A study on the radial expansion reactivity of a metal-fueled sodium-cooled fast reactor via a physics experiment.

• An experimental model of the radial expansion reactivity in a SFR was proposed. • The model reflects well the spectral component of the radial expansion reactivity. • Measured reactivities during experiment were compared with calculated values. • The difference in the calculation/experiment ratio vary from −4.3% to 9.2%. For a metal-fueled SFR (Sodium-cooled Fast Reactor), the negative reactivity feedback due to the thermal expansion of the support grid which is known as a radial expansion reactivity, provides a principal safety mechanism in most severe accidents. In this paper, an experimental model of the radial expansion reactivity in a metal-fueled SFR is proposed, and experimental models are established in a collaboration between Korea Atomic Energy Research Institute (KAERI) and Institute for Physics and Power Engineering (IPPE). Modeling of the radial expansion reactivity in a realistic experiment condition is very difficult due to physical limitation of experimental facility. Hence, a sparse perturbation method suggested by authors was employed for reasonable modeling of the radial expansion phenomenon. Measured values were compared with calculated ones using the MCNP transport code with the ENDF/B-VII.0 library. The energy-dependent radial expansion reactivity components of the planned experimental model showed good agreement with those of the target Prototype Gen IV SFR core. Errors of C/M (calculation/measurement ratios) varied from −4.3% to 9.2%. Considering the 1 σ uncertainty in the C/M, 5% in maximum, errors of calculation/measurement ratios were within 2 σ uncertainty range. [ABSTRACT FROM AUTHOR]