Fuel Assembly Leakage Unit 4, Cycle 22 of Paks NPP

Cs. Szécsényi, G. Bóna, B. Torma, T. Burján, Paks NPP Ltd., Hungary

19th Symposium of AER on VVER Reactor Physics and Reactor Safety (2009, Varna, Bulgaria)
Core Surveillance and Monitoring


At the beginning of Cycle 22, Unit 4, Paks NPP the Iodine isotopes activity concentrations
raised irregularly in the water of the primary circuit. Analysis supposed that from 1 to 10 fuel
rods in one or more newly loaded follower assemblies had lost their integrity. Due to the fact
it was not necessary to shut down the reactor, but at the end of the cycle sipping tests were
performed for the entire core to find out the facts using a telescope sipping device supplied by
H&B Co., Germany.
This paper describes the circumstances of the emergence of the problem, the operational
inspection and limitation rules in Paks NPP, the theoretical analysis to estimate the scope and
kind of the problem, the sipping device and the measurement/evaluation methods applied for
the practical tests, fulfilment the tests, the results and their evaluation and the conclusions
regarding the event.

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