Thermal-hydraulic model of the helium-cooled pebble bed test blanket module for ITER FEAT

Abstract

Within the European fusion programme several test blanket modules (TBMs) are under development to be tested in the International Thermonuclear Experimental Reactor (ITER). The TBM prepared by Forschungszentrum Karlsruhe GmbH represents the helium-cooled pebble bed blanket (HCPB) considered as a viable concept for future fusion reactors. A safety assessment has to demonstrate that the HCPB TBM with its own cooling system does not impede the safe operation of ITER under normal and accidental conditions. For conducting the highly transient accident sequences of the loss of coolant type, a RELAP model has been developed for the HCPB TBM system. The present report describes in detail the modelling for both the TBM proper as a network of numerous parallel and serial flow channels, and the external cooling circuit with circulator, heat exchanger, heater, piping system, etc. According to the RELAP/MOD3.2 manual breakdown, for each component the characteristics are defined in separate sections, i.e., hydrodynamics, heat structures, material properties, and power sources. While the results of the safety study are documented in a different report, this work includes selected results of the steady state behaviour of the system in terms of gross parameters, hydrodynamic quantities, and temperature distributions in coolant and heat structures. Lessons learned from code application and appropriate further model extensions are outlined. Detailed data and program listings are given in three appendices.