Plutonium-238 is a radioactive isotope used in radioisotope thermoelectric generators (RTGs) to power deep-space exploration probes.
The table shows how the activity of a sample of plutonium-238 varies over time.
Time (years)04488132176220Activity (kBq)16001131800566400283 \begin{array}{|c|c|c|c|c|c|c|} \hline \textbf{Time (years)} & 0 & 44 & 88 & 132 & 176 & 220 \\ \hline \textbf{Activity (kBq)} & 1600 & 1131 & 800 & 566 & 400 & 283 \\ \hline \end{array} Time (years)Activity (kBq)0160044113188800132566176400220283Explain step-by-step how a graph of activity (yyy-axis) against time (xxx-axis) is used to find the half-life of plutonium-238.
Use the data in the table directly to find the half-life of plutonium-238. Show your working.
The plutonium-238 is enclosed within a robust, multi-layered protective casing of carbon-composite and steel inside the RTG.
Plutonium-238 transfers thermal energy at a rate of 0.56 W0.56\text{ W}0.56 W for every gram of plutonium. Calculate the rate of thermal energy output from a core with a mass of 34.2 g34.2\text{ g}34.2 g.
When plutonium-238 decays, it emits alpha particles. Explain why space agency personnel can safely handle the outer casing of the RTG without receiving a radiation dose from these alpha particles.
Deep-space probes traveling to the outer solar system must operate continuously for several decades without any possibility of maintenance or solar power.
Explain why it is essential to use a radioisotope with a long half-life like plutonium-238 rather than an isotope with a short half-life of a few weeks.
