The man who crawls into the perilous heart of the Chernobyl reactor

The shattered remains of Chernobyl Reactor 4 are one of the most inhospitable places on Earth. Not only are the ruins physically dangerous, but they are also heavily irradiated, black, and enveloped by a crumbling concrete sarcophagus, which is, in turn, covered by the new secure containment structure.

But it’s critical that scientists understand what’s going on inside. And this task falls to Anatoly Doroshenko, a young scientist from the Institute for Safety Problems of Nuclear Power Plants (ISPNPP). He does what could be considered the most dangerous job on the planet: crawling deep within the reactor ruins to take measurements and samples, coming within 25 feet of the core, sometimes as often as once a month.

“It’s not scary,” Doroshenko tells me, as he stands next to a model of Chernobyl in the institute’s laboratory, in the exclusion zone around the plant. “I have been preparing for this for a long time. You just have to be in this moral state to accept it and the necessity of doing it.”

“It is indeed a strange feeling. I think it can be compared to the feeling of conquering Everest, flying in space or exploring the seabed. A certain adrenaline rush is always present.”

He has a list of tasks to complete with each search inside the reactor, but a limited time to complete them, so he must balance speed and caution. “You have to acquire the knowledge of what you are going to do, where you are going. You have to control yourself,” says Doroshenko. He repeats this second part twice, almost as a reminder to himself.

“You have to be aware that everything is contaminated. And if you touch something, you have to know what you are touching, because you don’t want to contaminate your clothes or yourself,” he says. “The bottom line is you have to be aware of your plans, because there’s only so much time you can be safe. You want to get the job done, and you also want to see something. [interesting]but this is not an excursion. You work there, so you have to be aware of everything you need to do and keep it in mind.

If Doroshenko visits the less dangerous parts of the reactor, he will wear a hat, protective gloves and a respirator. For the most contaminated areas, he will add a full suit to protect against dust, or even a third layer of polyethylene suit. It also has lead aprons that can be placed on top, but the weight and bulk make it difficult to negotiate tight spaces inside.

As a younger scientist, he was taken by an older employee to the main circulation pumps, which normally cooled Reactor 4 and were part of the safety tests that led to the 1986 disaster. “It’s a very important place to see and very well-known. We observed all the destruction caused by the explosion.”

“The main protection for us is knowledge, not suits,” explains researcher Olena Pareniuk from ISPNPP. “Anatoly is one of our key employees. He looks tired and a little depressed, like all of us, but he is doing a great job. We don’t have many young people who are proficient in dosimetry measurements.”

Doroshenko’s boss, Viktor Krasnov, acting director for science at ISPNPP, says generations of scientists have entered the reactor since 1986 to take measurements and install sensors. There they found themselves in confined spaces, pipes filled with radioactive water and large sections of corium – a mixture of molten fuel, concrete and metal formed in the 2,500°C heat following the disaster, which flowed and oozed through the ruins to form unusual shapes.

“The very first people who came here gave these slang names to all these objects: the elephant’s foot, the cat’s house, the dog’s house, the octopus beam, the mammoth beam,” says Krasnov. “Everything is destroyed inside, so all the routes are quite difficult.”

The risks are almost infinite. One of them is the 2,200-ton upper bioshield that once sat atop Reactor 4 and is now nicknamed Elena. It was tossed like a coin during the explosion and today lies at a 15-degree angle, leaning on the rubble. If it were to collapse, it could dislodge the precarious ruins and kick up large quantities of radioactive dust.

A longer-term risk, and part of the need for regular and precise measurements, comes from occasional spikes in nuclear activity. No one knows exactly where all the fuel is inside the reactor, and it sometimes becomes active.

When uranium or plutonium fuel radioactively decays, it emits neutrons, which can promote a fission reaction if the neutrons are captured by another radioactive nucleus. However, large amounts of water slow these neutrons, preventing them from being captured. Immediately after the disaster, the sarcophagus created dry conditions inside the reactor, causing a spike in neutrons.

Later, there was more water, in part because the concrete shelter was riddled with holes that let in birds and bad weather, so the humidity increased and the neutron flux decreased. “Right now, with the installation of the new safe containment, the humidity is lower, so we expect accidents to happen and we need to know this in advance,” says Krasnov. This is why it is essential that Doroshenko continues to climb inside to better understand the conditions.

Despite the rigorous safety procedures followed at Chernobyl, crawling inside an exploded reactor will never be safe. “I know the risks,” says Doroshenko. “So I worry about my health, because if I don’t take care of it, I can make mistakes. I don’t know if I will have health problems in the future, but I know that if I follow radiation protection standards, I can minimize these risks.”