RAS question
Which radioactive isotope, produced in Indian PHWRs, is widely used in cancer treatment?
Correct answer: (D) Cobalt-60.
Cobalt-60, produced in Indian PHWRs, is the radioactive isotope widely used in cancer treatment through teletherapy.
Explanation
Cobalt-60 is the answer because the question links reactor-produced radioisotopes with medical use. Indian PHWRs produce Cobalt-60, and it is extensively used in radiation therapy, especially teletherapy, for cancer treatment. The INIS record supports the medical mechanism: teletherapy treats cancer by focusing radiation from a source onto cancerous tissue from a distance. The INIS record also explains that cobalt metal is irradiated in a nuclear reactor to produce Cobalt-60, after which the source is loaded into teletherapy machines installed in hospitals. This makes Cobalt-60 distinct from nuclear-fuel materials: it is a reactor-produced radioisotope with a direct therapeutic role, and it also has industrial radiography use.
Why the other options are wrong
- (A) Plutonium-239 is associated with reactor fuel in fast breeders, whereas the cancer-treatment radioisotope identified here is Cobalt-60.
- (B) Thorium-232 is a fertile material for future reactors, not the teletherapy radioisotope used for cancer treatment.
- (C) Uranium-235 is a fissile reactor fuel material, not a medical teletherapy source for cancer treatment.
Concept
This tests applications of nuclear technology, especially the distinction between reactor fuel materials and reactor-produced radioisotopes. RAS repeats this area because it connects India's PHWR programme with practical uses in health care and industry.