For the calculation of concentration of activation products, ORIGEN2.2 was
used with ORLIBJ40 [2], which is a set of the one-group cross-section libraries
based on JENDL-4.0 [3]. The sensitivity coefficients are evaluated by executing
two different burn-up calculations under normal condition and under compositionchanged or cross-section-changed condition. In the former, the ORIGEN2.2 input
files are changed; in the latter, the cross-section library files are changed. Utility
programs to evaluate the sensitivity coefficients were prepared and used in these
analyses.
20.3 Sensitivity Analyses
20.3.1 Analyses Conditions
As stated in Sect. 20.1, activations of in-core structure materials, such as cladding
tubes, end plugs, and spacers of fuel assemblies and channel boxes, were investigated in this study. The materials of the in-core structures of PWR and BWR are
shown in Table 20.1. The compositions of Zircaloy-2, Zircaloy-4, SUS304 stainless
steel, and INCONEL alloy 718 are shown in Table 20.2. In Table 20.2, the average
value of the upper and lower limits of the standard specification was applied to the
calculation condition for additive elements and the upper limit was applied for
impurity elements. The effect of impurity elements that are not specified in the
standard are investigated in Sect. 20.3.4.
Typical conditions of BWR were assumed for the cross-section libraries and the
irradiation condition, because the difference between the conditions of PWR and
BWR is not so significant for the purpose of this study, which is clarifying the
dominant generation pathways of activation products.
The cross-section libraries used in these analyses (Table 20.3) were chosen to
correspond to the condition of the void ratio in the axial direction. A library made
with an average void ratio (40 %) was applied to cladding tubes, spacers, and
channel boxes for which the void ratio varies from 0 % to 70 %.
A BWR typical irradiation history consists of four cycles of irradiation of about
377 days with constant flux and 90 days of cooling time in the intervals of
irradiation (Fig. 20.1). Considering the period for processing of radioactive wastes,
Table 20.1 Materials of in-core structure
BWR
PWR
Cladding tube
Zircaloy-2
Zircaloy-4
Top end plug
SUS304
Bottom end plug
SUS304
Spacer
Plate: Zircaloy-2
Zircaloy-4 or
Spring: INCONEL alloy 718
INCONEL alloy 718
Channel box
Zircaloy-4
–
20 Sensitivity Analyses of Initial Compositions and Cross Sections. . .
235
used with ORLIBJ40 [2], which is a set of the one-group cross-section libraries
based on JENDL-4.0 [3]. The sensitivity coefficients are evaluated by executing
two different burn-up calculations under normal condition and under compositionchanged or cross-section-changed condition. In the former, the ORIGEN2.2 input
files are changed; in the latter, the cross-section library files are changed. Utility
programs to evaluate the sensitivity coefficients were prepared and used in these
analyses.
20.3 Sensitivity Analyses
20.3.1 Analyses Conditions
As stated in Sect. 20.1, activations of in-core structure materials, such as cladding
tubes, end plugs, and spacers of fuel assemblies and channel boxes, were investigated in this study. The materials of the in-core structures of PWR and BWR are
shown in Table 20.1. The compositions of Zircaloy-2, Zircaloy-4, SUS304 stainless
steel, and INCONEL alloy 718 are shown in Table 20.2. In Table 20.2, the average
value of the upper and lower limits of the standard specification was applied to the
calculation condition for additive elements and the upper limit was applied for
impurity elements. The effect of impurity elements that are not specified in the
standard are investigated in Sect. 20.3.4.
Typical conditions of BWR were assumed for the cross-section libraries and the
irradiation condition, because the difference between the conditions of PWR and
BWR is not so significant for the purpose of this study, which is clarifying the
dominant generation pathways of activation products.
The cross-section libraries used in these analyses (Table 20.3) were chosen to
correspond to the condition of the void ratio in the axial direction. A library made
with an average void ratio (40 %) was applied to cladding tubes, spacers, and
channel boxes for which the void ratio varies from 0 % to 70 %.
A BWR typical irradiation history consists of four cycles of irradiation of about
377 days with constant flux and 90 days of cooling time in the intervals of
irradiation (Fig. 20.1). Considering the period for processing of radioactive wastes,
Table 20.1 Materials of in-core structure
BWR
PWR
Cladding tube
Zircaloy-2
Zircaloy-4
Top end plug
SUS304
Bottom end plug
SUS304
Spacer
Plate: Zircaloy-2
Zircaloy-4 or
Spring: INCONEL alloy 718
INCONEL alloy 718
Channel box
Zircaloy-4
–
20 Sensitivity Analyses of Initial Compositions and Cross Sections. . .
235