Click on the alphabetic index to display terms beginning with the corresponding letter or search for a term below.


(in a CANDU reactor) a cylindrical reactor vessel which contains the heavy water moderator. It is penetrated from end to end by hundreds of calandria tubes which accommodate the pressure tubes containing the fuel and coolant.


CANadian Deuterium Uranium reactor, moderated and cooled by heavy water (except for the ACR design, which is cooled by light water). These are the most common PHWRs (cf heavy water reactor).


A cylinder spinning at high speed to physically separate gas components of slightly different mass, e.g. uranium hexafluoride with U-235 and U-238 atoms.

Chain reaction

A reaction that stimulates its own repetition, in particular where the neutrons originating from nuclear fission cause an ongoing series of fission reactions.


The metal tubes containing oxide fuel pellets (cf zircaloy).

Control rods

Devices to absorb neutrons so that the chain reaction in a reactor core may be slowed or stopped by inserting them further, or accelerated by withdrawing them.


Chemical process turning U3O8 into UF6 preparatory to enrichment.


The liquid or gas used to transfer heat from the reactor core to the steam generators or directly to the turbines.


The central part of a nuclear reactor containing the fuel elements and any moderator.

Critical mass

The smallest mass of fissile material that will support a self-sustaining chain reaction under specified conditions.


Condition of being able to sustain a nuclear chain reaction.

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