It is common that reputable scrap dealers tend to use lower acceptance limits than state exemption limits to avoid massive amounts of metal stockpiling which results in higher overall readings. Metal that exceeds the limits of the smelter’s acceptance criteria will be rejected and the scrap dealer prohibited from selling the scrap. Scrap yard gate monitors and “drive-over” units, are set to alert or alarm the scrap yard employee as to whether or not the load should be accepted, depending on the radiation levels detected. These monitors may not be set in µR/hr, but rather cpm, cps, dpm, or dps, even though they are reading gamma radiation. It is imperative that anyone sending metal to a scrap dealer inquires with the dealer prior to the delivery of the shipment as to their acceptance limits in the detected units. Most scrap yard employees will not be familiar with the monitor, so this communication needs to occur with management. Once the acceptance criteria is known, background readings should be established and compared to the background readings of the scrap yard. This is a key factor in the acceptance limit, and will prevent future issues if properly evaluated. If it is difficult to communicate with the scrap yard management regarding their acceptance limit, then it may be reasonable to detect background readings on a field NORM meter while at the scrap yard. If the gate monitors display the results in units other than µR/hr, then conversions could be completed to compare “apples to apples”.

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Norm Lady