Inspection programmes

In the present pressure tube inspection programme, the following parameters are being monitored:

• Irradiation induced dimensional changes, which include axial elongation.

• PT wall thickness and PT-CT gap at 6’O clock and presence of PT-CT contact if any.

• Location of GS.

• Service induced flaws.

• Deuterium concentration profile.

A number of tools and techniques have been developed for carrying out the aforementioned inspections. The diameter measurement and the sag measurement have not been part of the regular inspection programme. However, tools have been designed for carrying out such measurements for limited use in dry channel. The description of these tools and techniques are given in the subsequent paragraphs.

A tool for dry channel visual inspection called DRYVIS (dry channel visual inspection system) has been developed and is based on a pneumatically operated tube walker, which can be remotely made to crawl in the desired direction within a tubular component. The device can carry any transducer for carrying out inspection. In DRYVIS, the system comprises tube walker, radiation resistance video camera, a separate illumination head and grating for sizing of indications. This system has been used to carry out visual inspection within drained and defuelled pressure tubes, as well as calandria tubes.