Accidental aircraft crash

The research reactor may be located in an area where the risk of aircraft crash is not significant. In agreement with the basic principles discussed in Ref. [20], two approaches are recommended  

Obtaining fundamental data for aircraft crash protection calls for an extensive knowledge of air traffic in the vicinity of the facility. Basic studies can be undertaken to determine the following parameters  

In some Member States there is a need to evaluate the adequacy of the design of structures, systems and components of safety classes 1 to 3 in hazard category 1 to 3 facilities. This is usually done by installing physical barriers to vehicle intrusion, and providing sufficient stand-off distance to ensure the required performance. Reference [28] provides practical examples of this. 

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It is preferable to evaluate the external event hazard on a probabilistic basis. The frequency of occurrence of the parameters describing the severity of the external hazard (such as earthquake ground acceleration, wind speed, water elevation) is estimated by probabilistic methods. Statistical parameters used for extreme events include return period and annual probability of exceedance. The hazard from other rare external events such as accidental aircraft crashes or explosions reflects the frequency of occurrence of an event with postulated characteristics (quantity of explosive material, weight and velocity of the missile, etc.), as proper statistics may not be available for the area of interest. Performance goals depend on the external event categorization as defined in Section 2. For practical use they can be approximated by deriving the product (for continuous hazard levels it can be the convolution) between the annual probability of exceedance of an external event and the Pp induced by that specific external event. Probability values for performance... 

The probability of an accidental aircraft impact can be said to be acceptably low because of the regulatory and administrative arrangements that prohibit aircraft access close to UK nuclear power station sites. An aircraft crashing into the APIOOO will need a site-specific assessment to determine if this event is beyond design basis. 

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