Speaker
Toshiharu Takeishi
(Applied Quantum Physics and Nuclear Engineering)
Description
After the tritium handling operation, it is an important issues to take an appropriate disposal method of tritium handling facility contaminated with tritium. In Kyushu University, according to the relocation program to the new campus, decommissioning operation of tritium handling facility located in the former campus had been performed. This handling facility made of concrete was used for accelerator experiments with several tritium targets (370 GBq/target) from 1961 to around 1980. However, detailed experimental conditions are not found.
Prior to launch the total surveillance of handling facility, pre-measurement was performed for 325 surface smear points and 10 core sample points for depth profile on concrete floor and wall to determine the way of total surveillance. Remarkable amount of tritium contamination was observed in approximately 80 % of total surface smear points. Depth profile of tritium concentration obtained from core sample showed that most of highest contamination points existed in the point face the operation room but some of the highest points existed in the deeper point. This may be explained that during the experimental period, tritium released or leaked into the operation room penetrates into the concrete wall with concentration gradient. After shutdown of the accelerator experiments, tritium exists in the concrete wall transferred to the room air during long time after shutdown because no tritium exists in the room air. As the results, highest tritium concentration point was observed at the deeper point. Attention should be paid not only to measure tritium on the surface, but also to tritium exists in the inside of wall and detecting method in the decommissioning of tritium handling facility.
In the total surveillance, we took a scraping method from inner surface divided into 1m22 of area and re-scraping was performed when significant contamination was detected in the first surface measurement.
Co-authors
Kazunari Katayama
(Advanced Energy Engineering Science, Kyushu University, Fukuoka, Japan)
Ryotaro Yamamoto
(Advanced Energy Engineering Science, Kyushu University, Fukuoka, Japan)
Toshiharu Takeishi
(Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka, Japan)
Yoshiya Kawabata
(Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka, Japan)
