Ceramic installations

In combination with a gas-cooled high temperature reactor having discrete absorber material elements for shutting down said reactor and a core filled with spherical fuel elements,

• a graphite side reflector comprising at least one nose-shaped projection protruding radially into the reactor core from said graphite side reflector,
• said at least one nose-shaped projection comprising:
• (a) at least one vertically disposed cavity adapted to receive said discrete absorber material elements, (b) a vertically disposed, continuous opening which forms a passageway for communication between said cavity and the core of the reactor, and (c) blocking means cooperatively engaged with said projection and positioned within said continuous opening for preventing direct communication between said cavity and the core of the reactor,
• said opening having a maximum width adjacent said cavity which is less than the minimum dimension of said discrete absorber elements in order to prevent passage of said elements into said continuous opening for said cavity.