Could the Chernobyl accident happen at Koeberg? The answer is a definite ‘No’, and it is important to know why.
The question is topical in view of the recently acclaimed TV series (which I have not seen) and the book ‘Midnight in Chernobyl’ by Adam Higginbotham (which I have read). It is also topical for South Africa in the middle of our electricity shambles where we are considering energy sources for the new power stations we desperately need, and where nuclear is an option.
At 01h23 on Saturday 26 April 1986, Unit No 4 of the V I Lenin nuclear power station near Chernobyl in the Ukraine blew up, with an explosive force of about 60 tons of TNT. The reactor was destroyed, the lid of the building was blown aside, and vast amounts of radiation poured out into the surroundings.
The two primary reasons for the accident are quite simple but seldom explained in our local media. Before I describe them, I must explain briefly how a nuclear power reactor works. When a neutron, a sub-atomic particle, enters the nucleus of a few types of atoms, it splits the nucleus into two or more fragments by fission, releasing enormous energy and two or more neutrons, which in turn split other nuclei in a nuclear chain reaction. Such nuclei are fissile. The most commonly used fissile nucleus is uranium-235. Slow neutrons are more likely to cause fission, so a moderator slows them down. You also need a coolant to take heat from the reactor to make steam to drive the turbine and generator
Koeberg, like most reactors in the West and like the VVER reactors in Russia, uses water as a coolant and water as a moderator.Russia’s RBMK (Chernobyl-type) reactors used graphite as a moderator and water as a coolant. And that’s it. It is impossible to design a graphite/water reactor that will always be safe. Some Russians knew it but kept its dirty secret to themselves. Koeberg has a containment building and Chernobyl did not, which added to its dangers.
In ‘Midnight at Chernobyl’ a new engineer arrives from duty at VVER reactors. He was horrified at the RBMK. At the control panel, he asked, ‘How can you possibly control this hulking piece of shit!’
Under certain circumstances, both Koeberg and Chernobyl reactors can get bubbles of steam in the cooling water (‘voids’). In Koeberg, the voids slow the reactor down. In the Chernobyl design they can speed it up, which happened on 26 April 1986. The primary blame for the accident lay with those who designed the reactor and those who allowed it to be used.
Making it worse was an unbelievably stupid design of some of the control rods. These rods contain neutron poisons, which capture neutrons and stop fission. They are lowered into the reactor to shut it down. But some Chernobyl control rods had graphite tips, which speeded it up.
At midnight, Unit 4 prepared to do a test in which the turbine would be disconnected from the reactor to see if the slowing generator could provide enough electricity for a minute or so until the diesel generators kicked in. Reactor power was reduced. Things started to go horribly wrong. Red lights flashed. The reactor was becoming unstable. The operators wanted to postpone the test. But the engineer in charge, Anatoly Dyatlov, insisted they proceed. To boost the dying reactivity, he made them withdraw an illegal number of control rods. Power began suddenly to increase. This was because of steam voids. The operators panicked and dropped other control rods to shut down the reactor. Their graphite tips did the opposite. It was like pouring petrol onto a fire. Reactivity increased catastrophically and blew the reactor apart.
Then followed a nightmare of suffering and an epic of heroism. Brave, doomed liquidators, who had to go into the stricken building and try to contain the smashed reactor, suffered unimaginably high levels of radiation and died agonising deaths. The official death count for the liquidators was 31, but I think the real one was higher. The harm to the surrounding public was remarkably low. Apart from an increase in thyroid cancer, which caused the deaths of about nine children, there seem to be no public health consequences.
The horrible story of Chernobyl mirrors the horrible story of Soviet Russia, this shambling, massively inefficient, lying, fear-ridden, living corpse of a political system. The V I Lenin nuclear plant was aptly named since, if you are looking for profound cause, it was Lenin who began the whole ruinous experiment with communism in Russia, of which the Chernobyl accident was a consequence.
Nuclear power is the safest form of energy we know, and is our best option for future electricity. Koeberg, which has run well for 35 years, is a good example. Chernobyl’s RBMK reactors should never have been built, and would never have been allowed in the West.
[Picture: Pipodesign Philipp P Egli, https://commons.wikimedia.org/w/index.php?curid=5666707]
The views of the writer are not necessarily the views of the Daily Friend or the IRR
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