式高温气冷堆, 闪烁体, γ测量, 蒙特卡罗模拟, 燃料监测