Facilities at BARC, Trombay: which of the following best describes the nuclear research reactors at this site?

Introduction / Context:
The Bhabha Atomic Research Centre (BARC) at Trombay is India’s premier nuclear research complex housing research reactors, critical assemblies, and advanced laboratories. Exam questions often distinguish research facilities from commercial power plants and heavy-water production units located elsewhere.

Given Data / Assumptions:

• Focus is on the type of reactors/facilities historically associated with BARC Trombay.
• Commercial nuclear power generation units are typically sited away from BARC.
• Heavy water plants are separate industrial facilities at other locations.

Concept / Approach:
BARC historically hosted research reactors and critical assemblies such as Apsara (swimming-pool type), CIRUS (heavy-water moderated), ZERLINA (zero energy), Purnima series (critical assemblies), and Dhruva (high-flux research reactor). This portfolio highlights research and isotope/irradiation capabilities rather than commercial power generation or heavy-water production capacity on the same campus.

Step-by-Step Solution:
Identify the nature of BARC facilities: research/critical reactors.Note that commercial 420 MW class power units are not at BARC.Heavy water production plants of large capacity are located elsewhere.Therefore, the accurate statement is the one listing the research/critical facilities.

Verification / Alternative check:
Publicly available summaries distinguish Tarapur/Kudankulam/RAPS etc. (power stations) from BARC (research site). Heavy water plants (e.g., Kota, Manuguru, Thal, etc.) are separate industrial sites, not at BARC Trombay.

Why Other Options Are Wrong:

• 420 MW power plant: not a BARC Trombay facility.
• 100 t/yr heavy water plant: not located at BARC Trombay.
• "All of the above" cannot be true since (b) and (c) are false.
• "Only a power reactor": contradicts the research mission of BARC.

Common Pitfalls:
Conflating research reactors with commercial power stations; assuming heavy-water production is co-located with research reactors.

Final Answer:
Five research/critical facilities historically including Apsara, Cirus, Zerlina, Purnima, and Dhruva