# A Survey on Unmanned Surface Vehicles for Disaster Robotics: Main Challenges and Directions
## 4 Use of USVs in Environmental Disasters with Contaminants
### Radioactive Hazards  
As mentioned earlier, disasters usually are caused by natural or man-made events or a combination of them. They can spread rapidly, causing severe environmental damage with unknown contamination causes (e.g., nuclear pollution accidents, such as the Japan nuclear disaster in 2011). The 2011 incident at Japan's Fukushima nuclear power plant resulted in one third of involved rescue workers being subjected to high levels of nuclear radiation, facing a higher lifetime risk of cancer, while hundreds of thousands had to be evacuated from the Fukushima area [163]. In such emergencies,various professional and volunteer rescue workers collaborate, where they are subject to an extremely harsh and dangerous environment with high personal risk. Hence, recent research has explored the feasibility of using robots for conducting activities in harsh radioactive environments.  
Given the proximity of many nuclear reactor sites to large bodies of water, the deployment of USVs for monitoring or even support can be a natural fit [164; 165]. In particular, after the accident in Fukushima earthquake/tsunami, it became clear that radiation from reactors can indeed leak to the body of water in case of extreme events, endangering life and compromising rescue operations.  
Nuclear Biological Chemical sensors and robots, including an AEOS Marcy USV [166] have been integrated and tested in a radiological forensics field exercise in 2013. An international maritime interdiction operation experiment was conducted in the San Francisco Bay involving the connection of two radiation detection sensors to a mesh network consisting of multiple sources, including a Seafox USV [167] which was used for a drive-by search. The collaborative environment where experts can assess information from numerous locations/events simultaneously has shown to be favorable to detect radiation sources in military and homeland security operations. The authors mention management and networking issues, which must be addressed to pass control to the Coast Guard. We highlight that such a strategy could be extended to disaster sites such as Fukushima to detect radiation leaks in the ocean.  
[PERSON] et al. [168] designed a USV for radiation detection, heat map creation, and source localization in a controlled test environment in a \"disaster city\" where they deployed a Cesium-137 source. The study also involved the discovery of a proper path in detecting such source [169], considering that USVs cannot perform hard turns during raster monitoring of certain areas. [PERSON] et al. [170] detail its exercise from euRathlon's 2015 maritime SAR competition, employing multiple robots, including a USV (ROAZ), which can deploy other unmanned systems. They argue that the use of USVs for a rapid initial search and subsequent use of UUVs is powerful in scenarios such as the Fukushima disaster, to narrow down the search. The combination of USVs and UUVs is also explored in [171].  
Recently, researchers went back to the Bikini Atoll, where tests for the development of the atomic bomb were performed during WWII, to understand how nukes and accidents such as the Fukushima Daiichi have and will impact the environment [172]. They used a Jetyak USV, equipped with a sensor to sample water and detect radioactive compounds, to collect water samples from the area. The idea was that as the Jetyak floated across the lagoon, the sampling device would pump water through cesium extraction \"sponges\", to measure levels present in the lagoon.