Comparative analysis of VVER-1200 core inventory considering non-uniform and uniform reactor core power distribution

Abstract

The impact of reactor core power distribution on radionuclide inventory calculations in the VVER-1200 reactor was analyzed using the ORIGEN, focusing on 135 radionuclides categorized into seven groups. The study considers two core models: one utilizing the dual enrichment strategy (4.4 % and 4.9 %, averaging 4.68 %) and another with a uniform enrichment of 4.79 %. Under non-uniform power distribution, activation product activity is calculated as 2.252 × 10¹⁸ Bq for the mixed enrichment (4.4 % & 4.9 %) and 2.229 × 10¹⁸ Bq for the uniform 4.79 % enrichment. Under uniform power distribution, these values are 2.364 × 10¹⁸ Bq and 2.193 × 10¹⁸ Bq, respectively. Similarly, actinides and their daughters exhibit total activities of 8.279 × 10¹⁹ Bq and 8.190 × 10¹⁹ Bq under non-uniform power, compared to 8.662 × 10¹⁹ Bq and 8.003 × 10¹⁹ Bq under uniform power. Fission products dominate the radionuclide inventory, with total activities of 3.895 × 10²⁰ Bq and 3.893 × 10²⁰ Bq in non-uniform scenarios, versus 3.830 × 10²⁰ Bq and 3.826 × 10²⁰ Bq in uniform scenarios. Although the overall radionuclide inventory difference between uniform and non-uniform distributions is minimal, localized regions in non-uniform distributions exhibit higher activity due to high burnup. These findings are crucial for accident analysis, safety assessment, radioactive waste management, and the decommissioning of nuclear facilities.