Analyses of SEFOR experiments; Isothermal temperature coefficient (Core II) and power coefficient

Hazama, Taira ; Numata, Kazuyuki*

The SEFOR (South-West Experimental Fast Oxide Reactor) Doppler reactivity experiments have been analyzed on the isothermal temperature coefficient measured in SEFOR Core II, and on the power coefficient measured in SEFOR Cores I and II. Nominal values and uncertainties of the experimental data were re-evaluated, starting from a review of raw data in the original experimental reports. In particular, the power coefficient data were thoroughly re-evaluated, including fuel temperature data and associated uncertainties. The latest data on fuel thermal conductivity correlation was employed in the evaluation. As a result, experimental uncertainty of the power coefficient was reduced from 11% of reported value to 8%. In the temperature coefficient analysis, the calculated value overestimates the experimental value by 9%. The discrepancy exceeds sum of the experimental (3%) and analytical (4%) uncertainties. In the power coefficient analysis, the calculated values agree with experimental values within an experimental uncertainty of 8%. Benchmark data for the Doppler constants has been prepared based on the Power Doppler relativities. The resulting Doppler constants are different form existing benchmark data by about 4%. The change is mainly attributed to the update of fuel thermal conductivity correlation. The new values are more reasonable than the existing values in that C/E values do not depend on the core types.