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North Korea's nuclear programme: How advanced is it? North Korea's nuclear programme: How advanced is it?
(7 months later)
North Korea's nuclear programme remains a source of deep concern for the international community. Despite multiple efforts to curtail it, Pyongyang says it has conducted four nuclear tests and there are indications it is developing long-range missile technology. North Korea's nuclear programme remains a source of deep concern for the international community. Despite multiple efforts to curtail it, Pyongyang says it has conducted five nuclear tests, with the fifth supposedly its "most powerful" test to date.
Has North Korea got the bomb?Has North Korea got the bomb?
Technically yes, but not the means to deliver it via a missile - yet. Technically yes - North Korea has conducted several tests with nuclear bombs.
North Korea said it conducted four successful nuclear tests in 2006, 2009, 2013 and 2016. However, in order to launch a nuclear attack on its neighbours, it needs to be able to make a nuclear warhead small enough to fit on to a missile.
Analysts believe the first two tests used plutonium, but whether the North used plutonium or uranium as the starting material for the 2013 test is unclear. North Korea claims it has successfully "miniaturised" nuclear warheads - but this has never been independently verified, and some experts have cast doubt on the claims.
While these three were atomic bomb tests, North Korea said its test in January 2016 was of a more powerful hydrogen bomb. Again, the starting material is unclear and experts cast doubt given the size of the explosion registered. How powerful are North Korea's nuclear bombs?
North Korea says it has conducted five successful nuclear tests: in 2006, 2009, 2013 and in January and September 2016.
The yield of the bombs appears to have increased.
September 2016's test has indicated a device with an explosive yield of between 10 and 30 kilotonnes - which, if confirmed, would make it the North's strongest nuclear test ever.
The other big question is whether the devices being tested are atomic bombs, or hydrogen bombs, which are more powerful.
H-bombs use fusion - the merging of atoms - to unleash massive amounts of energy, whereas atomic bombs use nuclear fission, or the splitting of atoms.H-bombs use fusion - the merging of atoms - to unleash massive amounts of energy, whereas atomic bombs use nuclear fission, or the splitting of atoms.
Shortly after that test Pyongyang launched a satellite, a launch widely seen as a test of long-range missile technology. The 2006, 2009 and 2013 tests were all atomic bomb tests.
The US said in February it had intelligence indicating that North Korea could soon have enough plutonium for nuclear weapons and was taking steps in making a long-range missile system. North Korea claimed that its January 2016 test was of a hydrogen bomb.
What do we know about the North's nuclear programme? But experts cast doubt on the claim given the size of the explosion registered.
The Yongbyon site is thought to be its main nuclear facility. The North has pledged several times to halt operations there and even destroyed the cooling tower in 2008 as part of a disarmament-for-aid deal. Details of the fifth test have not yet been released.
However, the US never believed Pyongyang was fully disclosing all of its nuclear facilities - a suspicion bolstered when North Korea unveiled a uranium enrichment facility at Yongbyon, purportedly for electricity generation, to US scientist Siegfried Hecker in 2010. Plutonium or uranium?
In March 2013, after a war of words with the US and with new UN sanctions over the North's third nuclear test, Pyongyang vowed to restart all facilities at Yongbyon. Another question is what the starting material for the nuclear tests is.
In 2015 a US think tank said satellite pictures suggested the reactor at Yongbyon may have been restarted. Then in September, state media announced that "normal operation" had started at the production plant. Analysts believe the first two tests used plutonium, but whether the North used plutonium or uranium as the starting material for the 2013 test is unclear.
The January 2016 test was said to have been carried out at the Punggye-ri site. A successful uranium test would mark a significant leap forward in North Korea's nuclear programme. The North's plutonium stocks are finite, but if it could enrich uranium it could build up a nuclear stockpile.
Both the US and South Korea have also said that they believed the North had additional sites linked to a uranium-enrichment programme. The country has plentiful reserves of uranium ore. Plutonium enrichment also has to happen in large, easy-to-spot facilities, whereas uranium enrichment can more easily be carried out in secrecy.
What else do we know about the North's nuclear programme?
The Yongbyon site is thought to be its main nuclear facility, while the January and September 2016 tests were said to have been carried out at the Punggye-ri site.
The Yongbyon site processes spent fuel from power stations and has been the source of plutonium for North Korea's nuclear weapons programme.
Both the US and South Korea have also said that they believe the North has additional sites linked to a uranium-enrichment programme. The country has plentiful reserves of uranium ore.
What has the global community done about this?What has the global community done about this?
The US, Russia, China, Japan and South Korea have engaged the North in multiple rounds of negotiations known as six-party talks, but none of this has ultimately deterred Pyongyang. The US, Russia, China, Japan and South Korea engaged the North in multiple rounds of negotiations known as six-party talks.
In 2005, North Korea agreed to a landmark deal to give up its nuclear ambitions in return for economic aid and political concessions. But implementing it proved difficult and talks stalled in 2009. There were various attempts to agree disarmament deals with North Korea, but none of this has ultimately deterred Pyongyang.
Then in 2012, North Korea suddenly announced it would suspend nuclear activities and place a moratorium on missile tests in exchange for US food aid,. But this came to nothing when Pyongyang tried to launch a rocket in April that year. In 2005, North Korea agreed to a landmark deal to give up its nuclear ambitions in return for economic aid and political concessions.
The UN further tightened sanctions after the 2013 test. In 2008, it even destroyed the cooling tower at Yongbyon as part of the disarmament-for-aid deal.
The 2016 test brought another round of universal international condemnation, including from China, the North's main ally. But implementing the deal proved difficult and talks stalled in 2009.
Did recent tests advance North Korea's nuclear capabilities? The US never believed Pyongyang was fully disclosing all of its nuclear facilities - a suspicion bolstered when North Korea unveiled a uranium enrichment facility at Yongbyon, purportedly for electricity generation, to US scientist Siegfried Hecker in 2010.
After its 2013 test and again in 2015, North Korea claimed it had "miniaturised" a device, or made a device small enough to fit a nuclear warhead onto a missile - which the US cast doubt on. Then in 2012, North Korea suddenly announced it would suspend nuclear activities and place a moratorium on missile tests in exchange for US food aid.
Pyongyang also said the 2013 test had a much greater yield than the devices detonated in previous tests. It was indeed larger in force than previous ones, but monitors failed to detect radioactive isotopes - a key indicator - so uncertainty remains. But this came to nothing when Pyongyang tried to launch a rocket in April that year.
Claims of an underground test of a hydrogen bomb in January 2016 were met with plenty of scepticism. In March 2013, after a war of words with the US and with new UN sanctions over the North's third nuclear test, Pyongyang vowed to restart all facilities at Yongbyon.
Initial estimates put the blast in the 10 to 15 kiloton range, whereas a full thermonuclear blast would be closer to 100 kilotons. By 2015, normal operations there appeared to have resumed.
North Korea again claimed this was a successful test of a miniaturised device, and again it has not been verified. China's reaction to the tests has been closely watched - as it is the North's main trading partner, and only ally.
The 2016 tests brought international condemnation, including from China.
However, Beijing has generally been anxious not to do anything to destabilise its volatile neighbour.