Safety, security and radiation protection issues in advanced reactors

Abstract

Nuclear energy safety focuses on minimizing the risk of radioactive release into theenvironment. Advanced reactor systems, currently in the design phase, may offer both benefitsand drawbacks in safety due to their size, design, and chemical properties of their components(coolant, fuel, moderator). The operational safety of these systems is yet to be established,necessitating testing and demonstration to validate safety claims. Conventional nuclear plantsuse multiple independent and redundant active safety systems, which rely on electricity ormechanical operations. In contrast, advanced nuclear reactors incorporate passive and inherentsafety systems. These passive features include self-regulation of fission rates through negativefeedback mechanisms and adequate core cooling in case of electricity loss or failure of activesafety systems. Advanced reactor designs may offer both advantages and disadvantages interms of proliferation risk. Some designs are more resistant to proliferation due to factors likesealed core designs, infrequent refueling, smaller fissile material inventories, and remotemonitoring capabilities [1, 2]. However, certain advanced reactor characteristics, such asopaque coolants (e.g., sodium, lead, molten salts), can complicate inspection and monitoring.The IAEA highlights advanced reactor technologies, such as transportable reactors, pebble-bedHTGRs, and molten salt reactors, as particularly challenging to safeguard [3]. Advancedreactors using more highly enriched fuels, such as HALEU (5%-20% fissile isotopeenrichment), pose additional nonproliferation challenges [4, 5]. Even small reactors withHALEU could contain enough fissile material for multiple nuclear weapons. Some designsmay produce spent fuel with higher concentrations of desirable isotopes for weaponsproduction, increasing the risk of diversion. Some advanced reactors may rely on reprocessingand recycling, making them cost-effective but also creating materials attractive to thieves orcountries seeking weapons production. The radioactivity of nuclear waste presents uniquewaste management and facility contamination challenges [1]. reactors and someunconventional reactors may reduce the prevalence of long-lived waste products, potentiallylowering the health risk associated with spent fuel release. However, reprocessing-relatedliquid radioactive waste has been difficult and expensive to manage. Proponents argue futurereprocessing plants will improve waste disposal, but the impact of advanced reactors on theback end of the fuel cycle remains uncertain. Environmental impacts of nuclear energy mustalso be evaluated, considering air emissions, water discharges, and waste managementchallenges over the full life cycle [1]. Nuclear power has a limited greenhouse gas footprintand low emissions of conventional air pollutants. Advanced reactors are expected to havesimilar life-cycle air emissions to existing reactors. Advanced reactors could address cost, safety, waste management, and fuel supply challenges, allowing nuclear power to play asignificant role in reducing global greenhouse gas emissions.