Neutronics analysis for the ITER tritium and deposit monitor diagnostics

Abstract This paper presents new results of neutronics analysis performed in support for the design development of the tritium and deposit monitor (TDM) to be installed inside the ITER Equatorial Port Plug (EPP) #17. Neutronics analysis is performed with the local MCNP models of EPP#17 which comprises two adjacent diagnostics: TDM and Core-Imaging X-ray Spectrometer (CIXS). The MCNP 3D models were converted from the corresponding CAD models. Critical neutronics issues related to radiation streaming, nuclear heating and activation are discussed, and shielding design solutions are presented in this paper. To provide the possibility of personnel access to the Port Interspace area, the Shut-Down Dose Rate (SDDR) has been calculated with the results presented as map distributions and estimates in spherical detectors. Using the Rigorous 2-Step mesh-based (R2Smesh) method of SDDR calculations which combines the FISPACT activation and MCNP transport allowed us to distinguish different decay gamma sources in forming the SDDR. The SDDR results are presented for two variants of the EPP#17-CIXS models, with and without the monitor. Therefore, the contribution to SDDR from the monitor was deduced. This work provides only the relative values of SDDR. The absolute values will be obtained after the finalizing of the designing work for all the EPP#17 diagnostics. This is a forthcoming task of EPP#17 diagnostics integration into the ITER-global C-lite MCNP model.