Which system is part of the plant's major mechanical systems?

• A. Reactor coolant system
• B. Electrical distribution system
• C. Pneumatic controls
• D. Instrumentation desk

Answer: (A)

This question is about identifying systems that physically move fluids and remove heat in a plant. The reactor coolant system is the major mechanical loop because it forms the primary closed path that circulates coolant through the reactor core and related components, using pumps, piping, valves, and heat exchangers to remove heat and keep the reactor from overheating. Its role is to move large amounts of thermal energy and maintain the proper operating conditions, which is the essence of a major mechanical system. The other options don’t fit that category: the electrical distribution system handles power, not fluid movement; pneumatic controls are for actuating devices with compressed air and aren’t the primary heat-removal loop; and the instrumentation desk is a control-room element rather than a physical system that moves materials.