Speaker
Description
The management of high-level nuclear waste (HLW) from nuclear power plants is a significant issue to continue using nuclear energy in the future. To solve this, studies of nuclear transmutation system such as the accelerator-driven system (ADS) that transmute long-lived nuclides to shorter or stable ones due to neutron-induced reactions have been ongoing in recent years. Precise nuclear data for Minor Actinides (MA) are essential for the design of nuclear transmutation systems.
Am-243 is one of the most abundant MA isotopes in HLW. Cross section data for the neutron capture cross section of Am-243 are important for the calculation of nuclear reactor parameters of ADS. However, the current uncertainties of the cross section data are far from the required accuracy. The uncertainty of the capture cross section for the neutron energy range from 0.5 to 500 keV was evaluated to be 10% or higher, while the target uncertainty was set to 2% in a sensitivity study [1].
The measurements were performed using the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline at the Japan Proton Accelerator Research Complex (J-PARC). An intense pulsed neutron beam was produced via spallation reaction in the mercury target of the Materials and Life Science Experimental Facility (MLF) by the 3-GeV proton beam of the J-PARC facility. A time of flight (TOF) method using a NaI(Tl) detector was employed in these measurements and a pulse-height weighting technique was used to derive the neutron capture yield.
A sample of Am-243 with a mass of 38.14 mg (281.8 MBq) was used for the measurements. The neutron energy spectrum was obtained by measuring the 478 keV gamma-rays from the $^{10}$B(n,$\alpha \gamma$)$^7$Li reaction with a boron sample containing enriched $^{10}$B up to 90%. A preliminary value for the capture cross section of Am-243 will be presented in the contribution.
[1] Salvatore M et al., “Uncertainty and target accuracy assessment for innovation systems using recent covariance data evaluations., WPEC-26, OECD NEA. San Diego (CA): Elsevier; 2008.
