'Life of hard labour' in North Korean camp
"It was a life of hard labour," he says. "Thirty per cent of new prisoners would die. And we were so malnourished, we would eat rats and earthworms to survive."
Cheol-hwan lived in Yodok for a decade - paying the price for "political crimes" committed by his family.
Amnesty International says there are signs the number of people being sent to North Korea's political prison camps is growing, and that the new satellite maps show the system is thriving.
Torture reports Cheol-hwan traces the outline of the camp on the map with his finger - snaking through North Korea's mountainous countryside.
New rows of buildings have appeared in one section of the camp. They are not there in photographs from a decade ago.
"This is the guards' block," he points out. "And it's grown. I assume it's because they need a bigger security presence now."
I ask him where he lived and he points to a row of box-like houses a few hundred metres from the guard block, a single road leading in and out.
Reports from inside the camps are scarce. But many of those who do speak out tell horrific stories of torture, starvation and summary executions.
The new Amnesty report details accounts of water-boarding, sleep deprivation, bamboo pieces placed under the fingernails and imprisonment - sometimes for months on end - inside a 4ft (1.22m) by 4ft cell.
Cheol-hwan remembers the prison block inside his camp, where the troublesome inmates were kept. It was where torture and beatings took place, he says.
'No return' News is already filtering through the North Korean community here in Seoul of a wider crackdown taking place back home.
There is talk of listening posts, border fences and a sharp rise in public executions.
Kang Cheol-ho runs a church for North Korean defectors. He gets new arrivals every month and says the reports just get worse.
"I'm getting more and more dire testimonies all the time," he said. "That the clampdown is worse, the food situation is more severe and the authorities are making it clear, if you try and escape the country, you'll never get another chance.
"Nowadays, you'll be sent to one of these camps from which you may never return."
The rest of the story is here: http://www.bbc.co.uk/news/world-asia-pacific-13268857