This is the reactor lid for Unit 2, Chernobyl Nuclear Power Plant. Metal blocks protect the upper penetrations for some 2000 channels through the graphite moderator of the reactor. The colored lids house electric control-rod drive mechanisms and in-core instruments, while the unpainted ones cover fuel channels and one special channel used to irradiate silicon. To the side of the reactor lid are smaller covers for the upper steamwater pipelines and the lateral ionization chambers.
Reactor lid for Unit 2, Chernobyl Nuclear Power Plant.