Page 440 - Fundamentals of Magnetic Thermonuclear Reactor Design

Safety of Fusion Reactors Chapter | 14 417

l use of local shielding and personal protective clothing and equipment (pro-
tective suits, radiation shields, etc.);
l minimisation of radioactive contamination of the atmosphere, equipment
surfaces and premises.

The defence in depth protection principle is implemented by making use of
self-protecting capabilities inherent in the reactor and its systems and components.
A large part of RSs have low mobilisation rates. Most of them are activa-
tion products accumulating in structural materials, and tritium, implanted and
diffused into the IVC materials, and contained in some components of the tri-
tium plant and fuel cycle equipment. The escape of easily mobilising RSs (such
as radioactive dust, tritium co-deposited on IVC surfaces and absorbed in the
cryopumps, and activated corrosion products in the primary cooling circuits) is
prevented by the reactor’s structural components, in particular the vacuum ves-
sel, which acts as the first safety confinement barrier (Fig. 14.3) [18].
The cryostat housing the vacuum vessel forms the second confinement bar-
rier. Its purpose is to provide thermal protection for the superconducting mag-
net, whose fault would shut the reactor down automatically.

FIGURE 14.3 ITER confinement barriers. MDTS, The monitoring and detritiation system; NB,
neutral beam injector cell; VVPAA, vacuum vessel port access area; TCWS, tokamak cooling water
system; VVPSS, vacuum vessel pressure suppression system; HC/CAE, hot cells and casks with
activated equipment; DF, detritiation filter; SB–GB, secondary barrier–glove box. [18]