Design updates for helium cooling system of Indian LLCB blanket

Abstract

Lead–Lithium cooled Ceramic Breeder (LLCB) is one of the breeder blanket concept considered by India for fusion blanket. In the LLCB Test Blanket Module (TBM), the Pb-Li eutectic alloy and Lithium Metatitanate (Li2TiO3) in the form of pebbles used as tritium breeder materials. The Pb-Li alloy also acts as neutron multiplier and as coolant, extracting heat from TBM internals and Ceramic Breeders (CBs) zones filled with pebbles. The TBM First Wall (FW) and the Lead–Lithium Cooling System (LLCS) is cooled by high-pressure helium gas system. The conceptual design of LLCB concept as a test blanket module (TBM) for ITER has been approved in 2017. Helium Cooling System (HCS) is one of the major ancillary system has been designed for this concept. In the conceptual design of the LLCB Test Blanket System (TBS), two separate helium cooling loop have been considered for extracting heat from the test blanket. One helium coolant loop for extracting heat from the TBM FW and the other one from the LLCS. It is, however, found that installation and commissioning of the components of two high-pressure helium systems and the coolant purification system in the allocated space of Tokamak Cooling Water System (TCWS) Vault Annex (VA) is very challenging and the existing ancillary systems need to be optimized and made more compact. In view of this, studies have been carried out to optimize the process parameters, size of components, and the configuration of the helium system. In parallel, design optimization of TBM FW has also been carried out and several combinations of channel sizes, profile, and helium flow rate have been studied. This paper presents a new design configuration for the helium cooling system of the LLCB TBM. In this design, a single helium cooling loop has been devised complying with the cooling requirements of both the TBM first wall and the lead–lithium system. The main components and piping of the helium cooling system have been modelled in the modified version of RELAP/MOD4.0 and a preliminary transient analysis is carried out. In this paper, the process parameters, the process and instrumentations details, features of the new configuration, and the results of RELAP analysis of the helium cooling system are presented. The results of the thermo-hydraulic analysis of the TBM first wall with the optimized flow rate are also discussed.