Separation column inspection using off axis gamma scanning

A method of scanning a separation vessel, the method comprising:

• positioning a gamma radiation source and a detector on opposed sides of a separation vessel;
• positioning the gamma radiation source and the detector at a plurality of different vertical elevation pairs along a length of the separation vessel, wherein at each of the plurality of different vertical elevation pairs the gamma radiation source is at a different vertical elevation than the detector such that a radiation path between the gamma radiation source and the detector transects the separation vessel at a non-zero degree angle, and at each of the plurality of different vertical elevation pairs a vertical distance between the gamma radiation source and the detector is substantially a same distance;
• and
• at each of the different vertical elevation pairs, emitting gamma radiation by the gamma radiation source through the separation vessel and detecting, by the detector, radiation emitted by the gamma radiation source and passing through the separation vessel, and
• wherein the separation vessel comprises a plurality of trays with a spacing defined between adjacent trays of the plurality of trays, the vertical distance between the gamma radiation source and the detector at each of the plurality of different vertical elevation pairs is less than the spacing between adjacent trays, and greater than a thickness of at least one of the plurality of trays.