The Development of Novel Radioisotope Inspection Techniques to allow Determination of Liquid Levels within Submerged Tankers and the Integrity of Subsea Structures

This paper will describe the development of Neutron Backscatter Scans, a widely recognized technique in the processing industry for use in novel subsea applications. Neutron Backscatter has been widely used for over 40 years to define tank inventories, gas/liquid interfaces, liquid/liquid interfaces and solid accumulations. The technique works by sweeping the outside of the vessel and non-intrusively bombarding the process medium through the tank wall with "fast neutrons" Dependant upon the hydrogen content of the medium, a number of collisions take place between the hydrogen molecules and the fast neutrons converting them into slow neutrons which are detected. Recent market led requirements have led to the testing of this technique for a number of subsea applications. 1. Determination of Oil Levels in Submerged Oil Tankers 2. Integrity of Subsea Structures 3. Pipe in pipe annulus integrity The paper will give details of recent tests that have been performed to prove the ability of the neutron backscatter device. The paper will also cover the current limitations of the technique and describe future development work to overcome the limitations.