The Power Makers' Challenge by Martin Nicholson

Author:Martin Nicholson
Language: eng
Format: epub
Publisher: Springer London, London

15.1 Reactor Safety

Sorting out fact from fiction is often difficult. One objective way to assess the safety of a technology is to look at history. Fortunately with fission reactors we now have quite a bit of history to draw on. We have been using fission reactors to generate electricity for over 50 years. In that time, there have been just three significant accidents at commercial power stations, and only one created a serious radiation hazard to the public.

The first accident was in 1979 at Three Mile Island in the US, which experienced a partial core meltdown. The accident was caused by a technical malfunction followed by human error. Cooling-water pumps failed, preventing the steam generators from removing the heat from the reactor. An operator error prevented the backup system from operating and the reactor shutdown as it was supposed to under such circumstances. However, a pressure-relief valve designed to release increased pressure in the reactor failed to close properly once the pressure reduced. The open valve allowed radioactive cooling water to escape the reactor vessel causing the reactor core to overheat. The radioactive fuel stayed contained in the reactor vessel. Some trace radioactive gases were vented to relieve pressure on the containment dome, but it was relatively minor, exposing people in the immediate vicinity of the reactor to similar level of radiation they would get from a chest x-ray—frightening at the time, but not damaging to people’s health.

Even though the damage was contained, it did not stop anti-nuclear activists from demanding the shutdown of all nuclear power plants, and the event helped to stop the progress of building new nuclear plants in the US. As a result of the accident, existing and future plants were made safer and operating protocols were improved, and over the last 30 years there has not been a similar incident.

The second accident was at Chernobyl in Russia in 1986 and was much more serious than at Three Mile Island. The Chernobyl accident dispersed part of the radioactive core into the environment as airborne dust and a cloud of fallout drifted over Europe. Human error again played a part, but in this case the reactor was flawed in design and of a type that was never built in the West. The accident happened as a result of what seems to have been a badly managed system test of some of the electrical systems, which involved deactivating safety systems. System warnings were ignored by the operators and when they eventually tried to control the problem it was all too late. The reactor went out of control in a way a light water reactor would never do under the same circumstances. A steam explosion (not a nuclear explosion) blew the top off the reactor and without a containment building (which is mandatory in most countries) radioactive material escaped into the environment for several days. Thirty-one people died at the reactor site and further 16 accident cleanup workers later died by the exposure to the extremely high levels of radiation in the immediate vicinity.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.