Nuclear Physics and Energy

Boron rods are commonly used as control rods in nuclear reactors because Boron is an effective neutron absorber, helping to regulate the fission rate.

The moderator's primary function is to slow down fast neutrons produced by fission to thermal speeds, making them more likely to cause subsequent fission events.

Graphite is used in nuclear reactors to slow down fast neutrons produced by fission, making them more likely to cause further fission reactions. This makes it a moderator.

Purnima-I was an experimental research reactor at the Bhabha Atomic Research Centre (BARC) that used plutonium as fuel.

A moderator slows down fast neutrons produced during fission to thermal energies, making them more likely to cause further fission reactions. Common moderators include water, heavy water, and graphite.

Liquid sodium or sodium-potassium alloys are commonly used as coolants in fast breeder nuclear reactors due to their high thermal conductivity and high boiling point.

Pressurised Heavy Water Reactors (PHWR) are designed to use natural uranium as fuel, utilizing heavy water as both coolant and moderator.

In the context of 2007, Iran maintained its nuclear enrichment program despite international pressure and IAEA inspections, leading to the reported standoff.

Fusion bomb involves the principle pf nuclear fusion according to which when two lighter nuclei combine to form a bigger nucleius, then it is characterised by emission or liberation of tremendous amount of energy.

A nuclear reactor maintains a controlled chain reaction to produce energy, whereas an atomic bomb uses an uncontrolled chain reaction.

Part of the cooling system where the primary coolant bringing heat from the reactor is used to make steam for the turbine. Reactors may have up to four loops, each with a steam generator. It is not a component of Boiling Water Reactor (BWR).

These are the second generation of British gas-cooled reactors, using graphite moderator and carbon dioxide as coolant. The fuel is uranium oxide pellets, enriched to 2.5-3.5%, in stainless steel tubes. The carbon dioxide circulates through the core, reaching 650°C and then past steam generator tubes outside it, but still inside the concrete and steel pressure vessel. Control rods penetrate the moderator and a secondary shutdown system involves injecting nitrogen to the coolant.

The nuclear reactor core is the region with in a nuclear reactor where the nuclear fuel assemblies are located and the nuclear reaction consequently takes place. The core of the reactor contains all the nuclear fuels and generates all of the heat. It contains low-enriched uranium, controls systems and structural materials.The core contain hundreds of thousands of individual fuel pins.

Thermal reactors use slowed or thermal neutrons. Almost all current reactors are of this type. These contain neutron moderator materials that slow neutrons until their neutron temperature is thermalised, that is, until their kinetic energy approaches the average kinetic energy of the surrounding particles.

Both A and R are true, but R is not the reason for A. Hence, option (2) is correct.