SMRs may provide additional features, levels of safety, or barriers in the DID

approach. Some SMRs have implemented one or more of the following DID-

supporting features:

• Containment with higher design pressure which may provide an additional barrier or at least extend the time to radioactivity release. This is facilitated by more compact reactor and containment design.

• Passive cooling of the containment, avoiding its failure in certain loss of offsite power (LOOP) scenarios.

• Fully underground placement, potentially ameliorating a release of radioactivity.

• Significantly increased grace period may also be viewed as DID since it may allow a more systematic and better organized evacuation in case all previous barriers fail.