SASAKI Ken-ichi RIKKYO UNIV.DEPT.of INTERACTIVE SCIENCE.PROF., 理学部, 教授 (70022647)
SHIRAISHI Fumio RIKKYO UNIV.RES.INST.for ATOMIC ENERGY.PROF., 原子力研究所, 教授 (20062606)
TOMURA Kenji RIKKYO UNIV.RES.INST.for ATOMIC ENERGY.PROF., 原子力研究所, 教授 (20062549)
HARASAWA Susumu RIKKYO UNIV.RES.INST.for ATOMIC ENERGY.PROF., 原子力研究所, 教授 (90062546)
MATSUURA Tatsuo RIKKYO UNIV.RES.INST.for ATOMIC ENERGY.PROF.EMERITUS, 原子力研究所, 名誉教授 (00062498)
MASUNO Koushiro MASUNO SEISAKUSHO Co.Ltd. PRESIDENT (RESEARCHER)
Studies on developing a sensitive monitoring method of possible release of fission products (FP) from a fuel element have been made for a pool-type research reactor. It consists of introducing gas bubbles into reactor coolant water to extract effectively the dissolved fission rare gases, ^<89>Kr and ^<138>Xe, produced somewhere in the core, and counting their respective daughter nuclides, ^<89>Rb and ^<138>Cs with high efficiency.
The measurements were done by either method, (Method I) on a filter paper by sucking the bubbled gas and air covering water of the reactor tank, or (Method II) in the washing water of bubbled gas sampled into a bottle at the water surface. Various causes that influence the detection efficiency (DE) of the daughter nuclides in both methods were studied. These include the flow rate of introducing gas, position (depth and radial direction) of gas exit in the water, whether the coolant was circulated or not, and (for Method II) standing time of the sampled gas between the sampling and washing the gas with water. On the basis of these experimental data, we have designed and constructed an automatic fuel monitoring system of the continuous mode experiment, for routine use by adopting Method II.It is composed of an intermittent sampling of the bubbling gas into bottle at the water surface, conveying the bottle until near the detector, standing the bottle for a definite time, shaking the bottle, and measuring the nuclides contained in the water. The system have performed effectively measuring ^<138>Cs as a routine fuel monitoring system.