Radionuclide transport in a long‐term operation supercritical CO ₂ ‐cooled direct‐cycle small nuclear reactor

Abstract

Summary In recent years, to overcome the challenges of nuclear power plants due to their large scale, numerous types of small modular reactors are being designed worldwide. Small modular reactors are required to have a capability to operate in environmentally challenging regions with long refueling time. Supercritical CO2 (S‐CO2)‐cooled direct‐cycle reactor is one of the candidates that can meet these requirements. In order to evaluate if the design achieves this goal, transport of generated radionuclides from the long‐term operation has to be evaluated in order to estimate the radioactivity accumulation in the system. However, existing radionuclide transport evaluation method does not reflect the characteristics of supercritical fluids properly. In this paper, the fission product plate‐out behavior of Korea Advanced Institute of Science and Technology Micro Modular Reactor (KAIST‐MMR), a 10‐MWe class S‐CO2‐cooled fast reactor with direct S‐CO2 power conversion system, is studied. The evaluation methodology was developed via integrating suitable models while considering the shape of the nuclear fuel, component geometries, characteristics of a working fluid in supercritical state, and the fast reactor design. As a result of the analysis, the degree of plate‐out of KAIST‐MMR is not expected to have serious radioactivity accumulation within the components. Most of the sorption occurred at the turbine and recuperator hot‐side inlet region. In particular, the dose rate of the turbine was quite low, because the size of the turbine is very small.

Constructing a novel supercritical carbon dioxide power cycle with the capacity of process switching for the waste heat recovery

“…According to the system layout in Figure 1, S-CO 2 is divided into two flow streams at the cooler outlet. One stream is firstly compressed in Compressor1 (5,6), and then sequentially flows into LTR (6,7) and HTR (7,8) to be heated by the outlet S-CO 2 from turbine. Thereafter, S-CO 2 is further heated to a high temperature by the flue gas in Heater1.…”

“…4 In the supercritical region, the density of CO 2 is close to that of liquid, while the viscosity is more closer to that of gas. 5 These characteristics make S-CO 2 have high heat transfer efficiency and working capacity. What's more, CO 2 is inexpensive as a natural gas, which facilitates its widespread application.…”