DTO Waste Compliance Monitoring System at TFTR

Abstract

Disposal of tritium bearing atmospheres, typically nitrogen, at TFTR involves venting of these gases into a holding tank followed by periodic processing of these gases into tritium waste containers. The process involves oxidation of the waste gases followed by tritium oxide absorption onto the molecular sieve within the tritium waste containers. The tritium sorbed in the waste containers must be measured to ensure that the quantity of tritium sorbed is accurately known and is in keeping with the licenced capacity of the containers prior to their shipment of site. A DTO Waste Compliance Monitoring System has been designed and fabricated for on-line monitoring of the tritium sorbed in the molecular sieve tritium waste containers. The monitoring system is based on the in-line process tritium monitor qualified for HTO monitoring. The compliance monitoring system involves the use of three in-line tritium monitoring systems which are positioned prior to, between, and after the two tritium waste containers. The first tritium waste container absorbs the bulk of the tritium while the second waste container scavenges the breakthrough. The in-line tritium monitor system consists of a constricted main flow passage and a slip stream bypass, the latter containing an in-line process tritium monitor, a flow monitor, a thermocouple, and a humidification port. The flow rate through the main passage is typically 24 LPS while the flow rate through the bypass is about 15 NLPM. The in-line tritium monitor is out-fitted with a Keithley electrometer the output of which is connected to a data acquisition and control system. Time integration of the product of the total flow rate and difference in the upstream and downstream tritium concentrations along with appropriate background and temperature corrections results in the quantity of tritium sorbed on a tritium waste container.