Design Calculations for Gas Flow & Diffusion Behavior in the Large Diameter Container & Cask

Abstract

This report describes the calculations for the gas behavior in the void volumes or gas spaces of the sludge Large Diameter Container (LDC) and Cask. The objective is to prevent flammable gas conditions in the LDC and Cask gas spaces. This is achieved by the Active Inert Ventilation System (AIVS), which uses argon gas for dilution purposes. With AIVS, the oxygen content is kept below 4 to 5 vol% in the LDC, and the hydrogen content is kept below 4 vol% in the Cask before its purge at the KE Basin. After the Cask sweep-through purge with argon at the KE Basin, oxygen stays below 4 to 5% in the LDC until two LDC ports are opened at T Plant. The oxygen content stays below 4% in the Cask until the Cask lid is opened at T Plant. The analysis here assumes that any oxygen generated in the sludge is consumed by the uranium and uranium dioxide (SNF-18133, ''Gas Behavior in Large Diameter Containers (LDCs) During and Following Loading with 105K East Sludge''). Thus, oxygen production from radiolysis is not included in this report, but hydrogen from radiolysis and from chemical reactions between uranium and water are considered, depending on the scenario being analyzed. The analysis starts immediately after the final decant at K Basin, when argon is assumed to be the only gas in the LDC gas space, except for the normal water vapor. The oxygen ingress is calculated during the disconnecting of the lined hoses from the LDC, during the time that air is surrounding the LDC with two NucFil-type filters in place after the disconnect, before the Cask is sealed, and, finally, during the sweep-through Cask purge at the KE Basin. Dissolution of oxygen from water due to increasing sludge temperatures (mainly during hot transport to the T Plant) is also included. The analysis includes the gas behavior during the T-Plant operations, which include the venting after the LDC/Cask are received at T Plant, the Cask sweep-through purge, the LDC purge with forced argon delivery into the LDC with 1 open port, followed by the natural sweep-through purge with two open LDC ports.