Here are some of the event at Chernobyl for reference

"Radiation levels

The radiation levels in the worst-hit areas of the reactor building have been estimated to be 5.6 roentgens per second (R/s) (1.4 milliamperes per kilogram), equivalent to more than 20,000 roentgens per hour. A lethal dose is around 500 roentgens (0.13 coulombs per kilogram) over 5 hours, so in some areas, unprotected workers received fatal doses within minutes. However, a dosimeter capable of measuring up to 1,000 R/s (0.3 A/kg) was inaccessible because of the explosion, and another one failed when turned on. All remaining dosimeters had limits of 0.001 R/s (0.3 µA/kg) and therefore read "off scale." Thus, the reactor crew could ascertain only that the radiation levels were somewhere above 0.001 R/s (3.6 R/h, or 0.3 µA/kg), while the true levels were much, much higher in some areas.^[7]:42-50

Because of the inaccurate low readings, the reactor crew chief Alexander Akimov assumed that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 04:30 were dismissed under the assumption that the new dosimeter must have been defective.^[7]:42-50 Akimov stayed with his crew in the reactor building until morning, trying to pump water into the reactor. None of them wore any protective gear. Most, including Akimov, died from radiation exposure within three weeks.^[28]:247-48

[edit]Fire containment

Firefighter Leonid Telyatnikov, being decorated for bravery

Shortly after the accident, firefighters arrived to try to extinguish the fires. First on the scene was a Chernobyl Power Station firefighter brigade under the command of Lieutenant Volodymyr Pravik, who died on 9 May 1986 of acute radiation sickness. They were not told how dangerously radioactive the smoke and the debris were, and may not even have known that the accident was anything more than a regular electrical fire: "We didn't know it was the reactor. No one had told us."^[29]

Grigorii Khmel, the driver of one of the fire-engines, later described what happened:

We arrived there at 10 or 15 minutes to two in the morning ... We saw graphite scattered about. Misha asked: "What is graphite?" I kicked it away. But one of the fighters on the other truck picked it up. "It's hot," he said. The pieces of graphite were of different sizes, some big, some small enough to pick up ...
We didn't know much about radiation. Even those who worked there had no idea. There was no water left in the trucks. Misha filled the cistern and we aimed the water at the top. Then those boys who died went up to the roof—Vashchik Kolya and others, and Volodya Pravik ... They went up the ladder ... and I never saw them again.

However, Anatoli Zakharov, a fireman stationed in Chernobyl since 1980, offers a different description:

I remember joking to the others, "There must be an incredible amount of radiation here. We'll be lucky if we're all still alive in the morning."

Twenty years after the disaster, he claimed the firefighters from the Fire Station No. 2 were aware of the risks.

Of course we knew! If we'd followed regulations, we would never have gone near the reactor. But it was a moral obligation—our duty. We were like kamikaze.

The immediate priority was to extinguish fires on the roof of the station and the area around the building containing Reactor No. 4 to protect No. 3 and keep its core cooling systems intact. The fires were extinguished by 05:00, but many firefighters received high doses of radiation. The fire inside Reactor No. 4 continued to burn until 10 May 1986; it is possible that well over half of the graphite burned out.^[The fire was extinguished by a combined effort of helicopters dropping over 5,000 metric tons of sand, lead, clay, and boron onto the burning reactor and injection of liquid nitrogen. Ukrainian filmmaker Vladimir Shevchenko captured film footage of an Mi-8 helicopter as it collided with a nearby construction crane, causing the helicopter to fall near the damaged reactor building and kill its four-man crew.

From eyewitness accounts of the firefighters involved before they died (as reported on the CBC television series Witness), one described his experience of the radiation as "tasting like metal," and feeling a sensation similar to that of pins and needles all over his face. (This is similar to the description given by Louis Slotin, a Manhattan Project physicist who died days after a fatal radiation overdose from a criticality accident.)

The explosion and fire threw hot particles of the nuclear fuel and also far more dangerous fission products, radioactive isotopes such as caesium-137, iodine-131, strontium-90 and other radionuclides, into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.

]Timeline

• 1:26:03 – fire alarm activated
• 1:28 – arrival of local firefighters, Pravik's guard
• 1:35 – arrival of firefighters from Pripyat, Kibenok's guard
• 1:40 – arrival of Telyatnikov
• 2:10 – turbine hall roof fire extinguished
• 2:30 – main reactor hall roof fires suppressed
• 3:30 – arrival of Kiev firefighters
• 4:50 – fires mostly localized
• 6:35 – all fires extinguished^‡

^‡With the exception of the fire contained inside Reactor 4, which continued to burn for many days"




^{" It seems that things got under control a lot quicker than the accidents at the 2 Japanese nuclear plants. We thank Wikipedia for providing the public with the most wonderful knowledge.}