# The Nuclear Installations (Prescribed Sites and Transport) Regulations 2018, Paragraph 2


In any case where the isotopic composition of a radioactive substance is not known or is only partially known, the quantity ratio for that substance must be calculated by using the values specified in the appropriate column in Part 1 for “other radionuclides not listed above” for any radionuclide that has not been identified or where the quantity of a radionuclide is uncertain.

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Source: https://www.legislation.gov.uk/uksi/2018/42/schedule/2/paragraph/2 (the official version)
Page: https://openlegislation.uk/nuclear-installations-prescribed-sites-and-transport-regulations-2018/schedule-2/paragraph-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.