Radiography for Building Renovation

摘要

One last word is appropriate to those unfamiliar with concrete radiographic test-ing. Concrete is a variable radiation ab-sorber compared to a fairly predictable one such as steel. To establish and maintain proper exposure times with the chosen radiation source, especially where exact floor thickness is unknown or variable, a direct reading pocket dosimeter may be placed behind the film to record a relative dose. The dosimeter reading necessary to achieve a proper film density will have to be determined experimentally. Generally, the fastest lead screen industrial radiography films available are ideal for concrete radiographic testing. The lead screens themselves do not have to be code quality and a 0.3 mm (0.01 in.) thickness front and back will suffice. If the exposure geometry is correct as outlined above, the radiographic sensitivity using fast film with lead screens will be adequate for interpretation. Successful fluorescent screen techniques have been reported. However, due to the cost of the screens themselves and their usually required hard cassettes, the savings in exposure times may not save money overall. Handling of these heavy cassettes may well be a formidable challenge to the radiographer hauling armloads of them up flights of stairs.