America’s dangerous nuclear headache: old plutonium with nowhere to go

The U.S. Energy Department's Savannah River Site, with the unfinished building which was meant to make plutonium safe but now may not be finished until 2048, is seen in this aerial image, taken near Aiken, South Carolina, U. S. January 31, 2018. High Flyer © 2018/Handout via REUTERS

By Scot J. Paltrow

AMARILLO, Texas (Reuters) – In a sprawling plant near Amarillo, Texas, rows of workers perform by hand one of the most dangerous jobs in American industry. Contract workers at the U.S. Department of Energy’s Pantex facility gingerly remove the plutonium cores from retired nuclear warheads.

Although many safety rules are in place, a slip of the hand could mean disaster.

In Energy Department facilities around the country, there are 54 metric tons of surplus plutonium. Pantex, the plant near Amarillo, holds so much plutonium that it has exceeded the 20,000 cores, called “pits,” regulations allow it to hold in its temporary storage facility. There are enough cores there to cause thousands of megatons of nuclear explosions. More are added each day.

The delicate, potentially deadly dismantling of nuclear warheads at Pantex, while little noticed, has grown increasingly urgent to keep the United States from exceeding a limit of 1,550 warheads permitted under a 2010 treaty with Russia. The United States wants to dismantle older warheads so that it can substitute some of them with newer, more lethal weapons. Russia, too, is building new, dangerous weapons.

The United States has a vast amount of deadly plutonium, which terrorists would love to get their hands on. Under another agreement, Washington and Moscow each are required to render unusable for weapons 34 metric tons of plutonium. The purpose is twofold: keep the material out of the hands of bad guys, and eliminate the possibility of the two countries themselves using it again for weapons. An Energy Department website says the two countries combined have 68 metric tons designated for destruction – enough to make 17,000 nuclear weapons. But the United States has no permanent plan for what to do with its share.

Plutonium must be made permanently inaccessible because it has a radioactive half-life of 24,000 years.

“A MUCH MORE DANGEROUS SITUATION”

Edwin Lyman, a physicist at the Union of Concerned Scientists, a science advocacy group based in Washington, says solving the problem of plutonium storage is urgent. In an increasingly unstable world, with terrorism, heightened international tensions and non-nuclear countries coveting the bomb, he says, the risk is that this metal of mass annihilation will be used again. William Potter, director of the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies, told Reuters: “We are in a much more dangerous situation today than we were in the Cold War.”

Washington has not even begun to take the steps needed to acquire additional space for burying plutonium more than 2,000 feet below ground – the depth considered safe. Much of America’s plutonium currently is stored in a building at the Savannah River Site in South Carolina – like Pantex, an Energy Department site. Savannah River used to house a reactor. Local opponents of the storage, such as Tom Clements, director of SRS Watch, contend the facility was never built for holding plutonium and say there is a risk of leakage and accidents in which large amounts of radioactivity are released.

The Energy Department has a small experimental storage site underground in New Mexico. The department controls the radioactive materials – plutonium, uranium and tritium – used in America’s nuclear weapons and in the reactors of nuclear-powered aircraft carriers and submarines. In a Senate hearing in June 2017, Energy Secretary Rick Perry said the Energy Department has been in talks with New Mexico officials to enlarge the site. Environmental groups there have strongly opposed expansion.

Under an agreement with Russia, the United States was to convert 34 metric tons of plutonium into fuel for civilian reactors that generate electricity. The fuel is known as MOX, for “mixed oxide fuel.” Plutonium and uranium are converted into chemical compounds called oxides, and mixed together in fuel rods for civilian nuclear power plants. The two metals are converted into oxides because these can’t cause nuclear explosions. But the U.S. effort has run into severe delays and cost overruns.

The alternative method is known as dilute-and-dispose. It involves blending plutonium with an inert material and storing it in casks. The casks, however, are projected to last only 50 years before beginning to leak, and so would need to be buried permanently deep underground.

THE MOX MESS

President Donald Trump has sided with the Energy Department in wanting to kill the MOX project because of the extreme cost overruns and delays. The Energy Department, beginning in the Obama administration, favored closing down the MOX project for the same reason, but Congress overruled it. The federal budget adopted in February, however, specifies a means for ending the project, if a study shows that dilute-and-dispose would be at least 50 percent cheaper than making MOX.

The National Nuclear Security Administration, the part of the Energy Department that oversees the nuclear sites and materials, favors switching to the dilute-and-dispose method. In recent testimony before a House of Representatives subcommittee, Lisa Gordon-Hagerty, the new NNSA administrator, said that method would “cost billions less” than completing the MOX plant.

Plutonium is a versatile nuclear bomb material. Terrorists would need only 11 kilograms or less to make a bomb, Lyman says.

Its ordinarily limited radioactivity makes plutonium safe for terrorists or other thieves to transport with little risk of radiation injury. It goes undetected by most sensors. It radiates alpha particles, relatively large on an atomic scale, which means the thin glass of a test tube, the leather of a briefcase, or even air or skin stop them. The danger from handling small amounts is inhaling plutonium dust. In that case, the dust spreads from the lungs throughout the body, causing multiple kinds of cancer.

The federal government now has no solution in sight to dispose of the plutonium permanently. Its one effort to make it unusable for bombs has turned into what the White House and Energy Department say is a costly failure. The MOX project, at the Energy Department’s Savannah River Site in South Carolina, has been kept on life support by Congress thanks to the influence of South Carolina Senator Lindsey Graham and other lawmakers. The MOX plant employs about 2,000 people in Graham’s state.

Graham and other Congressional backers say MOX is the best way to keep plutonium out of the hands of terrorists. They note too that the pact with Russia requires the United States to use MOX as the method for disposal.

A spokeswoman for Graham declined to comment on his behalf but sent a link to a YouTube video of a Senate hearing in March. In the hearing, Graham, referring to steps already taken to limit work on the MOX plant, said: “What I think we’ve done is ended the biggest non-proliferation program in the world, and I’m going to try and fix that.”

Today’s plutonium glut mainly is a legacy of the Cold War. The quantities now seem surreal. By 1967 the U.S. nuclear arsenal reached its apex, with 37,000 warheads. The Soviet Union’s peak came in the 1970s, with approximately 45,000. These were enough to destroy life on Earth thousands of times over.

A RADIOACTIVE PEACE DIVIDEND

Amid the terror and aggressiveness then of government and military leaders on both sides, little or no thought was given what to do with the warheads should the risk of mass annihilation ebb.

Daniel Ellsberg, best known for leaking in 1971 the Pentagon Papers about the Vietnam war, in the early 1960s was an adviser to the Air Force and White House on nuclear policy. He recently published a book detailing and criticizing the nuclear policy debates and decisions of that era. In a phone interview, he said disposal of weapons was never considered at the time.

“I don’t think one person gave one moment of thought to that,” Ellsberg said. “No one thought that the Cold War would end.”

Treaties that dramatically reduced U.S. and Russian nuclear arsenals were signed soon after the Soviet Union fell. It was then that the magnitude of the problem – disposing of the surplus plutonium – dawned on the two countries.

Scientists proffered ideas, nearly all involving making the plutonium forbiddingly dangerous for malefactors to transport and burying it deep underground.

Instead, under a 2000 treaty, the United States agreed to transform the 34 metric tons of plutonium into MOX, unusable for bombs. Russia agreed to destroy the same quantity using a special type of reactor. But the United States had never before built a MOX plant. No U.S. civilian reactor had ever used MOX as fuel.

This misplaced optimism led to one of the costliest snafus ever in U.S. government construction. Work began in 2007 to build a MOX plant that was to be operational by November 2016. The Energy Department now estimates that, if allowed to proceed, it will not be finished until 2048. In 2007 the Energy Department said the total cost would be $4.8 billion. Now it estimates the cost at more than $17 billion.

Building of the plant began when detailed designs were between 20 percent and 40 percent complete. But once initial construction finished, the contractor, under instructions from the Energy Department, breezed ahead without architectural plans.

Reports from the Union of Concerned Scientists said rooms were built for laboratories and offices where none were needed. Ventilation ducts and electrical wiring were in the wrong places. Plumbing was a maze of misplaced pipes. The contractor later had to rip out much of its work and start over.

The contractor is a consortium of companies I Areva MOX Services. It includes CB&I (formerly Chicago Bridge and Iron), based in the Netherlands, and Areva, which specializes in nuclear-related and alternative power projects, majority owned by the French government.

GIVING IT AWAY

In an e-mailed statement to Reuters, the consortium said it expects to finish the facility. It said “the project is over 70 percent physically complete.”

But Gordon-Hagerty, the National Nuclear Security Administration’s new chief, testified in March before a House Appropriations Subcommittee that it is “nowhere near” 50% complete. Government Accountability Office reports criticized the Energy Department for awarding a “cost plus” contract, which guarantees a profit regardless of how much work is done.

In an emailed response to questions for this article, Lindsey Geisler, a spokesperson for the NNSA, said that in 2011, after the contract had been awarded, “NNSA recognized the need to institute project management reforms.” She said the NNSA established a new office to better oversee contracting and acquisition, and that practices have improved significantly.

Echoing other critics, Frank von Hippel, a Princeton University professor who researches nuclear arms control and policymaking, said weak oversight continues. “The problem at DOE is that the quality of managers, with some exceptions, is quite low,” he said. “Contractors just milk them for money.”

An Energy Department panel reported in 2016 that there is no US market for MOX. To use MOX fuel rods, civilian power plants would have to modify their reactors, requiring lengthy relicensing by the Nuclear Regulatory Commission. The report said the best the Energy Department could hope for was to give the stuff away.

(Edited by Michael Williams)

Tunnel collapses at Washington nuclear waste plant; no radiation released

A 20-foot wide hole over a decommissioned plutonium-handling rail tunnel is shown at the Hanford Nuclear Reservation in Hanford Site, Washington, U.S., May 9, 2017. Courtesy Department of Energy/Handout via REUTERS

By Tom James and Scott DiSavino

(Reuters) – A tunnel partly collapsed on Tuesday at a plutonium-handling facility at the Hanford Nuclear Reservation in Washington state, but there was no indication workers or the public were exposed to radiation, federal officials said.

Workers evacuated or took cover and turned off ventilation systems after damage was discovered in the wall of a transport tunnel about 170 miles (270 km) east of Seattle, officials with the Department of Energy’s Hanford Joint Information Center said.

The damage was more serious than initially reported, and the take-cover order was expanded to cover the entire facility after response crews found a 400-square-foot section of the decommissioned rail tunnel had collapsed, center spokesman Destry Henderson said in a video posted on Facebook.

“The roof had caved in, about a 20-foot section of that tunnel, which is about a hundred feet long,” he said.

“This is purely precautionary. No employees were hurt and there is no indication of a spread of radiological contamination,” Henderson said of the shelter order.

No spent nuclear fuel is stored in the tunnel, Energy Department officials said. Energy Department Secretary Rick Perry has been briefed on the incident.

Tom Carpenter, the executive director with watchdog organization Hanford Challenge who has spoken with workers at the site since the incident, called the tunnel collapse worrisome and said the evacuation was the correct call.

“There is a big hole there and radiation could be beaming out,” he said.

“It’s not clear to me that they know whether particulate radiation has escaped,” Carpenter added. “If there is a cloud of radioactive particulates, then that can have an impact on worker health and the community. It does not take a lot for those particulates to end up in someone’s lung.”

The site is in southeastern Washington on the Columbia River. Operated by the federal government, it was established in the 1940s and manufactured plutonium that was used in the first nuclear bomb as well as other nuclear weapons. It is now being dismantled and cleaned up by the Energy Department.

Mostly decommissioned, Hanford has been a subject of controversy and conflict between state and local authorities, including a lawsuit over worker safety and ongoing cleanup delays. Carpenter called it the most contaminated U.S. site.

Carpenter said he expects total cleanup costs could reach $300 billion to $500 billion.

(Reporting by Tom James in Seattle and Scott DiSavino in New York; Writing by Ben Klayman; Editing by Cynthia Osterman and Lisa Shumaker)

North Korea appears to have restarted plutonium reactor: think tank

North Korea's Scientific center where they may be producing plutonium for nuclear weapons

By David Brunnstrom

WASHINGTON (Reuters) – New commercial satellite imagery indicates North Korea has resumed operation of a reactor at its main nuclear site used to produce plutonium for its nuclear weapons program, a U.S. think tank said on Friday.

Washington’s 38 North North Korea monitoring project said previous analysis from Jan. 18 showed signs that North Korea was preparing to restart the reactor at Yongbyon, having unloaded spent fuel rods for reprocessing to produce additional plutonium for its nuclear weapons stockpile.

“Imagery from January 22 shows a water plume (most probably warm) originating from the cooling water outlet of the reactor, an indication that the reactor is very likely operating,” it said in a report.

It said it was impossible to estimate at what power level the reactor was running, “although it may be considerable.” A 38 North Korea report last week said operations at the reactor had been suspended since late 2015.

North Korea has maintained its nuclear and missile programs in violation of repeated rounds of international sanctions.

News of the apparent reactor restart comes at a time of rising concern about North Korea’s weapons programs, which could present the new administration of U.S. President Donald Trump with its first major crisis.

A report by leading U.S.-based nuclear expert Siegfried Hecker published by 38 North last September estimated North Korea had stockpiles of 32 to 54 kg (70 to 119 pounds) of plutonium, enough for 6 to 8 bombs, and had the capacity to produce 6 kg, or approximately one bomb’s worth, per year.

North Korea also produces highly enriched uranium for atomic bombs and would have sufficient fissile material for approximately 20 bombs by the end of last year, and the capacity to produce seven more a year, that report said.

In a New Year speech, North Korean leader Kim Jong Un said his country was close to test launching an Intercontinental Ballistic Missile (ICBM) and state media has said a launch could come at any time.

Trump’s defense secretary plans to visit Japan and South Korea next week and shared concerns about North Korea are expected to top his agenda.

(Reporting by David Brunnstrom; Editing by James Dalgleish)

Russia’s Putin suspends plutonium cleanup accord with U.S. because of ‘unfriendly’ acts

Putin at award ceremony

By Dmitry Solovyov

MOSCOW (Reuters) – Russian President Vladimir Putin on Monday suspended an agreement with the United States for disposal of weapons-grade plutonium because of “unfriendly” acts by Washington, the Kremlin said.

A Kremlin spokesman said Putin had signed a decree suspending the 2010 agreement under which each side committed to destroy tonnes of weapons-grade material because Washington had not been implementing it and because of current tensions in relations.

The two former Cold War adversaries are at loggerheads over a raft of issues including Ukraine, where Russia annexed Crimea in 2014 and supports pro-Moscow separatists, and the conflict in Syria.

The deal, signed in 2000 but which did not come into force until 2010, was being suspended due to “the emergence of a threat to strategic stability and as a result of unfriendly actions by the United States of America towards the Russian Federation”, the preamble to the decree said.

It also said that Washington had failed “to ensure the implementation of its obligations to utilize surplus weapons-grade plutonium”.

The 2010 agreement, signed by Russian Foreign Minister Sergei Lavrov and then-U.S. Secretary of State Hillary Clinton, called on each side to dispose of 34 tonnes of plutonium by burning in nuclear reactors.

Clinton said at the time that that was enough material to make almost 17,000 nuclear weapons. Both sides then viewed the deal as a sign of increased cooperation between the two former adversaries toward a joint goal of nuclear non-proliferation.

“For quite a long time, Russia had been implementing it (the agreement) unilaterally,” Kremlin spokesman Dmitry Peskov told a conference call with journalists on Monday.

“Now, taking into account this tension (in relations) in general … the Russian side considers it impossible for the current state of things to last any longer.”

Ties between Moscow and Washington plunged to freezing point over Crimea and Russian support for separatists in eastern Ukraine after protests in Kiev toppled pro-Russian President Viktor Yanukovich.

Washington led a campaign to impose Western economic sanctions on Russia for its role in the Ukraine crisis.

Relations soured further last year when Russia deployed its warplanes to an air base in Syria to provide support for Syrian President Bashar al-Assad’s troops fighting rebels.

The rift has widened in recent weeks, with Moscow accusing Washington of not delivering on its promise to separate units of moderate Syrian opposition from “terrorists”.

Huge cost overruns have also long been another threat to the project originally estimated at a total of $5.7 billion.

(Reporting by Dmitry Solovyov; Editing by Richard Balmforth)

North Korea ramps up uranium enrichment, enough for six nuclear bombs a year: experts

Kim Jong Un of North Korea

By Jack Kim and James Pearson

SEOUL (Reuters) – North Korea will have enough material for about 20 nuclear bombs by the end of this year, with ramped-up uranium enrichment facilities and an existing stockpile of plutonium, according to new assessments by weapons experts.

The North has evaded a decade of U.N. sanctions to develop the uranium enrichment process, enabling it to run an effectively self-sufficient nuclear program that is capable of producing around six nuclear bombs a year, they said.

The true nuclear capability of the isolated and secretive state is impossible to verify. But after Pyongyang conducted its fifth and most powerful nuclear test last week and, according to South Korea, was preparing for another, it appears to have no shortage of material to test with.

North Korea has an abundance of uranium reserves and has been working covertly for well over a decade on a project to enrich the material to weapons-grade level, the experts say.

That project, believed to have been expanded significantly, is likely the source of up to 150 kilograms (330 pounds) of highly enriched uranium a year, said Siegfried Hecker, a leading expert on the North’s nuclear program.

That quantity is enough for roughly six nuclear bombs, Hecker, who toured the North’s main Yongbyon nuclear facility in 2010, wrote in a report on the 38 North website of Johns Hopkins University in Washington published on Monday.

Added to an estimated 32- to 54 kilogram plutonium stockpile, the North will have sufficient fissile material for about 20 bombs by the end of 2016, Hecker said.

North Korea said its latest test proved it was capable of mounting a nuclear warhead on a medium-range ballistic missile, but its claims to be able to miniaturize a nuclear device have never been independently verified. [nL3N1BL1ND]

Assessments of the North’s plutonium stockpile are generally consistent and believed to be accurate because experts and governments can estimate plutonium production levels from telltale signs of reactor operation in satellite imagery.

South Korean Defence Minister Han Min-koo this year estimated the North’s plutonium stockpile at about 40 kilograms.

But Hecker, a former director of the U.S. Los Alamos National Laboratory, where nuclear weapons have been designed, has called North Korea’s uranium enrichment program “their new nuclear wildcard,” because Western experts do not know how advanced it is.

PAKISTAN CONNECTION

Jeffrey Lewis of the California-based Middlebury Institute of International Studies said North Korea had an unconstrained source of fissile material, both plutonium from the Yongbyon reactor and highly-enriched uranium from at least one and probably two sites.

“The primary constraint on its program is gone,” Lewis said. Weapons-grade plutonium has to be extracted from spent fuel taken out of reactors and then reprocessed, and therefore would be limited in quantity. A uranium enrichment program greatly boosts production of material for weapons.

The known history of the uranium enrichment project dates to 2003, when the North was confronted by the United States with evidence of a clandestine program to build a facility to enrich uranium with the help of Pakistan.

Former Pakistani President Pervez Musharraf said in his memoirs that A.Q. Khan, the father of that country’s nuclear program, transferred two dozen centrifuges to the North and some technical expertise around 1999.

“It was also clear that the suspected Pakistani connection had taken place, as the centrifuge design resembled Pakistan’s P-2 centrifuge,” Hecker said in a report in May.

Hecker reported being shown around a two-story building in the Yongbyon complex in November 2010 that a North Korean engineer said contained 2,000 centrifuges and a control room Hecker called “astonishingly modern.”

By 2009, the North had likely acquired the technology to be able to expand the uranium project indigenously, Joshua Pollack, editor of the U.S.-based Nonproliferation Review, has said.

North Korea has not explicitly admitted to operating the centrifuges to produce weapons-enriched uranium, instead claiming they were intended to generate fuel for a light water reactor it was going to build.

Despite sanctions, by now North Korea is probably largely self-sufficient in operating its nuclear program, although it may still struggle to produce some material and items, Lewis said.

“While we saw this work in Iran, over time countries can adjust to sanctions,” he said.

(Editing by Raju Gopalakrishnan)

North Korea appeared to resume plutonium production this year

File photo of North Korean flag flying on a mast at the Permanent Mission of North Korea in Geneva

VIENNA (Reuters) – North Korea appeared to resume activities this year aimed at producing plutonium, which can be used in the core of an atomic bomb, the U.N. nuclear watchdog has confirmed, though it added that signs of those activities stopped last month.

Pyongyang vowed in 2013 to restart all nuclear facilities, including the main reactor at its Yongbyon site that had been shut down and has been at the heart of its weapons program.

It said last year that Yongbyon was operating and that it was working to improve the “quality and quantity” of its nuclear weapons. It has since carried out what is widely believed to have been its fourth nuclear test.

“From the first quarter of 2016, there were multiple indications consistent with the radiochemical laboratory’s operation,” International Atomic Energy Agency (IAEA) chief Yukiya Amano said in a report to the agency’s annual General Conference, referring to a site used to reprocess plutonium.

“Such indications ceased in early July 2016,” Amano said in the report posted online and dated Friday. Those indications included deliveries of chemical tanks and the operation of a steam plant linked to the lab, the report said.

The IAEA, which has no access to North Korea and mainly monitors its activities by satellite, said last year it had seen signs of a resumption of activity at Yongbyon, including at the main reactor.

There were signs the reactor had been running in the past year, with a pause between October and December, probably to refill it with enough fuel for the next two years, according to the report dated Friday.

Amano said in June that the agency had seen signs of reprocessing, the production of plutonium from spent reactor fuel, at Yongbyon.

Japan’s Kyodo news agency last week quoted North Korea as saying it had resumed plutonium production by reprocessing and had no plans to stop nuclear tests as long as perceived U.S. threats remain.

North Korea’s Atomic Energy Institute, which has jurisdiction over Yongbyon, also told Kyodo it had been producing highly enriched uranium necessary for nuclear arms and power “as scheduled”.

“There were indications consistent with the use of the reported centrifuge enrichment facility,” Amano’s report to the General Conference, which will be held at the end of September, said, adding that construction work had been carried out around the building that houses the facility.

“There were new construction and refurbishment activities on the (Yongbyon) site, which are broadly consistent with (North Korea’s) statement that all the nuclear facilities in Yongbyon have been ‘rearranged, changed or readjusted’,” it added.

(Reporting by Francois Murphy; Editing by Dominic Evans)

North Korea says it has resumed plutonium production: Kyodo

North Korean flag

TOKYO (Reuters) – North Korea says it has resumed plutonium production by reprocessing spent fuel rods and has no plans to stop nuclear tests as long as perceived U.S. threats remain, Japan’s Kyodo news agency reported on Wednesday.

North Korea’s Atomic Energy Institute, which has jurisdiction over its main Yongbyon nuclear facilities, also told Kyodo it had been producing highly enriched uranium necessary for nuclear arms and power “as scheduled”.

“We have reprocessed spent nuclear fuel rods removed from a graphite-moderated reactor,” the institute told Kyodo in a written interview.

The institute did not mention the amount of plutonium or enriched uranium it had produced, Kyodo said.

The U.N. nuclear watchdog, the International Atomic Energy Agency (IAEA), said in June North Korea appeared to have reopened the Yongbyon plant to produce plutonium from spent fuel of a reactor central to its atomic weapons drive.

North Korea vowed in 2013 to restart all nuclear facilities, including the main reactor at its Yongbyon site that had been shut down.

North Korea had said in September that Yongbyon was operating and that it was working to improve the “quality and quantity” of its nuclear weapons.

North Korea conducted its fourth nuclear test in January.

According to Kyodo, the North Korean institute said it had already succeeded in making “lighter and diversifying” nuclear weapons, and that it had no intention of halting nuclear tests.

“Under conditions that the United States constantly threatens us with nuclear weapons, we will not discontinue nuclear tests,” the institute was quoted by Kyodo as saying.

North Korea will also build a 100,000-kilowatt light-water nuclear reactor for experimental use, the institute was quoted as saying, but it did not provide further details.

Little is known about the quantities of weapons-grade uranium or plutonium that North Korea possesses, or its ability to produce either, though plutonium from spent fuel at Yongbyon is widely believed to have been used in its nuclear bombs.

North Korea has come under tightening international pressure over its nuclear weapons program, including tougher U.N. sanctions adopted in March backed by its lone major ally China.

(Reporting by Elaine Lies; Editing by Robert Birsel)

North Korea restarts plutonium production for nuclear bombs

North Korean leader Kim Jong Un visits the construction site of Ryongaksan soap factory in this undated photo released by North Korea's Korean Central News Agency

By Jonathan Landay, David Brunnstrom and Matt Spetalnick

WASHINGTON (Reuters) – North Korea has restarted production of plutonium fuel, a senior U.S. State Department official said on Tuesday, showing that it plans to pursue its nuclear weapons program in defiance of international sanctions.

The U.S. assessment came a day after the U.N. nuclear watchdog said it had “indications” that Pyongyang has reactivated a plant to recover plutonium from spent reactor fuel at Yongbyon, its main nuclear complex.

The latest developments suggest North Korea’s reclusive regime is working to ensure a steady supply of materials for its drive to build warheads, despite tightened international sanctions after its fourth nuclear test in January.

The U.S. official, who spoke on condition of anonymity, said that Washington is worried by the new plutonium reprocessing effort, but he offered no explicit word on any U.S. response.

“Everything in North Korea is a cause for concern,” the official told Reuters.

“They take the spent fuel from the 5 megawatt reactor at Yongbyon and let it cool and then take it to the reprocessing facility, and that’s where they’ve obtained the plutonium for their previous nuclear tests. So they are repeating that process,” the official said. “That’s what they’re doing.”

North Korea, which conducted its fourth nuclear test in January, vowed in 2013 to restart all nuclear facilities, including the main reactor and the smaller plant at Yongbyon, which was shut down in 2007 as part of an international disarmament-for-aid deal that later collapsed.

The International Atomic Energy Agency (IAEA), which has no access to North Korea and mainly monitors its activities by satellite, said last year it had seen signs of a resumption of activity at Yongbyon.

IAEA chief Yukiya Amano told a news conference in Vienna on Monday that there have been indications of renewed plutonium reprocessing activities at Yongbyon. Reprocessing involves extracting plutonium from spent reactor fuel, one route to obtaining bomb fuel other than uranium enrichment.

“I would agree that there are indications,” the U.S. official said.

The official declined to confirm whether this determination was made from satellite imagery or intelligence sources, or to say how much plutonium North Korea could produce by this method.

South Korea’s Unification Ministry spokesman Cheong Joon-hee said Seoul was closely watching movements related to the North’s nuclear facility “with grave concern” but declined to comment directly on plutonium production.

A spokesman for China’s Foreign Ministry said China, North Korea’s lone major ally, has always promoted the denuclearization of the Korean peninsula and a resolution of the issue via talks.

“We hope all parties can work hard together to put the nuclear issue back on the track of dialogue and negotiations,” spokesman Hong Lei told reporters.

SHROUDED IN SECRECY

North Korea announced at a rare congress of its ruling Workers’ Party last month that it would strengthen its defensive nuclear weapons capability.

It had already declared itself “a responsible nuclear weapons state” and disavowed the use of nuclear weapons unless its sovereignty is first infringed by others with nuclear arms.

While North Korea in the past has often obtained key components for its nuclear program from other countries despite international sanctions, there was no sign of any recent outside procurement involved in reactivating its plutonium reprocessing, the U.S. official said.

There is little proven knowledge about the quantities of weapons-grade uranium or plutonium that North Korea possesses, or its ability to produce either, though plutonium from spent fuel at Yongbyon is widely believed to have been used in its nuclear bombs.

South Korean Defense Minister Han Min-koo said last month the North probably had about 40 kg (88 lb) of plutonium. That would be enough to make eight to 10 bombs, according to experts.

Operating the 5 megawatt reactor could yield about 5-6 kg of plutonium a year, they said.

Experts at the U.S.-Korea Institute at Johns Hopkins University’s School of Advanced International Studies in Washington predicted last year that North Korea’s nuclear weapons stockpile could grow to 20, 50 or 100 bombs within five years, from an estimated 10 to 16 weapons at that time.

North Korea has come under tightening international pressure over its nuclear weapons program, including tougher U.N. sanctions adopted in March backed by China, following its most recent nuclear blast and ballistic missile tests.

The website 38 North reported last week, based on commercial satellite imagery, that exhaust plumes had been detected twice in May from the thermal plant at Yongbyon’s Radiochemical Laboratory, the site’s main reprocessing installation.

The Institute for Science and International Security also reported exhaust emissions from a chimney at the plant, which it said was often associated with reprocessing activities there.

(Additional reporting by Jack Kim in Seoul and Ben Blanchard in Beijing; Editing by James Dalgleish and Nick Macfie)

North Korea says to push nuclear program defying UN sanctions

Foreign reporters gather around screens broadcasting address by North Korean leader Kim Jong Un to the Workers' Party of Korea (WPK) congress, at a hotel in central Pyongyang

By James Pearson

PYONGYANG (Reuters) – Secretive North Korea said it will strengthen self-defensive nuclear weapons capability, its KCNA news agency reported on Monday, a decision adopted in defiance of U.N. resolutions at a rare congress of its ruling Workers’ Party.

The congress is the first in 36 years and North Korea granted visas to scores of foreign journalists to coincide with the gathering.

Their movements have been closely monitored and one BBC journalist, not reporting directly on the congress, was expelled along with two colleagues, after a top official said he had “distorted facts and realities” in his coverage.

Young leader Kim Jong Un, who assumed power in 2011 after his father’s sudden death, took on the new title of party chairman on the fourth day of the congress on Monday, media reported.

The promotion – his previous party title was first secretary – had been predicted by analysts who had expected Kim would use the congress to consolidate his power.

North Korea has come under tightening international pressure over its nuclear weapons program, including tougher U.N. sanctions adopted in March backed by lone major ally China, following its most recent nuclear test in January.

The congress’s decision on strengthening the capability of its nuclear weapons formalizes North Korea’s position.

It had already declared itself “a responsible nuclear weapons state” and disavowed the use of nuclear weapons unless its sovereignty is first infringed by others with nuclear arms.

“We will consistently take hold on the strategic line of simultaneously pushing forward the economic construction and the building of nuclear force and boost self-defensive nuclear force both in quality and quantity as long as the imperialists persist in their nuclear threat and arbitrary practices,” KCNA said, citing the congress.

The two Koreas remain in a technical state of war since their 1950-53 conflict ended in a truce, not a peace treaty. North Korea regularly threatens the South and its major ally, the United States, which it accuses of planning a nuclear attack.

Since the latest round of U.N. resolutions, North Korea has pressed ahead with its nuclear and missile development, and said it had succeeded in miniaturizing a nuclear warhead and launching a submarine-based ballistic missile.

RIVAL KOREAS

South Korea condemned the North’s claim to be a nuclear weapons state, saying it would continue to exert pressure on Pyongyang until it abandons its nuclear ambitions.

North Korea is believed by western experts to have about 40 kg of plutonium, enough to build eight to 12 nuclear weapons.

On the weekend, Kim took a conciliatory position on ties with the South, saying military talks were needed to discuss ways to ease tension.

South Korea rejected the proposal as meaningless.

“We have not given up on dialogue,” South Korean Unification Ministry spokesman Cheong Joon-hee told a briefing. “But it is only when the North shows sincerity about decentralization that genuine dialogue is possible.”

The unusually large group of 128 foreign media members in Pyongyang for the congress, which opened on Friday, had not been given any access to the proceedings until Monday afternoon, when a group of about 30 of them were let in to the April 25 House of Culture for several minutes after nearly three hours of security checks.

There, Kim entered and was received by a wildly cheering audience of delegates, according to reporters who got in.

A closing date has not been made public but South Korea officials said earlier they expected the congress to last four or five days.

The expulsion of BBC journalist Rupert Wingfield-Hayes grabbed headlines in foreign media on Monday. He had been in the country ahead of the congress to cover the visit of a group of Nobel laureates.

Earlier on Monday, visiting media were taken to a textile factory named after Kim Jong Suk, the wife of state founder Kim Il Sung and the grandmother of the current leader. They have been taken to a string of show-case sites including a maternity hospital, electric cable factory and children’s centre.

(Additional reporting by Jack Kim and Ju-min Park in Seoul; Editing by Tony Munroe and Robert Birsel)