Tritium inventory in the first wall of JET

At the start of the shutdown following the DTE1 experiment at JET there remained 6.2 g of tritium in the JET vacuum vessel. An attempt has been made to establish the location of this tritium by measuring components taken from the vessel. A total of 2.0 g of tritium was recovered by out-gassing and 1.5 g was originally estimated for the flakes/deposits from measurement of collected flakes. Measurements on tiles removed from the vessel indicate that all the vessel tiles contain less tritium than expected at ∼0.1 g. Some uncertainty exists about the location of the remaining tritium. Further investigation has shown that a significant quantity of flakes (more than originally estimated) exists in the sub divertor region. It is believed that the missing tritium is present in the flakes in the sub divertor region. However, until this material can be collected and quantified other possible sources cannot be excluded. The reasons for the formation of the flakes/deposits are discussed.