Abstract
For the next generation of fast reactors, global objectives are required in terms of safety, sustainability, waste minimization and non-proliferation issues. Concerning safety issues, particular efforts have been made in order to obtain core designs that can be resilient to accidental transients. In that frame, the CEA held R&D program toward a GEN-IV-like core concept that could meet those requirements: the ASTRID project. Based on heterogeneous core geometry (axial inner fertile layer, large upper sodium plenum) the ASTRID core shows improved behavior in case of unprotected loss of flow. It has been found that Doppler Effect plays a dominant role for the considered transients to deal with in the safety demonstration. The prediction of the Doppler Effect by neutronic simulation codes require experimental validation, the reason for which static tests conducted within SEFOR (South-West Experimental Fast Oxide Reactor) –a fast reactor fueled with mixed PuO2-UO2 and cooled with sodium –are being used. The SEFOR experimental tests are being analyzed with the ERANOS code package using nuclear data libraries of different evaluations: JEFF-3.1.1, JEFF-3.2, ENDF-B/VII.1 and JENDL4. The C/E values on the SEFOR Doppler Effect range from 1.01 to 1.07 with an experimental uncertainty of ±0.06. With the use of perturbation break down in energy and isotope, this paper identifies the reasons for such large C/E spread and identifies the differences and similarities of the SEFOR Doppler Effect with the ASTRID one.
Highlights
The SEFOR Doppler experiments have unique and valuable features of measuring whole core Doppler reactivity effect induced in various situations, such as steady-state at power levels of 20 MW, oscillation tests and prompt critical transients up to 10.000 MW
The prediction of the Doppler Effect by neutronic simulation codes require experimental validation, the reason for which transient tests conducted within SEFOR (South-West Experimental Fast Oxide Reactor), a fast reactor fueled with mixed PuO2-UO2 and cooled with sodium are being used
The SEFOR experimental tests are being analyzed with the ERANOS code package using nuclear data libraries of different evaluations: JEFF-3.1.1, JEFF-3.2, ENDF-B/VII.1 and JENDL4
Summary
The SEFOR Doppler experiments have unique and valuable features of measuring whole core Doppler reactivity effect induced in various situations, such as steady-state at power levels of 20 MW, oscillation tests and prompt critical transients up to 10.000 MW. SEFOR presents characteristics similar to sodium fast reactors, such as ASTRID [2]; this paper describes analyses and results obtained for the SEFOR Doppler coefficient, obtained with several nuclear data libraries, and their relevance regarding ASTRID Doppler one. The second is due to the RZ representation of the full core in ERANOS: since the B4C rods are not explicitly represented (and to reduce spatial effects), their compositions have been homogenized with the outer sodium region Previous CEA interpretation (with ERANOS/JEF2) for the reactivity effects of sharp transient change in fuel temperature gave C/ESEFOR I = 0.96±0.15 and C/ESEFOR II = 1.05±0.15 [3]. Calculated quantities with different nuclear data libraries are given and C/E are discussed
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