UPTON, NY -- Aggressive efforts to address radioactive tritium groundwater contamination continue at the U.S. Department of Energy's Brookhaven National Laboratory (BNL). Both the Environmental Protection Agency (EPA) and the Suffolk County Department of Health Services have stated that the contamination poses no public health threat. The most recent findings are summarized below. More detailed information is also provided.
No drinking water, either on or off the Laboratory site, is affected by the HFBR-related tritium contamination. Daily tests of BNL's drinking water have confirmed that it is not contaminated with tritium. Additional wells are being installed at the site boundary south of the HFBR to confirm that the contamination has not reached the boundary.
DOE and BNL are currently working with regulators to determine the most effective methods for remediating the contaminated water. DOE has directed BNL to take the necessary actions to begin pumping from the plume's leading edge by April 20, 1997.
Groundwater Monitoring: New Results
More than 400 groundwater samples have been analyzed since January 1997. Based on these analyses, DOE and BNL believe that the plume is moving southward from the reactor in a narrow strip, at depths of up to 100 feet. The most recent 80 samples were taken from four of seven wells located about a third of a mile (1900 feet) south of the HFBR, on the BNL site. Preliminary data released March 4 were from two of the four wells. Data from the three remaining wells are expected soon.
Fifteen to 20 samples were taken from each well at depths ranging from 30 feet to 200 feet below the surface to create a "vertical profile" of the groundwater. Two of the four wells had tritium above the drinking water standard. The highest concentrations of tritium found in each of the four wells were 88,800; 70,200; 14,600; and 2,590 pCi/L, respectively. These concentrations were found at a depth of approximately 100 feet.
Based on results from these wells and from wells on the BNL site's southern boundary, announced in February 1997, DOE and BNL are now focusing on the area between the two sets of wells to find the leading edge of the contamination. A new series of 19 vertical-profile wells has been installed just over two-thirds of a mile south of the HFBR. More will be installed further south, including new wells on the boundary. Samples from three wells at the site boundary taken in February 1997 showed only background levels of tritium.
Other results recently received from testing laboratories show low levels of radioactive cobalt-60 in four temporary on-site wells over a mile from the southern boundary that were installed as part of the ongoing tritium investigation. The cobalt levels range from less than 1 pCi/L up to 6.6 pCi/L (EPA proposed drinking water standard is 200 pCi/L). The cobalt is not believed to have come from the HFBR. Investigations to find the cobalt's source are under way. Although tritium concentrations can be determined in a few days, complete analyses for other radionuclides can take several weeks.
Historical Data on Tritium in Lab Potable Well
BNL and DOE have also been reviewing historical groundwater monitoring data across the site, focusing on a now-unused BNL drinking water well located in the center of the BNL site, about 900 feet south of the HFBR. These data show that the well contained low-level tritium.
The well provided drinking water to BNL's supply system until 1986. Routine water monitoring at the well starting in the mid-1970s showed expected background levels of tritium. In 1985, however, higher tritium readings (1,080 pCi/L) were obtained far below the drinking water standard of 20,000 pCi/L, but above natural background levels (approximately 200 pCi/L), and previous readings. In 1986, the average tritium level in the well increased to 2,103 pCi/L. The well also began showing signs of contamination with the organic chemical trichloroethane.
Because the level of organic contamination (100 parts per billion [ppb]) was above the drinking water standard (50 ppb in 1986; 5 ppb today), the well was taken out of service. Although no official explanation was reported at the time, the tritium levels were attributed to leaks in nearby BNL sewer lines. Radioactive contaminants were below the drinking water standard, and BNL combines water from several wells to make up its drinking water supply.
A conservative analysis shows that no worker could have received more than 0.1 millirem per year from this source, even if this well were the worker's only supply of drinking water. The EPA standard for radionuclides in drinking water is 4 millirem per year. There was never any threat to employee or visitor health.
Finding the Tritium Source
BNL officials recently completed a test, more sensitive than those used previously, to determine the rate at which the HFBR's spent fuel pool may be leaking. This test suggests that the pool (containing tritium at a concentration of 130 million pCi/L) may be leaking an estimated 7 to 14 gallons of water each day. The leak-rate monitoring test examined the level of water in the pool over a period of several days. The test takes into account variations in pool level due to evaporation and temperature. It is precise to within three or four gallons a day.
The leak-rate measurement will soon be corroborated by groundwater monitoring directly below the pool, which is expected to help identify the source of the tritium contamination. As agreed to by Federal, state, and local regulators, two thin horizontal borings, drilled under the HFBR building, will serve as monitoring wells. A&L Underground, Inc. of Olathe, Kansas, plans to begin drilling early this week, using specialized directional boring techniques that will reach 50 feet below the building's foundation into the water table. Drilling the wells will not affect the structural integrity of the HFBR.
The horizontal borings, with five-inch diameters, will allow water samples to be taken 20 feet below the lowest part of the pool to better identify the source of the tritium leak. The HFBR will remain shut down until the contamination's source has been pinpointed and the spent fuel pool has been fitted with a stainless steel liner to prevent further leaks, a process that is expected to take about a year.
DOE and BNL will continue to provide information about the tritium contamination investigation as it becomes available.
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