Real Interview Transcript: BARC OCES Scientific Officer (Mechanical) Mumbai Board
Candidate profile: B.Tech Mechanical Engineering (8.9 CGPA). Interview duration: 75 minutes at BARC Training School Hostel, Mumbai.
In-Depth Interview Questions & Model Solutions
Q1Board Chairman: "Please go to the whiteboard. Draw a 3D stress element and derive the state of pure shear from Mohr’s Circle."
Candidate drew 3D stress tensor element with normal stresses σx, σy and shear stresses τxy. On Mohr circle, candidate plotted (σx = 0, τ = τ0) and (σy = 0, τ = -τ0). Showed that on planes oriented at 45 degrees, principal stresses are σ1 = +τ0 (tensile) and σ2 = -τ0 (compressive). Explained why brittle materials (like cast iron or chalk) fail in tension at a 45-degree helix under pure torsion.
Q2Panelist 3 (Heat Transfer): "Why is liquid sodium used as a coolant in Fast Breeder Reactors (FBR) instead of water?"
Candidate Answer: "Sir, in a Fast Breeder Reactor, neutrons must not be slowed down (moderated) so that Uranium-238 can capture fast neutrons and breed Plutonium-239. Water contains hydrogen atoms that act as an efficient neutron moderator. Liquid sodium has a low neutron moderation cross-section, an exceptionally high boiling point (883°C at atmospheric pressure) eliminating high-pressure vessel requirements, and very high thermal conductivity (~85 W/m·K) facilitating efficient core heat removal without boiling."
Technical Panel Interview Strategy Tips
- BARC interviews focus 100% on core physical and mathematical derivations on the whiteboard.
- Never guess; be rigorous in explaining assumptions.