Recently, portable radiography has been performed in many facilities. In portable radiography, the distance between the radiological technologist and the patient is often close. Thus, exposure assessment and radiation protection for radiological technologist is important. However, the use status of personal protective equipment and the recognition of exposure differ depending on the facility and the individual. In addition, no detailed survey on the current state of portable radiography has been reported. Therefore, we conducted a questionnaire survey for radiological technologist involved in portable radiography. As the result of the questionnaire survey, it became clear that the protection status of radiological technologists during portable radiography varies depending on the facility, gender, and age. There were some opinions that it was difficult to keep away from the patient during portable radiography. In that case, it is desirable to wear protective equipment such as a protector.

 The regulation for isotopes which emit radiation with extremely long half-lives such as Calsium-48 (t_1/2＝1.9×10¹⁹ year) or Bismuth-209 (t_1/2＝2.01×10¹⁹ year) was examined. At permission usage facilities pertaining to unsealed radioisotopes, all the radiation-emitting isotopes have to be controlled as radioisotopes regardless of their quantities or half-lives, even if radioactivity of these isotopes rarely exceeds the lower bound quantities (as with “exemption levels”). This is because the lower bound quantities are evaluated in terms of integrated radioactivity of all the unsealed radiation-emitting isotopes placed in a factory or place of business. In most of such cases, these isotopes can be excluded from the subject of radiation control by considering the regulation on the concentration limit for the unsealed radiation-emitting isotope even at the permission usage facilities pertaining to unsealed radioisotopes.

 The aim of this study is to report our experiences we had on decommissioning of four unsealed radioisotopes facilities during five years, 2010-2015. In this study, we investigated not only the relationship between decommissioning cost and facility's scale or radioisotope use, but also the purpose and cost of facility renovation. In addition, the problems conducting decommissioning of the facilities and the effect were also done a survey for the radiation protection supervisors or safety manager.