Exp) Option b is the correct answer.

Radioisotope thermoelectric generators (RTGs) convert heat from radioactive decay into electricity using thermocouples. They power spacecraft and remote installations, providing reliable energy for decades. RTGs are crucial for missions where solar power is impractical, such as deep space exploration, due to their longevity and durability in harsh environments.

Statement 1 is incorrect. RTGs are not miniature fission reactors. Instead, they rely on the natural radioactive decay of plutonium-238 to generate heat, which is then converted into electricity using thermocouples. No nuclear fission occurs in RTGs.

Statement 2 is correct. RTGs provide electrical power for spacecraft, especially in situations where solar power is impractical or insufficient. They have been used in more than two dozen U.S. space missions since 1961.

Statement 3 is correct: As per the given combination of options RTGs can use Plutonium-238, which is a byproduct of weapons development.

Note: Many standard sources including NASA clearly mention that Plutonium-238 is not a weapon grade material. So according to us, the answer should be 2 only. But there is no such option available, so we are considering 2 and 3 (option b) as the answer until UPSC releases the final answer key.

Source:https://science.nasa.gov/mission/cassini/radioisotope-thermoelectric-generator/

https://www.wired.com/images_blogs/wiredscience/2013/09/final72005faqs.pdf

https://www.acs.org/education/whatischemistry/landmarks/plutonium-238-production.html

https://world-nuclear.org/information-library/nuclear-fuel-cycle/fuel-recycling/plutonium#:~:text=The%20decay%20heat%20of%20Pu,satellites%2C%20navigation%20beacons%2C%20etc.

http://large.stanford.edu/courses/2022/ph241/spaugh1/