Page 444 - Fundamentals of Magnetic Thermonuclear Reactor Design

Safety of Fusion Reactors Chapter | 14 421

TABLE 14.4 Summary of Releases for Hypothetical Events
% of the No-evacuation threshold
Weather conditions
Event Average Conservative
Loss of coolant from cooling systems <1 <20
accompanied by failure of all plasma
heating system windows (the ‘wet bypass’)
Loss of two barriers at the vacuum chamber <1 <10
entrance (the ‘dry bypass’)
Failure of two of the tritium plant ∼1 15
confinement barriers
Decay heat from IVC under loss of electric <1 <1
power supply
Ex-vessel/in-vessel loss of coolant associated <1 <1
with failure of the plasma discharge
suppression system
Magnetic field energy release <1 <1

would lead to environmental releases of up to 15 g tritium (as oxide) and 11 g of
dust, which is less than 20% of the no-evacuation threshold.
The consequences of natural and human-induced disasters have also been an-
alysed. Assessments have been made for the SL-2 class earthquake (assumed to
have a peak ground acceleration of 0.2 g horizontal and vertical with a return pe-
riod of 10,000 years), a crash of a jet aircraft with around 4000 L of fuel in tanks
and a Cessna type propeller-driven aeroplane. They showed that the required
primary safety function is performed, keeping releases below prescribed limits.

14.4.4 Conclusions
The general conclusion from the preceding discussion is that the ITER is ade-
quately designed in terms of safety of the population and the environment and is
not critically reliant on the functioning of safety systems. This is proved by re-
cent refined calculations, which suggest that radioactive effluents will be lower
than those assessed earlier. It is supported by parametric analyses.
Consequently, the guaranteed radiation safety concept underlying the ITER
design can be viewed as a basic one. It is premised on the following:
l Technical solutions that have long been tested in different power engineer-
ing applications. They include the use of water as a coolant and stainless
steel as the principal structural material for the vacuum vessel and the in-
vessel components.
l Intrinsic self-protection capacity.