At night, the demand for electricity supplied by a fission nuclear reactor decreases. How is the fission nuclear reaction controlled to avoid overproduction of electricity?

A fission chain reaction continues when neutrons released by fission strike other fuel nuclei. Neutron-absorbing control rods slow the reaction by removing neutrons; increasing their exposure to the fuel reduces the number of fissions and the reactor’s power output. Therefore, the correct choice is “The exposure between the fuel rods and a neutron-absorbing material is increased.”

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