Overview of Vacuum Drying Methods and Factors Affecting the Quantity of Residual Water – Public Version

NRC initiated a research activity with the Center for Nuclear Waste Regulatory Analyses (CNWRA®) to develop a conceptual test plan for measuring the quantity of residual water remaining in a canister following vacuum drying to the criterion referenced in NUREG–1536. While residual water may be considered as unbound or bound (i.e., physi- or chemisorbed), the focus of this test plan is only the unbound water. This activity consists of the preparation of two technical letter reports. The first is the present report, which describes current industry drying practices and capabilities. It also reviews canister and fuel assembly designs to determine design features or characteristics that could affect the quantity of residual water after drying. Based on this information, recommendations are made for parameters to evaluate in the test plan. The second report will be the conceptual test plan itself. The contents of this report are as follows:
• Section 2 describes the setup and operation of typical industry vacuum drying systems.
• Section 3 describes the characteristics of fuel assemblies and canisters that may affect the quantity of residual water after drying.
• Section 4 describes measurement techniques and equipment that may be employed to measure the quantity of residual water.
• Section 5 provides a summary of the report.