ENVIRONMENTAL MONITORING FOR TRITIUM AT JET

JET progressively established elements of an environmental monitoring programme well in advance of tritium operation in order to determine b aseline levels. Prior to the first JET tritium experiment (PTE) in 199 1, an extensive programme was in place and agreed with the regulatory authority. This consisted of tritium in air, rain, ground and river wa ter, and crops on and off the JET site. Air is sampled continuously an d averaged monthly. Other samples are taken quarterly or, at an approp riate point in the growing season. The discharges of tritium from the JET stacks are monitored by on-line instrumentation and silica gel-bas ed samplers. The performance of these is described and improvements ar ising from the PTE experience are discussed. In particular the implica tions of tritiated methane on sampling and analysis are considered.The results of environmental monitoring are presented and comparisons mad e with predictions from discharges made during the PTE and subsequent operations. The implications of washout on the site liquid discharge a uthorisation is considered. From a comparison of observed and predicte d concentrations, routine releases of tritium from JET will have insig nificant environmental impact.