Typical thermal cycle performance: the net efficiency (electrical output divided by reactor thermal power) of an ordinary light-water-cooled, steam-cycle nuclear power plant is about what percent?

Introduction / Context:
Light-water reactors (LWRs) such as BWRs and PWRs produce thermal energy in the core and convert a fraction of that heat into electricity through a Rankine steam cycle. Net efficiency accounts for all auxiliary loads and realistic turbine-condenser temperatures.

Given Data / Assumptions:

• Condenser operates near ambient cooling-water temperatures.
• Turbine inlet steam conditions typical of LWRs, not supercritical fossil units.
• Auxiliary power consumption and heat losses are included in “net.”

Concept / Approach:
Because LWR core outlet temperatures are modest versus modern fossil supercritical plants, the achievable Carnot fraction is lower, leading to net plant efficiencies around the low-30% range. Typical values cluster around 30–35% depending on site cooling temperature, turbine design, and plant age.

Step-by-Step Solution:
1) Recognise Rankine limitations with saturated or slightly superheated steam at moderate pressure/temperature.2) Account for auxiliary loads (pumps, fans, control/cleanup systems) to move from gross to net efficiency.3) The representative textbook value is about 32%.

Verification / Alternative check:
Thermodynamic models with typical PWR primary outlet ~315–325 C and BWR steam conditions yield net electrical efficiencies ≈ 0.30–0.33 under standard cooling.

Why Other Options Are Wrong:
52% and 72% are characteristic of advanced combined cycles or idealised models, not LWR Rankine plants.88% is physically impossible for a heat engine with realistic temperature limits.

Common Pitfalls:
Confusing thermal efficiency (boiler/turbine) with capacity factor; ignoring seasonal condenser temperature effects that swing a few percentage points.

Final Answer:
32