Chernobyl, Ukraine - In the early morning of a balmy spring day, the main entrance to the Chernobyl Exclusion Zone at Dytyatky is utterly barren.



A grey stuccoed booth with flimsy-looking maroon roof houses several Ukrainian guards. There is nothing for them to do but wave through the occasional contractor's car or step out for a cigarette. Were it not for the meagre stop sign, a few conspicuously placed hazard symbols, and an old yellow boom gate, this would feel like any other road in Ukraine.



But it is, in fact, the busiest road in and out of the 30km exclusion zone at the heart of one of the worst man-made disasters in human history.

A radioactive adventure park

Thirty years ago, on April 26, 1986, at 1:23am, Moscow time, a massive power surge attributable to poor design and mismanagement led to a series of explosions inside the fourth reactor at the Chernobyl nuclear power plant, in Pripyat, Ukraine. The blasts managed to eviscerate the 2,000-tonne upper plate of the reactor and destroy its core.

According to the Organisation for Economic Co-operation and Development's Nuclear Energy Agency, the two explosions produced a shower of hot and highly radioactive debris. The resulting plume of radioactive smoke rose about one kilometre into the air and began to make its way across Europe.



Soviet firefighters were immediately dispatched to bring the resulting fires around the nuclear plant under control. It took them 10 days to do so, and at least 28 of them are known to have died as a result of exposure to radiation during that time.

Ukraine: Chernobyl disaster visiting on the 30th anniversary

The World Nuclear Association says that during those 10 days, the world experienced the largest uncontrolled radioactive release in human history.

Now, around the 30th anniversary, a line of buses has formed by 9:45am. Each is packed with excited tourists anxiously awaiting the 10am opening of the zone.



For the 10,000 tourists who enter each year, Chernobyl has become a sort of adventure park, offering a glimpse into the remnants of a world left behind.

But for the men of the 633rd fire brigade of Ivano-Frankivsk, in Ukraine - who look slightly shocked at the unfolding pandemonium of the tourist horde - this area represents the worst 48 days of their lives.

Into the zone

In July 1986, only three months after the accident, and when relatively little was yet known about the consequences, the men of the 633rd received notifications that they would be sent to Chernobyl. At that time, the Soviet Union kept a tight grip on information, and constantly reassured citizens that the situation there was under control.

"We really didn't know what we were going into. We had no way of knowing. We just received knocks on the door, and papers that said we were being sent to work," says Yaroslav Melnik, the group's commander.

The men and women who were quickly and quietly herded from across the Soviet Union to eliminate the effects of the accident eventually came to be known as "liquidators".



Around one million Soviet military reservists, firefighters, police officers, and civilians served within the exclusion zone from the time of the accident until the Soviet Union began to crumble away.

Return to Chernobyl

Thirty years on, this group of men from Ivano-Frankivsk are returning to Chernobyl together for the first time.



The memories quickly flood back as they approach the exclusion zone. As daylight dims and night settles in, they find the spot they believe was their base during the 48 days they spent as liquidators in Chernobyl.

"I'm sure ... [this is] the very same place we were stationed from July 18 to September 3, 1986," says Melnik.



"From this place, we would drive to the reactors, where we were tasked with the deactivation of the third and fourth reactors, but we also helped build the containment sarcophagus.



"We worked in three shifts, but only for five to seven minutes at a time because of the danger. After finishing, we'd throw our clothes in the garbage."



Forgotten by the state

Although they are now seen as heroes across the former Soviet Union, the liquidators say they were quickly forgotten by the state.



In 1991, Ukraine's parliament, the Rada, drafted a law to entitle these men and women to certain benefits, based on their time in the zone, and the diseases they acquired as a result. But by 1997, the Ukrainian government had begun cracking down on what they believed were fraudulent benefit claims.



Melnik says the accusations were nonsense drummed up by a corrupt and bankrupt government.



In the aftermath, 168 members of his battalion lost their benefits, which ranged from monthly payments to free transportation. Ever since, Melnik has spent many of his days working to restore these benefits - to the men who are still alive and the family members of those who have died.



"We've accomplished a lot," he says. "We've returned liquidator status to 96 members. We have a case where we returned benefits to the family of a man seven years after his death."

How many will die as a result of Chernobyl?

Estimates of the number of liquidators who died or became ill as a result of their work vary substantially, but the men of the 633rd say that out of the 259 from their group, 71 have died. Melnik says that 68 have been designated as invalids by a state committee, which investigates their health and determines whether or not their diseases are attributable to Chernobyl.

Dr Dimitry Bazyka, the current director-general of the National Research Centre for Radiation Medicine in Kiev, says that approximately 20,000 liquidators die each year. However, he urges caution when blaming the liquidators' diseases and deaths on radiation.



"The attribution of diseases to Chernobyl and radiation is a very complicated thing, and it isn't well researched," he says. "The last time a serious effort was made was in 2005, so now were are 10 years on."



He says his years of experience and research have led him to believe that the liquidators may have more control over their health than they realise.

"People who are exposed need to know that their health is in their hands," he says. "If they have an active life, strengthening their health, the effects won't be great. It's not right to sit and wait for diseases to come to you."

Others, like Dr Keith Baverstock, who led the Radiation Protection Programme at the World Health Organization, disagree.



"Most people only talk about a few tens of deaths from Chernobyl," he says. "They apply this rule of thumb that, if it's due to radiation, it's a specific type of cancer. To them, anything outside that is not attributable to radiation, which is very wrong. The people who didn't think it was a problem still don't think it was a problem."

While the official United Nations estimate puts the death toll at just 4,000, in Baverstock's estimation, it is more like 30,000 to 60,000 people across Europe.

On his side are many others, such as Dr Richard Garwin, who designed the first hydrogen bomb and served as an adviser to US presidents. In a rebuttal to the UN estimate written in 2005, he stated that there should be 24,000 expected deaths from the accident in Chernobyl.



Furthermore, a lengthy 2011 report from the German affiliate of International Physicians for the Prevention of Nuclear War indicates that as far back as 1992, a prominent scientist named Georgiy F Lepin from Minsk, who was acting as the vice president of the Union of Chernobyl Liquidators, was already claiming that 70,000 liquidators were invalids, and 13,000 had died.



Does Chernobyl pose a new threat today?

All of this is why Canadian scientist Dr Timothy Mousseau, a professor of biological sciences at the University of South Carolina and a long-time Chernobyl researcher, is sounding the alarm over a new threat coming from within Chernobyl - one with which the firefighters of the 633rd battalion are all too familiar.

Although it may seem difficult to grasp at first, he says the danger of forest fires in Chernobyl is higher than it has ever been for two reasons. The first is climate change, which is believed to be causing forest fires to spike worldwide, and the second is the management of the Chernobyl exclusion zone itself.

"You walk through the forests of Chernobyl and the trees are all still sitting on the ground and they're largely intact," he says. "The leaves that fell the previous fall are still sitting there undecomposed."

Mousseau believes that all of this highly radioactive organic matter could act as fast fuel in a fire. "When it dries out, it becomes a big fire hazard. This fuel load enables the generation of much hotter fires, and potentially catastrophic forest fires."



He believes this threat is now more acute because "there's just no money for the management of the forests, especially with the war that's going on [in eastern Ukraine]".

"Any kind of discretionary funds that Ukraine owns are going to the war with the Russians, so their budgets are down considerably because of that, and then, of course, the Ukrainian currency is down considerably. It is 20 percent of what it was just a few years ago, so there is an incredible inflation on everything.



"They can't afford to buy equipment, they can't afford anything. The war has also been drafting young guys away, so you've had a number of guys just disappearing from Chernobyl and going off to join the war effort."

'We caused this catastrophe'



Inside the exclusion zone, it becomes easier to understand Mousseau's concerns.

The deputy commander of fire services for the zone, a 41-year-old from Kiev named Alexander Borovsky, describes the far from ideal conditions in which they work.

"We have 300 guys in total, and we work in an area of 2,600 square kilometres. The equipment we have is just basic," he admits.

The fire trucks assigned to these firefighters are the same model - the ZU-131 AC40 - that fought the enormous radioactive fires 30 years ago. In many other places, they would be hidden away in storage warehouses and treated as classics, but here, in the exclusion zone, they are the first responders' primary tool.

"We know there's no money, so we make do with what we have," says Borovsky. "We caused this catastrophe as humans and we should care more about another one, but there's no money."

He says that the war in the east has had an effect. "Of course, everything goes to fighting the war instead of to us."



And, he adds, his men haven't even received their monthly danger stipend of 1,700 Ukrainian hryvnias ($67) since January.

'When it burns, we learn'

With so few people in the zone at any time, there are men hired to alert the firefighters to any problems. They spend their work days sitting in one of six decrepit Soviet-era fire towers, the tops of which sway wildly in the wind 46 metres above the ground.

Serhiy Kostovsky has been doing this for 12 years and laughs when asked what sort of training he has received. "No one ever trained us," he says. "When it burns, we learn."

He says that the state pays him the equivalent of $75 per month to do this work, and although he feels that spending so much of his life in the zone puts him at risk, he hasn't been able to find any other work in Ukraine.

Kostovsky says that in all of his years working in the zone, 2015 was the worst year for fires. "There were a lot of fires and the big ones blazed closer to the nuclear station," he says. "It was the biggest fire I have ever seen here ... Some guys who have worked here 20 years were astonished. It was just a huge fire."

"It was very hot last year - it was a drought," he continues, seeming to confirm Mousseau's concerns about the impact of climate change. "I think the very hot summer was one of the reasons of the fires. If it's very hot in summer, even a simple bottle glass can cause a huge fire. The hotter and hotter weather is causing these fires. Everything is so dry, the territory is huge and it's hard to control it all. We try our best, but it's hard to control it."

Borovsky says last year's fires didn't reach the most radioactive parts of the zone, but Mousseau insists that one of the three fires did, in fact, touch the "red forest", the 10 square kilometre area surrounding the Chernobyl Power Plant.

When asked how big a risk the fires pose in Chernobyl, Mousseau says it's very difficult to say at this point. "The danger depends on the meteorological circumstances," he says. "If there was a major fire burning through the most radioactive areas, and it was blowing steadily in one direction towards a populated area, and there was rain at that time, then there would be the potential for the deposition of significant amounts of radioactivity."

WATCH: Babushkas of Chernobyl

He suggests that a closer look at the events of 1986 reveals the current dangers.

"At the time of the accident, there was this huge fire for 10 days, and it was sort of like a mini volcano injecting radionuclides into the atmosphere.



"This allowed them to be transported for thousands of miles, and so there are very significant hot spots in Scandinavia, there are hot spots in the UK and Scotland, where it just happened to combine this radioactive cloud with smoke particles in it, wafting over that part of Britain, and because it was raining at the time, it just dropped a pile of it in one place. The sheep in that part of Scotland were just recently cleared for human consumption - the wool, not the meat.



"In Germany, we hear that one in three wild boars being shot by hunters is not fit for human consumption because the caesium levels are too high, and that caesium comes from Chernobyl."

In his mind, the potential fallout isn't the most worrying threat, because even the worst forest fire would not be in the same category as the reactor meltdown. But, he explains, "What's really scary is that no one is paying any attention to it. No one even cares to look at what the fallout could be".