An advanced nuclear fuel of PLUS7™ for OPR1000s and APR1400s in Korea has been developed and irradiated in PWR nuclear power reactors. It has high performance characteristics from the safety and economy points of view comparing to the current fuel. Zirconium-based nuclear fuel structural components are grown and/or deformed under the circumstances of high temperature and irradiation. Excessive growth or deformation should be prevented not to interfere with adjacent fuels or reactor internals. After development for three (3) years from 1999, this fuel was verified successfully using four (4) LTAs in Ulchin unit 3. After each cycle, irradiation-related performance items were measured using the precise measurement systems in poolside and evaluated. After three (3) cycle irradiations, one discharged fuel assembly was disassembled and examined in detail. Finally, ten (10) rods including skeleton were sent to PIE test facility for further detailed examination. After in-reactor verification using LTAs, eight (8) OPR1000s were replaced with this advanced fuel. In the mean while, the surveillance program using the commercially supplied fuels was launched to reconfirm irradiation-related parameters such as growth, creep, corrosion and deformation, etc. Four (4) fuel assemblies which consist of two (2) assemblies to be discharged after two (2) cycle irradiations and the other two (2) to be discharged after three (3) cycle irradiations were selected for this surveillance program. In this paper, irradiation-induced parameters such as fuel assembly width and length growth, assembly bow and twist etc. are updated.

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