Fuel transfer to keep Wylfa 1 running

09 August 2012

The UK's last operating Magnox reactor, Wylfa 1, will be able to continue generating electricity until September 2014 after regulatory approval was given for the transfer of partially-used fuel from its shut down sister unit.

Wylfa pile cap (Magnox)
Fuel will be transferred between the two units using Wylfa's refuelling machine (Image: Magnox)

The two units at Wylfa were both scheduled to shut down at the end of 2012, but Magnox Ltd - which manages and operates the Wylfa plant on behalf of owner the Nuclear Decommissioning Authority (NDA) - decided to shut down unit 2 in April so that unit 1 could continue operating until 2014 in order to fully utilize existing stocks of fuel, which is no longer being manufactured.

The plant received its final delivery of fresh Magnox fuel in December 2011 and Magnox Ltd requested regulatory approval to transfer partially used fuel from unit 2 to unit 1. This is relatively simple task thanks to a shared service floor and refuelling machine.

Although the inter-reactor fuel transfer (IRX) process has already been used at the now shut down Oldbury Magnox plant, it is the first time it will be carried out at Wylfa. Magnox Ltd was therefore required to conduct a review of its safety case. It identified a number of changes to its operating rules needed to ensure that the process could be implemented safely at Wylfa.

Magnox Ltd intends to take some of the partially-used fuel out of unit 2 and place it within the core of unit 1. However, as the Wylfa plant has limited capacity for storing used fuel, fully-used fuel from unit 1 will be temporarily stored in the core of unit 2 before it is later transferred offsite for reprocessing.

The Office for Nuclear Regulation (ONR), following several independent reviews, has now given its approval for the IRX process to be implemented at Wylfa. However, in order to ensure that the used fuel from unit 1 is sufficiently cooled before being transferred to the other unit, Magnox Ltd will be required to hold this fuel in a cooled storage facility for at least 60 days. The regulator made this requirement as, "In some fault conditions, there may not be sufficient cooling in the shut down reactor to keep fuel which has been recently removed from the operating reactor sufficiently cool."

According to Magnox Ltd, "The additional income from Wylfa and Oldbury, which closed in February after generating electricity for four years longer than originally scheduled, is so far estimated to be worth around £600 million ($940 million)."

Energy minister Charles Hendry said, "Wylfa has been generating electricity for homes across the country for over four decades now. This move, based on comprehensive safety assessments, is good for our energy security. It will enable Wylfa to continue generating for two more years, safeguarding jobs and bringing in additional commercial income, which will help contribute to the costs of our nuclear decommissioning program management of the nuclear legacy."

Magnox reactors are graphite-moderated, gas-cooled and use all-metal, un-enriched uranium fuel. They can trace their roots back to the earliest days of nuclear technology: the world's first commercial nuclear power station, Calder Hall, was a Magnox reactor. The design takes its name from the magnesium alloy cladding used on the uranium fuel. The UK built a fleet of 26 Magnox reactors of which Wylfa's two 490 MWe units, commissioned in 1971, were the last and the biggest.

Researched and written
by World Nuclear News