[en] The safety concept of the PHWR is principally based on the same safety features as the light water PWR, e.g. reactor building consisting of a spherical steel containment and an outer concrete building with vented annulus inbetween. However, there are some specialities adherent to the heavy water reactor. Safety related systems are designed to be both, diverse and redundant. The moderator cooling system can be used as a high pressure heat removal sysem and thus is an addition to the heat removal via the steam generators. For reactor shut-down a control rod system and a boron injection system exist independently. (orig./HP)