235U prompt neutron fission spectrum data sensitivity/uncertainty effects in fuel cycle performance parameters
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The impact of 235U fission spectrum variations on the time evolution of keff, the mass and activity inventory at EOL and on the VHTR's TRU destruction rate in an AP1000-VHTR fuel cycle was investigated. Discrepancies in the prompt neutron fission spectrum evaluations of 235U were also assessed by comparing ENDF/B-VII.0 evaluations to those found in ENDF/B-VI.8, JENDL-3.3, JEFF-3.1 and CENDL-3.1. The prompt neutron fission spectrum evaluations of 235U are in good agreement for energies above 61keV and below 3.08MeV, regardless of the library. For ENDF/B-VI.8, JEFF-3.1 and CENDL-3.1 this range can be extended to 10eV. Evaluations of the prompt neutron fission spectrum are only discrepant for energies above 8.5MeV, regardless of the library. The chosen alterations of the prompt neutron fission of 235U can significantly affect the masses and activities of 233U, 236Np, 236Pu and 237Pu at EOL of the VHTR. The mass and activity of other isotopes are minimally affected (by less than 3%). However, all the previously-mentioned nuclides are found in trace amount in the reactor. Therefore these significant modifications in the mass and activity have minimal impact on the VHTR behavior and its capacity to transmute TRUs. keff is lower by at best 1.3% and at worst 1.7% when the tail of the fission spectrum has been significantly distorted. 2012 by Marie-H. Cuvelier, Pavel V. Tsvetkov.
