Friday, January 22, 2010
Tritium and Health
The tritiated water was discovered in the test well around the time the walkers were headed to Montpelier. I went to Montpelier for their press conference and their cookies, and I had a sign "Yes Vermont Yankee." One woman jokingly offered me a portion of her orange juice, saying: "Here's some tritiated water, drink it." I shot back: "Yeah, give me that water, but YOU are going to have to eat a banana!"
Indeed, both bananas and tritium are beta-emitters, which means they emit an electron and some energy. It turns out that the beta emissions from the potassium in the banana are more energetic than those from tritium, and also potassium stays in the body longer than water does. I asked a friend who is a health physicist to do a calculation: 2 liters of test well water (20,000 pCi from tritium) equaled how many bananas? The answer: two liters of test-well water is the biological equivalent dose of eating part of a banana. One-twentieth of a banana, to be precise. In other words, to encounter the equivalent dose as you would receive from eating a banana, you would have to drink forty liters of test-well water. That's a lot of water.
The State of California has tritium limits which are lower than the EPA limits. For consistency, these limits should be matched with limits on banana consumption (two a year).
Idaho State University suggests that, if you get more tritium than you prefer (let's say you ate a tritium-containing rifle sight device) you could flush it out by drinking a lot of non-tritiated water. It's probably better to avoid eating the rifle sight.
Another take on the test well is described in the medicine and research blog, Big Medicine. Their calculations show that drinking water with this level of tritium for a year would yield an exposure of four millirems per year. For comparison, background radiation is about 300 millirems per year, and a cross-country plane trip increases exposure by three millirems, due to cosmic radiation.
In other words, if the test well tritium were found in drinking water it would not be a public health risk. And of course, this level isn't even in drinking water. It's in a test well. Test wells have been monitored for years around the plant, and this is the first time tritium has appeared.
If the anti-Vermont Yankee woman in Montpelier really had tritiated water available from the test well, I would have enjoyed a glass or two, quite cheerfully. We were standing near the cafeteria, so I could have bought a banana for her. Luckily for her peace of mind, I didn't.
I decided not to tell the woman in Montpelier what my doctor told me. My doctor said that since I am getting older, I need to think about protecting my bones. I should take calcium pills and vitamin D pills, and eat bananas several times a week. I'm supposed to eat the bananas for the potassium.