Page 253 - Fundamentals of Magnetic Thermonuclear Reactor Design

234 Fundamentals of Magnetic Thermonuclear Reactor Design

cuit (with water temperature of up to 90°C), high-pressure hot municipal distilled
water forced-flow circuit (with water temperature and pressure of up to 130°C
and 4.2 MPa, respectively), and a water-recirculation system. The system al-
lows hot water-pressure to be increased pneumatically using inert gas. A high-
pressure helium closed loop is also available to enable on-line heat removal from
gas-cooled objects under study and cooling rate control.
The facility has a range of gauging and diagnostic instruments, including
video cameras, infrared cameras (20°C–2000°C), pyrometers (160°C–2500°C),
X-ray receivers, a multi-channel thermocouple measurement system, a mass-
spectrometer and acoustic signal receivers (20 Hz to 25 kHz).
Diagnostic equipment including X-ray sensors, thermographic cameras, py-
rometers and video cameras, are mounted on the working chamber’s upper lid.
There are 60 gauging channels and 16 management channels. The gauging and
diagnostic system is part of a local computer network.
The IDTF test bench is comparable to the TSEFEY-M facility by experi-
mental and diagnostic capabilities, but has a much larger chamber and a much
more powerful electron gun. It is used for comprehensive testing of full-scale
mockups of the FW components.

7.3.3 Prevention of Destructive Events

The first wall, expected to perform its functions effectively for two decades and
retain its structural integrity, has to be designed with consideration for potential
destructive processes.
In the course of a reactor’s operation, armour tiles grow thinner due to ero-
sion, which leads to surface temperature decrease and reduces the influx of im-
purities in the plasma. However, damage or deterioration may occur, raising the
temperature of the tiles, which, in turn, may speed up the thermal and ion ero-
sion processes. The most likely damages include cracking and/or detachment of
the tiles, and the radiation-stimulated decrease in the armour material thermal
conductivity.
The development of microcracks parallel to the heat flow does not affect
the heat-sinking capacity of the tiles and presents no risk. Examples include
recrystallisation cracks, normal to a surface, that may result from solidification
of a melted surface (Fig. 7.8AA). However, cracks that extend the full thickness
of a tile (Fig. 7.8B) are a hazard: stresses arise at the tile–substrate interface
due to dissimilar physical–mechanical properties of different materials. They
may promote further cracking growth into the substrate material, which is unac-
ceptable. To damp the interface stresses, it is reasonable to use a high-plasticity
intermediate layer or modify the substrate using the contour profiling technique.
Cracks running parallel to the tile surface decrease the tile’s thermal con-
ductivity and increase the surface temperature (Figure 7.8C). Small cracks on
individual tiles, caused by accidental defects, do not materially affect the aggre-
gate flow of impurities. However, an en masse cracking, caused, for example, by