Boron-Containing Materials:

Boron is a meaningful control material for thermal (and other) reactors. The extremely high thermal- absorption cross section of 10B (boron-10) and the low cost of boron has led to huge use of boron-holding materials in control rods and burnable poisons for  thermal  reactors. An absorption cross section of boron is huge over a considerable range of neutron energies which making it appropriate for not just control materials but also for neutron shielding.

Boron is nonmetallic and is not appropriate for control rod use in its pure form. For reactor use, it is commonly incorporated into a metallic material. Two of such composite materials are defines below.

Stainless-steel alloys or dispersions along with boron have been employed to a few extents in reactor control. A performance of boron-stainless-steel materials is limited since of the ¹⁰B (n,α  ) reaction. The absorption reaction is one of transmutation, ¹⁰B + ¹n→⁷Li + ⁴α , with the α-particle produced becoming a helium atom. The production of atoms having about twice the volume of the original atoms leads to severe swelling; therefore these materials have not been used as control rods in commercial power reactors.