1. 1) Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors, Article 61-2 (in Japanese).
2. 2) Ministry of Economy, Trade and Industry, Ordinance for confirmation of radioactive concentration of materials (2005) (in Japanese).
3. 3) Nuclear Regulation Authority Japan; Kuriaransu seido no jisseki [Achievement of Clearance System (as of December 2020)]. Available at: https://www.nsr.go.jp/activity/regulation/nuclearfuel/haiki4_jisseki.html, Accessed 6 April 2021 (in Japanese).
4. 4) Nuclear Regulation Authority Japan; Ordinance for confirmation of radioactive concentration of materials used at factory etc. (2020) (in Japanese).
5. 5) International Atomic Energy Agency; Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, General Safety Requirements Part 3 (No. GSR Part 3) (2014).