Radiation source terms analysis and the classification of radioactive waste for the decommissioning of the first HWRR nuclear reactor in China

Abstract

Abstract Nuclear reactor will face the problem of decommissioning due to the high radioactivity of their components and the consideration of environmental safety when the operating period ends. The Heavy Water Research Reactor (HWRR) is the first large-scale research reactor to be decommissioned in China. The second phase of decommissioning involves the highly radioactive reactor block, so the source terms of the main reactor internals need to be evaluated. Based on the operating history, the complex three-dimensional geometry, materials and other information of HWRR reactor, this paper calculates and analyzes the activity of radionuclides of reactor internals. The results indicate that 14C, 54Mn, 55Fe, 60Co, 63Ni, and 152Eu are the main radioactive nuclides. The total activity of radioactive nuclides was 2.36E + 15Bq at the safe shutdown time at the end of 2007, 4.27E + 13Bq at the end of 2021, and 1.83E + 13Bq at the end of 2025. In addition, the ratio of the theoretical activity values to the sampling results is within 2.5 times and is conservative. The inner shell, outer shell, cooling water tank, sand layer, and heavy concrete shielding layer are all low-level waste. These data can provide reference for the preparation of the second phase of HWRR reactor decommissioning and the subsequent disposal of radioactive waste.