Fuel Management and cycles

Question 1

When must you refuel

Answer 1

When the reactor can no longer sustain a chain reaction ie reactivity has fallen to 0

Question 2

How is most convenient to relate reactivity of a reactor

Answer 2

To Burnup, the amount of (thermal) energy that is released per unit mass of (fissionable) fuel, which has a linear relationship with reactivity in certain types of reactor (not so in other types)

Question 3

What are burnable poisons

Answer 3

Burnable poisons (BPs) are neutron absorbers,

whose effect in reduc-
ing the fuel’s reactivity decreases as neutrons are absorbed.

The loading of BPs reduces the flux (and thus the power) in fresh fuel assemblies, and they
can therefore be used to overcome power peaking problems

Question 4

Factors a LP (loading pattern) designer must consider

Answer 4

(a) to limit the magnitude of any local power peaking,
(b) to limit the amount of radial neutron leakage from the core so as to reduce the irradiation
damage to the pressure vessel,
(c) to maximise the average burnup accumulated by the fuel, or
(d) to maximise the overall reactivity of the core (which is, in fact, configuration dependent)
so as to reduce the amount of fresh fuel required.