On-line refueling of nuclear power plants

Figure 1. The face of a CANDU reactor core, with hundreds of pressure tubes that are able to be refueled during operation.[1]

On-line refueling is a technique used in certain nuclear reactors, which allows nuclear fuel to be removed or added during operation. This is important, since most nuclear power plants like the common pressurized water reactor have to shutdown in order to refuel. This increases the time that a power plant is active and available, which means the capacity factor may be fairly high. The longest running nuclear reactor was a CANDU reactor, Pickering 7, that used on-line refueling. It ran for 894 days without shutdown.[2]

The reduced time that a power plant must be shut down is just one of the benefits of using on-line refueling. The rearrangement of fuel with a reactor core can balance the thermal load, increase fuel use and reduce nuclear waste. It is also suitable for the production of nuclear weapons, as the needed fuel for weapon-grade isotopes can be extracted without having to shut the reactor down.

Reactors that permit on-line refueling include, but are not limited to:


All of the above reactors are cooled in pressurized channels, rather than in pressure vessels. This characteristic is what allows for on-line refueling. Gas-cooled reactors such as the Magnox reactor can also be refueled while operating.

The video below shows the refueling mechanism of the proposed Advanced CANDU Reactor, which has never been built. Its process is very similar to the CANDU-6 reactor refueling which is currently used, and demonstrates the technological feat of such a process.

For Further Reading

References

  1. Introduction to CANDU 6- Part 3 Moderator, HTS, Heavy Water, by D.A. Meneley and Y.Q. Ruan. [Online], Available: https://canteach.candu.org/Image%20Library1/Forms/DispForm.aspx?ID=285&RootFolder=/Image%20Library1/19980103-Intro_to_CANDU6_China
  2. CANDU Owners Group. (June 25 2015). CANDU Reactors [Online], Available: http://www.candu.org/candu_reactors.html
  3. Bruce Power. (June 25 2015). How is a CANDU reactor refueled? [Online], Available: http://www.brucepower.com/4420/master-faqs/nuclear-energy-faqs/how-is-a-candu-reactor-refueled/