Precipitation samples are gathered when sufficient precipitation occurs to allow for the collection of the minimum sample volume of approximately 50 mL. Samples are taken of monthly composites from Idaho Falls, and weekly from the EFS, Howe and Atomic City. Precipitation samples are analyzed for tritium. During the third quarter of 2017, precipitation events slowed but still yielded 14 samples.
Tritium was measured above the 3s values in four of the 14 samples. These results are listed in Table C-5 (Appendix C). Low levels of tritium exist in the environment at all times as a result of cosmic ray reactions with water molecules in the upper atmosphere and the remnants of fallout from nuclear weapons testing. When detected, tritium values have remained well within the historical range and the range measured across the country by the EPA Radnet program (EPA 2017). Most samples have values up to about 150 pCi/L, with occasional values ranging up to about 300-400 pCi/L. The maximum value in the third quarter was 118 pCi/L in a September sample from the EFS. The overall average for most sets of tritium data in almost all media is usually about 100 pCi/L. During the third quarter concentrations were below the average value at 65.6 pCi/L
The Big Lost River (BLR) continued to flow on the INL Site for one month during the third quarter. Samples were collected at five locations (plus a duplicate) in July. A control sample was collected from Birch Creek. All samples were analyzed for gross alpha, gross beta, tritium, and gamma-emitting radionuclides. Results are listed in Table C-6 of Appendix C for the month of July.
Because of the high snow accumulation in the winter of 2016-17, large volumes of water were released from the Mackay Reservoir. Over the 5-year period from when the river last ran, loose sediment from frequent winds was deposited into the empty river bed. The first set of samples from the BLR contained high amounts of sediment. Previously during the second quarter, analyses were attempted before filtration. High amounts of sediment in the water samples prevents accurate analyses for gross alpha and gross beta. The lab determined more accurate results would be obtained by filtering all the remaining BLR water samples prior to analysis. All samples from the BLR in the third quarter were filtered before analysis.
Gross alpha activity was detected in all samples. The highest reported gross alpha activity was 2.62 pCi/L in a filtered sample from the BLR Control at Birch Creek. Gross beta activity was detected in all samples but one, the BLR Control sample at Birch Creek. The highest reported gross beta value was 3.45 pCi/L in a filtered sample from BLR at the EFS. Tritium was also detected in three samples with the highest reported value of 78.7 pCi/L at NRF. Concentrations were similar to those found in atmospheric moisture and precipitation samples, indicating a natural source, and were consistent with previous years.
No manmade gamma-emitting radionuclides were detected during the third quarter.
Radiation has always been a part of the natural environment in the form of cosmic radiation, cosmogenic radionuclides [carbon-14 (14C), Beryllium-7 (7Be), and tritium (3H)], and naturally occurring radionuclides, such as potassium-40 (40K), and the thorium, uranium, and actinium series radionuclides which have very long half lives. Additionally, human-made radionuclides were distributed throughout the world beginning in the early 1940s. Atmospheric testing of nuclear weapons from 1945 through 1980 and nuclear power plant accidents, such as the Chernobyl accident in the former Soviet Union during 1986, have resulted in fallout of detectable radionuclides around the world. This natural and manmade global fallout radioactivity is referred to as background radiation. MORE
The primary concern regarding radioactivity is the amount of energy deposited by particles or gamma radiation to the surrounding environment. It is possible that the energy from radiation may damage living tissue. When radiation interacts with the atoms of a given substance, it can alter the number of electrons associated with those atoms (usually removing orbital electrons). This is called ionization. MORE