Professor Siegfried Hecker of Stanford University's Centre for International Security and Cooperation in the US is one of the few outsiders to have visited North Korea's Yongbyon nuclear facility.
|Siegfried Hecker pictured on a visit to the Yongbyon nuclear plant in February
He made the trips in an unofficial capacity to assess North Korea's nuclear programme.
He told Al Jazeera what he saw on his visits to the plant, and how likely he thinks it is that North Korea will give up its nuclear programme.
What was Yongbyon like? How sophisticated was the plant?
It reminded me of the the Russian closed nuclear cities that you used to see.
As we approached Yongbyon there was one set of guard buildings and then lots of concrete-style guard buildings where plant workers lived.
The single greatest impression I had as I arrived was that its a really huge place. A significant facility.
Then we were shown the main building that contains the nuclear reactor. Again its a really huge place.
Inside, the buildings reminded me very much of ones built in a Soviet style.
The equipment inside seemed to be functioning well, but everything seemed very outdated, although it was adequate to get the job done.
However, the North Korean scientists themselves were very efficient at what they did - they were very impressive.
What did the plant tell you about how nuclear material was handled?
|Hecker said he was impressed by the technicians he met at Yongbyon
The reactor itself seemed safe and, as I said, the staff were very competetent.
In the spent fuel pool building, however, there was significant contamination - that building did not meet Western safety standards.
One has to be extremely careful when handling radioactive material - its a very tricky process - and they were not up to modern safety standards [in that particular building].
Do you think Yongbyon was built entirely by North Korea, as the government claims, or do you think there was outside help?
There was no question in my mind that the central facilities at the plant were built by North Korea.
They had significant help in installation and training from the Soviet Union.
But in the 1970's, the North Koreans decided to go solo.
They are masters at reverse engineering and the technology looked very much like nuclear facilities found in the early UK nuclear programme.
I spoke with the scientists there and there was no doubt in my mind that they understood the entire process.
Were you allowed to see everything you wanted to see on your visit?
|The Yongbyon plant is about 100km outisde of North Korea's capital, Pyongyang
I've been to North Korea five times and Yongbyon three times.
The first time I visited Yongbyon, in 2004, they had carefully scripted my visit.
They allowed me to physically handle the plutonium in a test tube, but they would not allow me into the laboratory itself.
But during my visits in 2007 and 2008 I was allowed to take pictures inside the building with my own camera.
By the time of the second visit they had also improved safety standards and I was required to wear a contamination suit.
Do you believe North Korea is serious about abandoning its nuclear programme?
I believe they are serious about abandoning plutonium production - they are serious and sincere.
However, they still have between 30 and 40 kilograms of plutonium that could be used to make weapons.
Getting rid of that will take some time.