What is tritium? (Posted December 7, 2005)
Tritium is a hydrogen atom that has an additional 2 neutrons in the nucleus. The Earth's atmosphere contains small amounts of tritium produced naturally when cosmic rays strike air molecules. Although tritium can be a gas, its most common form is in water. A weak radionuclide that decays into ordinary helium and beta particles, tritium has a half-life of 12.3 years. Small amounts of tritium are routinely produced here at Fermilab during particle beam collisions in our experiments.

What are the health risks of tritium? (Posted December 7, 2005)
As tritium decays into ordinary helium, it emits a low-energy beta particle. Beta particles deposit energy in the body. The beta particle from tritium has such low energy that it cannot penetrate the outer layer of human skin. Therefore, the main hazard associated with tritium is internal exposure through ingestion. The body excretes ingested tritium in about two weeks. Thus, tritium is only harmful if it is ingested in large amounts over long periods of time. High doses of tritium over a sustained period can cause cancer. To keep people safe, federal agencies set limits on the amount of tritium in water. Federal surface water standards set a limit of 2,000 picocuries per milliliter. The water of Indian Creek is surface water, not drinking water. Federal drinking water standards set a limit of 20 picocuries per milliliter.

How much tritium did we find? (Updated Frequently)
We measured levels of tritium at 3.3 picocuries per milliliter in a water sample from Indian Creek, taken just inside the Fermilab property on November 2 (with test results available on November 14). Samples taken on December 12 and analyzed by the Illinois Emergency Management Agency confirmed the accuracy of Fermilab's measurements. All levels of tritium measured in Indian Creek and in Fermilab surface water are well below the federal surface water standards for tritium of 2000 picocuries per milliliter, and we are taking every possible step to keep the levels of tritium as low as reasonably achievable. We frequently update a Web page with results from samples taken from Indian Creek.

Where did this material come from? (Updated February 6)
Tritium is a byproduct of accelerator operations here at Fermilab. Water with low levels of tritium is pumped out of the accelerator tunnels and used in our onsite industrial cooling systems and cooling ponds. The tritium found in Indian Creek stems from the NuMI/MINOS experiment begun in February 2005.

How did it get into the creek? (Updated July 12)
Indian Creek is a small creek that originates on the Fermilab site and leaves the lab at its southwest corner. A pipe connecting two cooling ponds near Indian Creek allowed water to escape from these ponds and ultimately to reach the creek. Samples taken from the cooling ponds adjacent to Indian Creek have shown low levels of tritium, comparable to those found in the creek. Water with low levels of tritium that had already escaped the cooling ponds remained in the soil and reached Indian Creek for some time. Since the end of February, we have not detected tritium in Indian Creek.

What are we doing about it? (Updated March 31, 2008)
We are taking every possible step to make sure that we have identified all pathways of water containing tritium with the objective of reducing the level of tritium in Indian Creek and the Fermilab ponds to the lowest possible level.

• We shut off the flow of water in the pipe that we suspected to have a leak. We inspected the underground pipe, which connects two cooling ponds, found it to be defective, and we repaired it. The work was completed in June 2006.
• We began rerouting the flow of all water that could potentially contain tritium so that it does not flow into Indian Creek but instead remains in ponds on the Fermilab site.
• We consulted the Fermilab Community Task Force for Public Participation in December 2005 and started a dialog with neighbors and other stakeholders to establish long-term goals and their implementation.
• We identified and eliminated the largest contributor to the low levels of tritium found in the Fermilab cooling ponds. Since December 2005, we are capturing water with higher levels of tritium in the NuMI experimental area and are treating this water separately.
• We reconfigured the flow of water from the NuMI experimental area to evaporate a large fraction of the water through direct use in the Fermilab cooling system. (Work completed in early May 2006.)
• We also found that high humidity in the NuMI underground area contributed to tritium reaching the Fermilab surface waters. We installed the first dehumidification systems in one area of the NuMI complex in May 2006, followed by the installation of a second system in a second area in October 2007. These systems significantly reduce the amount of tritium reaching the surface water.
• Together, all measures implemented since December 2005 reduce the amount of tritium that otherwise would reach the Fermilab surface waters by about a factor of seven. We will continue to look for additional ways of reducing the tritium levels in Fermilab surface waters.
• We continue to periodically sample water in Indian Creek and the surrounding areas to ensure that levels of tritium are reduced to the greatest extent achievable and are posting the results on the Fermilab Web site. Since the end of February 2006, we have not detected tritium in Indian Creek. However, we realize that water with low levels of tritium may occasionally leave the Fermilab site, for example after heavy rain storms.
• We continue to perform extensive monitoring throughout the site to check for any changes in the now lower levels of tritium.
• In March 2008, we informed our neighbors of our plans for the NOvA experiment, which uses the same method as the MINOS experiment. NOvA requires an approximately three times more powerful particle beam in the NuMI underground hall. Because the beam is more powerful, it will also produce more tritium. In a letter to our neighbors, Director Pier Oddone shared with our neighbors the draft environmental assessment for the NOvA experiment. The amount of tritium in surface waters on the Fermilab site will remain well within the federal water standards, and we will continue to take every possible step to keep the levels of tritium as low as reasonably achievable.

Where can you get more information?
We will provide you regular updates on this situation as we implement our solutions. If you have any concerns or questions about this situation, please call Judy Jackson, Fermilab's Office of Public Affairs, at 630-840-3351. We welcome your questions and will be pleased to provide additional information.