Void effect
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The formation of steam or the ingress of gas bubbles
in the moderator and/or the coolant influence the criticality of the
reactor. The void effect can be decisively influenced by the design
of the reactor core. Since e.g. in the case of a thermal reactor there
is an optimum ratio of moderator to fuel volume, there is a void effect
with positive coefficient in an excessively moderated reactor. An increase
in the steam bubble portion increases the neutron multiplication factor
and thus the reactor power. In a reactor undermoderated due to the core
design the conditions are the other way around; here the increase of
the steam bubble portion reduces the neutron multiplication factor and
thus the reactor power. Therefore, an inherently safe reactor regarding
steam bubbles and gas ingress must always be slightly undermoderated;
it has a negative void coefficient. See 'steam
bubble coefficient'.
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11 - 15 March 2018
Munich, Germany
30 September - 04 October 2018
Prague, Czech Republic |
