Preliminary Design of Neutron Flux and Spectrum Diagnostics in NT-TBM

A special neutron diagnostic system is proposed that facilitates the measurement of neutron fluxes and spectra in the neutronics and tritium production-test blanket module (NT-TBM) without interrupting the operation of the International Thermal-nuclear Experimental Reactor (ITER), for studying the multiplication rate in the neutron multiplier and breeding ratio of tritium in the breeder. This system includes an encapsulated foil activation system, micro-fission chamber detectors (MFC), and a compact neutron spectrometer using a natural diamond detector (NDD). A helium coolant loop with a reasonable diameter is designed carefully for every measurement channel that ensures that the neutron detectors and preamplifiers would work well under a high temperature scenario and that the filling rates of the neutron multiplier (beryllium pebble) and tritium breeder material (Li4SiO4) would not decrease excessively (the expected value≥80%) due to the dimensions of the helium coolant loop.