These Regulations amend the Nuclear Installation Security Regulations 2003 (S.I. 2003/403) (the ‘Principal Regulations’) to apply those Regulations to a nuclear site from the point a nuclear site licence is issued (under the Nuclear Installations Act 1965 (c. 57)) for the period until nuclear material is removed from the site as part of the decommissioning of that site. These Regulations also extend (with amendments) the Principal Regulations to a nuclear construction site in prescribed circumstances.