Security of Inherent Safety and Reduction of Environmental Effects during High Temperature Gas Cooled Reactor Accidents

本研究的目的是建立一个高温气冷堆（HTGR）的概念，其中的热量可以被动地和安全地在事故期间和释放的放射性活动是有限的，即使在燃料故障。在这项研究中，所有类型的反应堆采用包覆燃料颗粒被认为是。东京工业大学核反应堆研究实验室的核反应堆物理、核材料、核反应堆工程等各个领域的专家参与了这项研究。日本原子能研究所的一位专家也加入了这项研究。本文的主要研究成果如下：首先，研究了高温气冷堆反应性事故和失水事故的分析方法，研究了反应堆在事故过程中的行为。此外，还研究了一个高通量反应堆，它具有类似的核心高温气冷堆的各种事故，并证实，事故终止没有释放裂变产物从cated燃料颗粒。对不同堆型的球形燃料球堆芯模型进行了热工水力学实验。一旦空气进入芯中，芯中的石墨可能被氧化。可能导致严重事故。因此，研究了加热石墨与空气或水蒸气的反应。研究了在核燃料包覆颗粒中起重要作用的SiC材料的辐射损伤。为了提高安全性，还对热管在核反应堆中的应用进行了研究。与此相关，召开了一次国际小型核反应堆专家会议。

The aim of this study is to construct a concept of High Temperature Gas Cooled Reactor (HTGR), for which the heat can removed passively and safely during accidents and the release of radio activity are limited even at fuel failures. In this study, all kinds of reactors employing coated fuel particles are considered. The specialists in various field such as nuclear reactor physics, nuclear material, nuclear reactor engineering in Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology have been involved cooperatively for this study. And a specialist from Japan Atomic Research Institute also has joined to this study. Summary of many results of this study is described as follows.First, the analytical methods were studied for reactivity accidents and loss of coolant accidents for HTGR, and the behavior of the reactor during accidents were investigated. Furthermore a high flux reactor which has the similar core to HTGR were also studied for various accidents, and it was confirmed that the accidents were terminated without releasing the fission products from the cated fuel particles. Thermal hydraulics experiments were performed for a core model with spherical fuel balls used for various reactor designs. Once the air inserts into the core, graphite in the core may be oxidized. It may lead to serious accidents. So reactions of heated graphite and air or steam were studied. Radiation damage of SiC, which plays important role to contain radioactive fission products into the coated fuel particle, was studied. To increase the safety, utilization of heat pipe for the nuclear reactor was also investigated.Related to this study, an international specialists meeting for small nuclear reactors was held.