Three Mile Island Nuclear Plant Units 1 & 2

Nuclear power has a major advantage over fossil fuel power sources when it comes to global warming. Generating power from nuclear fuel does not produce any carbon dioxide. Shouldn’t we be retiring our coal-fired power plants and replacing them with nuclear plants?

The public is concerned about nuclear power for two reasons. The first is the question of what to do with the nuclear waste. I talked about that in my previous article on ‘Nuclear Fuel is Renewable’. The second major concern is about nuclear plant safety.

What does it mean to be safe? A nuclear accident could affect millions of people through increased exposure to radiation. How about comparing nuclear plants to the coal-fired power plants they would replace. People generally consider them to be safe.

Coal contains a large amount of dangerous compounds including trace amounts of uranium and thorium. These are naturally occurring radioactive compounds. While the amount of these compounds in coal is a very small percentage, large amounts of coal are burned in a coal-fired power plant. A 1,000 MW coal plant will release as much as 5 tons of uranium and 13 tons of thorium into the atmosphere each year. That is many orders of magnitude greater than the radiation released from a typical nuclear plant.

Coal plants also releases huge quantities mercury into the atmosphere. It is estimated that as Much as 48 tons of mercury are emitted from U.S. coal-fired power plants into the atmosphere each year. (The tall smokestack is used to disperse these pollutants over a very large area so they don’t kill all the people in the immediate vicinity of the plant.) In addition, large amounts of sulfur dioxide and nitrous oxides produce respiratory problems in people and damage our forests. About 70,000 people die each year from the effects of air pollution, more than the 40,000 people who die each year in automobile accidents. Based on the emissions, I would rather live next to a nuclear plant than a coal plant.

What about 3 Mile Island? What about the potential for a catastrophic release of radiation into the environment? What does that accident tell us about nuclear plant safety? Three Mile Island Unit 2 was the worst civilian nuclear accident in US history. A pressure safety valve stuck open at the plant, releasing a large volume of water from the cooling system. The plant operators made some serious errors in dealing with the problem, which caused a loss of cooling water in the reactor and a partial melt-down of the reactor core. A small amount of radioactive material (mainly krypton gas) was released from the plant. Radioactive krypton gas is not particularly dangerous as it is an inert gas. It does not collect in the body and disperses rapidly into the atmosphere.

The plant was shutdown successfully. There was no loss of life or injury. The amount of radiation released from the plant was estimated to produce a dose of 1 millirem of radiation exposure. This compares to average background radiation exposure from natural sources of 100 to 125 millirem per person per year. Numerous studies on health effects from the accident have not shown any correlation to the accident. The only people who suffered from the accident were the shareholders of General Public Utilities, who lost several billion dollars when the reactor was destroyed.

If an accident like this can happen, does that mean nuclear plants are not safe? Since the time of the Three Mile Island accident, nuclear plant operators and the government have done a lot to make the operation safer. They have increased the amount of safety equipment and safety inspections. Operators of nuclear plants are better qualified and better trained. Operators today have to be engineers with a through understanding of the thermodynamics of nuclear plant operation. New nuclear plant designs use passive cooling systems. The type of accident at Three Mile Island shouldn’t be possible with these new plant designs as the reactor is designed so it can’t melt down. Does that make the plants safe?

The steps taken since 3 Mile Island have made nuclear plant operation much safer. There is still the potential that another nuclear plant may have a serious accident. That however, does not make the plants un-safe. Three Mile Island suffered about the worst nuclear disaster that a plant should ever face. The idiot proof safety system, the containment vessel, worked as intended. The containment vessel is the usually dome shaped structure (barrel shape at Three Mile Island) made of 4 to 6 foot thick steel-reinforced concrete. It is a passive safety system that is designed to keep all the dangerous materials inside so it can’t escape into the environment. Plant designs and operation have improved, which is good, but it is the demonstrated successful working of the containment system that makes me feel that nuclear plants are safe. Three Mile Island is an actual demonstration that dangerous radioactive materials can be contained in the event of a worst case nuclear accident.

Note: The Chernobyl nuclear accident occurred in a plant without a containment vessel.