| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1728852 | Annals of Nuclear Energy | 2012 | 8 Pages |
Thermal upscattering has considerable impact on the neutronic analysis of light water reactors. This phenomenon is more significant for reactors with advanced fuels having high plutonium content: Mixed Oxide (MOX) fuels. In this paper, a sensitivity analysis for the impact of upscattering boundary energy on the integral results of MOX and UO2 fuels in light water reactors is performed using WIMSD-5B code. For investigating the impact on the effective cross sections, a spectrum calculation code Microtrans is developed which employs an improved ultrafine group method. Moreover, the impact on the effective cross sections of important resonances of fuel nuclides in thermal and epithermal energy ranges is studied in detail. Calculation results show that changing the upsacttering boundary from 0.625 eV to 4 eV leads to more than 1000 pcm decrease in Keff in MOX fuels due to large resonances of Pu isotopes in thermal energy range, while this impact is about 120 pcm for UO2 fuels. In addition, thermal upscattering has significant impact on the effective cross sections below 10 eV.
► Changing the upscattering energy from 0.625 eV to 4 eV causes a decrease of 1040 pcm in Keff for MOX fuels. ► In UO2 fuels, Keff decreases about 120 pcm. ► Effective group cross sections below 4 eV are changed considerably. ► Fission reaction in thermal energy groups changes up to 20%. ► Pu-240 resonance in 1.05 eV is mostly influenced.
