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摘要

A rod which contains a burnable neutron absorber material (40) is used for the initial compensation of excess reactivity present in the reactor core. Such a burnable neutron absorber rod (22) is constructed such that it also contains a moderator, at least when operating, for example by arranging for the primary coolant, which serves simultaneously as moderator, to flow through the cladding (24, 30). This results in increased neutron moderation in the region of the neutron absorber rod, which accelerates the depletion of the neutron absorber during the operating time. It is achieved as a result that after decrement of the excess reactivity, the neutron absorber is also consumed and thus its neutron poisoning effect is cancelled, so that the service life or the degree of burn-up of the reactor core can be improved. IMAGE