Radiation risk from everyday plant operations consists of risks to employees, and risks to the general public both in the immediate vicinity of the plant and further afield. Risks to the employees at the plant are managed through protective equipment and clothing, and through the use of radiation badges. Tasks at nuclear power plants are designed to keep employees well below the maximum allowable threshold for radiation exposure, and continuous wearing of the radiation badge gives the plant worker assurance that health is not at risk.
The radiation risk to the public from modern nuclear plants with state-of-the-art safety systems is extremely small. This is true because the release of harmful amounts of radiation requires not only that the reactor experience a major failure (reactors are strictly prohibited from releasing radiation during normal operating conditions) but that the containment system designed to prevent radiation release must fail as well. The chances of both events happening are infinitesimally small in countries with strong safety standards such as the United States or France. A comparison of failures at different plants illustrates this point. In the case of Three Mile Island, the failure of the reactor was a very low probability event that nevertheless cost the utility, and its customer base, a significant financial amount in terms of both the loss of the reactor and the
resulting cleanup requirements. Any operator in the nuclear energy marketplace has a very strong incentive to design and operate its plants so that such an event will not be repeated. However, the containment system did keep the contaminated fuel and coolant from escaping, and there was no perceptible health effect on the public in the subsequent months and years. Operators did in the days after the accident release contaminated steam and hydrogen to the atmosphere, but after making the judgment that the released material would not pose a health risk. Furthermore, after TMI, plant operators made changes to control equipment to further reduce the risk of a repeat accident of this type.
The Chernobyl accident had the unfortunate effect of persuading many members of the public that nuclear power is inherently dangerous in any country. However, one of the key failures of the Chernobyl design was precisely the lack of a comprehensive containment system that succeeded at TMI to prevent the escape of large amounts of radioactive material. RBMK designs of the Chernobyl type are being phased out or upgraded to international safety standards, and once this task is complete, it will no longer be accurate to make assessments of the safety of nuclear power on the basis of the Chernobyl accident.
More recently, an accident at the Kashiwazaki plant in Japan caused by an earthquake in July 2007 caused the shutdown of the plant for repairs for several months, and the release of some amount of radioactive coolant water that the IAEA later judged not to pose a significant risk to human health. This event provides further evidence that the risks from nuclear plant malfunctions, including those caused by events such as earthquakes, are primarily financial and not risks of mortality. The experience did show the financial vulnerability of nuclear power in a seismically active region, and other sources of energy may have an advantage in terms of their ability to withstand or recover from such an event. However, the safety systems of the plant were in general successful in preventing a Chernobyl-type release of harmful materials, which would be an extremely unlikely event.
Differences between actual and perceived risks from nuclear power are discussed in later sections in this chapter.
