Question

How to find current activity of cobalt source by known one field dose?

Answer 1

Source

The commonly used sources of radiation are cobalt-60, a radioactive element emitting γ-rays, or an accelerator producing a beam of electrons.

Cobalt-60 is produced by neutron bombardment of stable cobalt in a nuclear reactor. Small nickel-plated slugs of the radioactive metal are loaded into a sealed alloy cylinder typically 10 × 450 mm and doubly encapsulated in a corrosion-resistant steel pencil. An array of such pencils is built into a rack typically 1–2 m2. Cobalt-60 decays continuously. The time taken to lose 50% of its initial activity, i.e., its half-life, is 5.26 years. Usually 10% of the cobalt-60 is replenished annually.