SAITO Yasushi KURRI,Technician, 原子炉実験所, 教務職員 (40283684)
FUJINE Shigenori KURRI,Instructor, 原子炉実験所, 助手 (90027441)
HIBIKI Takashi KURRI,Associate Professor, 原子炉実験所, 助教授 (30228746)
MISHIMA Kaichiro KURRI,Professor, 原子炉実験所, 教授 (60027472)
KANDA Keiji KURRI,Professor, 原子炉実験所, 教授 (10027419)
In this project, the following studies were performed to establish neutron radiography with the complementary characteristics to X-ray or gamma-ray radiography as an advanced measuring technique :
(1)Improvement of temporal resolution
High-frame-rate neutron radiography system with the maximum recording speed of 1000 frame/s was constructed by gathering up-to-date technologies such as a high flux steady neutron beam, a high-perfomance converter, a high-sensitivity camera, and an image intensifier with double micro channel plates. Two-phase flow in a metallic rectangular duct was visualized successfully at the recording speed of 1000 frame/s. Temporal resolution limit of high-frame-rate neutron radiography was estimated by statistics analysis of neutron number measurement in a low neutron flux field and light-decay characteristics of a converter.
(2)Development of quantification method of thermal neutron radiographic image
Void fraction measurement method was developed by taking account of scattered neutrons (SIGMA-scaling method). The SIGMA-scaling method was verified by experiments, a Monte Carlo simulation, and a simplified neutronic medel. It was demonstrated that the image processing method enabled flow measurements such as flow regime, bubble rise velocity, bubble size distribution, interfacial area concentration, liquid velocity field, and so on.
(3)Application to transient thermal hydraulic phenomena
The high-frame-rate neutron radiography system and the quantification method devepoled in this study were applied to various thermal hydraulic phenomena : visualization of vertical upward air-water flow in a narrow rectangular duct, void fraction measurement of vertical upward air-water flow in small diameter round tubes, visualization and measurement of premixing phenomena in a steam explosion, and flow measurement of molten metal-nitrogen gas two-phase flow with a large density ratio in relation to a severe accident study in a fast breeder reactor.