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The maintenance and repair of reinforced concrete structures, especially those submerged in the sea-water, require effective inspection and monitoring techniques for assessing the state of corrosion in reinforcement material. An underwater inspection system was developed which is able to monitor the reinforcement corrosion. The system is ROV equipped with the sealed tube neutron generator (NG). By rotating the NG and by using the associated alpha particle technique it is possible to measure the concrete cover depth together with the reinforcing bar diameter. The possibility to estimate the carbon and chloride content in the concrete was investigated. Iron plates of different thickness, covered by 6 cm thick concrete block, were successfully detected and the thickness of the concrete cover was estimated. In addition, reinforced bar of one and three centimeters in diameter was identified and measured.

In order to demonstrate the possibility of identifying the material within the objects on the sea floor we have performed tests with the 14 MeV sealed tube neutron generator incorporated inside a small submarine, SURVEYOR, submerged in the test basin filled with sea water. The materials inside the investigated objects were identified by measuring the gamma ray spectra and by using the window on the measured alpha- gamma time spectrum. In addition, we describe our field test facility and measurements done at this location in the framework of the EU FP7 project UNCOSS. The existence of a data base of potentially explosive devices on the floor of coastal sea, especially ports and waterways, is of paramount importance. However, the sea floor is littered by number of different objects and the water is not very transparent on such locations. This makes the identification of objects extremely difficult even on known locations. We discuss how to position the SURVEYOR when the object investigated for the presence of explosive has been identified by other sensors (camera, sonar, magnetometer, etc.).