The design and employment of a system to vent and/or pump vacuum spaces with possible tritium contamination

Maintenance and associated line breaks are a requirement for any operating vacuum systems. When the vacuum systems are potentially contaminated with tritium, the maintenance crews are faced with opening a line that may contain significant quantities of airborne tritium. Every isolatable section of complex vacuum systems cannot contain an active tritium monitor, therefore, an alternate method of tritium measurement must be used in preparation for a line break. At TFTR, the method used to determine the quantity of tritium at risk prior to a line break is accomplished by Operations Procedure OP-VAC-656 (Approved Method for Venting and Pumping a Vacuum Space That Has Possible Tritium Contamination). This procedure describes the method to safely vent a vacuum space that has been exposed to possible contamination with tritium, to measure the concentration of airborne tritium and to provide a set of options for pumping and purging based on the tritium concentration. The procedure describes the minimum compliment of components needed to safely perform the process. At the present time at TFTR there are at least four different sets of components that meet the requirements of OP-VAC-656. Each of these special setups are used because of the unique system requirements in the different areas of TFTR.