Fusion Science and Technology / Volume 54 / Number 1 / July 2008 / Pages 101-106
Technical Paper / Blanket Design
Within the framework of the development of technology for a fusion reactor, the need of tritium breeding in order to reach fuel self-sufficiency is a major issue.
The systems allowing this tritium production (breeding blanket) have to deal with a main difficulty that comes from the tendency for tritium to diffuse through hot metallic walls. Because of the double function of the blanket: i) breeding the necessary Tritium and ii) efficiently extracting the deposited heat, the coolantcontaining metallic surfaces used to promote the heat transfer lead also to a non negligible mass transfer of tritium from the breeder material towards the coolant.
In order to improve the management of tritium, different studies have been launched in this field with applications to DEMO breeding blankets and to the corresponding Test Blanket Module (TBM) to be tested in ITER. The present paper is focused on the case of the helium cooled lithium lead (HCLL) blanket which is one of the two TBMs proposed by EU for testing in ITER.
The study determines, for different scenarios of ITER operation (short pulse, long pulse and trains of back-to-back pulses), the flux of tritium between each circuit (mainly PbLi breeder and He coolant), and the inventories of tritium in each circuit. The establishment of mass balance equations for tritium in each circuit leads to a set of non linear differential equations solved in transient conditions since ITER pulses are too short to reach steady state. These equations rely mainly on Fick's law with a link to the tritium Sievert's constant in each metal.