Questions and Answers
The use of tritium at Berkeley Lab's National Tritium Labeling Facility has been the subject of intense public discussion with community representatives for some time. In response to citizen concerns, the Laboratory has prepared answers to a series of most frequently asked questions about tritium and its scientific applications at the Laboratory.
Q: What is tritium?
A: Tritium is a radioactive form of hydrogen. Chemically, tritium behaves like stable hydrogen and is usually found attached to molecules in place of hydrogen. For example, a water molecule may exchange one of its hydrogen atoms for a tritium atom, resulting in "tritiated water." Tritium is constantly produced both by natural processes (the interaction of cosmic rays with the atmosphere) and by human-made processes. Tritium is used in a wide variety of consumer products such as illuminated watches, thermostat dials, and exit signs. Both the natural and human sources contribute to a worldwide background level of tritium.
Q: Why is tritium used at Berkeley Lab?
A: Berkeley Lab's National Tritium Labeling Facility (NTLF) was established as a National Institutes of Health national resource center in 1982. The Facility's role is to conduct research, to help biomedical researchers study cell metabolism, and test new products that can be useful in curing disease. Facility staff and visiting researchers "label" pharmaceuticals and other materials with tritium (replacing hydrogen atoms with tritium atoms). For example, a potential cancer drug might be labeled so that researchers can trace where the tritium-labeled drug is deposited in the body and evaluate its effectiveness in treating a particular type of cancer.
Because tritium is radioactive, it can be easily distinguished and measured, where the "nonlabeled" material could be hard to find in the body.
The NTLF is unique in the United States as it provides the technology to do labeling and analysis at the same location.
Q: What are the regulatory limits on exposures to radiation?
A: The government establishes exposure limits for radioactive materials. For the general public, the radiation limit is 100 millirem per year, for all exposure pathways. For occupational workers, the limit is 5,000 millirem per year. The radiation exposure limit established by the U.S. Environmental Protection Agency (EPA) is an annual dose of 10 millirem for air emissions (inhalation pathway) above background per year to any individual. A Berkeley resident receives an average annual background radiation dose of approximately 260 millirem from natural and human-made sources. A goal of limiting radiation exposure to 4 millirem per year is the basis for the drinking water standards established under the EPA's Safe Drinking Water Act. (The drinking water standard, based on drinking 2 liters of water per day, for tritium is 20,000 picoCuries [pCi/L] per liter. A picoCurie is a trillionth, or 0.000000000001, of a Curie).
Q: How much tritium from the National Tritium Labeling Facility goes into the environment?
A: Small quantities of tritiated water vapor (HTO) are emitted from the NTLF. Berkeley Lab takes samples of stack air emissions, ambient air, rainfall, groundwater, creeks, sewers, and vegetation to measure emission and environmental levels. The Laboratory publishes these sample results annually and sends the reports to various agencies including the DOE, EPA, and the UC Berkeley Main (Doe) Library.
As required by EPA regulation, Berkeley Lab calculates the annual doses to members of the public using stack emission data and an EPA-approved method. In 1998, 115 Curies of tritium were emitted from the NTLF, resulting in a maximum dose to the public of 0.27 millirem for the year. This dose is less than 3% of the 10 millirem per year public exposure limit established by the EPA.
Berkeley Lab has detected low levels of tritium in soil, rain water, groundwater, creeks and vegetation. Occasionally, the levels detected in rainwater, soil and vegetation at some locations around the NTLF have been above 20,000 pCi/L, which is the EPA threshold for drinking water. However, in these cases the drinking water standard does not apply since none of this water is used for human consumption, and none flows into sources of public drinking water.
Tritium has been detected in the groundwater in the vicinity of the NTLF. This groundwater tritium is being investigated as part of the Environmental Restoration Program at Berkeley Lab. An extensive system of monitoring wells has been installed at the Lab, including many in the vicinity of the NTLF. The highest level of tritium detected in groundwater has been 35,800 pCi/l in a slope stability well. This water may have come from rain since a properly developed monitoring well five feet away has never exceeded 6,000 pCi/l. No tritium has been detected in groundwater at or outside the Laboratory fenceline. Continuous monitoring to fully characterize tritium in groundwater is being done in coordination with federal, state and local regulators and with the community.
Q: What is Berkeley Lab doing to minimize tritium emissions?
A: Even though stack air emissions have been far below the dose standard prescribed by the EPA, the NTLF has pursued improvements to achieve even further reductions. Emissions have been reduced as a result of improvements in the efficiency of labeling techniques used at the NTLF, increased size of the tritium exhaust filters, changes in storage procedures, improved disposal methods, and redesign of equipment to contain the tritium.
Today, about 80 percent of the tritium used in the research process is recycled and reused. Most of the rest is captured on silica gel and safely packaged for storage and eventual disposal. Less than one percent escapes to the environment.
Q: How can the community be assured that the Laboratory's tritium assessments are correct, and what is Berkeley Lab doing to resolve the issue?
A: The Lab has committed $100,000 to support an independent third-party tritium emission assessment. This is being led by a working group that includes regulatory officials, from the U.S. Environmental Protection Agency, the California Department of Health Services, the California Department of Toxic Substances Control, the City of Berkeley, the City of Oakland, the University of California at Berkeley, and two community organizations (Community Environmental Advisory Commission and the Committee to Minimize Toxic Waste). This group has been chartered to review current data, draft a new comprehensive sampling/monitoring plan, perform the sampling/monitoring, have the data independently evaluated/assessed, and communicate the findings to the public.
This independent assessment will be performed in addition to the Laboratory's current comprehensive monitoring program, which meets all regulatory requirements.
Further Information on Tritium
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