The dt neutron emission from JET H-mode deuterium discharges with Zeff < 2.5 and plasma currents 1 < Ip < 3MA is analyzed on the basis of all neutron diagnostics information available on JET. This emission is mainly due to the triton burn-up process and is used to determine the fast triton confinement. A simplified model for Triton Burn-up Neutron (TBN) emission has been used and provides an adequate description of the dt emission. Prompt (first orbit) triton losses are found to amount typically to 50, 20 and 10% at Ip =1, 2 and 3MA, respectively. Additional losses (such as losses due to "neoclassical" Coulomb collisions) may also play a role especially at the lowest current values. Neutron emission spectroscopy measurements with the MPR spectrometer have detected a contribution to the dt emission due to residual tritium. Tritium concentration tends to increase with increasing impurity content being at the 15% level for the selected (low Zeff) discharges analyzed in this paper. For the higher Zeff values frequently observed in JET the TBN analysis faces a number of difficulties and more direct approaches for fast ion studies should be considered.