Criticality Experiments with Tightly Packed Lattices of Low-Enriched UO2 Rods
Isabelle Duhamel1, Emmanuel Girault2, PHYSOR - 2006, 10-14/09/06, Vancouver, Canada
Critical experiments dealing with “tightly packed lattices” were carried out in the testing equipment “Apparatus B” of the C.E.A experimental criticality facility at Valduc. They involved water-moderated low-enriched UO2 fuel rods arrays reflected by water or polyethylene. These configurations were performed with different square pitches corresponding to a range of EALF values (Energy of Average Lethargy causing Fission) from 0.106 to 0.899 eV.
These experiments were sub-critical approaches extrapolated to critical with the multiplication factor reached being very close to 1.000. All 27 experiments presented in this paper are acceptable for use as benchmark experiments.
These experiments have been investigated with CRISTAL V1.0 criticality package using nuclear data based on the JEF2.2 data file. Calculation‑experiments comparison has highlighted a small under‑prediction (less than 0.5 %) for under-moderated lattices, whereas for well-thermalised ones, a good agreement is observed. Moreover, no visible trend has been noticed with the CH2 reflector, allowing being confident about the accuracy of the CH2 cross-sections in thermal and epithermal energy range.
1 Institut de Radioprotection et de Sûreté Nucléaire (IRSN), BP 17 - 92262 Fontenay-aux-Roses Cedex, France
2 Commissariat à l’Energie Atomique (CEA), Centre de Valduc, 21120 Is-Sur-Tille, France