Power uprating activities at the Paks NuclearPower Plant, Hungary

The original design output power of the Paks NPP was ۴۴۰ MW(e). Early upratingactivities took place in the late ۱۹۹۰s. These modifications were related to the turbinesand did not involve very significant I&C changes. After this first uprating, the newnominal power was ۴۶۵ MW(e)/unit. A further uprating from ۴۶۵ MW(e) to ۵۰۰ MW(e)took place in the ۲۰۰۵-۲۰۰۹. The second step of power uprating required several I&Csystems to be upgraded and some set points to be altered. This paper provides ageneral overview of the uprate and detailed descriptions of the I&C related changes.The accuracy of the feedwater flow measurement is one of the critical I&C issues inpower uprating. The problems usually come from venturi fouling. It needs to be notedthat in Paks venture, elements are not used for feedwater flow detection. The appliedorifices may suffer from different types of problems, such as from edge deterioration.Therefore, the originally welded orifices have been changed to flange mounted onesand can be removed for size checking periodically. Currently, this is done every fouryears and the orifices are replaced whenever necessary. Hence, feedwatermeasurement accuracy does not play a critical role in the Paks power uprating processand, therefore, is not described in this paper

Keywords:

Power uprating , accuracy , I&C systems , VERONA , in-core monitoring , pressurecontroller