Experience in Operating Large Gamma-Radiation Installations

The Spent Fuel Element Pond at AERE, Harwell. The Spent Fuel Element Pond at Harwell was built to provide a multi-megacuriesource of gamma radiation using the spent fuel elements of DIDO and PLUTO. The materials which have been processed include medical equipment on pilot and production scales, polyethylene insulation, mechanical rigs for long-term irradiation of lubricating oils and a wide range of experimental samples. The handling and distribution of the spent fuel elements in the pond has included considerations of criticality, contamination and heat dissipation. The decay of the short-lived components of the gross fission products in the fuel elements entails frequent radiation dose level measurements. When high efficiency of radiation utilization and good uniformity of dosage are required, the materials are rearranged during treatment. The Package Irradiation Plant at Wantage The gamma radiation processing plant at the Wantage Research Laboratory was designed to provide a wide choice of dose levels of radiation on a semi-production scale. The plant has been in operation since mid-1960, and experience has been gained in the treatment of materials for experimental Work and in routine irradiations of medical equipment. The safety system for the protection of the staff against accidental irradiation has proved simple and effective. The conveyor system which handles individual packages has given some trouble, particularly in the automatic input store which is outside the concrete shield. Both mechanical and acoustic guard systems have been developed which are capable of stopping the conveyors in a fraction of a second. The behaviour of metal surfaces in the irradiation chamber has been noted; the effects of ozone, humiditv and gamma radiation have befen less than expected. The behaviour of several lubricants in the irradiation chamber have also been noted. (author)