Safety comparison of common power reactor types: which reactor configuration is generally considered most prone to radiological hazards due to the working fluid path and in-core boiling characteristics?

Introduction / Context:
Different reactor types manage the primary coolant and steam cycle differently, which affects how radioactive species might reach the power conversion equipment and the environment under fault conditions. A high-level GK comparison often asks which design is intrinsically more prone to radiological transport if barriers are breached.

Given Data / Assumptions:

• We compare typical textbook features at a general level.
• In BWRs, boiling occurs in the core; the same water that becomes radioactive in the core goes to the turbine.
• In PWRs, a separate secondary loop generates steam, isolating primary radioactivity from the turbine.

Concept / Approach:
Because BWR steam is produced directly in the reactor core, the steam delivered to the turbine is part of the radioactive primary circuit. This can elevate the potential for radioactivity in turbine systems and, during abnormal events, increase pathways for release compared with systems in which the primary coolant is fully separated from the steam cycle. Gas-cooled and sodium-cooled reactors have different hazards (e.g., chemical reactivity of sodium), but the question focuses on radiological hazard potential linked to working fluid paths.

Step-by-Step Solution:
Identify which design sends primary working fluid to the turbine: BWR.Recognize that PWRs isolate primary radioactivity via steam generators.Note gas-cooled and sodium-cooled systems generally do not boil the primary in-core to drive the turbine directly.Select BWR as comparatively more prone to radiological hazards in GK framing.

Verification / Alternative check:
Plant system diagrams show the BWR’s single-loop direct cycle. Maintenance procedures in BWR turbine halls often include radiological controls not required in PWR secondary systems.

Why Other Options Are Wrong:
PWR/PHWR: Have primary–secondary separation, limiting turbine-side radioactivity.Gas-cooled reactors: Different considerations; not direct-cycle radioactivity to turbine.Sodium-cooled fast reactors: Chemical hazards are notable but radiological transport to turbines is not via direct boiling steam from core.

Common Pitfalls:
Conflating “hazard” broadly (chemical, thermal, neutronic) with the specific radiological transport pathway that the question targets.

Final Answer:
Boiling water reactor (BWR)