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Reactor Thermal Power Calculator

Work out reactor thermal power instantly with clear inputs, formula shown and shareable results.

About Reactor Thermal Power Calculator

Core thermal power is a simple energy balance on the coolant: mass flow times specific heat times temperature rise. Pressurised water reactors run a 30-40 degree rise across the core at around 155 bar, where water's specific heat is about 5.5 kJ/kg.K rather than the 4.18 of ambient water.

Formula

Core heat balance

Thermal power (kW) = mass flow (kg/s) x cp (kJ/kg.K) x (T_out - T_in)

Worked example

With the default values below, Reactor Thermal Power Calculator returns Reactor Thermal Power of 3,465.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Coolant Mass Flowminimum 0 kg/s
18,000 kg/s
Core Inlet Temperatureminimum -50 degrees C
292 degrees C
Core Outlet Temperatureminimum -50 degrees C
327 degrees C
Coolant Specific Heatminimum 0 kJ/kg.K
5.5 kJ/kg.K

Results

Reactor Thermal Power
3,465.00
Core Temperature Rise
35.00
Indicative Electrical Power
1,143.45
Heat Removed Per Kilogram Of Coolant
192.500

Step by step

  1. 1Values used
  2. 2Core heat balance
  3. 3Reactor Thermal Power= 3,465.00
  4. 4Core Temperature Rise= 35.00
  5. 5Indicative Electrical Power= 1,143.45
  6. 6Heat Removed Per Kilogram Of Coolant= 192.500

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Reactor power measurement and limits are safety-critical and governed by the plant licence. This calculation is illustrative only.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Reactor power measurement and limits are safety-critical and governed by the plant licence. This calculation is illustrative only.

Frequently Asked Questions

Why is specific heat higher than 4.18?

At 300 C and high pressure, water approaches its critical region and its specific heat rises substantially. Using the ambient value would understate power by 25% or more.

How is thermal power actually measured?

By a secondary-side heat balance using feedwater flow, temperature and steam conditions, calibrated against a primary-side calculation. Thermal power measurement uncertainty directly limits licensed output.

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