Safety aspects in the use of 9 MV industrial linac for open field radiography

Electron Accelerators are used for industrial radiography in various industries. Usually fixed accelerators in a well-shielded enclosure are used for radiography. However, in some special cases it is desired to have portable accelerators to carry out the radiography work at site. In many military applications the heavy objects are checked at the site, for which portable accelerators are preferred. X-ray intensity emanating from an industrial accelerator is very high. Proper safety precaution needs to be adopted by the radiation workers as well as other non-radiation workers involved in the open field radiography work and other supporting activities. A case of 9 MV linear accelerators to be used for open field radiography is being discussed here. Portable shielding thickness, which is to be given in the primary and secondary direction is evaluated numerically and suggested in the paper. As the portable radiography enclosure is open top and has limited wall height, more air volume above the enclosure is likely to get irradiated. Although the wall shielding is adequate, there is possibility of high radiation level around the radiography enclosure due to sky-shine radiation. Sky-shine radiation level is evaluated numerically and is presented in this paper. For the protection of the radiation and non-radiation workers about 100 m cordoning off is recommended. Operators sit inside a cabin of the transport car located outside the cordoning area. Various safety precautions and interlock facility to be adopted for safe radiography work practices are described in this paper. (author)