Development of covariance capabilities in EMPIRE code

Conference · Tue Jun 24 04:00:00 EDT 2008

OSTI ID:939949

Herman, M; Pigni, M T; Oblozinsky, P; Mughabghab, S F; Mattoon, C M; Capote, R; Cho, Young-Sik; Trkov, A

The nuclear reaction code EMPIRE has been extended to provide evaluation capabilities for neutron cross section covariances in the thermal, resolved resonance, unresolved resonance and fast neutron regions. The Atlas of Neutron Resonances by Mughabghab is used as a primary source of information on uncertainties at low energies. Care is taken to ensure consistency among the resonance parameter uncertainties and those for thermal cross sections. The resulting resonance parameter covariances are formatted in the ENDF-6 File 32. In the fast neutron range our methodology is based on model calculations with the code EMPIRE combined with experimental data through several available approaches. The model-based covariances can be obtained using deterministic (Kalman) or stochastic (Monte Carlo) propagation of model parameter uncertainties. We show that these two procedures yield comparable results. The Kalman filter and/or the generalized least square fitting procedures are employed to incorporate experimental information. We compare the two approaches analyzing results for the major reaction channels on {sup 89}Y. We also discuss a long-standing issue of unreasonably low uncertainties and link it to the rigidity of the model.

• Research Organization: Brookhaven National Laboratory
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 939949
• Report Number(s): BNL--81624-2008-CP; KB0301041
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CROSS SECTIONS
EVALUATION
FAST NEUTRONS
NEUTRONS
NUCLEAR REACTIONS
RESONANCE