After 45 years of operation, the reactor one was shut down in February 2012, reported BBC.

As part of defueling, hazardous gases, chemicals and spent fuel are removed from the reactor and the fuel elements are transferred to cooling ponds, while the entire process can take years to complete.

In 2012, defueling was carried out on reactor two, while Oldbury’s first reactor was shut down in June 2011 and is now over 16% complete.

The Nuclear Decommission Authority has earlier described defueling as a "complex, lengthy process".

The authority said that spent fuel contained 99% of a site’s radioactive inventory.

Oldbury site director Mike Heaton was quoted by the publication as saying, "There are over 25,000 elements in the reactor, so this is a major step forward towards decommissioning the site, but there is a long way to go."

The Oldbury nuclear power station is located on the south bank of the River Severn near the village of Oldbury-on-Severn in South Gloucestershire, England. It has two reactors each with a generating capacity of 217MW.