Protecting Nuclear Facilities against Nature’s Fury

In general, all the nuclear facilities are designed to withstand certain amount (?) of natural events such as earthquake, floods, rains, etc. Therefore, there has been a misconception since the early days that human error and mechanical failure are the major variables with higher risk of radiological releases to the environment. Nuclear power plants all over the world are exposed to natural hazards, such as hurricanes, floods, fires, tsunamis, volcanoes and earthquakes. The event in one country may cause damages in other neighboring country.

With safety always a key concern, engineers, safety specialists and architects also have to take the extreme natural forces into consideration while designing the plants. Mitigative measures are expected to be in place. When the earthquake hit the Kashiwazaki-Kariwa nuclear power plant in Japan, four reactors shut down automatically. Water containing radioactive material was released into the sea. There was no adverse effect on human health or the environment. It was observed that the structure, systems and components that are important to safety were actually built robust enough to withstand the earthquake. However, it was noted that the plant´s design seismic hazard inputs were underestimated.

Subsequently, the IAEA has revised the existing set of safety standards on site selection and evaluation to analyze the impact of external hazards such as earthquake using the best available and updated knowledge.

There are further questions to be answered by the designers and regulators. The very first question is up to what level of the stated hazard one should accept as adequately safe design? What about the after-effects: such as of earthquake generated tsunami? One such disaster occurred in the Indian Ocean on the morning of Sunday, 26 December 2004. Over 200,000 people were killed. Can nuclear facilities built generally on the sea shores withstand such type of natural fury? How much safety in design? Is there any limit? Can we build economically viable SAFE nuclear facilities?