Understanding the Possible Causes of a Nuclear Power Failure
Electricity from nuclear energy is possible due to the fact that heat energy is released in nuclear fission reactions (splitting up of an unstable radioactive nucleus on bombarding it with neutrons). This heat is used to convert water into steam which is used to run turbine for the production of electricity.
According to Merriam-Webster Dictionary fission is “the splitting of an atomic nucleus resulting in the release of large amount of energy”.
The greater the quality and quantity of the heat, greater is the power generation efficiency. But if the heat crosses the threshold level, the reactor (the core part in which the nuclear fission occurs) may explode. So it is important to maintain the temperature of the reactor below the threshold level for the proper operation of the reactor. The reactor is surrounded by a coolant. Commonly used coolants include liquid helium and water.
After being in continuous contact with the hot reactor, the coolant also becomes hot and loses its purpose. It is for this purpose, nuclear reactors are usually built near a large water resource like sea. This seawater is allowed to flow around the vessel containing the coolant and helps reduce the temperature of the coolant thereby controlling the temperature of the reactor. The major precaution to be taken in a nuclear reactor is that the reactor and the coolant vessel should withstand high temperature; radioactivity and it should not collapse. If the nuclear reactor breaks down, then the sea water and the coolant may mix with each other and the probability of sea water becoming radioactive is high.
The difference between a nuclear bomb and a nuclear reactor is that the former is an uncontrolled chain reaction whereas the latter is a controlled one. In other words, the reaction rate in atomic bombs is rapid while the reactions in nuclear reactors are maintained to occur at a slower rate by the use of moderators. Not all radioactive elements can be used as in fission. Only certain materials are fissile and the amount of fissile fuel (i.e. the number of nuclei undergoing fission) should not be greater than a particular level known as critical quantity above which reaction cannot be controlled.
So the commonly possible reasons for the breakdown of a nuclear reactor include
- Reactor temperature reaching catastrophic peaks
- Coolant vessel collapsing (due to either natural or man-made disaster)
- Fuel exceeding the critical quantity
- Failure in controlling the reaction rate
- Power failure resulting in the failure of reaction controlling mechanisms
* Image Courtesy Top of Primary Containment Vessel, Unit 4 (02813323) by IAEA Imagebank licensed under CC BY-SA 2.0