In nuclear facilities, controlling radiation exposure to operating personnel within limits specified by the regulatory body is mandatory; it is required to maintain the radiation level in occupancy areas “as low as reasonably achievable” (ALARA). Highly radioactive sources, materials, and components are enclosed in concrete cells, known as hot cells. Masterslave manipulators (MSMs) are used for the remote handling of equipment located in the hot cell. The MSM is fitted into the hot cell with liner bricks made of lead. The liner brick assembly is a lead poured structure with a steel lining, which gives an effective longitudinal shielding thickness of 250 mm when fitted into the cell with the MSM. Conventional nondestructive testing (NDT) methods such as radiographic testing (RT) and ultrasonic testing have limitations with respect to thickness and coarse-grained structures. Gamma radiometry, which is based on the principle of differential attenuation of radiation, has been developed and adopted in similar applications (Suresh Kumar et al. 2011). It is a challenge to optimize the gamma source strength required for testing, taking into account the sensitivity of the radiation detector and shielding thickness of the component under testing. This paper focuses on the choice of the radiation source and its strength, the experimental approach, the theoretical modeling undertaken for dose-rate estimation, and the actual measurement of radiation during the radiometric testing of MSM liner bricks.
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