The most important effects of neutron irradiation on beryllium are swelling, embrittlement and tritium retention. The helium produced by the Be-9(n, 2n)2(4)He reaction is the cause of beryllium swelling and, at high neutron fluences, the main cause of tritium retention which is produced by simultaneous reactions. It was, therefore, decided to develop a computer code capable of describing the helium and tritium behaviour in beryllium. The approach used was to modify an existing code available for the modelling of fission gas behaviour in UO2 irradiated in fission reactors. A new model describing the trapping effects on tritium due to chemical reactions and capture in helium-bubbles has been included in the code. The resulting code ANFIBE (ANalysis of Fusion Irradiated BEryllium) allows the calculation of gas distribution, induced swelling and helium and tritium release from beryllium. Good agreement between experimental and calculated swelling and tritium release has been found.
