Modeling photon-induced reactions on ${}^{233–238}\mathrm{U}$ actinide targets

Comprehensive calculations of photon-induced reactions on ${}^{233–238}\mathrm{U}$ targets for incident photon energies from 3 up to 30 MeV are undertaken with the statistical model code empire-3.2 Malta. Results are compared with the experimental data from EXFOR and with the current evaluations. The differences and the similarities between the models and parameters used in calculations of photon- and neutron-induced reactions on the same nuclei are discussed with focus on fission. The role of the extended optical model for fission that includes partial damping in the continuum in improving the description of the measured data is pointed out.

Figure 1

Triple-humped fission barriers of light actinides (explanations provided in text).

Figure 2

Transmission mechanisms through triple-humped fission barriers (explanations provided in text).

Figure 3

JENDL-PD total cross section (green line), IAEA-PD nonelastic cross section (red line), calculated total (dashed blue line), and nonelastic (blue line) cross sections for ${}^{233–238}\mathrm{U}$ compared with experimental data from EXFOR [42, 43]. Note that the photoinduced reactions ($\gamma$, non) and ($\gamma$, tot) are denoted in legend as (G, NON) and (G, TOT), correspondingly.

Figure 4

Photoreaction cross sections for ${}^{233–238}\mathrm{U}$ calculated with empire code: total (light-red), photoabsorption (green), fission (black), ($\gamma ,\gamma$) (red), ($\gamma ,n$) (blue), ($\gamma ,2n$) (magenta), ($\gamma ,3n$) (light blue). Note that the photoreaction cross sections ($\gamma$, ...) are denoted in the legend as (G, ...), correspondingly.

Figure 5

Calculated neutron-emission cross sections [($\gamma ,n$) blue solid line, ($\gamma ,2n$) blue dashed line, ($\gamma ,3n$) blue dotted line] for ${}^{233–238}\mathrm{U}$ compared with evaluated $(G,X)$ cross sections (JENDL-PD green line, IAEA-PD red line) and the experimental data from EXFOR [42, 46, 47]. Note that the neutron-emission cross sections ($\gamma$, ...) are denoted in the legend as (G, ...).

Figure 6

IAEA-PD evaluation (red line) and empire calculation (blue line) for ${}^{238}\mathrm{U}(\gamma ,n)$ (left panel) and ${}^{238}\mathrm{U}(\gamma ,2n)$ (right panel) compared with experimental data from EXFOR [47, 48, 49, 50, 51, 52]. Note that the $(\gamma ,n)$ and $(\gamma ,2n)$ cross sections are denoted in the legend as (G,N) and (G,$2N$), correspondingly.

Figure 7

The effect of considering different degrees of damping of the class III vibrational states corresponding to discrete fission barriers and to barriers in the lower limit of continuum on the fission cross section of ${}^{233,234}\mathrm{U}$. Fission cross sections (red line), the contributions of the discrete fission channels (blue line) and of the channels in continuum (black line), considering partial (solid line) and full (dashed line). Note that the ($\gamma ,f$) cross sections are denoted in legend as (G,F).

Figure 8

empire calculations (blue line) and JENDL-PD (green line), IAEA-PD (red line) evaluations for the photofission cross sections of ${}^{233–238}\mathrm{U}$ compared with experimental data from EXFOR [42, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76]. Note that the $(\gamma ,f)$ cross sections are denoted in the legend as (G,F).

Figure 9

empire calculations (blue line) and JENDL-PD (green line), IAEA-PD (red line) evaluations for the photofission cross sections of ${}^{233–238}\mathrm{U}$ in the incident energy range 5–20 MeV compared with experimental data from EXFOR [42, 46, 47, 48, 49, 51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76]. Note that the $(\gamma ,f)$ cross sections are denoted in the legend as (G,F).