(a)[1]
Calculate the activity per unit mass for the steel.
(b(i))[1]
When the activity per unit mass caused by contamination is greater than $400\,\text{Bq kg}^{-1}$, special storage precautions are necessary. Nickel-63 is a $\beta$-emitter with a half-life of $92$ years. The largest energy of an emitted $\beta$-particle is $0.067\,\text{MeV}$. Use your answer in (a) to calculate the energy, in $\text{J}$, released each second in a mass of $1.0\,\text{kg}$ of steel due to the radioactive decay of the nickel.
(b(ii))[1]
Use your answer in (i) to suggest, with a reason, if the steel will be at a high temperature.
(b(iii))[3]
Use your answer in (a) to determine the time interval before special storage precautions for the steel are no longer needed.