While the investigation and remediation of the High Flux Beam Reactor tritium plume has been a major focus of the U.S. Department of Energy and Brookhaven National Laboratory since January, recent attention has shifted to an underground collection tank associated with the former Brookhaven Graphite Research Reactor (BGRR).
The tank was identified in December 1996 during preliminary review of past operations at the BGRR, in preparation for future remediation activities in the area. The tank was built to collect drainage from pipes connected to the fan house for the BGRR, which was shut down in 1968, as well as the base of the High Flux Beam Reactor stack.
Approximately 750 gallons of water were removed from the concrete-walled tank on March 12, 1997, and analysis of the water in the tank showed significantly elevated levels of tritium and strontium-90, radium-226 and cesium-137.
Monitoring well results
Results from 13 temporary monitoring wells installed approximately 45 feet south of the tank show tritium in groundwater at concentrations up to 14,700 picocuries/liter (pCi/L), below the drinking water standard of 20,000 pCi/L. Strontium-90 has also been detected at concentrations as high as 566 pCi/L, approximately 70 times the drinking water standard of 8 pCi/L.
The contaminants appear to have leaked from a non-watertight seal located approximately five feet above the bottom of the collection tank. The tank is now being monitored on a daily basis, and there is no continuing source of contamination.
Although the strontium-90 levels are well above the drinking water standard, the strontium is not expected to have traveled far from the tank area due to its relatively slow movement in groundwater (approximately 25 feet/year). The tank itself is located approximately a mile-and-a-half north of the site's southern boundary. At a rate of 25 feet/year, it would take this contamination more than 300 years to reach the site boundary. None of the Lab's water supply wells have been impacted.
More monitoring planned
This contamination is unrelated to the tritium plume south of the High Flux Beam Reactor. Contamination in this area will be addressed under the ongoing Operable Unit III investigation. DOE and BNL are currently installing more monitoring wells to determine the southern extent of the contamination.
The HFBR tritium plume pumping system, meanwhile, has been operating since May 12, after BNL agreed to a Suffolk County request for the installation of an additional six monitoring wells to further delineate the extent of the HFBR plume.
The results from the sampling of those wells, located on the Lab site approximately one mile north of the Lab's southern boundary, are now available. Only one of the wells showed tritium concentrations above the drinking water standard, at a peak of 35,000 pCi/L. The results helped BNL to confirm the southern extent of tritium at concentrations above the drinking water standard. Other wells helped to confirm the east/west extent of the plume.
Other important results have been obtained from samples taken from five monitoring wells in the vicinity of the tritium extraction wells. Radiological analysis of these samples showed only the low levels of tritium associated with the HFBR plume, along with the background levels normally observed that are associated with naturally ocurring radioactive materials in the soil.