采用蒙特卡罗程序MCNP/4B模拟计算了功率为30 kW的低浓化医院中子照射器的堆芯物理参数，设计了合理的堆芯布置方案、²³⁵U富集度、控制棒价值、后备反应性和停堆深度，得到固有安全性较高、寿期达10年且无需换料、采用低浓化UO₂燃料的医院中子照射器的堆芯物理设计方案，为后续反应堆工程设计以及硼中子俘获治疗肿瘤用中子束的设计提供理论依据。

The core physics properties of 30 kW In-Hospital Neutron Irradiator-Mark 1(IHNI-1) reactor loaded low-enrichment fuel are simulated by using MCNP/4B Monte Carlo code. The arrangement scheme of core, ²³⁵U enrichment, control rods' value, excess reactivity and shutdown margin are also reasonably introduced. The results show that the physics scheme of IHNI-1 reactor which possesses some particular characteristics, such as high inherent safety, 10 years lifetime without any refueling and low-enrichment UO₂ fuel, has been discovered in the paper and it will provide theoretic basis for reactor engineering design and neutron beam design for Boron Neutron Capture Therapy in the future.