[en] In the Hamaoka nuclear power plant, when the microbe adhered on the sea water heat exchanger tube of a reactor building closed cooling sea water system, the phenomenon to which heat exchanger entrance difference pressure rises for a short period of time occurred. For this reason, a measure for difference pressure rise control was desired. Then, as a result of doing a model test paying attention to practical use of gaseous microbubble water, CO_2 acquired the prospect of being effective to adhesion control and removal of the adhered microbe. It was based on these results and the verification examination was done. (author)