ISO 16117:2013 provides a methodology to estimate a reasonably maximal value of the number of fissions of a postulated criticality accident.

The fission number estimate, associated with its postulated criticality accident, impacts the accident emergency planning and response because it is used for the estimation of radiation doses and of radioactive materials release.

ISO 16117:2013 does apply to nuclear facilities, plants, laboratories, storage, and transportation of fissile material (but not to nuclear power reactor cores) where a credible criticality accident may occur.