Apr. 7--Steam laced with radioactive tritium escaped Thursday from a valve at an Exelon Nuclear power plant in Will County as the company was holding an information night to tell residents how it planned to start cleaning up tritium from previous spills.

Much of the steam--which escaped from the west side of the Braidwood Generating Station plant--condensed and about 500 gallons of water pooled on plant grounds, Exelon Nuclear spokesman Craig Nesbit said. Some of that water flowed into a ditch that lies between the plant and the village of Godley, he said.

Though tritium in the pooled water on plant grounds was measured at levels more than twice federal drinking- and ground-water limits, tests on water in the ditch showed no detectable levels of tritium, Nesbit said.

Those immediate tests would not detect some elevated tritium levels, and samples were sent to a lab for more precise testing, Nesbit said.

Exelon brought out earth-moving equipment and created a dirt berm around the ditch. It also placed an insertable bladder to create a dam, Nesbit said.

The steam started to escape about 1:30 p.m. and was stopped about 6 p.m., he said.

Rich Bibly, who lives near an underground pipe that carries water with tritium to the Kankakee River, where it is legally dumped, was on his way to the Exelon information night when he heard about the escaping steam. He took a detour to the plant and saw the steam escaping about 5:45 p.m.

"It just boggles the mind," he said. "How can it just keep happening?"

In recent months, Exelon disclosed that water with tritium spilled four times from the underground pipe between 1996 and 2003. Those spills contaminated groundwater outside the plant and led to four recent lawsuits, one filed by Atty. Gen. Lisa Madigan and State's Atty. James Glasgow, against Exelon.

Glasgow was at the Exelon meeting, as were representatives from the Illinois Environmental Protection Agency, which has cited Exelon for the groundwater contamination. So was the Nuclear Regulatory Agency, which is probing spills at Braidwood and two other nuclear power plants Exelon owns in Illinois.

Tritium, a byproduct of nuclear generation, can enter the body through ingestion, absorption or inhalation. Chronic exposure can increase the risk of cancer, birth defects and genetic damage. County, state and federal officials have said the levels of tritium in groundwater outside the Braidwood plant are not a public health threat.

hdardick@tribune.com