Evaluation of Sodium Radioactivity in the Primary System of the Prototype Fast Reactor Monju

Abstract

In this study, the sodium radioactivity of ²⁴Na and ²²Na in the primary system measured in the prototype fast breeder reactor Monju was evaluated, and the reliability of the measurements and calculations was examined. The calculated-to-experiment values and their uncertainties for ²⁴Na and ²²Na radioactivities were 0.97 to 1.07 and 8.1% to 11.0% and 1.03 to 1.16 and 23.3% to 24.1%, respectively, using the JENDL-4.0 nuclear data library. The ²²Na radioactivity calculated with ENDF/B-VIII.0 was larger by 40% than those calculated with JENDL-4.0 and JEFF-3.3 due to the ²³Na(n,2n) cross-section discrepancy. The importance of the ²²Na neutron capture effect is also confirmed herein for the accurate evaluation of the ²²Na radioactivity. The experimental data were judged to be useful for validating the calculation method for improving the reliability of future designs of sodium-cooled fast reactors.

Keywords:

• Sodium fast reactor
• sodium radioactivity
• validation
• prototype fast reactor Monju

Acknowledgments

The authors would like to express their special thanks to the Radiation and Chemistry Management Section in the Monju for providing the measured data, to A. Takegoshi and H. Katagiri of the NESI, Inc., for their help in the calculation, and to the Reactor Core and Plant System Evaluation Group in the JAEA for editing and providing the ²²Na cross-section data.

Disclosure Statement

No potential conflict of interest was reported by the authors.