Radiation dose estimation on rubber gaskets for remote repair of leaky helium flange joints in Cirus reactor

Full text: The paper describes the analysis of the neutronic and gamma radiation dose on the rubber gaskets located within the reactor structure of Cirus after nearly 35 years of reactor operation. These gaskets are used in the flange joints of helium cover gas pipelines, some of which developed leak. This cumulative radiation dose was required to assess the compressive properties of the irradiated gaskets. After estimating the dose, fresh gaskets were procured and irradiated to comparable gamma dose. These gaskets were then tested in a universal testing machine and load versus deflection data were generated. A remote repair method of clamping the leaky flanges was developed. The data were used in the detailed piping analysis and the sequence and the extent of compression of flange joints was decided. Split sealing clamps were remotely installed and tightened to reduce the leaks significantly