Complex sentence: Sodium-23 is a very weak absorber of neutrons, the absorption of a neutron producing sodium-24, which has a half-life of 15 hours, decaying to magnesium-24.
Split into simpler sentences: Sodium-23 is a very weak absorber of neutrons. When it does absorb a neutron it produces sodium-24, which has a half-life of 15 hours and decays in to magnesium-24.