Development of Covariance Capabilities in EMPIRE Code

Journal Article · Mon Dec 15 04:00:00 EST 2008 · Nuclear Data Sheets

DOI:https://doi.org/10.1016/j.nds.2008.11.005· OSTI ID:21163763

Pigni, M T; Oblozinsky, P; Mughabghab, S F; Mattoon, C M ^[1]; Capote, R ^[2]; Cho, Young-Sik ^[3]; Trkov, A ^[4]

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1. National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)
2. Nuclear Data Section, IAEA, Vienna (Austria)
3. KAERI, Daejeon (Korea, Republic of)
4. Jozef Stefan Institute, Ljubljana (Slovenia)

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.

• OSTI ID: 21163763
• Journal Information: Nuclear Data Sheets, Journal Name: Nuclear Data Sheets Journal Issue: 12 Vol. 109; ISSN NDTSBA; ISSN 0090-3752
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
COMPARATIVE EVALUATIONS
CROSS SECTIONS
DATA COVARIANCES
E CODES
EXPERIMENTAL DATA
FAST NEUTRONS
LEAST SQUARE FIT
MONTE CARLO METHOD
NUCLEAR DATA COLLECTIONS
NUCLEAR REACTIONS
STOCHASTIC PROCESSES
YTTRIUM 89