Safety case issues have much in common with those of the AGR, discussed further in Section 12.4. Issues specific to Magnox plant include:

• air ingress (leading to oxidation of the fuel and core) and loss of cooling capacity following failure of boiler ducts (not possible where boilers are contained within the pressure vessel)

• brittle fracture of the pressure vessel

• single — or multi-channel fires involving the oxidation of cladding and fuel (and potentially channel blockage)

• reactivity faults, including local removal of control rods

In general, gas-cooled thermal reactor designs are much less sensitive to loss of coolant sequences than are water-cooled reactors due to the combination of the inherently low heat transfer between fuel and coolant combined with the very high thermal capacity of the core including moderator. This makes rapid response much less of an issue than in PWR and BWR designs.