Plasma Facing Component Testing.pdf

The SATIR test-bed is a non-destructive examination (NDE) equipment installed at Tore Supra to test actively cooled plasma facing components (PFCs). The test-bed uses thermal transient excitation and infrared imaging to detect defects in the components. Hot and cold water flow successively in the cooling tube of the component, and the surface temperature is recorded with an infrared camera. Defects are detected by a slower temperature response above unbrazed areas.

The connection between temperature differences and defect sizes is the main difficulty. It is established by tests of standard defects and thermal transient calculations of defective geometries. SATIR has been in use for two years and has proved to be very valuable to test industrial components as well as prototypes.

The test procedure involves choosing hot and cold water durations and sampling frequency depending on the element being tested. Mock-up aimed at developments are tested individually and get a customized analysis. Elements from large fabrication series are tested simultaneously with a sound reference element, which is chosen after test in a high heat flux test-bed.

The thermal analysis is based on the difference between the time response of each couple of points (test and reference). These points are located at the same relative positions on the tiles to allow comparison. The temperatures are extracted from the film, usually from a 3*3 pixel matrix. The thermal analysis is normalized linearly to calculate the real temperature difference between the points.

Maximum temperature differences are then deduced from the normalized curves and displayed on the screen. In the case of the inner first wall, the temperature differences were also corrected from the various wall thicknesses measured on the stainless steel heat sink. A maximal temperature difference is authorized. When an element shows a temperature lag that exceeds the limit, it is more thoroughly investigated and can be rejected.

Setting the limit is the greatest difficulty. Two methods are employed: test of standard defects and finite element calculations. The standard defects are either fabricated or created on sound elements. The results of the thermal analysis are presented in table 1, which shows the temperature differences and defect sizes for three pairs of points.