Component part of some research reactors for generation of thermal neutrons for experiments. The column consists of a large moderatorMaterial used to "decelerate" fast neutrons to low energies,... accumulation (often graphite) in addition to the corePart of the nuclear reactor where the fission chain reaction... or the reflectorMaterial layer immediately around the core of a nuclear reac... of the reactorSystem used to initiate, maintain and control a fission chai.... Neutrons exiting the reactorSystem used to initiate, maintain and control a fission chai... enter the thermal column where they decelerated. The proportion of thermal neutrons in the overall neutronUncharged elementary particle with a mass of 1.67492716 ·10... spectrum is therefore considerably increased.