*4.3.2 232Th fission rates in ThO2/DU cylinders*

Experimental and simulative studies of THFR are carried out on three sets of ThO2/DU cylinder assemblies to validate the evaluated thorium fission cross section and code [9, 10]. The size of each ThO2 cylinder and DU cylinder is ϕ300 × 50 mm. The ThO2 cylinders with PEO contents of 7.28, 1.1, and 0.55% are named as number 1, number 2, and number 3, respectively. The DU cylinder is named as number 4. Three sets of cylinder assemblies are combined with different cylinders, and named as "3 + 2 + 1," "4 + 2 + 1" (as shown in **Figure 3**) and "3 + 4 + 2 + 1" assembly, respectively.

**43**

**Figure 11.**

*C/E distribution in the three sets of assemblies.*

sured level is negligible.

*232Th reaction rates in ThO2 cylinder.*

**Figure 10.**

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

THFR in the axial direction of the assemblies is obtained by using the activation

In order to gain more experimental results, it is necessary to design a new integral experiment employing thorium transport medium in which the ingredient is single and precisely known, and to determine THFR based on more kinds of fission

method as described above, with experimental uncertainties about 5.6–5.9%. THFRs are calculated by using MCNP code with ENDF/B-VII.0 and ENDF/B-

VII.1. The calculations are 5–21% smaller than experimental ones, while the calculations with ENDF/B-VII.0 show better agreement with experimental ones. C/E distributions in the three assemblies are presented in **Figure 11**. The influence of the PEO in the ThO2 cylinders is also evaluated by MCNP simulation employing ENDF/B-VII.0. The results show that the PEO influence on THFR under the mea-

**Figure 9.** *C/E ratio of 232Th reaction rates in the DU shell.*

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

#### **Figure 10.**

*Nuclear Fusion - One Noble Goal and a Variety of Scientific and Technological Challenges*

**42**

**Figure 9.**

*C/E ratio of 232Th reaction rates in the DU shell.*

*232Th reaction rates in ThO2 cylinder.*

THFR in the axial direction of the assemblies is obtained by using the activation method as described above, with experimental uncertainties about 5.6–5.9%.

THFRs are calculated by using MCNP code with ENDF/B-VII.0 and ENDF/B-VII.1. The calculations are 5–21% smaller than experimental ones, while the calculations with ENDF/B-VII.0 show better agreement with experimental ones. C/E distributions in the three assemblies are presented in **Figure 11**. The influence of the PEO in the ThO2 cylinders is also evaluated by MCNP simulation employing ENDF/B-VII.0. The results show that the PEO influence on THFR under the measured level is negligible.

In order to gain more experimental results, it is necessary to design a new integral experiment employing thorium transport medium in which the ingredient is single and precisely known, and to determine THFR based on more kinds of fission

**Figure 11.** *C/E distribution in the three sets of assemblies.*

products, as described below. The stage results could provide reference for the evaluation of neutron-induced thorium fission cross section, and the conceptual design margin of the subcritical blanket.
