Describe how the reactor at Three Mile Island (or Chernobyl) was supposed to work. What went wrong and what are the implications of the accident?
On 26th April 1986, what was described as "The world's worst nuclear disaster" occurred at the Chernobyl nuclear power plant in the Ukraine. 190 tons of highly radioactive uranium and graphite were expelled into the atmosphere. The result was an international ecological disaster and as such the issue of safety in nuclear reactors like that at Chernobyl needs to be addressed and the dangers assessed.
The staffs at Chernobyl nuclear plant were to complete one final test that would serve as a proof that their power plant would survive a sudden energy blackout. The goal of the test was to show that the nuclear reactor 4 could be "rebooted" in the absence of any external energy sources
However, there were a number of dangerous measures taken in the operating procedure.
The test required the automatic control system to be switched off. Also, the emergency core cooling system was also turned off for the duration of the test because the chief plant engineer decided it, based on the fear that it will be dangerous if the cooling water from the emergency tanks enters into the hot reactor. Finally, both emergency diesel generators were turned off, in order to simulate a "pure" experiment.
During the test several things went wrong. With the automatic control system off the operators could not maintain the rector power under the devised limit. The power required for the test was only a few hundred MW however the reactor went 10 times lower than expected (30MW thermal)
At this point the reactor should have been shutdown, and a regular start-up been scheduled the next months. But an immediate restart was attempted...