Experimental verification of neutron capture cross section of Np in variable neutron field at KURRI-LINAC

Takahashi, Yoshiyuki*; Hori, Junichi*; Sano, Tadafumi*; Yashima, Hiroshi*; Nakamura, Shoji  ; Harada, Hideo   

To improve the accuracy of nuclear data on minor actinides (MAs) and long-lived fission products (LLFPs), the project entitled as "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)" has been started in Japan from October 2013. In this study, we proposed the thermal capture cross section measurement methods using variable neutron fields, developed in the Kyoto University Research Reactor Institute - Linear Accelerator (KURRI-LINAC), and investigated neutron spectra in these fields using TOF and activation methods. In this study, the variable neutron field for the measurements of neutron capture reaction rate of MAs was developed with the moderator activated boric-acid solution at KURRI-LINAC. The measurement of neutron capture reaction rate of Np was carried out in the variable neutron spectrum field. The three cases of boric-acid concentration of the light water moderator, namely 0, 850 and 2740 ppm, were used for the experiment. As a result, the reaction rate of Np was 2.7810 [/s] within 2% statistical error in the condition of 850 ppm boric-acid concentration. In the conference, the detail of the experiment will be reported.