Monte Carlo time dependent modelling of the MYRRHA core based on SERPENT2

Bernat Ballester Vázquez, Augusto Hernandez Solis, Pablo Romojaro

    Research output

    69 Downloads (Pure)


    Transient phenomena are of major importance in the safety analysis of new reactor designs. At the moment, while MYRRHA is in the process of being licensed, engineers and scientists at SCK CEN are performing all the necessary safety studies in the design to ensure it complies with the regulations. Part of such studies are the calculations of the dynamic behaviour of the reactor in
    transient scenarios, which can range from movements of control rods bundles that take place regularly in the operation of a nuclear reactor to accident conditions.
    Knowing the time-dependent evolution of the reactivity in the core is essential, as it is a parameter that is required for determining the neutron population, power or thermal-hydraulic behaviour of the reactor, but calculating it is not a simple task. Usually, the approach followed is to approximate the time-dependent reactivity by determining a static reactivity instead, which is not dependant on time and can be more easily calculated. This static reactivity is then used as an input in the point kinetics equations, to measure the evolution of the neutron population, and in thermal-hydraulic codes, to study the feedback effects and other safety-related parameters.
    However, in the last years the general improvements in computational power and the development of dynamic tools in various Monte Carlo neutron transport codes offer the possibility of calculating the reactivity, as well as other parameters of interest, using a fully time-dependent approach. As Monte Carlo method does not introduce major simplifications in the calculations, they allow to reach best-estimate solutions, which makes the Monte Carlo approach an interesting possibility.
    In this work, the possibility of using time-dependent Monte Carlo simulations for the safety analysis of the MYRRHA reactor is explored. The approach for performing such calculations, together with case studies using various models are presented. An assessment of the main challenges and shortcomings that need to be overcome for the use of the method in the future is also included.
    At the moment, though, the Monte Carlo method is not yet applicable in safety studies, and static methods are preferred instead. In an effort to provide the safety team with a reliable tool to calculate the reactivity of the core in a transient situation, the method currently used at SCK CEN is evaluated and compared with the dynamic Monte Carlo simulations. Additionally, an alternative approach for the calculation of the static reactivity, derived from perturbation theory, is proposed and studied.
    Original languageEnglish
    QualificationMaster of Science
    Awarding Institution
    • Universitat Politècnica de Catalunya
    • Hernandez Solis, Augusto, SCK CEN Mentor
    • Romojaro, Pablo, SCK CEN Mentor
    • de Blas del Hoyo, Alfredo, Supervisor, External person
    Date of Award13 May 2022
    StatePublished - 13 May 2022

    Cite this