The Radioactive Material (Road Transport) (Great Britain) Regulations 1996

4.  For each Type B package, it shall be ensured by examination and/or appropriate tests that all closures, valves, and other openings of the containment system through which the radioactive contents might escape are properly closed and, where appropriate, sealed in the manner for which the demonstrations of compliance with the requirements of paragraph 8 of Schedule 12 were made. In the case of a package where containment is provided by radioactive material in special form, compliance may be demonstrated by possession of a valid special form radioactive material approval certificate issued in accordance with regulation 17.