May 31, 2019 13:51
An investigation has revealed that the abrupt surge of power output from one of the oldest reactors in Korea, Hanbit 1, early this month was caused by operators who pulled out more fuel rods than planned during a diagnostic test. They detected the problem within two minutes and put the rods back into the reactor, causing the power to go down to zero. But the sudden surge of up to 18 percent caused an increase in a steam generator's water level that automatically switched on an auxiliary pump that sent cooling water into it. After the incident, the reactor remained on standby for about 10 hours until authorities ordered the facility to stop running.
Experts focused on the safety of Korea's nuclear plants. But Jang Jeong-wook, an economist at Japan's Matsuyama University, wrote in an op-ed piece that it is a "perpetuated myth" that a power surge of up to 25 percent at a nuclear reactor is within safe limits. Korea Hydro and Nuclear Power clearly erred in pulling out too many fuel rods, but leaving the plant on standby for 10 hours cannot be seen as an attempt to hide the problem, and comparing it to the Chernobyl disaster is politically motivated hysteria.
The Hanbit 1 reactor is programmed to shut down automatically if power output surges 25 percent. Nuclear reactors are designed to minimize nuclear fission reactions when the temperatures of coolants or fuel rise. This is why the Hanbit 1 reactor is fundamentally different from Chernobyl, which was unable to halt nuclear fission when temperatures soared so that a meltdown occurred. Jang wrote that this is like claiming that airbags can protect passengers of a car traveling 100 km/h on a 60 km/h road. But such claims disregard the fundamental mechanism of modern nuclear reactors. Korean nuclear reactors are not like airbags, but are designed to stop running the moment they travel more than 60 km/h. In other words, they are analogous to vehicles with automatic shutdown functions with gasoline flow stopping automatically if they go beyond the speed limit.
There are also claims that nuclear plant accidents often result from a combination of factors, like a lack of coolant water, an earthquake or a failure in the automatic shutdown. But such claims stem from ignorance. Water is used to cool nuclear reactors but also works as a moderator. It is needed to create chain reactions by slowing down the speed of neutrons that result from nuclear fission. Without water, chain reactions cannot take place. Even a catastrophic earthquake would not prevent a nuclear reactor from shutting down. The mechanism operating control rods is part of the same structure as a reactor, and they are connected to the upper part of a reactor by magnets, so a halt in power supply causes them to be automatically inserted into the reactor.
Then there is the claim that the outer shell of nuclear reactors is not safe enough to contain them. But that is also false. The Three Mile Island accident in the U.S. in 1979 caused half of the reactor to melt, but then-President Jimmy Carter was able to visit the facility just three days after the accident without a safety suit, because the outer shell had securely contained the radiation.
Of course there can be a variety of views about nuclear power, but fear-mongering based on ignorance and political calculation must not be allowed to obscure our judgement.
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