*4.3.3 232Th reaction rates in ThO2 powder cylinder*

The ThO2 power cylinder assembly for measuring 232Th reaction rates is shown in **Figure 4**. The 232Th reaction rates are measured by the same method as described above.

The experimental uncertainties are 3.1% for THCR, 5.5% for THFR, and 7.0% for THNR in the ThO2 powder cylinder.

The experiment is simulated by using the MCNP code with different evaluated data [10, 11]. The C/E ratio of 232Th reaction rates with ENDF/B-VII.0 are shown in **Figure 12**. The ranges of C/E ratio are 0.96–0.98 for THCR, 0.96–0.99 for THFR, and 0.74–0.76 for THNR. The results show that calculations and experiments for THCR and THFR are well consistent within the range of experimental uncertainties. The distributions of 232Th reaction rates in the experiments and calculations are shown in [13–15].

The calculations for THNR underestimate the experiments. Fractions with different energies in ThO2 powder cylinder are calculated by using ENDF/B-VII.0, and neutrons of energy more than 6.5 MeV account for 62–72% in the whole energy range, which is the largest among the assemblies, as shown in **Figure 5**. The suggestion described above is that 232Th(n,2n) reaction cross sections should be studied further.
