The limiting factors which determine the maximum power and temperatures at which the reactor can be operated, and the optimisation of the reactor for maximum electrical generation within those limits, are covered elsewhere in this volume. This section is con­cerned with deviations from steady power, i. e., the kinetic behaviour of reactor parameters. Consider the formula:

Power = gas flow x specific heat x temperature rise

The temperature rise is from reactor inlet to outlet. Although this formula may not be suitable for accu­rate calculations, it is adequate for the purposes of this discussion. In this section we shall consider:

• Changes in power at constant gas flow and its ef­fect on temperatures.

• Chances in gas flow at nominally constant tem­perature and its effect on reactor power.

• Changes in temperature at constant gas flow and its effect on reactor power,

Note that a change in power does not affect gas flow unless the change is so large that blowers which are steam-driven, either directly (Oldbury and Dun­geness A) or indirectly via auxiliary turbine-generators (Bradwell and Hinkley Point.4), are affected by re­ductions in steam flow.

Although some of the factors, particularly power and temperature, are interactive, giving rise to com­plex dynamic behaviour of the reactor parameters, in this discussion we shall endeavour as far as possi­ble to consider the effect of changing one variable at a time. It is hoped that this will aid the under­standing of the principles.