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Prediction of neutron source, tritium production and activation for longpulse
operation of the ITER Neutral Beam Test Facility
S. J. Cox, A. Emmanoulidis, T. T. C. Jones and M. J. Loughlin
EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire,
OX14 3DB, United Kingdom.
Abstract : A Local Mixing Model (LMM)1 has been utilised to compute the evolution of the
hydrogen isotope content within the implantation zone of the CuCrZr target material of the
beam-stopping elements of the ITER Neutral Beam Test Facility, together with the beamtarget
fusion reaction rate calculated by taking account of the slowing-down of the 1MeV
incoming projectile ion within the implantation layer. An important modification of the LMM
code is to treat the tritium reaction product ions, resulting from D-D reactions, as a constituent
of the incident beam. Although the treatment of tritium in the LMM is not ideal, this and other
simplifying assumptions either do not significantly affect the predictions, or ensure
conservatism in the results when used as input to the safety analysis of the facility. For
example, it is shown that T->D “beam-target” reactions always dominate over those of D->T,
which overcomes the problem of uncertainty, in the model, of the distribution of tritium
trapped within the implantation layer; in contrast there is little uncertainty that this region will
rapidly approach deuterium saturation for long-pulse (£ 1hr) operation. Using the computed
sources as input, neutronics and activation calculations for the NBTF components have been
carried out using the MCNP/FISPACT. As expected, long-pulse operational requirements
lead to neutron activation and tritium production levels which have non-negligible but
manageable radiological consequences.
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Synopsis (pdf)