*4.3.4 232Th fission rate based on 135I in ThO2 powder cylinder*

The ThO2 power cylinder assembly for developing the activation method of measuring THFR is shown in **Figure 4**. THFR in the axial direction of the cylinder is determined by measuring the 1260.409 keV gamma emitted from 232Th fission product 135I, with experimental uncertainties of 6.2% [14]. The experiment is simulated by using the MCNP code with ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0, and CENDL-3.1. The calculations and experiments are in good agreement within experimental uncertainties. The activation method to determine THFR is developed

**45**

**Figure 13.**

*Ratios of 232Th capture to fission in the three assemblies.*

*Fusion Neutronics Experiments for Thorium Assemblies DOI: http://dx.doi.org/10.5772/intechopen.81582*

evaluated data is presented in the [14].

**4.4 Breeding properties**

powder cylinder are obtained.

spectra in ThO2 powder cylinder is low.

*4.4.1 Fuel breeding*

shell is quite high.

*4.4.2 Neutron breeding*

shell is high.

and the data obtained in this work could provide reference for the validation of thorium fission parameters. The C/E ratio of 232Th fission rates based on different

The primary conversion rate is one of the important parameters in the conceptual design of subcritical blanket. The relative reaction rate ratio of 232Th capture to fission as the fissile production rate indicates fuel breeding in the fuel burn-up unit [12]. The ratios of 232Th capture to fission measured in PE shell, DU shell, and ThO2

The ratios are about 10.76–20.17 with the increase in radius of the PE shell. It is demonstrated that the fuel breeding efficiency under the neutron spectra in the PE

The ratios are about 6.71–12.23 with the increase in radius of the DU shell. It is demonstrated that the fuel breeding efficiency under the neutron spectra in DU

The ratios are only about 0.11–0.19 with the increase in radius of the ThO2 powder cylinder. It is demonstrated that the fuel breeding efficiency under the neutron

The results show that the ratios are relevant to neutron spectra in the assemblies.

The bred neutrons from 232Th(n,2n) and 232Th(n,f) react with thorium or relevant nuclides to maintain the Th/U fuel cycle. THNRs in three assemblies, that is, under different neutron spectra, are compared and shown in **Figure 14**. The results show that the 232Th(n,2n) reaction rates are relevant to the fraction of high-energy neutrons in the assemblies as described above, and the decreasing trend of THNR with the increase in distance to the neutron source are similar for three assemblies.

The ratios in the three assemblies are compared and shown in **Figure 13**.

**Figure 12.** *C/E ratio of 232Th reaction rates in ThO2 powder cylinder.*

and the data obtained in this work could provide reference for the validation of thorium fission parameters. The C/E ratio of 232Th fission rates based on different evaluated data is presented in the [14].
