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Kondo, Masaaki; Sekita, Kenji; Emori, Koichi; Sakaba, Nariaki; Kimishima, Satoru; Kuroha, Misao; Noji, Kiyoshi; Aono, Tetsuya; Hayakawa, Masato
JAEA-Testing 2006-002, 55 Pages, 2006/07
JAEA-Testing-2006-002.pdf:6.36MB
The leakage rate test for the reactor containment vessel of HTTR is conducted in accordance with the absolute pressure method provided in Japan Electric Association Code(JEAC4203). Although leakage test of a reactor containment vessel is, in general, performed in condition of reactor coolant pressure boundary to be opened in order to simulate an accident, the peculiar test method to HTTR which use the helium gas as reactor coolant has been established, in which the pressure boundary is closed to avoid the release of fission products into the environment of the reactor containment vessel. The system for measuring and calculating the data for evaluating the leakage rate for containment vessel of HTTR was developed followed by any modifications. Recently, the system has been improved for more accurate and reliable one with any useful functions including real time monitoring any conditions related to the test. In addition, the configuration of containment vessel boundary for the test and the calibration method for the detectors for measuring temperature in containment vessel have been modified by reflecting the revision of the Code mentioned above. This report describes the method, system configuration, and procedures for the leakage rate test for reactor containment vessel of HTTR.
Noji, Kiyoshi; Kameyama, Yasuhiko; Emori, Koichi; Aono, Tetsuya
JAEA-Testing 2006-003, 47 Pages, 2006/06
JAEA-Testing-2006-003.pdf:7.43MB
The FFD (Fuel Failure Detection) System has been installed in the HTTR in order to detects the abnormal release of fission products from the fuel during the operations. The FFD system samples the primary coolant from the high-temperature plenum division of the reactor core divided into seven regions. The system detects short life fission product(FP) gases from each region. The damaged region can be specified by the FFD system. In the design, it was considered that the change in the sampling flow rate during operation was not necessary. However, it became clear that the measured value became unstable because of a fluctuation of the sampling flow rate due to change in the primary coolant pressure during operation. Moreover, it was difficult to change the sampling flow rate during operation. The sampling flow rate was controlled by manual valves located in the service area where the entry is limited during operation. Therefore, an improvement was carried out to control the sampling flow rate from the outside of the service area. The stable measured value was obtained by the improvement. Moreover, noise reduction, improvement of oil level gauge of compressors gives excellent operation of the FFD. This report summarizes the maintenance work of detectors (precipitator), equipment and improvement items of the system.