介绍了医院中子照射器及其相关系统的设计情况，描述了医院中子照射器的性能和特性。为验证医院中子照射器的固有安全特性，进行了4.2 mk反应性释放实验。实验结果表明，反应堆功率快速上升，在229 s时，功率达到85.7 kW峰值，随后，由于燃料元件多普勒效应和慢化剂的负温度效应会非能动地把功率限制在允许的安全水平之下。满功率运行时，各个工艺房间γ剂量率小于1 μSv/h，且中子剂量率为本底水平，具有低辐射特点。

The design of in hospital neutron irradiator (IHNI) and its systems were introduced, and the performance and characteristics of IHNI were described. In order to test the inherent safety of IHNI, the experiment of 4.2 mk reactivity release was done. The experimental results showed that the peak power of IHNI was 85.7 kW at the time of 229 s after 4.2 mk reactivity release, and then, the power decreased owing to the negative temperature coefficient of moderator. The radiation dose rates at different rooms were lower than the standard value.

李义国（1964—），男，山东莱西县人，研究员，研究方向为反应堆物理