Transmutation of long-lived fission products in an advanced nuclear energy system

X Y Sun,Z C Zhu,W Luo,H Y Lan,X Z Cai,Y M Song,Q Y Gao,J G Chen

doi:10.1038/s41598-022-06344-y

Abstract

Disposal of long-lived fission products (LLFPs) produced in reactors has been paid a lot attention for sustainable and clean nuclear energy. Although a few transmutation means have been proposed to address this issue, there are still scientific and/or engineering challenges to achieve efficient transmutation of LLFPs. In this study, we propose a novel concept of advanced nuclear energy system (ANES) for transmuting LLFPs efficiently without isotopic separation. The ANES comprises intense photoneutron source (PNS) and subcritical reactor, which consist of lead–bismuth (Pb-Bi) layer, beryllium (Be) layer, and fuel, LLFPs and shield assemblies. The PNS is produced by bombarding radioactive cesium and iodine target with a laser-Compton scattering (LCS) γ-ray beam. We investigate the effect of the ANES system layout on transmutation efficiency by Monte Carlo simulations. It is found that a proper combination of the Pb-Bi layer and the Be layer can increase the utilization efficiency of the PNS by a factor of ~ 10, which helps to decrease by almost the same factor the LCS γ-beam intensity required for driving the ANES. Supposing that the ANES operates over 20 years at a normal thermal power of 500 MWt, five LLFPs including 99Tc, 129I, 107Pd, 137Cs and 79Se could be transmuted by more than 30%. Their effective half-lives thus decrease drastically from ~ 106 to less than 102 years. It is suggested that this successful implementation of the ANES paves the avenue towards practical transmutation of LLFPs without isotopic separation.

Highlights

Disposal of long-lived fission products (LLFPs) produced in reactors has been paid a lot attention for sustainable and clean nuclear energy
With the inspiration of accelerator-driven subcritical systems (ADS) implementation, we introduce a novel concept on advanced nuclear energy system (ANES) that is driven by a photoneutron source (PNS)
As an laser-Compton scattering (LCS) γ-ray beam of high intensity irradiating the transmutation target (e.g., cesium and iodine (CsI) target), a substantial population of neutrons are produced through photoneutron reactions, generating an intense PNS

Summary

Introduction

Disposal of long-lived fission products (LLFPs) produced in reactors has been paid a lot attention for sustainable and clean nuclear energy. While the TRUs inventory can be reduced significantly by recycling and incinerating them in advanced reactors, these LLFPs will likely dominate the long-term dose associated with radionuclide release from the geologic repository, owing to their high solubility in underground water and high activeness to move to the geosphere. To address this problem, transmutation of LLFPs into stable or short-lived isotopes has been suggested, which should follow the principle of “as low as reasonably achievable (ALARA)”[5,6]. The ADS availability has been evaluated[22,23,24] and a preliminary ADS facility for studying nuclear transmutation is being constructed in C hina[25,26]

Methods

Results

Conclusion