Methodology for Aircraft Crash Release Frequency Screening.

DOE-STD-3014-96

Step 21. If the total impact frequency is below the guideline value, the safety risk is

below the level of concern; stop the analysis and document the results. If the total impact

frequency is greater than the guideline value, it is necessary to identify the aircraft

categories/subcategories to be used for the structural response and release frequency

analyses. A certain amount of judgment is required in making this selection. It is

recommended that the analyst interact with the facility structural engineers and/or

analysts to identify a subset of those aircraft categories/subcategories that are significant

contributors to the impact frequencies.

Methodology for Aircraft Crash Release Frequency Screening. The assessment of

5.4

impact frequency, as evaluated above, assumes that all impacts will lead to facility

damage and a possible release of radioactive or hazardous chemical material. This

assumption is due to the lack of information about the response of the structure to impact

during the impact frequency stage of the analysis. Following completion of the structural

analysis, as described in Chapter 6, it is possible to determine the initial release

frequency, which is the total impact frequency minus the impact frequencies of the aircraft

categories/subcategories shown to have little or no effect on the facility, i.e., will not lead

to a release. This section explains the process of calculating the initial release frequency

using results from the structural analysis.

The approach for the initial release frequency analysis is to exclude those aircraft

categories/subcategories that are known and/or shown by the structural response

analysis to inflict little or no damage should they impact the facility. The major

assumption in this analysis is that if any of the impact locations analyzed in the structural

response analysis for a particular aircraft category/subcategory can be shown to cause

sufficient damage to lead to release, then all impact locations will lead to a release. This

simplifies the analysis. The screening is performed in the following steps:

Step 1. From the structural response analysis results, identify the aircraft

categories/subcategories whose impact into the facility would result in little or no damage

to the facility, i.e., would not result in a release.