Abstract
We changed the purging tanks into the ground type from the underground type, because we could not check a leakage of radioactive wastewater from the underground purging tanks by visual inspection. At the drainage in our radioisotope facility, the wall of underground purging tanks were reused as a protective wall in leakage of radioactive wastewater, and new purging tanks were built in the place among the protective wall. The new tanks are made of stainless steel, and its surface condition can be checked by visual inspection. The process of the construction was divided into the three terms since the radioisotope facility couldn't be closed during the construction. The kinds and quantities of radioisotopes which can be used in our radioisotope facility were reduced because the treatment capacity of the drainage was decreased during the construction. We made efforts especially to prevent a radiation accident during the construction. As the result, it is realized again that a person of radiation control duties plays an important role to prevent the accident when a contamination test or trial run of the system are conducted, heavy things are being carried, or the underground purging tanks are being dismantled.
