Use of inherent safety features and safety-by-design eliminates certain accident initiators. Use of passive safety systems makes their functioning more probable when something does happen, and removes dependence on an external power source.

The combined impact reflected in most SMR designs is to reduce significantly the CDF (core damage frequency, per reactor-year) and LERF (large and early release frequency, per reactor-year) probabilities. Thus, CDF values of 1.0 X 10-7 to 1.0 X 10-8 per reactor-year are typically claimed for SMRs, with LERF probabilities usually at least one order of magnitude lower than CDF. This, if proven correct, would allow operating 10 000 reactors for 100 years with only a small probability of an accident leading to core damage, and practically negligible probability of any radiation release. In contrast, the Generation-II CDF values of 1.0 X 10-4 to 1.0 X 10-5 imply that for 400 reactors operating over 50 years a CDF event should not be excluded, and they in fact did happen. While the consequences of all commercial nuclear accidents combined are orders of magnitude smaller than the health effects that would have been caused by producing the same amount of electricity by fossil fuel, they have negatively impacted public opinion, and iPWR SMRs (and advanced reactors in general) could help address that public concern.