Comparisons between the infinite matrix Ãœ3-ray dose rates to CaF₂, obsidian, and LiF were obtained by exposing these phosphors at the center of a concrete cube (1 m side) doped with 3000 ppm natural U. The results obtained with the dosimeters, encapsulated in A1, glass, nylon, and Cu were compared with those calculated from the U concentration. Using 50-cm cubes containing U, Th, and K, a threshold position for a NaI(T1) scintillator was found such that the count rate is proportional to the dose rate in CaF, independent of the natural emitter present. A cosmic ray correction is derived. -- AATA