DOE OSTI2018
The global nuclear power industry, and to a lesser extent, the decommissioning and demolition of old nuclear weapons plants, obviously present challenges to those in the radioactive waste management field. Some if not many of these challenges have already been dealt with, and resolved, in the steel industry, including its recycling component. This paper presents proven state-of-the-art radiation detection systems used in steel and related recycling facilities, emphasizing current, reliable and flexible technologies for characterization, volume reduction, and remote handling of recyclable solid wastes contaminated and, just as important, not contaminated, with a wide range of radioactive isotopes. It will also cover features of remotely operated waste handling equipment effective in reducing or eliminating exposure of workers engaged in decontamination and demolition work on active and/or inactive nuclear installations. The industry group identified above has a long-standing policy regarding any radioactivity in potentially recyclable as well as waste materials it receives: if it is detected, it is rejected. The US Steel Manufacturers Association (SMA) put it this way in one of their Public Policy Statements: 'SMA members have not, and will not, accept scrap that is known to be radioactively contaminated' (emphasis included in the original) (1). This policy, adopted around the globe, obviously has major implications for decommissioning and demolition projects. To put it bluntly, if rad-contaminated metal, concrete, or other materials are sent to a facility for possible recycling, reuse or even disposal, they may well be rejected. If so, the materials will be returned to the generator--at the generator's cost-and a new solution will have to be found. This also results in additional costs for the generator. Facilities in the steel making and metal recycling industries have access to, and routinely count on, a wide range of proven detection technologies and techniques for monitoring incoming shipments and sorting the materials in them. The approaches range from using sensitive handheld instruments for pinpointing and isolating small devices such as isotope-containing gauges and radium dials all the way up to technologies effective for large volumes and weights of contaminated construction and demolition material. In this latter realm, the most suitable, robust, and field-proven system for decommissioning and demolition work is a radiation detection system fitted to a grappling and/or magnetic device, known as the Crickets{sup TM} technology, which automatically scans bulk material with no added effort or time in material handling operations. Highly versatile, a Crickets{sup TM} system can be put to work on any material-handling system, including grapples handling volumes ranging from 1 up to 18 cubic yards, while detecting radioactivity in real-time over a very wide dose range, from nSv to Sv levels. Other field-proven real-time measuring radiation detection devices can be fixed to conveyor belts with traverse speeds up 3 meters/second, also measuring in real time and over the same dose range, allowing both recyclable and waste materials with a pre-set level of radioactivity to be diverted off the belt. Finally, there are highly sensitive radiation portal installations for detecting radiation from materials being transported by vehicles, including those with roll-offs, dump trailers, and other containers, again in real-time and for the same dose ranges. For vehicles, the speed must be carefully controlled-the vehicles need to travel from 5 to 10 km/h through the scanning zone to ensure that maximum detection capability is maintained. When radiation detection systems at recycling and steel making facilities detect radioactive material in an incoming shipment, these facilities have a zero tolerance for accepting the cargo. Therefore, it is imperative that material from a demolition operation that is slated to be sent for recycling or other reuse be checked at the point of demolition at similar detection levels to avoid possible rejection later of a shipment because of its radioactivity. In addition to measuring overall radiation levels (for example, total gamma), when necessary, combinations of different radiation detection media can be used to detect the presence and intensities of specific isotopes such as U-235, Cs-137, Co-60, Am-241, etc., again in real-time and over a similar dose range. These detection technologies can be fixed or transportable. More important for the rad-waste management profession, this overall systems approach can be tailored and adapted during use on-site in any dismantling, demolition or remediation project, to allow materials to be thoroughly scanned before being released to the recycling stream for reuse, or to appropriate long-term storage and disposal facilities. Potentially recyclable materials with contamination such as steel beams and rebar will set off alarms at recycling facilities, resulting in unnecessary added expenses to the generator, primarily due to increased transportation costs, time delays and additional rad-waste handling and disposal charges. Additionally, there are situations where relatively lightly contaminated materials, once identified and appropriately characterized, can be reused in new construction applications, such as concrete from demolition being used in the base layer for roads or recycled steel used for repair or construction of bridges. In other cases, specific smaller volumes can be sent to specialized rad-waste disposal sites. These radiation detection systems can also be custom tailored to ensure proper handling and disposition of contaminated materials destined for reuse in specific applications where, for example, acceptable levels of radioactivity in NORM or TENORM can be reused or safely disposed of. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗