BUCHANAN — Indian Point officials say they believe they’ve tracked the source of a radioactive strontium leak at the nuclear plant to the defunct Indian Point 1’s spent-fuel pool.

They have begun using chemical filters to lower radiation levels in the pool while they try to control the leak.

Company engineers and hydrologists took that action after an underground sump designed to collect runoff from emergency water-cooling operations showed strontium levels 10 times higher than anywhere else on the property.

The most recent sampling of the collection sump showed strontium levels of 296 picocuries per liter, about 25 times the allowable levels for drinking water.

Nuclear Regulatory Commission inspectors and state health officials have said radiation has not been found in any drinking water sources on or off the site, though they and company officials acknowledge the irradiated water is likely making its way to the Hudson River.

Environmentalists and some local residents have not been assured by either the company or the NRC, expressing continuing and sometimes angry concern that no one is sure just how much radiation is traveling to nearby water sources.

Earlier underground water samples showed strontium levels of about 30 picocuries per liter at the highest concentrations, within about 150 feet of the Hudson River.

“You’d expect to find higher concentrations (of strontium) as you get closer to the source, and that’s what we’ve found,” said Donald Mayer, Indian Point’s lead official on the leaks of irradiated water that began showing up in August. “The numbers near the river haven’t changed.”

Mayer said the suspected water source is about 400 feet from the Hudson River, filling a third of a 30,000-gallon, concrete-lined pool.

The irradiated water leaks have been a problem since late summer for Entergy Nuclear Northeast, the owner of the three nuclear plants in Buchanan.

Tritium was the first radioactive isotope to show up after a hairline crack was discovered in the base of Indian Point 2’s spent-fuel pool during excavation. Company officials are still tracking the source and extent of that leak.

The company dug 23 wells to map the underground water plume, and the samples taken showed strontium as well.

Mayer said yesterday that the higher strontium levels in the sump have prompted the company to plot out 12 more wells to surround the Indian Point 1 spent-fuel area, at an estimated cost of $2 million.

NRC spokesman Neil Sheehan confirmed yesterday that the strontium levels elsewhere on the site have remained stable and the agency approved of Entergy’s current plans for additional wells, and the chemical filtering to lower strontium levels in Indian Point 1’s spent-fuel pool.

Entergy officials said yesterday that strontium levels inside the spent-fuel pool were about 200,000 picocuries per liter.

That pool has been leaking between 25 and 50 gallons of irradiated water a day since the early 1990s. Entergy bought the plants from Consolidated Edison in 2001, expecting to contain the leak until the pool could be drained.

Currently, that water is captured by curtain drains underneath the pool that direct the water to a treatment area before it is released to the Hudson River at radiation levels permitted by the Environmental Protection Agency.

Mayer and other company hydrology experts say the believe the curtain-drain system may not be collecting everything it is supposed to and the new ring of wells should detect the amount of water escaping.

The strontium readings are not higher than one would expect in that area because the concrete and dirt surrounding the pool act as a filter for the radioactive isotopes.

Company officials are working on moving the spent fuel from Indian Point 1 to dry cask storage being built at the site and scheduled for completion late in 2007.

Once that move is made, the spent-fuel pool water — which cools the used rods of uranium and acts as a protective shield — can be drained, treated and released, officials said.

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