Experiments w*ere carried out during the early devel­opment of AGR to measure G(-CH4) (the number of molecules of methane destroyed per 100 eV of energy adsorbed) both in small capsules in various radiation by test facilities and in the Windscale AGR. The bypass plant for the early AGR were based on this data, which showed that the rate of methane destruction was dependent on the radiation dose ab­sorbed, the methane concentration, the inverse of the carbon monoxide concentration and a small depend­ence on the inverse of the water concentration. In addition it was found that a small background meth­ane concentration was formed even if no methane was added. It was also demonstrated that G(-CH4) depended on the presence or absence of graphite. This work was extended during the early operation of Hinkley Point В AGR and the major controlling para­meters confirmed. The resulting relationships are given by:

G(-CH4) = N84 |{CH4) — (СН4)ь exp <-2518.T)]/(CO) For in-pore gas

G(-CH4) = 3232[(CH4) — <CH4)b exp (-2467/T)J/{(CO)

* 64.9 (H:0)]

where (CH4), (CH4)t>, (CO) and (EGO) are in kg/ kg СО?, (СН4)ь is the background methane concentration at the given CO and H;0 concentration in the absence of methane addition, and T is the temperature K.

To calculate the overall methane destruction rate the irradiated gas in the reactor is divided into volumes of isodose and isotemperature and the individual methane destruction rates integrated using

dCH4/dt = 5.976 x КГ-‘ x MDG <-CH4) kg h

where M is the mass of CO:, kg D is the dose rate, w g

The equivalent mass of carbon monoxide and water formed, required for the design of the recombination unit and drier, is then calculated from CH4 + 3CO; 4CO + 2H20.