design basis
as defined in Council Directive 2009/71/ Euratom of 25 June 2009 establishing a Community…, Article 3, point (9) (Definitions)
9.
‘design basis’ means the range of conditions and events taken explicitly into account in the design, including upgrades, of a nuclear installation, according to established criteria, so that the installation can withstand them without exceeding authorised limits by the planned operation of safety systems;