SINGAPORE Six times, Sergei Belyakov says, he has been through the doorway to hell and back.
The Ukrainian-American was a volunteer "jumper" who helped clean up after the nuclear disaster in the town of Chernobyl in the former Soviet Union in April, 1986.
These are people who jump into a radioactive area to clear debris or mend pipes and run to safety before radiation reaches lethal levels.
Tokyo Electric Power Co (TEPCO) is trying to get jumpers -- reportedly for $5,000 a day -- to bring its damaged nuclear power plant in northern Japan under control after it was severely damaged by last month's earthquake and tsunami, the world's worst nuclear crisis since Chernobyl.
Six times during his 40-day tenure at Chernobyl, Belyakov was one of the hundreds crouching in the covered stairway leading to the roof of nuclear reactors 3 and 4. Outside, radioactivity was so high that it could kill within minutes.
"It was the doorway to hell," he told Reuters, recalling events of 25 years ago. "Right at the door there was an elaborate and professionally done drawing on the wall, like a fresco, which showed you the roof in 3-D.
"The guy (at the door) tells you, you go here, you do this, you go around this, this ladder is not good so don't go there because you may fall with it. You mentally imprint what you need to do, you follow that. Then you run."
He would hack away at highly toxic asphalt on the roof and toss it down to be buried, but for a very limited time. The longest he spent on the roof was two minutes, the shortest between 30-40 seconds.
"The guy yells (to) you or you have your own judgment (to come back). Once you are done, you go down. There were 700-900 people collected on that staircase. It was a moving, never-ending chain of people."
Now 55 and a U.S. citizen, Belyakov is a scientist working in Singapore for research group Albany Molecular Research Inc. But he says those days in 1986 are seared in his mind.
The first time on the roof, he said, was the worst. "The goggles were sweaty and I perhaps lost 10 pounds just in these few moments because it was completely a shocking experience."
Belyakov was an associate professor at a Ukrainian university in 1986. He first sensed something was wrong at Chernobyl while he was on a fishing holiday and noticed that water levels in the Dnipro River were plummeting, a sign that dams upstream had been closed.
It was weeks before Soviet authorities acknowledged the gravity of the crisis. Belyakov, also an army reservist who had been trained in chemical warfare defense, volunteered to help despite his wife's objections.
"She wasn't happy obviously, but I put my foot down. I did not expect the scale of what I am going to experience. If I knew that in advance, I perhaps would think twice.
He was called up in July, and sent to Chernobyl. He would spend 23 shifts at the plant itself, protected only by lead sheets below waist level at the front and the back. Other gear include heavy gloves and respirators, but these could not protect against radioactivity.
Workers had to leave when they were exposed to 2 Roentgen of radiation per day, about 240 millisieverts. The U.S. Environmental Protection Agency says a dose of 500 millisieverts would cause nausea and 1,000 would cause hemorrhage.
After sustaining 25 Roentgen of radiation, the Chernobyl workers were sent home. Many have since died prematurely. Belyakov says he knows of at least five other men who worked there who died within 10 years.
But as many of them reach their mid-50s, it is hard to isolate the Chernobyl radiation as a cause of death, he said.
"I was blessed perhaps," Belyakov says. He was ill for several months, but shows no visible signs now and is a keen basketball player.
"The action of radiation on a living organism is extremely different -- there are people who can sustain that very well, unfortunately there are people who get just a pinch of what a normal human being would get and it would be lethal."
Belyakov shrugged off comments about personal bravery.
"You do it step by step," he said.
"You break down your task -- I have to make 100 steps to the ladder, then I have to climb through the ladder, then I have to make 70 steps right side, then I have to make three or four cuts of that asphalt, then I have to grab a shovel, collect the pieces and toss it out.
"You kind of break your task into small details. And each small task doesn't look that scary."
Belyakov did not get much for his heroics.
"There was enough for us to buy an 18 day long travel trip to India," he said. "It was our first trip abroad. It was fascinating, I still cherish it.
Asked if he had any advice for those considering similar work at the Fukushima plant in Japan, he said: "Being brave doesn't mean that it comes from your nature.
"It comes from your logic, it comes from your good mind and ability to analyze your situation and make sound decisions. As long as you are capable of sustaining the pressure and sustaining the fear, you can do pretty much whatever you want.
"I can eat pressure for breakfast."
(Editing by Jonathan Thatcher)