Leak-testing Performance at the Bohunice NPP

In 1986, in-core sipping equipment designed and manufactured by Siemens KWU was purchased [22,23]. Since then, fiiU core sipping tests have been performed in all cases where the occurrence of a leak has been demonstrated by operational data. The decision to perform sipping tests was taken based on primary coolant activity measurements obtained during reactor operation and iodine spike analysis. 

The extent to which fission products are released from the fuel rods to the coolant inside the channel is dependent on the increase in the temperature of the fuel. During leak testing, the flow of coolant through the assembly is throttled by blocking its upper end. The decay heat produces a rise in the temperature of the fuel and thus 

In a defective rod, the fission gases expand and escape through the leak into the surrounding water. The resulting increase in fission product activity can be measured in water samples taken from the assembly. These samples are analysed using a germanium detector. The nuclides and Xe are used to identify 

The in-core sipping equipment used at the Bohunice NPP was also employed once at the Paks NPP in Hungary (1991) and twice at the Dukovany NPP (1991, 1992) in the Czech Republic. 

3 Occurrence of Leaking Fuel Assemblies and Probable Causes of Leaks 

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