(Reference 7), which does a range of calculations and selects the worst
case. Alternatively, Reference 3 contains a simplified screening
Hazardous Material Onsite Exposure Determination. In the rare instance
when assessment of exposure to onsite personnel outside the facility is
desired (see discussion in Appendix A, Section A.1.2), the onsite
evaluation guideline, per Section 4.1, is that individuals should not be
exposed to a concentration in excess of ERPG-3 (or an equivalent
measure) at a distance of 300 m (984 ft) in Atmospheric Dispersion
Category D with a windspeed of 4.25m/s (14 ft/sec). Reference 3
contains a tabulation of release rates for various chemicals that will just
meet this criterion.
Other Methods. For both radioactive and chemical releases, other techniques may
be proposed and will be evaluated for sufficiency on a case-by-case basis by the
cognizant safety authority.
Comparison to Guidelines. The exposure to the maximally exposed individual at or
beyond the site boundary will be compared to the exposure screening guidelines.
If the exposure screening guidelines are met, no additional analysis of aircraft
impact is required. If the exposure screening guidelines cannot be met, a more
detailed analysis will be performed, based on both an assessment of the aircraft
impact frequency (Chapter 5) and an evaluation of the structural response of the
facility/operation subjected to aircraft impact (Chapter 6), in accordance with the
approach described in Chapter 3.
Exposure Evaluation. The purpose of exposure evaluation is to determine, based on the
specific level of damage and phenomenology associated with a spectrum of aircraft
crashes into the subject facility, the extent to which individual members of the public
and/or site workers may be exposed to a release of radioactive or hazardous chemical
material. This section provides an overview of the evaluation approach. Further details
are provided in Appendix D.