# State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios
###### Abstract
Considering other detection strategies, [PERSON] [7] suggested an RN threat detection solution based on a network of radiation detectors at existing road traffic-monitoring system locations (e.g., stop light or red light cameras), while [PERSON] et al. [4] concluded that mobile radiation detection (MRD) technology with at least one-tenth of the RPM efficiency can have the same or greater impact on the wrongdoer's success rate. MRDs have the advantage of performing discrete operations and can be deployed to major thoroughfares or to protect a potential target. However, there is a lower control over the geometry, and the MRD performance is highly dependent on their placement. In the same way, to monitor an unintended release of radionuclides, as is the case of a nuclear reactor accident, there are fixed online radiation monitoring systems in the vicinity of the power plant. However, the information gathered by these devices are confined to their location and, in the situation of a natural disaster, like happened in Fukushima, these detectors may fail [8]. This can lead to a lack of information about the radiation levels and consequently in bad, inaccurate, and delayed decisions. The rapid deployment of an MRD system can help to monitor locations not covered by the fixed network or be the main detection system in an RN event [9], for example, to evaluate the activity and direction of the radioactive plume spread on the ground (due to fallout) or in the air (e.g., using an air sampler). This mobility allows coverage of large areas and reduction of survey times. Other scenarios where it is important the use of mobile detection systems are: (i) areas with high concentration of naturally occurring radioactive materials (NORMs), normally associated with large survey areas and dose rates near background radiation, and (ii) the inspection, maintenance and repair activities in nuclear energy facilities, particle accelerators, targets, and irradiation facilities, characterized by dose rates ranging from low to high, and, eventually, the presence of high magnetic fields and high temperatures. The use of mobile detection systems may allow to improve the detection efficiency of RN materials by decreasing the distance between detector and source and the effects of air or materials' attenuation. For each scenario described, one might be interested in the location, identification, and quantification of a radioactive source or the mapping of a contaminated area. Due to their long range in air, gamma-rays and neutrons are preferable indicated for mobile detection systems. This review article encompasses mobile detection systems carried by a person (e.g., handheld and backpack equipment), as well as detectors coupled to ground-based vehicles (e.g., trucks, vans, and cars) and air-based vehicles, like fixed-wing or rotatory wing aircrafts. Both ground-based and air-based vehicles can be manned or unmanned. Since unmanned vehicles can be used in dull, dirty and dangerous missions, their use is of great interest in RN events, particularly when the radiation field is unknown (e.g., RN accident or incident and RN threat) or poses radiological risk to humans. Despite the use of unmanned ground vehicles (UGVs) in nuclear accidents as in Chernobyl (1986) and Fukushima (2011) ([PERSON] et al., 2020), only after the Fukushima accident did unmanned aerial vehicles (UAVs) start to be used as platforms for radiation monitoring and mapping ([PERSON] et al., 2020).