Geometric optimization of a novel passive flow limiter for nuclear heating reactors.

• To reduce the leakage mass flow rate in the Loss-of-Coolant Accidents of the nuclear heating reactor , we designed a novel passive flow limiter that can completely block the flow by the inside moveable ball under the large pressure difference. • The dimensionless critical flow rate η of the passive flow limiter was established by mathematical analysis , and the appropriate range of η was determined. • Investigation of the relationship between hydraulic performance and geometric parameters of the passive flow limiter by three-dimensional numerical simulations. • Comparison and evaluations of the numerical results and the discussion on the optimal design of the passive flow limiter. A novel passive flow limiter was designed for the NHR200-II nuclear heating reactor to reduce the break mass flow rate in loss-of-coolant accidents (LOCAs). The flow limiter is mainly composed of a multisection cylindrical flow passage and an internal movable ball, and the flow passage would be blocked automatically by the movable ball while the flow in the passage was accelerated during a LOCA transient. The dimensionless critical flow rate η was identified as the key performance parameter of the limiter. Important geometric parameters, such as the axial distance H , the shape of the throat section, the blockage ratio of the ball in the pipe, and the front length L were studied numerically to optimize the structure of the passive flow limiter. The dimensionless critical flow rate η was found to increase rapidly with the axial distance H. The downstream throat shape of the passive flow limiter also affects the performance. The blockage ratio has a relatively small effect on the dimensionless critical flow rate η , and the dimensionless critical flow rate decreases with the increasing front length L. [ABSTRACT FROM AUTHOR]