Suggested methods for determining residual tritium in process beds

摘要

This memorandum has been written as a response to an H-Area EH Issue No. 3 milestone (SRTC FY93 Controlled Milestone 15C70) which requires WSRC to (open quotes)develop methodology for determining residual tritium in process equipment.(close quotes) An estimate of the tritium residing in process equipment sent for disposal must be reported on a Waste Stream Characterization Form. Currently, these estimates are crude and their technical bases are not well documented. The process equipment addressed in this report may be divided into two categories, routine and non-routine, based on their generation frequency. Magnesium Beds, Uranium Beds, and Gold Traps are regularly sent for disposal depending on the process load; Zeolite Beds and Catalyst Beds are rarely removed from the Tritium Facilities, as they may be regenerated. In general, there are two main sources of residual tritium that which resides in hydroxyl groups on internal surfaces and deposits, and that which has permeated the stainless steel walls and components. The tritiated hydroxyl groups may be exchangeable with gas phase deuterium, and minimized by oxidation at elevated temperatures. The tritium which has diffused into stainless steel is difficult to remove and amounts to a minor portion of the total tritium heel; this value may be calculated by a proven computer program and is on the order of 1--5 Ci per bed. Zeolite Beds are a unique case, as the packing material contains a substantial portion of crystalline hydrate (2% by weight), even after bake out at 500(degrees)C The solid state hydrate will assimilate tritium from adsorbed waters, and calculations show a typical Z-bed may contain 50,000 Ci of residual tritium. It is proposed that a calorimeter be designed and constructed to measure the tritium in Z-beds directly, and that steps be taken to reduce the residual tritium by extraction with deuterated water.