Which isotope is produced by activation of corrosion products?

• A. Co-60
• B. Ar-41
• C. N-16
• D. F-18

Answer: (A)

Activation of corrosion products mainly yields cobalt-60 because corrosion films form on metal surfaces from cobalt-containing impurities in stainless steels and nickel alloys. When these surfaces are exposed to reactor neutrons, the cobalt-59 in those impurities captures a neutron and becomes cobalt-60. This activated cobalt then plates out on surfaces and piping, creating persistent gamma radiation sources that drive much of the plant’s occupational exposure and hot spots. Co-60 emits strong gamma rays (high-energy photons) and has a long enough half-life to remain radiologically significant, making it the classic example of activation products from corrosion.

The other isotopes come from different activation pathways. Argon-41 is created mainly from argon in the surrounding air activated by neutrons in the plant’s ventilation byproducts, not from corrosion products. Nitrogen-16 arises from fast-neutron interactions in the coolant water (for example, O-16(n,p)N-16) and has a very short half-life, so it’s a transient coolant activation product. Fluorine-18 is produced in medical cyclotrons and is not related to activation of corrosion products in a reactor.