2022 Annual Meeting
Evaluating in-Line Sensing Methods for Iodine Detection in Hanford Site Groundwater
Contaminants, such as iodine-129, are found in the groundwater beneath the Hanford
Site (Richland, Washington) from legacy nuclear waste storage originating from the Cold War
Era. Iodine-129 is radioactive with a half-life of nearly 16 million years and is known to cause
negative health effects when consumed in drinking water. To treat most groundwater
contamination, the Hanford Site relies on pump and treat (P&T) facilities to extract the
contaminated water for treatment above-ground before reinjecting clean water back into the
subsurface. One technology used to remove contaminants is ion exchange (IX) resins, for which
predicting contaminant loading capacity is key to facility operations. The IX columns capture
contaminants using resins that target specific contaminants of concern in the groundwater.
Once the resins are saturated and the contaminants break through, they must be regenerated
or replaced and disposed of. Contaminant breakthrough is currently detected by testing
subsamples of the effluent, but this method is costly in terms of both time and money. Instead,
in-line sensing allows for automatic, continuous effluent readings. While IX at Hanford does not
currently target iodine-129, treatment may be required under future P&T influent conditions.
This project aims to assess whether ion-selective electrodes (ISEs) and/or UV-visible
spectroscopy could be developed into in-line sensors for identifying when iodine is no longer
removed by IX. An iodide ISE and single-beam UV-Visible spectrophotometer were used to
investigate a range of iodide concentrations to determine the effects of stirring, use of an ionic
strength adjuster, volume, storage solution, and presence of other ions on the ISE.
Representative artificial groundwater was used to better predict the response of the sensors to
contaminants in a groundwater setting. Results of these tests, technical challenges, and future
work to explore using this approach to develop sensors for other Hanford Site groundwater
contaminants is also discussed.
Site (Richland, Washington) from legacy nuclear waste storage originating from the Cold War
Era. Iodine-129 is radioactive with a half-life of nearly 16 million years and is known to cause
negative health effects when consumed in drinking water. To treat most groundwater
contamination, the Hanford Site relies on pump and treat (P&T) facilities to extract the
contaminated water for treatment above-ground before reinjecting clean water back into the
subsurface. One technology used to remove contaminants is ion exchange (IX) resins, for which
predicting contaminant loading capacity is key to facility operations. The IX columns capture
contaminants using resins that target specific contaminants of concern in the groundwater.
Once the resins are saturated and the contaminants break through, they must be regenerated
or replaced and disposed of. Contaminant breakthrough is currently detected by testing
subsamples of the effluent, but this method is costly in terms of both time and money. Instead,
in-line sensing allows for automatic, continuous effluent readings. While IX at Hanford does not
currently target iodine-129, treatment may be required under future P&T influent conditions.
This project aims to assess whether ion-selective electrodes (ISEs) and/or UV-visible
spectroscopy could be developed into in-line sensors for identifying when iodine is no longer
removed by IX. An iodide ISE and single-beam UV-Visible spectrophotometer were used to
investigate a range of iodide concentrations to determine the effects of stirring, use of an ionic
strength adjuster, volume, storage solution, and presence of other ions on the ISE.
Representative artificial groundwater was used to better predict the response of the sensors to
contaminants in a groundwater setting. Results of these tests, technical challenges, and future
work to explore using this approach to develop sensors for other Hanford Site groundwater
contaminants is also discussed.