Aircraft impact/crashes containment

The reactor building is in the center of the plant. In addition to two HTR modules, it contains some auxiliary and ancillary systems. Components of the start-up and cool-down systems, the steam generator fast discharge systems, and the intermediate cooling systems are installed in the annex to the reactor building. The two modular units are separated from each other by a central service area. An outer protective shell encloses the inner building structure. It fulfills the requirements for protecting the reactor plant from external impacts (e.g. aircraft crash). 

The upper hemisphere of the steel shell is surrounded by a shielding made of reinforced concrete with a wall thickness of about 2 m. This shielding protects the nuclear part of the plant against any external impact (e. g. gas explosion, military aircraft crash) it also significantly reduces the likelihood that radionuclides will escape to the environment. The interspace between the steel shell and the secondary containment is held at sub-atmospheric pressure, so that any radionuclides penetrating the steel shell via leaks in the event of a loss-of-coolant accident would be transported by the annulus air extraction system to the standby filters and retained here, thus preventing release to the environment. 

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