1. MPT/P8-13
Results of KTM Lithium Divertor Model Testing on the Tokamak KTM and Future Plans
I.Tazhibayeva, G. Shapovalov, T. Kulsartov, Yu. Ponkratov, I.Lyublinski, A.Vertkov, E.Azizov, S. Mirnov, V. Lazarev, G. Mazzitelli
Uniqueness of the project’s results included the demonstration of prominent resistance of lithium CPS to plasma effects in comparison with traditional solid materials, decrease of power flux on a surface of in-vessel elements due to lithium radiation, and achievement of higher plasma discharge parameters.
The prototype model of lithium divertor on the basis of capillary porous systems of tokamak is a box-like element with a channel for coolant flow (eutectic alloy Na-K) and a tank for feeding the receiving surface with lithium. The planned energy flow on the lithium surface under nominal parameters of tokamak KTM (up to 10 MW/m2) is a 750 kJ during 5s discharge. Two consecutive stages of the experiments were carried out with un-cooled model of lithium divertor and then with the cooled one.
The vacuum conditions in the KTM discharge chamber were greatly improved after installation of un-cooled module and removal of the protective foil, in particular, partial pressures of the main gases typical for vacuum systems decreased in order of magnitude and some peaks disappeared altogether. The most prominent effect of open surface of liquid lithium in the tokamak’s chamber was a fall of intensity of Н2О peak and simultaneous rise of Н2 peak.
Thermal-hydraulic tests of lithium divertor model cooled with Na-K were conducted at the auxiliary test-bench, which is based on the KTM transport-sluice device. Initial temperature of lithium surface (200oC) and its stabilization at the level of up to 550oC during plasma discharge was kept by a flow of Na-K coolant; coolant temperature and circulation parameters were regulated by the external system for thermo-stabilization (STS). Tests with Na-K coolant proved operability of all the subsystems and elements of the thermo-stabilization systems during the tests under temperature range from 20 to 200oC. The tests allowed to obtain the values of coolant flow rate and dependence of coolant flow rate from the pressure of compressed nitrogen, supplied into gas system of STS stand.
It is expected, that demonstration of lithium CPS advantages for real tokamak conditions will lead to growth of demand for manufacturing of in-vessel devices based on this technology .