With reference to radioisotope thermoelectric generators (RTGs), consider the following statements : 1. RTGs are miniature fission reactors. 2. RTGs are used for powering the onboard systems of spacecrafts. 3. RTGs can use Plutonium-238, which is a by-product of weapons development. Which of the statements given above are correct ?

States that radioactive decay produces high temperatures in Earth's interior and contrasts that scientists consider the possibility of self-sustained nuclear fission 'as in a human-made reactor'.

A student could use this to distinguish heat from natural radioactive decay versus heat from a self-sustained fission chain reaction (the latter being what a reactor does) and ask which process RTGs rely on.

Identifies uranium-235 and plutonium-239 as materials used for fission in nuclear arms, implying that fission requires specific fissile isotopes and chain reactions.

A student can check whether RTGs use those fissile isotopes and whether RTGs operate via chain reactions or simple radioactive decay.

Describes thorium and uranium as nuclear fuels and mentions use in reactors/engines, illustrating that 'nuclear fuel' usually refers to materials used in reactors (breeding, sustained reactions).

Use this pattern to compare the isotopic fuel in reactors versus the isotope used in RTGs (if known) to see if RTGs use reactor-style fuel.

Defines nuclear energy as using nuclear reactions to produce steam that drives generators — describing the typical reactor-scale energy-conversion chain driven by controlled reactions.

A student could contrast this reactor model (reaction→steam→turbine) with the RTG model (decay heat→thermoelectric devices) to test if RTGs match the reactor pattern.

Explains that altering atomic structure releases energy used to generate electric power and names uranium/thorium as materials used for atomic power, reinforcing that 'atomic power' usually involves deliberate nuclear processes with specific fuels.

A student might ask whether RTGs perform the same type of atomic alteration (sustained fission) as large power stations or rely on spontaneous decay of radioisotopes.

States that altering atomic structure releases heat which is then used to generate electric power — establishes a general rule: nuclear processes produce heat that can be converted to electricity.

A student could extend this by asking whether a compact device that uses heat from radioactive decay to generate electricity (an RTG) is practical for powering systems where other power sources are limited.

Explains that geothermal (ground) heat is captured and used to drive turbines and generate electricity — demonstrates the general principle of converting local heat sources into electrical power.

One could analogously consider whether heat from radioactive decay (another local heat source) could be used similarly in environments where conventional generation is unavailable.

Mentions the existence of radio-nuclides such as uranium and thorium that produce terrestrial radiation — shows the availability of radioactive materials that can be sources of heat/radiation.

A student could combine this with the rule that nuclear materials release heat to infer that radioisotopes might serve as compact heat sources for remote power needs.

Describes fuel cells as modular power systems suitable for small-scale decentralized and remote locations — provides an example of specialized power systems used where grid power is unavailable.

Using this pattern, a student could consider RTGs as another class of specialized power supply designed for remote/isolated applications like spacecraft.

Refers to the MESSENGER spacecraft obtaining images and conducting observations — indicates spacecraft operate in environments where onboard power sources must support instruments.

A student could combine knowledge that spacecraft need dependable onboard power with the earlier clues about nuclear heat → electricity to evaluate whether RTGs are a plausible option for such missions.

States that radioactive decay is a source of heat (general rule: decay produces heat energy).

A student could combine this with the fact RTGs convert decay heat to electricity to infer RTGs plausibly use a radioactive isotope as their heat source.

Mentions plutonium (here Pu-239) as a nuclear material, illustrating that multiple plutonium isotopes exist and are used for specific nuclear applications.

A student could use this to reason that a different plutonium isotope (e.g., one chosen for heat-producing decay rather than fission) might be chosen for RTGs.

Notes plutonium as an element heavier than uranium and discusses uranium/plutonium in the context of nuclear energy materials.

A student could infer that plutonium isotopes are relevant nuclear materials and consider that some isotopes could be used as heat sources in devices that harness nuclear energy.

Explains that altering atomic structure (nuclear processes) releases heat used to generate power and lists uranium/thorium as nuclear fuel examples.

A student could generalize that nuclear decay/transformations provide heat for power devices and therefore seek which specific isotopes (like Pu-238) are suitable for small heat sources such as RTGs.