SI 2019/195. The Nuclear Safeguards (Fissionable Material and Relevant International Agreements) (EU Exit) Regulations 2019. Comes into force on Brexit day. After Brexit day nuclear safeguards in the United Kingdom, will no longer be regulated by the EURATOM treaty. These Regulations define Fissionable Material and list the relevant international agreements for the purposes of section 112(1A) of the Energy Act 2013