Study on estimation of radioactivity in insulation materials of neutron detectors

In-core detectors play a crucial role in providing the neutron flux data in nuclear reactors during start-up. These detectors are placed in a dry thimble well inside the reactor core where the temperature may reach beyond 300°C. These detectors need to be protected from such a high temperature for their durability and longevity. This is achieved by encapsulation with ceramic insulators which will protect the detector thermally and electrically. For this purpose, two types of materials are widely used viz. ceramic spacers and adhesive ceramic tapes. An irradiation study of the above two types of materials can generate data of activation products and hence an effective radiological surveillance during their periodic maintenance. From the estimation study done it is found that there are some signature radio nuclides forming in both the materials which will help in identifying the issues like leak in the dry thimble nozzle. Presence of ¹⁸²Ta and ⁴⁶Sc along with regular activation products in air activity samples will help in the investigation when Ceramic spacer and Ceramic tape are used respectively