DETECTING WATER IN DRY STORAGE CANISTERS FOR USED FUEL

摘要

This work focuses specifically on methods for detecting water inside of dry cask storage systems (DCSSs). Ideally, the environment inside of a DCSS confinement is inert and free of water to prevent potential corrosion of used fuel cladding or other internal hardware. However, there is some uncertainty about the amount of residual water potentially left behind in a DCSS as a result of drying processes, and assumptions about the possible quantities of residual water or its potential significance have not yet been corroborated with field experience for periods of extended storage. Considering the complex spatial and time-dependent temperature profiles in dry storage casks, water may be in liquid or gas phase depending on where it is located in the cask and how long the cask has been in storage. This paper describes some concepts and presents initial feasibility assessments for sensing liquid and gas phase water in vertically and horizontally oriented dry storage casks with transducers mounted exterior to the confinement boundary. The feasibility of detecting small amounts of liquid water inside of vertically and horizontally oriented dry storage canisters with externally mounted sensors was demonstrated empirically with laboratory measurements. The feasibility analysis for gas phase water indicates that gas phase water may be detected in the fill gas at concentration levels of approximately 4000 ppm to 7000 ppm (2 to 3.5 moles).