North Korea may have restarted one of its nuclear reactors, satellite pictures taken earlier this year suggest.
According to the Institute for Science and International Security, images of the Yongbyon plant show patterns of melting snow indicating new activity.
Yongbyon’s reactor was shut down in 2007 but was restarted in 2013.
Six-nation talks aimed at ending North Korea’s nuclear program have been stalled since early 2009.
The think-tank’s report says that its assessment in late 2014 was that the reactor at Yongbyon, in the country’s west, had been “shut down or partially shut down” but more recent images suggested the plant “may be operating at low power or intermittently”.
As well as the patterns of melting snow, the satellite photos are also said to capture a stream of warm water coming out of the reactor’s discharge pipeline and steam rising off the turbine.
In 2008, North Korea walked away from six-party talks with South Korea, the US, China, Japan and Russia on its denuclearization.
The other countries have since tried to persuade North Korea to return to the negotiating table.
Earlier this year North Korea offered to stop nuclear tests if the US stopped holding military drills with Seoul, but the offer was rejected.
North Korea has conducted three nuclear tests, in 2006, 2009 and 2013.
North Korea is reactivating facilities at its moth-balled Yongbyon nuclear reactor, a US think-tank says.
Start-up could be one to two months away, it said, but there was uncertainty over the availability of fuel rods to power the reactor.
Pyongyang vowed to restart the reactor, which makes weapons-grade plutonium, in April amid severe regional tensions.
The Yongbyon reactor was shut down in July 2007 as part of a disarmament-for-aid deal.
The cooling tower at the facility was later destroyed, but then the disarmament deal stalled.
North Korea’s decision to restart followed its third nuclear test on February 12, which led to expanded UN sanctions.
The information came from the 38 North website, which is part of the US-Korea Institute at Johns Hopkins University in the US.
Its report said that recent satellite imagery showed that North Korea had “essentially finished repairing the cooling system necessary to restart and operate the reactor”.
North Korea is reactivating facilities at its moth-balled Yongbyon nuclear reactor
The cooling tower that was destroyed had not been repaired, but instead a secondary cooling system had been employed. Work was also ongoing at a spent fuel facility, it said.
Piles of construction materials were visible at the site and what could be a new drainage ditch for water from the reactor building was being dug, it said.
The reactor “may be one to two months from start-up. However, the availability of fresh fuel rods to power the reactor – a key factor that will determine when the North will restart the facility – remains unclear,” it said.
Once operational, the reactor could produce “approximately six kilograms of plutonium per year that can be used for manufacturing nuclear weapons”, it added.
North Korea has conducted three nuclear tests since 2006. Analysts believe the first two tests used plutonium as the fissile material, but it is not known whether the third used plutonium or uranium.
While North Korea has depleted its stocks of “reactor-grade” plutonium needed to make the weapons-grade variety, it has plentiful reserves of uranium ore. It also has a uranium enrichment facility at Yongbyon which a US scientist said could be converted to produce highly enriched uranium bomb fuel.
After UN sanctions were expanded following the most recent nuclear test, in February, North Korea issued multiple threats against US and regional interests, vowed to reactivate Yongbyon and cut both official communications and key business ties with South Korea.
Operations at the jointly-run inter-Korean Kaesong industrial zone remain suspended – the first such stoppage since the project began.
But the threats have diminished in recent weeks and last month, North Korea sent a top envoy to Beijing – its first such move since its nuclear test.
Later this week, the US and Chinese presidents meet in California for their first summit, with North Korea likely to be high on the agenda.
Japan has decided to switch off its last working nuclear reactor, as part of the safety drive since the March 2011 tsunami triggered a meltdown at the Fukushima plant.
The third reactor at the Tomari plant, in Hokkaido prefecture, is shutting down for routine maintenance.
The move leaves Japan without energy from atomic power for the first time for more than 40 years.
Until last year, Japan got 30% of its power from nuclear energy.
Hundreds of people marched through Tokyo, waving banners to celebrate what they hope will be the end of nuclear power in Japan.
Since the Fukushima disaster, all Japan’s reactors have been shut down for routine maintenance. They must withstand tests against earthquakes and tsunamis, and local authorities must give their consent in order for plants to restart.
So far, none have.
The third reactor at the Tomari plant, in Hokkaido prefecture, is shutting down for routine maintenance
Two reactors at the Ohi plant in western Japan have been declared safe. The government says they should be restarted to combat looming shortages.
However, regional authorities would still have to give their approval.
Ministers have warned Japan faces a summer of power shortages.
The government could force the issue, but so far has been reluctant to move against public opinion.
Organizers of the anti-nuclear march in the capital estimated turnout at 5,500.
Demonstrators carried banners shaped as giant fish. The “Koinobori” banners, traditionally the symbol of Children’s Day, have been adopted by the anti-nuclear movement.
“There are so many nuclear plants, but not a single one will be up and running today, and that’s because of our efforts,” campaigner Masashi Ishikawa told the crowd.
Engineers began the process of shutting down the final Tomari reactor, inserting control rods to bring the fission process to an end.
All operations at the plant will have stopped by 14:00 GMT, a spokesman told Associated Press.
Japan will then be without nuclear power for the first time since 1970.
Businesses have warned of severe consequences for manufacturing if no nuclear plants are allowed to re-start.
In the meantime, Japan has increased its fossil fuel imports, with electricity companies pressing old power plants into service.
If the country can get through the steamy summer without blackouts, calls to make the nuclear shutdown permanent will get louder.
The six-reactor Fukushima Daiichi nuclear plant was badly damaged by the March 2011 earthquake and tsunami.
Blasts occurred at four of the reactors after the cooling systems went offline, triggering radiation leaks and forcing the evacuation of thousands of people.
A 20 km (12 miles) exclusion zone remains in place around the plant.