Speaker
Description
As engineering discussions of the feasibility of new reactor systems, it is necessary to evaluate the impact of the fuels and materials for the neutronics characteristics such as criticality, conversion rate, and fuel balance. It is important to perform the validation of 232Th and 233U nuclear data for a thorium-based nuclear reactor, because those nuclear data contribute significantly to the neutronics characteristics of the reactor.
We have measured the fission cross section of 233U by the neutron time-of-flight method using a 12 m flight path and a 46-MeV electron linear accelerator at the Institute for Integrated Radiation and Nuclear Science, Kyoto University (KURNS-LINAC). Experiments were performed with two different linac operation modes. One was for low-energy measurement below about 1 eV with 50 Hz and an average current of about 18 μA. Another was for high-energy measurement above 1 eV with 200 Hz and an average current of about 72 μA. In the latter case, a Cd sheet with 0.5-mm thickness was inserted into the TOF beam line to prevent the overlap component from the previous pulse due to high frequency. Pulse width was 100 ns for both operation modes.
A back-to-back type fission chamber was used for the detection of the fission fragments and to discriminate the decayed alpha-particles. A sample of uranium-233 oxide was electrodeposited on the stainless steel disk (28 mm in diameter and 0.2 mm thickness). A relative measurement to the 6Li(n,α) standard reaction was also made using a 6Li-glass detector, and normalized to the evaluated value from the JENDL-4.0 at thermal neutron energy. We have obtained the fission cross sections of 233U in the energy region from 0.002 eV to 1 keV.
The present results were compared with the previous experimental data and the evaluated values. Moreover, the resonance parameters were obtained by using SAMMY code for the principal resonances below about 100 eV.