*4.3.1 232Th fission and (n,2n) reaction rates in ThO2 cylinder*

The ThO2 assembly for measuring 232Th reaction rates in three ThO2 cylinders with the thickness of 150 mm (without DU cylinder) is shown in **Figure 3**. The 232Th fission and (n,2n) reaction rates are measured by the same method as described above.

The experimental uncertainties are 5.3–5.5% for THFR and 7.1% for THNR [9, 10]. The 232Th reaction rates are calculated by using MCNP code with ENDF/B-VII.0. The ranges of C/E are 0.77–0.91 for THFR, and 0.92–1.0 [12] for THNR, respectively. The results show that the calculations generally underestimate the experiments for THFR. The PEO influence on THFR is described below. The distributions of 232Th reaction rates by the experiments and calculations are shown in **Figure 10**.
