MHD pressure drop estimate for the WCLL in-magnet PbLi loop

Abstract

In the Water-Cooled Lithium Lead (WCLL) blanket, the eutectic alloy lithium-lead (PbLi) is used as tritium breeder and carrier, neutron multiplier, and heat transfer medium. The PbLi hydraulic loop section in the range of the reactor field coils, which includes the blanket and a non-negligible length of the connection pipes, is affected by intense magnetic fields which cause the transition to a MHD regime. Lorentz forces oppose the fluid motion and cause pressure losses several orders of magnitude higher than for the ordinary hydrodynamic regime. An accurate estimate of the MHD pressure drop is mandatory to properly design the PbLi loop and to optimize the flow path in the blanket. In this paper, the so-called “in-magnet” section of the PbLi loop is divided into three main regions (feeding and draining pipe, manifold, and breeding zone) which are further discretized into basic hydraulic elements. Analytical correlations and numerical results available in the literature are then used to calculate the MHD pressure drop terms for each element and then the overall loss. The study highlights that the highest contribution to pressure loss is made by the spinal manifold and connection pipes. Optimization strategies are suggested to minimize losses in these elements.