Tritium Production Rate (TPR) and in-system spectrum measurements were performed on a Li2O test assembly (with and without beryllium multiplier) at the FNS facility at JAERI in addition to other neutronics parameters that include source neutron characterization and in-system reaction rates discussed in a companion paper. These activities are part of an on-going collaborative program between JAERI and the US. Calculations for the neutronic parameters were performed independently by both parties based on various 3-D Monte Carlo and 2-D discrete ordinales codes and data libraries. Local and zonal TPRs were measured by various techniques and comparisons were made to predictions. The calculated to measured values, C/E, for integrated zonal TPR from natural lithium are typically C/E = 0.97–1.07 but local TPR has larger uncertainties (C/E = 0.85–1.13). Predicted enhancement in tritium breeding upon including the Be multiplier is in the order of 7–8% while measurements indicate an approximately 10% increase in integrated TPR. The in-system spectra are well-predicted at En > 10 MeV by various codes as compared to NE213 measurements, although calculation tends to overpredict the 14.1 MeV peak. Large discrepancies, however, were observed in the energy range 1.01 MeV < En < 10.1 MeV where calculations were larger than measurements. It was shown from the analysis that the 7Li(n,total) is overestimated in JENDL3-PR1 due to overestimation in 7Li(n,elastic), 7Li(n,γ) and 7Li(n,d) reactions and that 7Li(n,n′α) is underestimated by 8–10%. The analysis also revealed that JENDL3-PR1 data for oxygen and iron overmoderate neutron energies through (n,inelastic) and (n,elastic) reactions in comparison to ENDF/B-V data. Further improvement is also required in the secondary energy/angular distribution of the 9Be(n,2n) reactions.
Determination of tritium breeding ratio in a PbLi spherical blanket by leakage neutron spectra