Scrap processors could encounter radioactive scrap metal from a number of sources, including decommissioned nuclear power plants, the oil and gas industry and end-of-life medical equipment. Radioactive scrap not only poses a danger to individuals working in a scrap yard, it also could lead to problems with machinery, require extensive cleanup and result in the possible temporary shutdown of a yard, according to the U.S. Occupational Health and Safety Administration (OSHA). Radioactive scrap sources also could cause major problems for consuming mills if not detected at the scrap yard.
Yard personnel must have a basic understanding of radiation and detection equipment to ensure they are responding properly to potentially radioactive sources of scrap. “You don’t have to be a physicist to handle an alarm from a radiation-detection system,” says Steve Steranka, president of RadComm Radiation Detection Systems, Oakville, Ontario. “Understanding what the readings are and looking for probable causes is critical to avoid unnecessary unrest and handling of the cause of the alarm condition.”
Radiation monitoring systems can be used to detect gamma radiation from source materials in scrap loads. Fixed systems typically are installed at a yard’s truck or rail scale, but other locations can include smaller nonferrous scales, sorting areas, infeed and downstream conveyors, grapples and magnets, he says.
Because metal itself is an insulator of radiation, the Institute of Scrap Recycling Industries (ISRI), Washington, advises monitoring scrap not only as it enters the yard but also throughout the production process and in outbound loads.
Radiation safety basics
According to ISRI, allowable exposure limits for most scrap yard workers are 2 milliroentgens per hour, not to exceed 100 milliroentgens per year. ISRI recommends that scrap yards use 1 milliroentgen per hour for their action level, setting radiation monitors accordingly. The association suggests that when hand-held radiation detectors reach 1 milliroentgen per hour, personnel should be moved away from the area. If the reading reaches 2 milliroentgens per hour, the area in question should be covered with other scrap, employees moved away and the appropriate authorities notified.
When it comes to radiation-detection systems, Steranka says systems generally have three levels of alarms, with Level 1 presenting the lowest risk and Level 3 the highest risk. With a Level 3 alarm, he says a person qualified in radiation safety should be called in to handle the load.
If an alarm should indicate the possible presence of radioactive scrap in a load entering the yard, Steranka says the yard should have a safety plan in place to respond to the alarm. He also suggests that yard operators use the services of a local health physicist to learn about state regulations pertaining to radioactive sources and how to handle the various alarm levels.
False alarm or real thing?
Steranka says no radiation-detection system manufacturer can claim that its system does not false-positive alarm, and ISRI encourages its members to never assume an alarm is false. Steranka says there are many reasons for these false-positive alarms, such as material density changes, weather and improper algorithms for handling natural background radiation.
Radiation-detection systems traditionally are based on PVT, or polyvinyl toluene, scintillators, Steranka says, because they are more affordable and can be manufactured in large quantities. However, he adds that metal processors generally cannot compete with the large PVT systems used by steel mills. “As a result of this, their system detection capability has to run full out, resulting with higher risks for false-positive alarms.
“False-positive alarms are a nightmare for processors,” Steranka continues. They can result in tying up personnel to examine or deal with these loads, which costs money, he explains. Some yards could even lose product to another more tolerant buyer who has the resources to better handle such loads. Another potential cost to false-positive alarms is a loss of trust in the system’s capabilities, “ending up in ignored alarms,” he says.
RadComm has developed and is testing a radiation-detection system at several locations to address issues surrounding false-positive alarms, Steranka says. The new system combines artificial intelligence with a new radiation-detection medium that was not readily available previously. He adds that he expects the technology to be available by mid-2020.
If a scrap company accepts or further examines a load that has triggered an alarm on a truck- or rail-based radiation- detection system, ISRI suggests parking the truck in a designated area of the yard or moving the rail car back and awaiting instructions from the radiation safety officer (RSO). If an alarm on a conveyor goes off, ISRI says it’s best to assume a radioactive source is present. The association advises removing personnel from the area and contacting the RSO.
If a yard decides to survey a load that has triggered an alarm, ISRI says uncovering or dumping a load on the ground must be supervised by the RSO or another trained person. If retested, a vehicle must pass through the system three times without triggering an alarm before the load can be accepted.
When examining a load, ISRI advises surveying the perimeter first to ensure sources are not on top, putting workers at additional risk. The association suggests drawing a grid on the material with spray paint, creating specific areas to examine. Scrap found not to have a source present should be moved away from the other material to be tested. If readings greater than 1 milliroentgen per hour are detected during the scrap examination processes, the inspector should stop and notify the RSO, ISRI says.
While high turnover can make radiation safety training at a scrap yard more difficult, Steranka says workers only need to have a basic understanding of time, shielding and distance when they encounter potentially radioactive sources. Employees also must be aware of the yard’s protocols for handling radiation alarms and suspect loads.
The author is editor of Recycling Today and can be contacted at email@example.com.