Since August, officials at the Indian Point Nuclear Power Plants have been trying to locate a leak of water containing tritium, a radioactive form of hydrogen and one of the many radionuclides released by nuclear power plants.

Entergy Nuclear Northeast, owner of the Buchanan plants, has almost completed digging nine wells that they hope will characterize the level of tritium contamination at the site of the plants. Earlier this month water sampled from a well near the Unit Two spent fuel pool was highly contaminated with tritium. The 40-foot-deep pool stores used radioactive fuel assemblies.

The tritium levels near the spent fuel pool measured 600,000 picocuries per liter of water, which is 30 times the drinking water limit of 20,000 picocuries of tritium per liter set by the Environmental Protection Agency (EPA).

According to Neil Sheehan, spokesman for the Nuclear Regulatory Commission (NRC), the leak was believed to be coming from the spent fuel pool. Divers were sent into the pool in October to examine what they thought were cracks in the pool wall.

“There were three flaws in the pool, and they used a vacuum box device to see if they were leaking, and they determined they weren’t,” said Mr.

Sheehan. “They are still going to repair [the flaws] as a precaution. We are continuing to check the pool.”

Three new wells were dug adjacent to the Unit Two reactor building this week.

Mr. Sheehan said that only one of those wells was above the EPA limit; one measured 142,000 picocuries per liter, and the others were 42,300 and 63,900 picocuries per liter.

“Wells closest to the Hudson River yielded either just below the EPA drinking water limit or slightly above,” said Mr. Sheehan. “We are trying to paint a picture of the extent of the tritium contamination.”

Phillip Musegaas, policy analyst for Riverkeeper, a Tarrytown-based advocacy group monitoring the Hudson River, reservoirs, and aquifers, said his group is concerned about contaminated water moving toward the river.

“Our main concern is that there is no plume of tritiated water under the plant,” said Mr. Musegaas. “We are trying to find out if there’s a body of water either moving toward the river or going into the groundwater.”

Geological documentation from the original Indian Point licensing material shows that the plant is situated on a bowl-shaped depression, according to Mr. Musegaas.

“All the on-site groundwater generally moves toward the river,” he said.

“That lessens the risk of a plume of water moving north towards Peekskill or Buchanan. The NRC agrees with us that the groundwater flows from the northwest to southeast in a down’ angle toward the river.”

Mr. Sheehan said that there was no indication that the tritiated water was getting into the groundwater. But health effects of tritium in the water is a concern. In June the National Academies of Science released their seventh report, “Biological Effects of Ionizing Radiation,” on the health risks from exposure to low levels of ionizing radiation. The report confirmed, as it did in previous reports over the last 25 years, that there is no safe level of exposure to radiation and even very low doses can cause cancer.

The report also confirmed that tritium is carcinogenic and mutagenic, and human beings can be exposed to tritium through inhalation, absorption, or drinking contaminated water. Rapidly growing cells such as fetal tissue, genetic materials, and blood-forming organs are particularly sensitive to the effects of tritium.

The risk numbers in the report indicate that about 1 in 100 members of the public would get cancer if exposed to 100 millirads per year for a 70-year lifetime. An average chest X-ray delivers about 10 millirads. The U.S. Government considers 500 millirads per year safe if you live outside a nuclear power plant. Tritium is known to have a 12.3-year half-life.

“You need to understand that when they say it has a 12.3-year half-life it doesn’t mean it’s gone in 12.3 years; it means only half of it’s gone,” said Dan Hirsch of the Committee to Bridge the Gap, a nuclear watchdog group that studies the effects of radiation. “It doesn’t mean that all of it’s gone in 25 years. It takes approximately 250 years for it to decay to negligible levels.”

Water carries tritium and disperses into the water table. Mr. Hirsch said tritium moves more rapidly than other radionuclides. “If it’s the water of the spent fuel pool that has the leak, that will cause tritium to be found some distance away.”

According to the layout of the power plant, the well near Unit Two measuring 600,000 picocuries per liter is the farthest from the Hudson River.

Entergy spokesperson Jim Steets said that there’s no evidence that the tritium is traveling toward the river.

“It’s still early to come to any conclusions,” he said. “We are gathering information which can lead you in one direction and then in another direction.”

The reason for the different directions could be that site geology is mostly bedrock.

According to Mr. Hirsch, tracing tritium in wells dug in bedrock becomes very complicated.

“When you have fractured bedrock as the means of migration, it becomes very hard to pinpoint a plume,” he said. “You can put a well one place and not find it, put a well next to it and find it. You can have higher concentrations further away from the source. It’s not a nice neat plume. It can get very complicated to determine how far it’s gone, how wide it is, how deep it is, or where it came from.”

Mark Cox, the NRC senior resident at Indian Point Two, said that the initial plan was to dig nine wells. “We are still working to get those nine initial wells in,” he said. “Based on results from those nine wells we will determine whether we do an increase in scope or go ahead and treat the water.”

The typical remediation techniques are pumping the water out and getting the water to a monitored location, said Mr. Cox.

But Mr. Hirsch said tritium remediation is very difficult.

“It’s impossible to remove tritium,” he said. “Most contaminants are either dissolved or suspended in the water. If it’s suspended, you can filter it out; if it’s dissolved you can run it through things like charcoal ion resins.”

But because tritium combines with oxygen to form a liquid it actually is the water, said Mr. Hirsch. “It’s nothing you can filter out, nothing you can readily remove. You can get it out by breaking the water apart with electrolysis, which is immensely expensive. There may be some other technique, but it’s vastly more difficult to deal with than any other contaminant.”

There are other, heavier isotopes in the spent fuel pool, like strontium 90 and cesium 137, that don’t travel with water as well. “These are also very bad radionuclides,” said Mr. Hirsch. “But at least you can remove them from water.”

This week, results became known from water sampled from stormwater drains near the plant’s discharge canal. The canal feeds diluted water into the Hudson River.

“One of the stormwater drains had a reading above the EPA limit, which was 37,000 picocuries per liter,” said Mr. Sheehan. “The other was 12,000 picocuries.”

“Storm drains don¹t discharge directly into the discharge canal,” he said.

“There is a dilution effect, so by the time the water reaches the mouth of the river it is mixed with a greater volume of water.”

Mr. Sheehan was unable to say when the storm drains were previously monitored.

“These levels are conservative estimates,” said Mr. Steets. “We routinely discharge tritium into the discharge canal, and it measures about four-hundredths of one percent, or .04 percent of the normal discharges of tritium.”

Mr. Sheehan said the NRC was planning a public meeting sometime in January about the tritium.

“By then we should have results from all nine wells,” he said. “We are looking to wrap up the special inspection in December. In light of the fact that we are still drilling wells and taking samples, we would rather wait until Entergy has a better sense of the contamination and where they are going with it.”

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