Are nuclear plants intentionally built on fault lines?

Answer 1

No. Geology is considered, but there is no reason to site a reactor close to a fault line. In fact there is good reason to avoid siting reactors on an active fault line, such as the San Andreas fault.

Nonetheless, some nuclear reactors are sited very close to fault lines. One example is the Vermont Yankee Nuclear Power Station (VY), which is sited about 100 meters from a fault. Nuclear plants need to be sited where they can get large amounts of cooling water, and so many are put by rivers. Since rivers, such as the Connecticut River, by which VY sits, follows a fault line, some plants are put on such faults. The fault under the Connecticut river is considered very unlikely to produce an earthquake.

Part of the problem is that there are many faults. In fact it is hard to get away from them. Furthermore, it is not always possible to know much about the natures of the faults. The geology of the Ramapo fault was very poorly known, when the Indian Point Energy Center was built, and was regarded as nearly inactive. Serious geological study of the fault only began after a series of very small earthquakes happened in the late 1960's and 1970's, some years after the nuclear power plant was built. In fact, these earthquakes were at first thought to be vibrations from the collapse of Revolutionary War era iron mines.

Some nuclear plants in the United States were built without regard to hardening against earthquake. Several such plants were temporarily closed by Jimmy Carter so hardening could be done. Interestingly, three days after it went into shutdown, the Maine Yankee plant was hit by a small earthquake.

With the advent of the Japan Earthquake, I am appalled that our Govt. would allow the building these Nuclear Power plants along fault lines. It just goes to show the best and brightest are not in charge of our Govt. What happens when we have a 9-11 pt earthquake along the San Andreas fault line ? What , than we are going to have contaminated air and water. I am so angry over this and I pray that it doesn't happen. We need to change our viewpoints on alternative energies now ! We owe it to our children to make the necessary changes in our energy policy. What is it going to take in order for us to change ? Do we have to have a catastrophe like Japan in order to get the message ? I worried for our children and my little boy is so frightened, that he doesn't want to go to school if its going to be windy. I'm hoping that this is not just the tip of the iceberg.....

++If by "Japan" you were referring to the Fukishima incident, it's important to realise two things. Firstly, Japan is tectonically highly unstable anyway. Secondly, the earthquake and the tsunami it generated did not break the reactor, which responded by stopping as intended. Unfortunately you can't just switch off a reactor. Although the safety shut-down drops the moderator rods into the pile to reduce the fission to a mimimum, the fuel elements continue to react by themselves, producing heat. This heat should be removed by the coolant pumps continuing to run; but at Fukushima they had placed not only the national grid supply to the pumps almost at sea level, but also the emergency generators. The reactor survived the inundation - only to destroy itself because the site's own electrical supplies were destroyed by the tsunami.

The lesson is not "Don't use nuclear power", but "Make sure whatever natural disaster overtakes the area, you don't lose control of the reactor." In a bizarre twist, the Fukushima incident made Germany panic and close her own nuclear power-plants. Germany is in the middle of a very stable continent, and her Baltic coast is hardly likely to suffer from SW Pacific-style tsunamis - that's politicians who don't understand science and engineering, and the difference between risk and hazard, for you. (Yes we have them in the UK too - or ask the Italian State geologists.)

As for your child being frightened of the wind, who made him so? That incident has nothing whatever to do with the weather.