In India, why are some nuclear reactors kept under "IAEA Safeguards" while others are not ?

(a) Some use uranium and others use thorium
(b) Some use imported uranium and others use domestic supplies ✓ UPSC's answer
(c) Some are operated by foreign enterprises and others are operated by domestic enterprises
(d) Some are State-owned and others are privately-owned

Why the answer is (b)

• Under the 2008 India–US civil nuclear deal and India's Separation Plan, India placed its civilian reactors under IAEA safeguards while keeping strategic (military-linked) reactors outside.

• Reactors that run on imported uranium (from Russia, Kazakhstan, Canada, Australia) must be safeguarded so the fuel is verifiably used only for peaceful purposes; reactors fuelled with domestic uranium can remain unsafeguarded — option (b).

• Fuel type (a), operator nationality (c) and ownership (d) are not the basis; all Indian power reactors are State-owned (NPCIL) and none uses thorium commercially yet.

• Hence option (b).

Why the other options are wrong

(a) Some use uranium and others use thorium: No Indian power reactor runs commercially on thorium yet.
(c) Some are operated by foreign enterprises and others are operated by domestic enterprises: All Indian power reactors are operated by NPCIL/BHAVINI.
(d) Some are State-owned and others are privately-owned: There are no privately owned reactors in India.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.