Speaker
Description
Criticality safety analysis is needed at various stages of the nuclear fuel cycle, including the back-end of the fuel cycle, i.e. reprocessing, transport, storage and final disposal of spent nuclear fuel (SNF). In the past, criticality safety assessments for SNF management for out-of-reactor applications assumed that the fuel is in its most reactive condition, which is usually prior to irradiation of the fuel in a reactor. Since the 80's, an effort is being made by the nuclear industry, research organisations and regulatory authorities to use more realistic and less conservative estimates of the nuclear reactivity of SNF by accounting for the reduction in reactivity due to fuel burnup in a (sub-)criticality analysis. This concept is referred to as Burn Up Credit (BUC).
Specific programmes to validate nuclear data of fission products that are important for criticality safety studies based on a BUC approach reveal shortcomings in these data. To improve the status of cross sections for fission products for BUC approaches a dedicated programme was defined as part of a collaboration between the CEA Cadarache (France) and the JRC Geel (Belgium). It includes experiments at the time-of-flight facility GELINA to characterise the samples that were used for the MINERVE experiments [1,2,3] and to produce accurate total and capture cross section data to improve the evaluated data in the resonance region. This collaborative effort triggered the interest of other institutes and organisation such as the IFIN-HH (Romania), INFN Bologna (Italy) and INRNE (Bulgaria) by participating in the experiments at GELINA and assisting in the data reduction and analysis.
In this report, the status of cross section data for $^{103}$Rh, $^{107,109}$Ag and $^{155,157}$Gd is discussed and results of a resonance shape analysis of new capture and transmission experiments at GELINA are presented. In addition, recommendations to improve the evaluated cross section data in the resonance region for these nuclides are given.
[1] Gruel et al., “Interpretation of fission product oscillations in the MINERVE reactor, from thermal to epithermal spectra”, Nucl. Sci. Eng. 169 (2011) 229.
[2] Šalamon et al., “Neutron resonance transmission analysis of cylindrical samples used for reactivity worth measurements”, J. Radioanal. Nucl.Chem. 321 (2019) 519.
[3] Fei Ma et al., “Non-destructive analysis of samples with a complex geometry by NRTA”, J. Anal. At. Spectrom. 35 (2020) 478.