Page 436 - Fundamentals of Magnetic Thermonuclear Reactor Design

414 Fundamentals of Magnetic Thermonuclear Reactor Design

14.4 ITER DESIGN SOLUTIONS FOR RADIATION SAFETY
The practical implementation of the mentioned requirements can be illustrated
by ITER as the best-laid project. If we take the project materials as at the engi-
neering design completion phase, when the reactor site has not yet been identi-
fied, and the safety problems are considered using average weather, seismic and
other conditions, we will see that the adopted philosophy is consistent with the
codes and standards of all countries participating in the project. At the reactor
construction phase, the criteria and approaches are better defined, worked out in
detail and brought in line with the regulation of the host country [17].

14.4.1 Design Principles for ITER Radiation Safety
The reactor’s safety objectives at all phases of the reactor life cycle, including
decommissioning are as follows:
l To ensure, in normal operation, that exposure to hazards in premises and at
the release of hazardous effluents from the premises is controlled and kept
below prescribed limits.
l To minimise consequences of incidents, which should be less severe, if their
probability is higher.
l To mitigate accident consequences and ensure that there is no need for pub-
lic evacuation.
l To ensure that radioactive waste hazards are as low as reasonably achievable.

The key ITER design principles are
l safety as first priority;
l utmost use of the reactor’s intrinsic self-protection capabilities;
l compliance with dose and release limits established in accordance with the
IAEA and the ICRP recommendations [2,3];
l favourable safety features of the fusion reactor should be deployed to the
maximum extent feasible:
l no deviations from the basic reactor design for the performance improve-
ment or cost-saving purposes, which may jeopardise radiation safety;
l project robustness, that is, simplicity, reliability, fault tolerance, self-sustain-
ing, redundancy and controllable SISs;
l utmost use of the passive safety features; and
l no transfer of the safety functions to experimental structural components.

Non-radiation hazards in ITER include the toxic beryllium, concentrating
mainly in the FW cladding. Beryllium particulates arising in the vacuum cham-
ber due to wall sputtering and in hot cells as a result of treatment of the cladding
elements may get to the premises and to the environment. The methods for con-
trolling their migration are similar to those for tritium and activated materials.
Periodic removal of dust depositing on the divertor elements is considered as an
additional measure.