Abstract
The results of regular working environment measurements in our radioisotope facilities were about background levels. However, most of these are the data measured when unsealed radioisotopes were not used. High concentrations of radioisotopes were detected when measured during the time when unsealed 35S or 125I was used. These results were estimated far under the regulation levels. Thus, safety working environments are sufficiently guaranteed by suitable estimation and suitable handling under the strict regulation. Therefore, regulation would be relaxed in the field of education and research in such ways as estimation by calculation in place of the actual measurements, decrease of the number of monthly measurements, and measurements exemption for nonvolatile or low levels of isotopes. Working environment measurements would be still effective in cases where volatile radioisotopes are used in largequantities. They may provide a useful index if improvement of safe handling technique or equipments is required.
