Six commercial nuclear power plants have leaked radioactive tritium to nearby soil and groundwater, according to the Nuclear Regulatory Commission (NRC). The worst offender—Exelon's Braidwood facility in Illinois—leaked more than 6 million gal of radioactive cooling water from a faulty discharge pipe over a nine-year period, beginning in 1996. Although the plant owner knew of the leaks and fixed the pipe, it underestimated the significance of the leaks and failed to monitor them or to take remedial action. The owner did not report the full extent of the leaks to NRC or to the public until late 2005 after tritium was found in an off-site private well.
Both NRC and the Nuclear Energy Institute (NEI), a trade association, have begun investigations to determine whether other plants among the nation's 103 commercial nuclear reactors may have similar problems. The trade association has announced a voluntary program to report all similar leaks immediately and to issue a formal report within 30 days of a leak's discovery.
So far, along with Braidwood, power plants identified as having on-site tritium in soil or groundwater include Dresden, Clinton, and Byron in Illinois; Indian Point in New York; and Palo Verde in Arizona; according to NRC officials. Indian Point appears to be the only facility whose leaks come from spent fuel storage pools; the rest are piping related. But NRC officials say they are still studying the extent and causes of the leaks, and only at Braidwood has tritium migrated off-site. It is likely that nearly all nuclear reactors have some degree of tritium contamination on-site, however, because of the nature of the radioactive hydrogen isotope, particularly its ability to react with oxygen to form water.
Tritium is a weak β-emitter with a half-life of 12.3 years. It decays to helium. As with all ionizing radiation, exposure to tritium increases risk of cancer, and the Environmental Protection Agency has set a drinking water standard of 20,000 picocuries/L for tritiated water, assuming a person drinks 2 L/day for a lifetime.
At Braidwood, on-site groundwater monitoring wells found tritium as high as 282,000 picocuries/L—14 times the EPA drinking water standard. Near the site's northern border, levels in a monitoring well have reached 58,000 picocuries/L. NRC in a report released on May 25 estimates a plume of contamination extending almost one-half mile beyond the northern plant boundary. Low levels of tritium—about one-tenth the drinking water standard—have been found in private wells beyond the Exelon site.
The discovery by state and local inspectors of contamination in private wells in March 2005 led to more monitoring by Exelon, and finally in late November, Exelon formally reported to NRC the extent of the contamination. Since then, the company has drilled more than 300 monitoring wells, and two weeks ago, it began a remediation program at an area just north of the plant boundary on a 90-acre parcel it has now purchased. There, it is removing tritiated water from a contaminated shallow pond. Exelon is not contesting possible sanction. In fact, company spokesman Neal Miller says the company is to blame and takes full responsibility for the leaks and the cleanup.
There is a lot of anger aimed at Exelon by local residents and the State of Illinois, says David Lochbaum, a nuclear engineer with the Union of Concerned Scientists. "We worry that there is a growing trend of greater frequency and magnitude of these spills," he says. "Braidwood is the straw that broke the camel's back. This is the first time where contaminated water had gotten off-site and into someone else's backyard."
At Braidwood, three large leaks occurred in 1996, 1998, and 2000, discharging a total of 6.2 million gal of water from a 42-inch-diameter, five-mile-long discharge pipe. The pipe exits to the Kankakee River, where the flow is sufficient to dilute the radioactive water to levels below regulatory concern. However, vacuum breakers, needed to maintain constant pressure within the pipe, leaked while the pipe was carrying tritium-contaminated water to the river.
Tritium gets into discharge water most often when plant operators adjust the chemistry of liquids coursing through the reactor's primary coolant system. Frequently, operators must remove chemicals that have passed through the reactor's primary system and core and have picked up radioactive material. Most of the radioactive particles are filtered out before being released as overflow to a discharge pipe, but the hydrogen isotope tritium, bound to oxygen, passes through and is discharged with other wastes as water.
"You can't filter water from water," says Ralph Andersen, chief NEI health physicist and director of radiation protection. The spills were not unexpected, he says, and are part of operations for any industry. "Such discharges will have to be dealt with during decommissioning," he adds.
He says the company reported the occurrence of the leaks to NRC, but the company itself was unaware of the leaks' nature. "Braidwood acknowledges they made a mistake. They failed to do a complete assessment and failed to understand that eventually the tritium portion of this material would go into soil and ultimately migrate through groundwater and off-site."
Viktoria T. Mitlyng, an NRC spokeswoman, goes further. "The Braidwood operators did not evaluate the radiological hazard from the spills, calculate the dose to the public, monitor the impact of the spill, or report the spill in its annual report, which would allow the public and NRC to know of the threat to groundwater."
Mitlyng, Lochbaum, and Andersen all stress that no tritiated water has migrated off-site at levels that are a health threat. However, the company's failure to report the extent of the leaks to NRC raises concerns about industry regulation, which is largely based on self-monitoring and company diligence and honesty.
NRC oversees a company-run inspection program at each U.S. commercial reactor site, but if a reactor operator fails to report problems to the NRC resident inspectors stationed there, NRC doesn't know what has occurred. This reliance on self-reporting came within a hair of disaster at FirstEnergy's Davis Besse Nuclear Power Station in Ohio in 2002. There, the company failed to report years of corrosion to the reactor's vessel head, which could have led to loss of coolant and a core meltdown. The near-accident resulted in a highly critical internal NRC report of the incident and a $5.45 million fine for FirstEnergy, the largest fine in NRC history. It also demonstrated a gulf in the regulating system (C&EN, May 12, 2003, page 29).
"I am reluctant to compare this to Davis Besse," Mitlyng says. "In the case of Davis Besse, they were indicted for, basically, providing information that wasn't true—for lying. Here, the utility was sloppy. At Davis Besse, they were sloppy and liars.
"However, I do think it would have been beneficial for them to keep a closer eye out and, when millions of gallons of water are dumped on the ground, to go out and sample it. You know, just for the heck of it.
"Braidwood," Mitlyng adds, "is allowed to release certain amounts of tritium. All plants have some planned releases of nuclear material. But we have to make sure it is not harmful to the environment and public. When you have a pipe that is leaking thousands of gallons of water and that water may contain radioactive material, it is the plant's responsibility to tell us and to test for nuclear materials. This was not done.
"Our inspectors cannot oversee every single operation at a plant. That is why we have reporting requirements," she continues, "and that is why we have licensees required to conduct tests and make sure unplanned releases don't contain nuclear material-or at least tell us if it does.
"The leaks were not reported to us as leaks that contained nuclear material. A water leak doesn't concern us. As far as whether NRC resident inspectors were told of the leaks, we don't have any report or communication from the utility on that. We are still looking at who knew what when, but as far as we can see now, there were no reports that would have raised any alarms with us."
NRC has cited the company for four violations and has assembled an internal task force to study tritium problems nationally. The State of Illinois has sued Exelon for violations that could reach several million dollars. It has also passed a law requiring immediate notification of a spill and calling for more inspections.
The leaks come at a time when the nuclear industry appears on the verge of a new era for nuclear energy. President George W. Bush in late May urged that the U.S. aggressively move forward with construction of new nuclear plants. He called the industry "overregulated" and outlined a strategy of federal support that included construction loan guarantees, tax credits, and risk insurance. The head of NRC also told a Senate committee in May that 16 utility companies had plans to build 25 new nuclear power plants.
The current fleet of nuclear power plants is getting old. Most are drawing close to exceeding their 40-year license, and NRC has approved 20-year extensions for 42 plants. Age is a concern of nuclear critics.
Braidwood's two 1,150-MW reactors began commercial service in 1988 and are not old by industry standards. And Andersen is adamant that age had nothing to do with the leaks. He strongly argues that such a leak can happen to any discharge pipe—be it at a chemical company or nuclear power plant.
NEI's survey of nuclear facilities will be complete at the end of July; NRC has a "lessons learned" task force examining tritium leaks as well.
Lochbaum applauds the industry and NRC efforts and hopes they will lead to more sensitive instrumentation capable of measuring smaller leaks more quickly, rather than just digging more monitoring wells.
"We prefer prevention. It is better than reaction," he says. "But the call is up to the owner in our minds. The bottom line is, no matter what an NRC licensee does, there must be assurance that the stuff doesn't get to the fence line."