RICHLAND, Wash. – An EM Office of River Protection (ORP)-directed study recently helped determine accurate temperature measurement methods for heat dissipation from high-level and low-activity waste containers during the vitrification process at the Hanford Site’s Waste Treatment and Immobilization Plant (WTP). 

   The idea for the study, completed by DOE’s Pacific Northwest National Laboratory (PNNL) in February 2016, came from a 2013 ORP Grand Challenge workshop submission by glass scientist Albert Kruger and facility representative Ricky Bang, both of ORP.

   “When this study was proposed in the Grand Challenge, I recognized that this work could be used to validate the Low-Activity Waste (LAW) facility design and add to the WTP glass knowledge base,” explained WTP Federal Project Director Bill Hamel. “As I envisioned, this work has achieved both of those objectives.”

   The study results come as EM works to implement a path to glass for tank waste through the Direct-Feed Low-Activity Waste Initiative, which is intended to allow EM to begin vitrifying Hanford tank waste as soon as 2022. Vitrification involves combining the tank waste with glass-forming materials and then heating the mixture to 2,100 degrees Fahrenheit. The material is then poured into stainless steel containers, where it cools to a solid glass form facilitating long-term storage.

   The study determined that a combination of methods for testing the heat capacity, thermal diffusivity, and density of the canisters and containers was most effective in providing accurate measurements for assessing the capacity of the heating, ventilation, and air conditioning (HVAC) system during cooling of the canisters.

   The canisters must be cooled without overwhelming the HVAC system or slowing production at the plant. The amount of heat in a canister or container, and the rate at which it is released, depends on the thermal property of the glass, which will vary as the glass composition changes.   

   Since the tank waste batches entering the facility vary in nuclear and chemical composition, the glass formula has to be adjusted for each batch, meaning a single standard temperature measurement process for each container or canister is not accurate.  

   There have been many studies on the thermal properties of glass, but very few on nuclear waste glasses. Those studies, according to background information in the PNNL study, showed significant uncertainties in the thermal properties, owing to difficulties involved in experimental measurements. 

   The combination of methods identified in the study helps alleviate these uncertainties.

   Hamel said the study will be forwarded to Bechtel National, Inc., the WTP contractor, for inclusion in the LAW facility design.