Investigating Aerosol Deposition Mechanisms in a Spent Nuclear Fuel (SNF) Dry Storage Cask (DSC) Laboratory-Scale Model Under Variable Environmental Conditions

JAMES HENRY, Ren Garity, Moein Mousavi, Prasad Rangaraju, John Saylor, Nigel Kaye, Andrew Metcalf, Clemson University

     Abstract Number: 429
     Working Group: Aerosol Physics

Abstract
Spent nuclear fuel (SNF) storage remains a pressing issue in the U.S. due to limited long-term repository options. Dry storage casks (DSCs) are increasingly used at nuclear facilities to store SNF once wet storage pools reach capacity. These casks rely on natural airflow for passive cooling during radioactive decay. However, depending on a given DSC design and environmental exposure, they may be vulnerable to aerosol penetration, which, over long periods of exposure, can lead to stress corrosion cracking in the steel canister that holds the SNF. Understanding aerosol deposition mechanisms under variable environmental conditions is essential to improving DSC designs and reducing this risk of stress corrosion cracking going forward.

Aerosol deposition inside DSCs heavily depends on environmental factors such as temperature, humidity, and particle concentration. These conditions affect which deposition mechanisms dominate and where aerosols accumulate on the interior cask and canister surfaces. Laboratory studies that replicate these conditions can offer practical insights into aerosol behavior and inform better storage system designs.

A 1/6th scale laboratory model of a DSC was developed to investigate these phenomena. The model includes a heated steel cylinder simulating SNF temperatures up to 250° C, enclosed within a concrete overpack and surrounding environmental chamber. Instruments such as humidifiers and polydisperse aerosol generators control the enclosure's relative humidity and particle concentration. Optical particle counters at the cask's inlets and outlets monitor aerosol concentrations, allowing for deposition quantification via mass balance. Aerosol deposition is mapped along the cylinder surface to identify dominant deposition mechanism(s) under specific environmental conditions.

This study provides a controlled approach to understanding aerosol transport and deposition in DSCs, contributing to safer and more resilient nuclear waste storage strategies.