Depleted zinc oxide
The depletion of 64Zn is necessary, because this isotope is transformed into 65Zn by neutron capture. 65Zn with a half-life of 244.26 days emits gamma radiation with 1.115 MeV. 64Zn has a natural abundance of 48.6%, but in DZO it is reduced below 1%. Adding zinc oxide to the primary water loop of a boiling water reactor or pressurized water nuclear reactor reduces corrosion and therefore minimizes the amount of dissolved materials, especially 60Co.