Development of a thermal–hydraulic system code, TAPINS, for 10 MW regional energy reactor

Small modular reactors (SMRs) with integral system layout have been drawing a great deal of attention as alternative options to branch out the utilization of nuclear energy as well as to offer the inherent safety features. Serving to confirm the design basis and analyze the transient behavior of an integral reactor such as REX-10, a thermal–hydraulic system code named TAPINS (Thermal–hydraulic Analysis Program for INtegral reactor System) is developed in this study. The TAPINS supports the simple pre-processing to build up the frameworks of node diagram for the typical integral reactor configuration. The TAPINS basically consists of mathematical models for the reactor coolant system, the core, the once-through helical-coil steam generator, and the built-in steam–gas pressurizer. The hydrodynamic model of the TAPINS is formulated using the one-dimensional momentum integral model, which is based on the analytical integration of the momentum equation around the closed loop in the system. As a key contribution of the study, a dynamic model for the steam–gas pressurizer with non-condensable gas present is newly proposed and incorporated into the code. The TAPINS is validated by comparing against the experimental data from the pressurizer insurge tests conducted at MIT (Massachusetts Institute of Technology) and natural circulation tests in the RTF (REX-10 Test Facility) at RERI (Regional Energy Reactor Institute). From the comparison results, it is demonstrated that, notwithstanding a few simplifying assumptions and the undemanding solution method to facilitate solutions for transients, the TAPINS can provide a reasonable prediction on the performances and the transients of an integral reactor system operating on natural circulation.

► A thermal–hydraulic system code named TAPINS is developed for simulations of an integral reactor.
► The TAPINS is based on the one-dimensional momentum integral model.
► A dynamic model for the steam–gas pressurizer with non-condensable gas present is proposed.
► A series of pressurizer insurge test and natural circulation test are simulated by the TAPINS.
► It is proved that the TAPINS can provide reliable prediction of an integral reactor system on natural circulation.