Recently undesired Axial Offset Anomaly (AOA) was issued in the nuclear industry. AOA referring to an unexpected neutron flux depression is also known as Crud Induced Power Shift (CIPS). It was occurred by boron which is injected to controlling power level in the core but unfortunately boron working neutron absorber deposited on the fuel surface. Fuel assemblies removed from an AOA core has shown a thick porous deposition layer of crud on fuel clad surface. The deposition layer was induced by precipitation reactions of both boron species and crud during sub-cooled nucleate boiling.

“CRUD” is an abbreviating for “Chalk river unidentified deposition”. Combination of product as corrosion and oxidation material deposited in the core and it shows porous structure. For many researchers investigate the crud to characterize the composition for controlling operation. However, it has various characteristic because of environment characteristic. So it is difficult to decontamination.

CRUD removal system was recently developed as like ultrasonic mechanism. Ultrasonic mechanisms are developed but it has limitation for decontamination, therefor we investigate the other method as like hydrodynamic cavitation. Collapse of cavitation make the high shock pressure it can be helpful for decontamination.

For using the cavitation, firstly we investigate the cavitation effect as like magnitude of shock pressure.

Fig. 2-1 Vector of water velocity

Fig. 2-2 Effect of cavitation in case of using the sensitive film for investigating shock pressure

Fig. 2-3 Image of cavitation flow