Several of my regular sources of information about the happenings associated with nuclear energy, including John Wheeler’s This Week In Nuclear and Meredith Angwin’s Yes Vermont Yankeehave published stories about the recent flurry of news regarding the discovery of tritium in ground water on the site of the Vermont Yankee Nuclear Power Plant.
I have been following news about Vermont Yankee because the plant’s license is nearing expiration and because the situation in Vermont is unique in that the state actually has a say in whether or not the plant continues operating. Normally nuclear plant license extensions are decisions made by the Nuclear Regulatory Commission. I am also interested because Vermont is ranked near or at the top of the list of states in terms of lowest CO2 emissions per person, largely due to the electricity produced at Vermont Yankee. It would be almost tragic if the well operated plant was closed down prematurely.
I confess – I am interested in numbers and dabble in spreadsheets as part of my daily employment. I understand the definition of an “order of magnitude”, recognize the difference between a “milligram” and a “kilogram”, realize that spending a billion dollars is equivalent to giving 100,000 people a $10,000 check, and know that a curie is defined as the activity level of 1 gram of radium 226 (3.7 x 10^10 decays per second).
In other words, I am hopelessly unrepresentative of the average American. No matter how often someone repeats a story about thousands or even hundreds of thousands of picocuries of tritium, I cannot be frightened into action except when I realize that some people thing that is a big enough deal to cause them to advocate even a momentary interrupt production from an asset that supplies 620 Million watts of clean, affordable, emission free electricity.
Let me try to explain why I am not frightened. Here is what the Environmental Protection Agency says about the hazards of tritium (which is simply an isotope of hydrogen with two neutrons in its nucleus).
Health Effects of Tritium
How does tritium affect people’s health?
As with all ionizing radiation, exposure to tritium increases the risk of developing cancer. However, because it emits very low energy radiation and leaves the body relatively quickly, for a given amount of activity ingested, tritium is one of the least dangerous radionuclides. Since tritium is almost always found as water, it goes directly into soft tissues and organs. The associated dose to these tissues are generally uniform and dependent on the tissues’ water content.
With the knowledge that tritium is worth some minor concern because it is mildly radioactive, I then go through the mental process of determining if “thousands of picocuries” per liter is something to worry about. I know off the top of my head that the drinking water limit in the US is 20,000 picocuries per liter. I also know that a picocurie is just 0.000000000001 curies (1*10^-12) and that one of my heros, Admiral Hyman G. Rickover once volunteered during congressional testimony to drink primary coolant water from a nuclear plant, which has a much higher concentration.
What I was not quite sure of was the mass of one curie of tritium. It turns out to be 0.1 milligram (1 x 10^-4 grams). To the right is a photo of a 385 milligram aspirin; showing a photo of 0.1 milligrams of aspirin would require breaking that tiny tablet into 3,850 pieces.
I did a Google News search on the words “tritium leak Vermont” that produced 113 results, several with associated images of protesters carrying signs advocating an immediate plant shutdown. I read some of the articles and realized that they were stories about a few liters of water in the ground at the site of a nuclear power plant that each contained 0.000000028 curies of tritium. That is just 2.9 trillionths of a gram (2.9 x 10^-12) of tritium. For comparison, every liter of water contains about 111 grams of hydrogen, so the portion of hydrogen that is a tritium isotope is incredibly small – just 1 out of every 2.6 x 10^14 atoms.
The breathless calls for a shutdown of Vermont Yankee due to the quantity of tritium discovered is not just a tempest in a tea pot, it is more like vividly describing a swirl in a water droplet under a microscope and believing it should instill the same level of concern generated by Hurricane Katrina.
I cannot help but compare the tone of press reports that the forces arrayed against the intelligent use of nuclear fission energy are producing with regard to these “leaks” and the tone of press reports about two current oil leaks. If you do a search of news stories for this week, you can find at least two occurrences of large releases of petroleum products. One happened from a Siberian pipeline and is causing some concern by the WWF for its effects on tigers, one happened in Texas near Port Arthur.
In both cases, the amount of petroleum released onto the ground or into a body of water exceeds 450,000 gallons or about 1.5 million kilogramms (1,500,000,000 grams). Compare that quantity to just 2.9 X 10^-12 grams per liter in the tritiated water found in test wells at the Vermont Yankee nuclear power plant. It is difficult to grasp just how large a magnitude difference that is. Here is a chart comparing the mass of petroleum to the mass of tritium that would be found in a trillion liters of water that contains 28,000 picocuries of tritium per liter. Since the total quantity of tritium is just 2.9 grams in that case, it does not even show up on the chart, it is still in the line thickness of the x-axis.
What are the health effects of exposure to petroleum products?
Health effects from exposure to petroleum products vary depending on the concentration of the substance and the length of time that one is exposed. Breathing petroleum vapors can cause nervous system effects (such as headache, nausea, and dizziness) and respiratory irritation. Very high exposure can cause coma and death. Liquid petroleum products which come in contact with the skin can cause irritation and some can be absorbed through the skin. Chronic exposure to petroleum products may affect the nervous system, blood and kidneys. Gasoline contains small amounts of benzene, a known human carcinogen. Animals exposed to high levels of some petroleum products have developed liver and kidney tumors. Whether specific petroleum products can cause cancer in humans is not known; however, there is evidence that occupationally exposed people in the petroleum refining industry have an increased risk of skin cancer and leukemia.The real contrast in my mind is the fact that though there is some amount of coverage describing the oil spills and the effects, there is no one who is trying to use the spills as the justification for shutting down a valuable production facility or as a public relations weapon to beat up the management of the responsible companies. Certainly there is no one who is gleefully pointing to these oil leaks as a reason for attempting to shutdown the entire oil industry, but a blog post about tritium leaks starts with Comment: No to Nukes, they are dangerous and deadly! When oil leaks, people get concerned, but they take it in stride, minimize the harm and clean it up. No one would be willing to forgo all of the benefits that they obtain by burning oil merely because it is a liquid that sometimes leaks, even when it leaks in multi-tonne quantities.
Why is it that when tritium leaks, it is used to cause fear, uncertainty and doubt about the value of producing emission free, affordable electricity or heat using nuclear energy, even when the amount of material in question is measured in micrograms?
PS – Please feel free to check my numbers. I am perfectly capable of slipping a digit here and there.