A cobalt-60 source is used for cancer therapy

PHYSICS · Multi-part · CBSE · Physics · Nuclei · Nuclei

Problem

A cobalt-60 source is used for cancer therapy. The treatment unit must always deliver at least

2.0\,\text{GBq}

of activity. Cobalt-60 has a half-life of

5.3\,\text{yr}

. The institution plans to replace the source exactly one year after installation. (i) Derive an expression for the minimum initial activity

A_0

(at installation) required so that the activity does not fall below

2.0\,\text{GBq}

after one year. (ii) Using your expression, calculate numerically the minimum initial activity. (iii) Determine the mass of

^{60}\!\mathrm{Co}

corresponding to this initial activity. (Atomic mass of cobalt

=60\,\text{g mol}^{-1}

;

N_A = 6.02\times10^{23}\,\text{mol}^{-1}