Chernobyl Accident – How It Happened
Until I traveled to Chernobyl I never questioned the cause of the accident. I imagined some critical component malfunction, and I remember the bad jokes that quoted, “What’s this button for?”. Sadly, the latter is closer to the truth. An article written by Boris Gorbachev in 2003, reviewing causes of the accident, quotes a plant manager describing the lack of care among employees, saying:
“Can you imagine – it was possible to see an operator sitting on the control board. The one with buttons, tumblers….
- How can it be?…
- That`s how it was. He just sat down. Sat down on the control board. No kidding”.
The real culprit is the incredible accumulation of negligence and hubris. The plant directors were political appointees without experience in nuclear energy. Discipline was lax among plant employees; prior to the accident there were various reports of staff being drunk or playing hooky while on shift. Construction designs lacked key safety and redundancy features. Where construction plans were correct, the wrong building materials were used either by negligence or crookery.
The accident occurred during an experiment scheduled to test a potential safety emergency cooling feature of the reactor’s core. I simplify, but the experiment basically consisted in checking what would happen if all main power were lost, and the emergency systems also left without power. The reactor’s cooling systems would be offline and the reactor core would start to dangerously heat, but in theory, the momentum of the reactor’s turbines would generate enough energy while winding down to produce energy to feed the dead emergency cooling systems with new energy. This is akin to unplugging a patient’s artificial respirator and wondering how long he can hold his breath before you hook his machine up to a battery unit. The reactor core rapidly heated, and eventually the wrong button really was pressed.
At 01:23:40, April 25th, 1986 as recorded by the centralized control system EPS-5 button (also known as the AZ-5 button) was pressed, and emergency shutdown of the reactor was initiated. The reason the button was pressed is not known, but whatever the reason, once pressed it inserted the control rods into the reactor core. In theory the rods would neutralize the nuclear reactions in the core, and bring temperatures down. The environment around the rods was already so hot at the time of their deployment however, that the tips melted while entering the core and obstructed passage for complete insertion. At this point all hopes were lost.
Had the offline emergency cooling systems been activated first, the core temperature may have cooled enough for complete insertion of the rods. Without insertion of the rods, the nuclear reactions increased, temperatures continued to rise, and moments later a steam explosion blew the roof off Reactor #4. Seconds after that, another explosion (technically a nuclear excursion) blew radioactive elements into the sky.
Firemen Heroes of Chernobyl
The response from those on duty was heroic. Many of the staff gave their life trying to shut the reactor down, well aware of the radiation risks. Shortly after the accident, firefighters arrived to try to extinguish the fires. Their efforts likely helped avoid further explosions that would have resulted in greater release of radioactive material into the air. Within three weeks most of them died in intensive care units in Moscow.
Grigorii Khmel: “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.”
Anatoli Zakharov: “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.’ 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.”
I visited the graves of the first 28 victims of Chernobyl, the firemen and technicians who fought to control the fires and shut-down the reactor. When I arrived at Mitino Cemetery in Moscow, where they are buried, it was already two in the afternoon and getting dark. All 28 graves were covered in ice and snow. I cracked open the ice cocoons and discovered old flowers under the snow. Each headstone revealed a face carved in metal that stared back at me from the cold.
See Pripyat 25 Years Later: Complete Gallery