Page last updated at 08:17 GMT, Tuesday, 14 April 2009 09:17 UK

Satellite view of N Korea nuclear site

North Korea says it will restore its main nuclear reactor at Yongbyon to full working order, in response to UN criticism of its recent rocket launch.

The reactor was closed in July 2007 under a landmark international deal which promised Pyongyang aid and diplomatic concessions if it dismantled its nuclear facilities.

The closure of Yongbyon had been seen as a major breakthrough after years of tricky negotiations over North Korea's nuclear programme.

Explore the Yongbyon facility using the links on the image below.

5MW(e) Reactor50MW(e) ReactorRadiochemical LaboratoryFuel Fabrication Plant

5MW(e) reactor at Yongbyon ((Satellite image from 2006)

Construction of the gas-graphite reactor began in 1980. It is believed to have been made operational in 1986-1987.

The five megawatt reactor was used to produce electricity and heat for the town of Yongbyon - especially in 2004 when heavy oil supplies to the region were cut off.

It is also believed to have produced most of North Korea's plutonium stock.

A report by the non-partisan US-based Institute for Science and International Security (ISIS) says that before 2003, North Korea had an estimated total stock of roughly 28-39 kg of plutonium.

North Korea now has a total estimated plutonium stock of between 46kg and 64kg, of which about 28-50 kg is estimated to be in separated form and usable in nuclear weapons, ISIS reports.

Before Yongbyon was shut down, international observers tried to determine when the reactor was in use by watching for satellite images showing steam plumes from the cooling tower.

That cooling tower was destroyed in June 2008 as a symbolic gesture of commitment to talks on ending the nuclear programme.

Radiochemical Laboratory (Satellite image from 2006)

Work on this laboratory was started in 1986 and completed in 1990. The reprocessing facility separated weapons-grade plutonium-239 from the reactor's spent fuel, says think-tank GlobalSecurity.

In 2003, 8,000 spent fuel rods were reprocessed in the Radiochemical Laboratory, according to a report by US nuclear scientist Siegfried Hecker, who visited the facility as part of a US delegation in 2004.

He said the authorities claimed that the reprocessing capacity of the facility under normal operating conditions was 110 tonnes of spent uranium fuel per year.

Mr Hecker said the facility was no longer operating at the time of his visit, adding that everything had been cleaned up and there was no radiation hazard.

50MW(e) reactor (Satellite image from 2006)

Work on the 50MW reactor is believed to have started in 1984-1985, but was stopped in 1994, supposedly within a year of completion. Work is believed to have resumed in 2005 but has since stopped.

If it had been completed, the reactor could have increased North Korea's plutonium production by 10 times, according to the Institute for Science and International Security (ISIS). IAEA inspectors confirmed in July 2007 that the unfinished facility had also been shut down.

Fuel Fabrication Plant (Satellite image from 2006)

The complex is believed to have produced enough fuel for the initial loading of the core for the 50MW reactor, which was still under construction before the shutdown in July 2007.

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