Atomic Energy of Canada (AECL) is pursuing the market for plants with a rating of 600MWe and less, slightly enriched instead of natural uranium fuel and light-water coolant. Outgoing CEO R Allen Kilpatrick said that during the 1990s the company believed that marketing Candu-9 was “the way to go”, but now it is not relying on the 1000MWe PHWR because smaller units offer more flexibility. “People promoting the pebble-bed reactor are saying the same thing,” said Kilpatrick.

David Torgerson, AECL vice-president for research and product development, said that the company’s attempt to capitalise on the flexibility of the Candu in a wide range of power ratings and improve its economy would optimise the fuel channel, “since that is the building block around which the Candu reactor is designed.” The company aims to operate the channels at high power and smooth out the power distribution throughout the reactor core. This will not affect safety, said Torgerson, because of the progress made in materials science. He added that the next generation of fuel channels would be thicker, and that outlet temperatures would be increased from 310°C to 330°C. “We’re planning on seeing an increase in thermal efficiency of up to 36%,” he said.

Thermal transfer efficiency would be boosted by the use of Canflex heavy water fuel, which lowers the temperature of the fuel by 20% for a given power level.

AECL is also experimenting with eliminating the Candu’s requirement for heavy water as a coolant, as the use of light water together with slightly enriched uranium (SEU) will cut generation costs. The company estimates that SEU could reduce fuel costs by two thirds.