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?

The correct option is 2 and 3 only.

Let us analyze each statement step-by-step to understand why this option is correct:

Statement 1: "RTGs are miniature fission reactors." is incorrect.
Radioisotope Thermoelectric Generators (RTGs) are not fission reactors. Nuclear fission reactors operate by initiating and controlling a sustained nuclear chain reaction where heavy nuclei split. In contrast, an RTG is a passive power source that generates electricity from the heat released by the natural radioactive decay of unstable isotopes (such as Plutonium-238). It does not involve a chain reaction and has no moving parts.

Statement 2: "RTGs are used for powering the onboard systems of spacecrafts." is correct.
RTGs are highly reliable, long-lasting power sources ideal for deep-space missions where solar power is insufficient due to the distance from the Sun. Famous spacecraft like Voyager 1, Voyager 2, Cassini, and the Curiosity and Perseverance Mars rovers utilize RTGs to power their onboard scientific instruments and systems.

Statement 3: "RTGs can use Plutonium-238, which is a by-product of weapons development." is correct.
Plutonium-238 (Pu-238) is the most commonly used radioisotope in space RTGs due to its favorable half-life (about 87.7 years) and high heat output. It is produced by irradiating Neptunium-237 (which is recovered from spent nuclear fuel or produced as a by-product during the production of weapons-grade Plutonium-239 in nuclear reactors). Thus, it is historically linked as a by-product of weapons-related nuclear materials development.

Since statements 2 and 3 are correct, the correct combination is indeed 2 and 3 only.