Part 2 of 3 Parts (Please read Part 1 first)
PHWRs and CANDUs are well established small and medium reactors. All of Canada’s twenty commercial power reactors are the CANDU design. Argentina, China, India, South Korea, Pakistan, and Romania also have CANDU reactors. India has eighteen PHWRs that are based on the CANDU design. Altogether, the CANDU and PHWR reactors account for about ten percent of global commercial power reactors.
Currently there are about thirty countries considering, planning or starting nuclear programs. An additional twenty countries which are mostly developing nations have expressed interest in launching a national nuclear program in the future. Many consider CANDU/PHWR reactors an optimal choice for developing nations provided that they can be supplied with the right fuel.
CANDU/PHWR reactors usually burn natural uranium which is about seven tenths of a percent U-235. They need a more efficient moderator. The moderator in a reactor slows or moderates the speed of neutrons so that they hit the next nuclei at the right speed to fission them. In this case, this type of reactor utilizes heavy water (D2O) as a moderator.
The ANEEL fuel has a very high fuel burn-up rate of about fifty five thousand megawatt-day per ton of fuel (MWd/T) as compared to the natural uranium fuel used in the current fleet of CANDUs/PHWRs which has a burn-up rate of around seven thousand MWd/T. There are several important facts that follow from this.
When fuels have a higher burn-up rate that means that the fuel stays in the reactor longer and the operators get more energy out of the same amount of fuel. Also, a longer burn-up time means that more neutrons breed in during the fuel cycle. This includes plutonium-240, 241 and 242 which makes the spent fuel very expensive to convert into a form suitable for making nuclear weapons. This results in a serious reduction of nuclear proliferation risk.
In addition, the higher fuel burn-up rate of ANEEL will reduce the amount of nuclear waste by up to eighty percent. Considering that disposal of nuclear waste is a major global problem for nuclear power, reducing the quantity of spent nuclear fuel is a clear and important benefit. It also makes much less plutonium because more of the Pu is burned to make energy while making the spent fuel more proliferation resistance. Less spent fuel means less refueling, lower cost, reduced fuel handling and less waste volume to dispose of.
Opening a reactor to refuel poses risks for the plant workers and, often, some radioactive materials may be released into the atmosphere. Another benefit of the use of CANDU/PHWR reactors is that they do not have to be shut down in order to refuel. This means that they can be fueled while operating at full power. The Kaiga Unit-1 Indian PHWR reactor set a record of nine hundred and sixty two days of continuous operation. The Darlington Unit 1 CANDU reactor in Canada set a record of nine hundred and sixty-three days of uninterrupted operation.
Please read Part 3 next