Primary coolant system
Materials of the Heavy Water Systems of CANDU Reactors

A schematic diagram of the two loops of the primary heat transport system (PHTS) of a CANDU-6 reactor is shown in figure  3 . Each loop is in a figure-of-eight configuration, and the circuits are illustrated by four of the 380 fuel channels in the core. A fuel channel comprises a pressure tube with an end fitting at each end connected by a feeder pipe to a header and thence to a steam generator. The D ₂ O coolant is heated from 265 °C to 310 °C as it passes in one direction over twelve fuel bundles in a pressure tube and has typically up to 6 % steam quality from nucleate...