The preliminary design of PGNAA system of IHNI was completed and the system in accordance with the design was set up. For both detector shielding part and the neutron beam shielding part, the inner layer was natural LiF powder and the outer was lead.Then boron concentration measurement experiments using this system were finished.The results show that the the system can measure 10B concentration of 10 ppm, with 2 mL of the sample volume. 10B element measurement sensitivity was 0.822 cps/ppm. Also it was found that the natural LiF powder would produce a high background in the target part of the energy spectrum and affect the measurement accuracy.

The characteristic parameters of the neutron radiation fields produced by an in-hospital neutron irradiatior for boron neutron capture therapy(BNCT), such as neutron energy spectra, neutron flux density and neutron absorbed dose rate and their spatial distributions in free air, etc., were measured to verify the design effect. According to the traits of the irradiators, a measuring system composed of a multi-sphere spectrometer, a 235U fission ionization chamber, gold foils, a tissue equivalent proportional counter and thermoluminescent detectors was established. In order to improve the energy resolution in epithermal energy range and the ability to discriminate different neutron components, the Monte Carlo method was used for optimizing the detectors. The preliminary results show that the neutron flux densities of the irradiators achieve the expected levels.

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.

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.

This paper analyzes some improvement plans to prolong the single operation time of the Miniature Neutron Source Reactor (MNSR). Test results shows that after adding proper quantity of Be plates on the top Be plates box, the single operation time of MNSR can be greatly prolonged by installing the compensation Cd-plate outside the flank Be-reflector and making the plate and central control rod move together, without any change of central control rod and the original structure of the reactor core. The operation performance of MNSR can be improved.