Water Quality Control at Primary Cooling System of Crud Concentration Suppressed Boiling Water Reactor, (II): Evaluation of Cobalt-58 Behavior in Iron Crud Suppressed BWR

A possible accumulation mechanism of Ni and radioactive 58 Co ions in the reactor water of a low iron crud concentration plant was modeled based on a direct deposition of Ni ion on fuel cladding surfaces as a form of NiO, followed by the solid phase reaction between NiO and iron crud (α-Fe 2 O 3 ) to produce NiFe 2 O 4 . The calculated results agreed satisfactorily with measurements in the first Japanese standard BWR, Fukushima 2-2 (1,100 MWe). These calculations showed that controlling the Fe/Ni corrosion products ratio in the feed water to a value larger than 2 was effective to suppress 58 Co activity in the reactor water as well as Ni ion concentration.