Posts Tagged tritium
There is a political and public relations cauldron boiling in Vermont over a recently discovered tritium leak at the Vermont Yankee nuclear plant. Tritium is a mildly radioactive isotope of hydrogen and has a 10 day biological half-life when it is ingested by humans.
The leak is minute and completely inconsequential from a safety standpoint: the tritium levels very low. Only one ground water sample is slightly above federal drinking water standards (even though the sample points are far away from any sources of drinking water). In fact, the levels are so low that even if you drank water from the test wells, and nothing else, for an ENTIRE YEAR your radiation exposure would be only about 1/10 of what you would receive from one medical x-ray, and a small fraction of your exposure from the natural background radiation. Eating the same quantity of brazil nuts every day, one of the most naturally radioactive foods, would result in MORE exposure to radiation than bathing in the water in these test wells!
These facts have not stopped the antinuclear groups in the area from going berserk. They know when they have the upper hand on a public relations issue, and they are doing everything they can to take advantage of it. Adding fuel to the fire are allegations of false statements by plant officials. At a PSB hearing last spring a plant executive stated he did not believe there was any active buried piping containing radioactive fluids. The official said the plant would verify that was the case and would get back to the board, but reportedly they did not. Potentially adding to the communication difficulties - the phrases “Buried piping” and “underground piping” do NOT mean the same thing. To an engineer the term “buried” piping refers to piping that is buried underground in direct contact with the soil. Underground piping means the piping is below grade and could be located in a vault or concrete trench.
Plant personnel have apologized for the miscommunication and are actively looking for the source of the leak. Timing could not be worse because the VT public service commission has yet to make a ruling on Entergy’s proposal to create a new nuclear only generating company, and the VT state legislature has yet to vote on the plant’s request for a license extension.
Vermont Yankee has passed every NRC inspection in flying colors and is operated both safely and reliably. In fact, the plant recently earned the highest possible rating from the Institute of Nuclear Power Operations.
On November 24th a strange thing happened at the Kaiga nuclear plant in southern India. During a routine check for radiation exposure, about 65 maintenance workers tested positive for higher than normal levels of tritium in their urine. The plant is a CANDU reactor which uses heavy water as a moderator, and heavy water contains tritium. Tritium is an isotope of hydrogen with two neutrons and one proton. It is radioactive with about a 12 year half-life.
When plant officials investigated the source of the exposure they discovered someone had intentionally contaminated a cooler of drinking water with a vial of water containing tritium. The workers were sent to the local hospital for monitoring and were later sent home. No one required hospitalization and the highest exposure any of them received was about 3 rem, about 60% of the annual limit in the USA for occupational exposure. The tritium-containing heavy water is not chemically poisonous – it behaves in the human body like regular water. It has a biological half-life in humans of about 10 days, and that can be shortened by doing things to speed the fluid exchange process like drinking extra water, administering intravenous fluids, and in severe cases dialyses. Based on what I’ve read of the event and the levels of exposure it is most likely the workers were sent home and told to drink lots of water for the next several days.
Tritium decays by firing off a beta particle (essentially a high energy electron) leaving behind a helium-3 atom. Beta particles are relatively weak and can not penetrate the dead layer of skin on your body. It is of most concern when it is ingested into the body as it was in this case. As I said the total exposure here was nothing for the workers to be concerned about. There are some reports that the workers were sickened, but I’m unsure of the accuracy of these reports. It is more likely that people not familiar with the details believed the workers were sickened because they were sent to the hospital for monitoring.If the reports are true, then the illness was not caused by radiation.
The Indian authorities are investigating to determine who poisoned the drinking water, and why. There are several theories being considered; one related to anti-nuclear sentiments surrounding India’s expanding commercial nuclear energy plans, another related to the upcoming 25th anniversary of the Bopal chemical plant disaster that happened on December 3, 1981.
This was certainly an event that will cause the Indian government some concern, not because of the consequences, but because of the security implications. The workers affected are very lucky that the culprit used heavy water and not something truly toxic. Power plants have many, many chemicals on hand for a variety of industrial purposes, and some of them could have been lethal.
What REALLY caught my eye about this story was the irresponsible and inaccurate way the event was characterized in the press around the world. Almost every major news outlet called it a “radioactive leak” that “sickened workers.” It was not until hours later that a few started to carry scaled back headlines with more accurate accounts. I really have to wonder if any of these international news services have anyone on their staff with a clue about nuclear energy. If they did, and that person did just a small amount of legwork and fact checking they could have easily reached a correct conclusion: there was no leak, and workers were not sickened by radiation.
There are striking similarities between this story and the maintenance mishap last week at the Three Mile Island that caused airborne contamination inside their containment. Neither involved a leak, neither resulted in risk to the public, in both cases only plant workers were affected, and those affects were essentially so small as to be undetectable. Contrary to all this, in both cases news outlets blew their reporting: initial reports were grossly wrong, reported leaks when there were none, and reported worker health was being affected by radiation – also wrong.