temperature

Bv reference to the formula given at the beginning of this Section 5.5, it can be seen that a change in oas flow will give rise to a change in power if tern* perature is maintained constant. This is the situation in laree power changes, as mentioned earlier for re­actor start-up and shutdown, and is relevant also in this section when considering, for example, power changes to match changes in electrical generation, power changes for refuelling (AGR), boilers being brought into or taken out of service, and gas flow faults such as blower/circulator failure.

Clearly if the gas flow changes but neutron power does not change, then temperatures must change, and normally it is desirable to avoid large temperature changes; large upward swings might trip the reactor, downward swings might shut down a magnox reactor on ’temperature poisoning’ or cause wetting of the superheater region of the boiler tubes in an AGR. Therefore the neutron power is changed to match the gas flow and thereby keep temperature changes man­ageably small.