On the second anniversary of the world's worst manmade disaster — the Chernobyl nuclear explosion, Valery Legasov, Russia's top scientist, was found dead in his apartment on April 27, 1988.

He allegedly committed suicide. There was no suicide note but he left a series of recorded tapes detailing how disillusioned he had become of the government which attempted to suppress key details of the Chernobyl disaster. His recordings revealed crucial undisclosed facts about the catastrophe, as shown in HBO's latest documentary 'Chernobyl' releasing on May 6.

As the First Deputy Director of the Kurchatov Institute of Atomic Energy in Moscow, Legasov received a distress call on April 26, 1986, asking him to head to Chernobyl because some kind of explosion had happened there.

A special governmental commission was formed to be sent to Chernobyl, and Legasov represented the scientific circles in the commission.

His institute had created the RBMK reactors used in Chernobyl.

The 50-year-old was a specialist in chemistry and molecular physics, not nuclear reactors. He was called regardless because Legasov was the only high-ranking scientist available at the moment as the others were on holiday.

The workers of the Chernobyl Nuclear Power Plant, near Pripyat in Soviet Ukraine, were conducting a technical test on the night of April 25, 1986, to check security measures at the plant by simulating a station blackout due to a complete power-failure.

However, a combination of flaws in the process led to uncontrolled reactor conditions.

One of the staff members panicked and pushed the emergency stop button and, within nine seconds, the reactor in the fourth block which held almost 200 tonnes of radioactive fuel exploded, emitting large amounts of radiation into the atmosphere.

When Legasov reached Chernobyl with the commission members, no one could tell the extent of the meltdown in the first few hours. He saw an unusual specter as the plant was on fire, with the radioactive fuel making the sky look purple. He instantly knew that it was bad news.

Legasov, alongside the members of the commission, boarded a helicopter and hovered nearly 300 meters above the debris to determine whether the reactor holding the radioactive fuel was still intact. The radiation levels at that height were very dangerous but he was there long enough to realize that the reactor had exploded. Legasov understood that the situation was much worse than he had been led to believe.

Legasov realized that he had to reach a swift decision otherwise thousands of lives would be in jeopardy.

Before beginning the technical work on how to lower radiation levels, the first thing he demanded was the instant evacuation of people in the surrounding region, particularly Pripyat.

Nobody had thought of evacuation before Legasov mentioned it.

Moscow, however, did not authorize his plea right away. The scientist's demands were only met 36 hours after the explosion, Pripyat and the surrounding areas were evacuated by 2 or 3 pm, with only dogs left behind in streets.

In this photograph taken through a bus window workers walk near the sarcophagus that encloses stricken reactor number four at the Chernobyl nuclear power plant on the 30th anniversary of the Chernobyl nuclear accident on April 26, 2016 near Chornobyl, Ukraine. (Getty Images)

The scientist understood that the wind would take dangerous amounts of radiation to Kieve in a few days which was preparing for labor day celebrations on May 1, set to be attended by thousands. He insisted that the authorities should not hold the celebration, saying it would endanger people's lives.

However, an information blockade was sanctioned by Moscow to conceal the facts of the disaster from the residents and the rest of the world.

The Soviet Union, which considered itself perfect, did not want the world to know it had a nuclear disaster on its hands and canceling the Kieve celebration would make people suspicious.

Legasov lost this battle as thousands marched in Kieve just five days after the blast. (It was believed that they exposed themselves to large doses of radiation. The officials up to this very day denounced this claim.)

By this time, the world had become aware of what had happened. In Europe, Stockholm detected a high amount of radiation in the air.

With intense scrutiny and only a few hours left to avert another disaster, Legasov began his work on how to decrease the level of radiation coming from the reactor.

He made the decision to drop sand, burr and lead on the open reactor.

Helicopters were allotted to do the task, however, the choppers struggled to stay in place at the height of 200 meters with up to 200 degrees heat emanating from the reactor. One of the choppers got too close to the emanation and crashed.

The engineers who were throwing sacks of sand after a round of flight landed and vomited because of the dangerous level of radiation.

Legasov was also concerned about the groundwaters being contaminated and he returned to Moscow within 10 days and relayed the severity of the situation to the authorities. No one had any solutions.

Legasov, by this time, had been exposed to dangerous levels of radiation and it was showing. However, he went back to Chernobyl regardless, knowing well that his life had ended there.

A view of the town of Pripyat and the Chernobyl Fourth Reactor. Chernobyl, the site of the world''s worst nuclear disaster, was closed down for Good Friday December 15, 2000. (Getty Images)

The scientist celebrated his first triumph mid-May 1986 when the temperature of the reactor core and radiation levels had reduced and the disaster had been localized.

Legasov's job was done. However, he stayed there in an attempt to figure out what had caused the explosion.

The scientist, by this time, had established a reputation of sparring with officials in an effort to relay the truth.

The European countries, which had received a significant dose of radiation by this time, accused Moscow of contaminating the whole region and concealing the extent of the disaster.

Moscow, in an attempt to salvage its reputation, formed a team to compile a special report detailing the scale of the fallout to the International Atomic Energy Agency, the world's main nuclear watchdog.

Legasov was made in charge of presenting the report.

With an enormous task on his hand to save his country's face and answer infuriated world leaders, Legasov read out a 400-page report, fact-checked by him multiple times, and sat through three hours of grueling questioning. He gave every answer truthfully and was sincere in his approach, convincing the panel that the world must act together in the next steps.

At the end of the session, he was given a standing ovation for his efforts to contain the situation. He was ranked in the world's top ten scientists.

After this tremendous victory of Moscow, Legasov was nominated for the Hero of Socialist Labour, the highest award in the country. He had been conferred with every possible state award by the age of 49 for his scientific endeavors through the years except for the one.

However, he was denied the award.

By this time, the radiation had taken a toll on Legasov's body and he was rushed to the hospital. He couldn't sleep, his family feared it was cancer.

The scientist, allegedly on August 29, 1987, attempted suicide while he was still in the hospital. He was saved and he went to work submerging himself in researching what exactly occurred at Chernobyl and how to prevent such disasters from occurring in the future.

A Geiger counter shows a reading of 679,000 counts per minute near a metal claw contaminated with radioactivity in the ghost town of Pripyat not far from the Chernobyl nuclear power plant on August 18, 2017 in Pripyat, Ukraine. (Getty Images)

Legasov began writing articles, lashing out at the poor Soviet nuclear security and poorly qualified personnel employed at the plants, suggesting that Chernobyl could have happened sooner. He became skeptical of the Soviet political system. The scientist was again nominated for the highest civilian award and again denied the recognition.

He made a final push on the second anniversary of the disaster and presented a plan to the Academy of Sciences of making a special counsel to deal with the stagnation in Soviet science. His proposal was rejected, leaving him devastated.

Legasov was found hanged on the stairwell of his apartment the next morning of the Chernobyl anniversary. His alleged suicide sent shockwaves in the Soviet nuclear industry, leading to multiple changes in the country's nuclear security design.

Russian president Boris Yeltsin, on September 20, 1996, posthumously conferred the title of Hero of the Russian Federation on Legasov for the "courage and heroism" he showed during his investigation of the Chernobyl nuclear explosion.

Reports state that, when officials entered his office to check for radiation, the meter continued beeping with a significant amount of radiation from everything he had used. All of his belongings were burned.

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