How does Caltrans correlate probe readings to relative density?
California DOT utilizes three 250-liter (55-gallon) drums filled with concrete of known density to determine a calibration between interpreted concrete density and recorded gamma count rate. The well-established relationship is linear on a semi-log scale. Does GGL contaminate the CIDH pile with radiation? No. GGL utilizes a sealed radioactive source. Gamma radiation is emitted from the source, but it does not cause the concrete to become radioactive just like a microwave does not cause food to become radioactive. What are the nuclear regulatory requirements for a Gamma-Gamma Probe? The nuclear source for a Gamma-Gamma Probe is virtually identical to that for a soil nuclear density gauge. The probes are sealed double-encapsulated radiation sources, which makes severe accidents virtually impossible. However, Caltrans carefully complies with all regulatory requirements, limits exposure to trained operators with radiation badges, and actively seeks to reduce or eliminate the danger to the
