Slide Rule for Shielding Calculations from Radioisotope Applications Company (ca. 1950s)

The purpose of this slide rule was to allow an estimation of the exposure rate (mR/hr) at a chosen distance given the source activity (in millicuries) and the energy (in MeV) of the gamma rays. It also permits the exposure rate to be estimated with a specified thickness of shielding. Conversely, the thickness of shielding required to reduce the exposure rate to a given value can be determined.

As can be seen on the back of the calculator (photo to right), this was manufactured by Radioisotope Applications Company of Albany California and copyrighted in 1949.

Size: 5" diameter

Reference

Instruction Sheet. The RIACO Gamma Radiation and Shielding Estimator. No date.