The massive, arch-shaped, steel cover began moving into place on Monday over the cement-encased nuclear reactor at Chernobyl in Ukraine.

A catastrophic meltdown of Reactor Number 4 on April 26, 1986 killed at least 30 people on site and left thousands dead or dying. The accident occurred in what was then the western part of the Soviet Union. Moscow kept the incident hidden from the world for many days. Only when particle detectors in Scandinavia began recording elevated radiation levels did the Kremlin come clean.

"The start of the sliding of the arch over Reactor 4 at the Chernobyl nuclear power plant is the beginning of the end of a 30-year long fight with the consequences of the 1986 accident," Ukraine's Environment Minister Ostap Semerak said.

The ill-fated reactor is currently being protected by a concrete dome that was hastily built by Soviet rescue workers in the months after the accident occurred. It is in danger of leaking nuclear waste.

Ambitious engineering

The new cover, made of corrosion-resistant steel, is being financed primarily by The European Bank for Reconstruction and Development (EBRD) at a total cost of $1.6 billion (1.5 billion euros). The installation is due to be completed on November 29, which is the 30th anniversary of the destroyed reactor being covered by the original concrete sarcophagus.

The EBRD called the construction and sliding of the arch "one of the most ambitious projects in the history of engineering."

The shelter, which is 275 meters wide by 108 meters tall (843 by 354 feet), is being moved into place by a system of hydraulic jacks.

Ukraine's environment minister, Ostap Semerak, called the positioning of the so-called "safe confinement" structure a historic step.

Chernobyl: 30 years on Terrible accident It's considered to be the most severe nuclear disaster of all time: On April 26, 1986, an explosion and fire at the Chernobyl nuclear plant in Ukraine released massive amounts of radiation into the atmosphere. The Soviet Union, which at the time had jurisdiction over Chernobyl, didn't publicize that the accident had happened until the first radiation plume set off alarms in Sweden.

Chernobyl: 30 years on The fallout spreads Radioactive clouds spread in virtually every direction during the week after the meltdown at Chernobyl. Areas close to the plant - in Ukraine, Belarus and Russia - were heavily contaminated. Heightened levels of radiation were also measured across nearly all of Europe after the accident. The so-called 'exclusion zone' around Chernobyl remains off-limits to human habitation to this day.

Chernobyl: 30 years on Damaging radiation Aside from the dozens of people who died as a direct result of the accident, thousands more were later struck with cancer. An increase in mutations and birth defects was also noted among children of people exposed to radiation, as seen in this photo from 1989. Animals in the region also suffered from infertility or birth defects after the disaster.

Chernobyl: 30 years on Into the food chain Rainfall in the months after the Chernobyl reactor meltdown washed nuclear fallout into the foodchain, affecting livestock and wild game across Europe. Of the nearly half a million wild boars hunted and slaughtered in Germany in 2010, more than 1,000 contained higher-than-allowed levels of radioactive contamination.

Chernobyl: 30 years on Ghost towns Although the exclusion zone was evacuated and badly-affected areas were dismantled and buried, severe effects of the nuclear disaster are expected to continue in the area for at least another hundred years. Some heavily-contaminated regions won't be completely free from radiation and safe for human habitation for another 20,000 years, studies show.

Chernobyl: 30 years on New protective shell The concrete cap built over the nuclear plant right after the disaster has been showing signs of decay recently and needs to be replaced. A new steel containment shell is currently being built on-site with more than 2 billion euros (nearly $2.5 billion) of international funding. It will be slid into place over the old sarcophagus by 2016.

Chernobyl: 30 years on Animal numbers rising After humans left the Chernobyl area in 1986, wildlife moved back into the newly-available habitat. Although some plants have genetic mutations, biodiversity appears to have increased partially. Some scientists even think the radiation may be speeding up adaptation. The zone has become a type of involuntary park, with predators such as wolves and eagles, and reintroduced wild horses.

Chernobyl: 30 years on Preserved, until the next fire In March of this year, a study was published showing that trees in the nearby Red Forest - where trees turned a rusty color and died after the disaster - are decaying slower than normal. This is due to a lack of living microbes and organisms in the area. Due to this excess of dried wood, a catastrophic wildfire could result, which could destroy the forest completely.

Chernobyl: 30 years on Disaster renewed Nearly 25 years after the Chernobyl disaster spread fear across Europe, an earthquake and tsunami triggered a meltdown at the nuclear plant in Fukushima, Japan in March 2011. Some countries have since reacted by shifting their focus away from nuclear power and towards renewable energy. Germany has pledged to close its nuclear reactors by 2022.

Chernobyl: 30 years on Green energy? If the national renewable energy plan is maintained, the share of renewable energy could reach 13 percent by 2030. But foreign investors were somewhat scared off when the Ukrainian energy commission sharply reduced its feed-in tariff at the beginning of 2015. So although Ukraine has been working on renewable energy, its future seems uncertain. Author: Sonya Angelica Diehn



bik/se (AFP, AP, dpa)