Containment building with a window

A containment building comprising a wall made of a concrete material that delimits a space and at least one viewing module, said viewing module comprising at least one window arranged in an opening in the wall, said window having a frame in which at least one optical unit that provides protection from high-energy and/or neutron radiation is placed, said frame being fitted in the opening, the viewing module also having a protective element that comprises a sash bearing a pane and is arranged so as to close the opening at a face on the inside of the containment building, said viewing module thus comprising at least one interface between two surfaces,

• the containment building further comprising at least one sealing system arranged at the at least one interface, said sealing system comprising at least one hermetic chamber at a periphery of the interface, said at least one hermetic chamber being filled with a neutral gas, and said at least one sealing system comprises a pressure measurement device for measuring pressure in the at least one hermetic chamber and a gas injection device for injecting an amount of neutral gas into the at least one hermetic chamber depending on a value provided by the pressure measurement device.