I - DEFENCE-IN-DEPTH:

 1 - Fuel matrix

 2 - Fuel sheath

 3 - PHTS pressure boundary

 4 - Containment envelope

 5 - Exclusion area

II - A.L.A.R.A.

III - GROUPING:

 1 - Group 1 plant systems: SDS#1,

Containment system,

Normal plant power supply system, … etc.

 2 - Group 2 plant systems: SDS#2, ECCS, EWS, EPS, …. Etc.