Safety aspects in the use of high curiage radiography sources for field radiography

High pressure vessels and tanks of huge dimensions are extensively used for the storage of explosive liquids and gases at high pressure. Radiography examination of such vessels and tanks at erection site poses unique problems because of their huge size, large curved surfaces and dense scaffolding arrangements. The radiography techniques employed and the associated radiation safety aspects involved in the use of high curiage gamma radiography sources for the field radiography examination of high pressure petrochemical storage spheres of diameters varying from 10 M to 15 M and well thickness varying from 25 mm to 55 mm steel are described. The relative merits and demerits in respect of radiation safety, efficiency and time while using a remotely operated high curiage radiography equipment and a manually operated type of equipment are discussed. Methods are also suggested for achieving a better control on radiation safety during the use of manually operated type of equipments for such radiography jobs. (auth.)