An inverse calculation technique for optimization of gamma ray shielding designs

Abstract

A new computer code named as SHIELD DESIGN has been developed in Visual Basic Version 6.0 for precise estimation of shielding thickness in gamma ray shielding designs. In the conventional forward calculations using point kernel method, the sources and geometry are specified along with the shield thickness to obtain dose rates at desired locations. But in this code, a new computational technique based on inverse calculation and iterative procedures have been employed to estimate the shield thickness using the dose rate criteria as input information. This new technique enables quicker and easier way of shield design optimization by computing shield thickness required in a single run whereas in the forward shield design optimization method, dose rate computations need to be carried out for various shield thicknesses. The shielding thickness arrived with this code provides a first hand information to the designer to carry out forward calculations for accurate optimization. Also, the code is very useful to regulators for quicker verification of shield calculations submitted by the designers for approval. Further, various options available in this code extend its flexibility and user friendliness. This paper briefly presents the development and validation of the code, SHIELD DESIGN. The validation has been carried out by performing analyses of the gamma shielding design for some standard problems. The results were compared with those of renowned forward calculations, experimental measurements, NCRP-51 benchmarks and other gamma radiation shielding utilities like RAD-PRO and satisfactory agreement was observed. These validation tests demonstrate the precise estimation of shield thickness.