By Jeremy Laurence
SEOUL (Reuters) - Secretive North Korea is making rapid progress in building a uranium-fuelled reactor that poses an alarming safety risk, a nuclear expert said on Thursday.
Siegfried Hecker, who has visited the North's main Yongbyon nuclear facility four times since 2004 and was the last foreign expert to visit the site in late 2010, said he was very concerned the reactor could be technically flawed.
"In spite of their industrial difficulties they have continued to build it at a good pace," he told Reuters in a telephone interview from Stanford University in the United States.
"What alarms me is that I have never had the sense they had the sufficient regulatory oversight in order to be able to build this thing safely, and operate it safely," he said, adding the lightwater reactor could be operational in two years.
"From a technical standpoint, they should not proceed with the completion of the reactor and operate it on the basis of lack of connection with the international safety community. That is just too high of a risk."
A series of satellite images taken over the past year were proof that the impoverished state was serious about finishing the reactor, Hecker said, even as it struggled to feed millions of its undernourished population.
Analysts say the North's new young leader, Kim Jong-un, will continue with his father's militaristic policy, conscious that the support of the powerful army is vital to a third generation of Kim-family rule.
The United States and South Korea say the uranium enrichment facility and reactor are in breach of agreements reached with North Korea, and demand that it halt all nuclear activities before they will consider a resumption of aid.
The reactor appeared to be designed for generating electricity, Hecker said, but coupled with a nearby uranium enrichment facility, the complex could be converted for use in making an atomic bomb along with its plutonium program.
North Korea has tested nuclear devices twice and experts say it has enough fissile material to make six to eight nuclear bombs.
Pyongyang expelled international nuclear inspectors in 2009, a few months after aid-for-denuclearization talks broke down.
Hecker said the United States and South Korea found themselves in the dilemma of do they try force the North to stop construction of the experimental reactor, or do they allow North Korea to proceed and offer to help to avert a nuclear disaster?
"The international and political community has another couple of years to come to a resolution," said Hecker, who previously directed the Los Alamos National Laboratory where the atomic bomb was developed.
He said one solution, although difficult to swallow for the United States and South Korea, was to allow experts from China, the North's main ally and benefactor, to assess the facility's safety.
Hecker said the biggest concern was that a seismic event could trigger a power cut at Yongbyon, drawing a comparison to the meltdown at the Fukushima plant in Japan last year.
Although the Korean peninsula is not prone to major earthquakes, minor tremors are frequent. There is also concern about volcanic activity in the North.
The Yongbyon nuclear complex is little more than 100 km (60 miles) from China and about 200 km (120 miles) from South Korea.
(Editing by Robert Birsel)