Tritium

Recent increased interest from regulators and the public has led more organizations to consider the environmental impact and safety considerations of tritium handling.  Examples include the significance of the tritium isotope separation system on ITER licensing, remediation of ground water from power utilities and government facilities and concerns of high tritium concentrations within operational CANDU reactors.
GE Healthcare, formerly Amersham plc, has been producing tritium-labelled chemicals since the late 1940s. GE’s manufacturing site located near Cardiff, UK has installed a tritium waste treatment and enrichment facility to radically reduce tritium discharges to the environment.  This facility employs a continuous processing plant that recovers tritium from a complex mixture of tritiated organic and aqueous waste compounds.  Two isotope separation techniques are used to achieve a final pure tritium product, which is used in the manufacturing of labelled compounds.
Building upon this experience, together with Special Separations Applications Inc. (SSAI), GE has developed a large-scale diffusion-based isotope separation process as an alternative to conventional cryogenic distillation. Having a tritium inventory an order of magnitude lower than conventional cryogenic distillation, this process is attractive for heavy water detritiation, applicable to single and multi-unit CANDU reactors and research reactors as well as fusion applications.  Additionally, the new process has advantages of being cryogen-free, less complex, simple to operate and having improved conventional and radiological safety.

Integrating heavy water upgrading with detritiation in CANDU® stations has the potential to provide cost savings and simplicity in comparison to stations with separate heavy water upgrading and detritiation systems. This paper presents results of a concept study into alternative processes for managing heat transport and moderator system water quality, including a new non-cryogenic isotope separation process being developed by Special Separations Applications, Inc. (SSAI) and General Electric (GE) for tritium removal.  Overview descriptions are presented for the process design and process characteristics are described.

We have recently determined that human multidrug resistance protein (MRP) 3, which confers resistance to certain natural product agents and methotrexate (MTX), is competent in the MgATP-energized transport of MTX and the monoanionic bile constituent glycocholate as well as several glutathione and glucuronate conjugates. Of these capabilities, the facility of MRP3 in conferring resistance to and mediating the transport of MTX is of particular interest because it raises the possibility that this pump is a component of the previously described cellular efflux system for this antimetabolite. However, if this is to be the case, a critical property of cellular MTX efflux that must be addressed is its ability to mediate the export of MTX but not that of its intracellular polyglutamylated derivatives. Here we examine the role of MRP3 in these and related processes by determining the selectivity of this transporter for MTX, MTX polyglutamates, and physiological folates. In so doing, we show ...

The heavy water inventory of a typical PHWR constitutes about 12% of the capital cost of the PHWR.  The typical tritium production in a single unit PHWR is about 2x106 Ci/y.  Heavy water and tritium control are important aspects of PHWR operation, and this involves people, procedures, equipment and heavy water and tritium separation systems.  Station personnel are trained to understand the importance of heavy water management and the economics and environmental impact of tritiated heavy water losses.  The tritium and heavy water losses from a PHWR are both airborne and waterborne in nature.