Design and Qualification of ITER in Vessel Coil System Instrumentation

The ITER In Vessel Coil (IVC) System consists of two vertical stabilization (VS) coils and 27 Edge Localized Mode (ELM) coils, which are water cooled copper coils. The operational temperature range is 70 
$^{\circ }$
C to 240 
$^{\circ }$
C. For control and investment protection, two approaches to the dedicated instrumentation have been made. One being the mass flow, the other the temperature measurement. Both systems are non invasive to conserve the integrity of the cooling water system, which consists of stainless steel pipes at the position, where the measurement will be conducted. Furthermore they are installed in an harsh radiation environment, calling for specific materials and qualification processes. There is one measurement per coil or VS turn. The mass flow measurement is conducted with ultra-sonic mass flow meters, qualified for radiation environment. For the temperature measurement, N-type thermocouples are selected, due to their radiation hardness and robustness. Since the access after installation will be difficult, 100% redundancy is provided. Two thermocouples are located downstream after the electrical insulating break (IB) on every outlet. Since the location is after the IB, the measurement is conducted on the low voltage side. In this article the design and qualification of the thermocouples and the proposed mass flow meter are being presented. A brace to mechanically secure the thermocouples is developed and tested. It fulfills the needs of a low heat capacity and high stability, as well as the ability to remotely exchange the thermocouples if needed. Since the measurement accuracy is also dependent on the exact placement and used insulation, these topics are discussed as well.