Apparatuses and methods for producing neutrons for applications such as boron neutron capture therapy (BNCT) are described. An apparatus can include a rotary fixture with a coolant inlet and a coolant outlet, and a plurality of neutron-producing segments. Each neutron-producing segment of the plurality of neutron-producing segments is removably coupled to the rotary fixture, and includes a substrate having a coolant channel circuit defined therein and a solid neutron source layer disposed thereon. The coolant channel circuits are in fluid communication with the coolant inlet and the coolant outlet.