Chernobyl+20 was a NIOF advocacy campaign during 2006 to raise awareness about the rarely-known facts about Chernobyl on the accident’s 20th anniversary. Notably:
- Chernobyl’s design, known as the RBMK, was not a purpose-designed nuclear power plant. It was in fact a bomb factory. The Soviet designers’ attempt to integrate the incompatible aims of plutonium production and electricity generation resulted in a uniquely dangerous design.
- The design flaw that led to the accident was known to the US as early as 1950. No American nuclear power plant was ever designed or built like Chernobyl.
- The RBMK is not a shortcut. It is far more complex and expensive than a traditional light-water reactor, which is probably the biggest reason why it was never built outside of bomb programs.
- The Chernobyl accident was not an operational accident. Operators had to disable multiple independent safety systems in order to run a dangerous test. The test ended up draining the reactor’s coolant.
- Had the Chernobyl reactor been placed in an American nuclear power plant, there would have been no escape of radioactive materials due to the large concrete dome placed around Western reactors. Importantly, though, the lack of a containment structure at Chernobyl did not cause the accident; a safe reactor with no containment structure will not suffer an accident. Containment structures were required by regulators because the lack of operating experience and inadequate computing power in the 1950s prevented them from determining what would actually happen in a reactor accident. By the 1980s, nuclear engineering had advanced enough to calculate that most of the anticipated accidents were physically impossible–and that the traditional approach to safety (a practice known as defense-in-depth, or multiple backup systems) had caused more problems than it solved.
- Advanced reactors have been subjected to the test that caused the Chernobyl accident, and passed with no damage. Only weeks before the Chernobyl accident in April 1986, an identical test was run on the Integral Fast Reactor (a waste-eating reactor prototype in Idaho). The reactor’s inherent safety features, mainly based around the fact that hot metal expands, shut down the reactor without any human intervention.
- Chernobyl was not a nuclear explosion. When the coolant was drained by the test, Chernobyl’s biggest design flaw–the tendency for power to increase when coolant drains–caused a massive power spike. This boiled the water in the cooling system, which was not designed to handle the high pressure and burst. The pressure wave blew through the roof, carrying highly radioactive but short-lived fission products (split atoms) with it. Examining a picture of the reactor after the accident makes this clear; a nuclear explosion doesn’t blow up half a building and leave the surrounding area untouched.
- Chernobyl differs from the 1979 Three Mile Island accident in almost every way. Three Mile Island did not explode; its fuel simply overheated and melted after a stuck-open “safety” valve drained the reactor’s cooling water. Three Mile Island’s reactor was a tank of pressurized water with uranium rods suspended in it; it could operate only in the presence of cooling water. This was the opposite of Chernobyl; Chernobyl’s heat output went up when its coolant was drained! Three Mile Island’s fuel melted when the reduced amount of water was no longer able to carry away the reactor’s residual heat–and when the reactor’s operators shut down the emergency cooling system.
- Chernobyl’s control rod design had a number of flaws which made an emergency shutdown unsafe if there were fewer than thirty control rods in the reactor. During the accident, there was an attempted emergency shutdown with only six to eight control rods in the reactor–and it helped cause the power spike.
- The RBMK can be operated safely. For example, it is only really unstable at low power; a normally-operating RBMK isn’t terribly dangerous. However, given that it isn’t strictly speaking a nuclear power plant, and that other reactor designs don’t have to be correctly operated in order to be safe, we do not support the construction of Chernobyl-type nuclear power plants.
- The reactor had two critical masses because the Soviet designers had increased the reactor’s size not by redesigning it, but by simply making the fuel rods longer. Unfortunately, the control rods took 18 seconds to shut the reactor down, whereas the cooling system could overheat in six. This meant that a power spike could occur in the lower half of the reactor and cause the cooling system to burst before the control rods–inserted from the top–could ever reach it.
- The control system didn’t account for the tendency of certain fission products to absorb neutrons and slow the reaction down. When those fission products were blown out of the reactor by the burst cooling system’s pressure wave, there was a second power spike in the lower half of the reactor.
- Popular estimates of the death toll are based on dividing the amount of radiation emitted by the radioactive material ejected from the reactor by the number of people exposed to it, ignoring the amount of radiation that each person actually received or exposure to other carcinogens. Some estimates exceed the total number of people who have died in the area since the accident! Credible estimates of the death toll by the UN World Health Organization place the death toll between 100 and 4,000 (compare that with the 30,000 people who die every year from coal-induced respiratory diseases).
- Soviet emergency response was awful. Most of the cancer deaths resulting from the accident could have been prevented by immediately evacuating the surrounding area, and all of the immediate deaths among first-responders could have been prevented with basic radiation protection.
In summary, Chernobyl was a perfect storm of bad engineering and operator abuse that didn’t teach reactor designers anything they hadn’t known for 35-40 years. It was completely unnecessary, and that is the true tragedy.
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This page was written by Stewart Peterson on May 28, 2009
