Numerical Simulations of Passive Heat Removal from Mobile Microreactors

Abstract

As nuclear energy becomes increasingly vital to the goals of carbon neutrality by 2050, nuclear microreactors are being researched as an option for easily transportable energy. Designed to be transportable, factory fabricated, and self-adjusting, nuclear microreactors will fill in the gaps to help make the U.S. power grid more robust. Before designs can proceed, studies must be conducted on the safety of transporting these mobile microreactors while confined within a standard International Organization for Standardization (ISO) shipping container. Because of their mobile nature, microreactors will not have access to many of the engineered decay heat removal methods that traditional reactors utilize during shutdown. Current regulations state that the surface temperature of the microreactor needs to remain below 85°C while being transported on highways. This work investigates the surface temperature profiles of a mobile microreactor while confined within an ISO shipping container that does not allow forced convection to cool the outer reactor wall. Investigations have been performed for several configurations, including different reactor sizes, power levels, and scenarios with or without shielding around the reactor pressure vessel. This conservative safety analysis restricts the power level of the reactor to be less than 1 MW(electric). A more realistic analysis with the intermittent shutdown of shipping container air circulation demonstrates that a 4-MW(electric) reactor will reach 85°C per the Code of Federal Regulations limitations after 1 h.