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After the explosion 26 years ago, helicopter pilots dumped thousands of tonnes of sand to smother the fire, which burned for two weeks. Soldiers gathered radioactive rubble using wheelbarrows and shovels and tipped it on to the smouldering heap. Then the construction crews arrived: from May to November they built a containment structure called the sarcophagus (now named the Chernobyl nuclear power plant object shelter) over the reactor’s remains. But, in their haste to finish, the contractors didn’t seal it properly. The sarcophagus is failing. A 2006 report by the Chernobyl Forum — a group of UN agencies — described it as having been hastily built in horrendous conditions leading to “imperfections”. It is supported by the remains of Reactor Four, the structural stability of which is unknown. And its own structure has corroded over time. The same report summarised that “the main potential hazard of the shelter is a possible collapse”. That would mean another release of radioactive material into the environment.
Dodd is in Ukraine to prevent this. As the managing director of the 220-person project management unit (PMU), he’s responsible for building a new shelter over the top of the sarcophagus called the new safe confinement (NSC). The building, which will rise from one of the most treacherous construction sites on Earth, will be 108m tall and 150m wide, have an arch span of 257 metres and will weigh 29,000 tonnes. Unlike the hastily constructed sarcophagus, it is designed to last 100 years. The construction site is a concrete pad 180m west of the reactor; once finished, the NSC will be slid into place and properly sealed. Remote-controlled cranes suspended from its roof will then dismantle the sarcophagus and robots will remove all remaining radioactive material. The project is due to be finished by 2015. But every day the chances of the sarcophagus’s collapse increase.
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Schmieman, another American 65-year-old, began working on the NSC’s design in 2001 and helped choose the sliding arch from ten competing proposals. But problems remain. For instance, the NSC will contain two million cubic metres of free volume, meaning open space without partitions. According to him, all four structures with a similar volume (the Goodyear Airdock in Ohio, the US Navy Hangar One, Tustin Marine Corps air station and Nasa’s vehicle assembly building) have suffered from the same problem — what he calls “rain”. “When these four structures were enclosed they developed their own environments inside,” he says. “The atmosphere at the top of the building would become close to saturated and the inside surface only had to be a couple of degrees cooler than the atmosphere for water to condense on it. We’re especially concerned about that happening here, because if we have water inside it generates radioactive liquid waste.”
Read more at Chernobyl: the mission to difuse the world’s worst nuclear disaster site
