Improved type many kinds of enrichment initial charge core

No. 4 plant in Hamaoka Nuclear Power Station, Chubu Electric Power Co., Inc. started the commercial operation in September, 1993 after 48 months of construction period. It is the largest BWR plant with 1137 MWe and 3293 MWt output. The basic specifications of the plant and the core fuel are shown. In the design of the core fuel, the heightening of safety and reliability has priority, and the improved technology for bettering the core performance and operability was adopted positively. As the core fuel technology, new 8 x 8 zirconium-lined fuel, improved type many kinds of enrichment initial charge core, long life hafnium type control rods and so on were adopted. The zirconium-lined fuel is to reduce pellet-clad interaction, and increase the reliability. Moreover, the nuclear design of high reactivity fuel assemblies using uranium-saving technology was adopted. The core is composed of the fuels of three kinds of enrichment, and high enrichment fuel is arranged outside, thus the taking-out burnup of initial charge fuel increases. The improvement of the design of initial charge core, the improved type many kinds of enrichment initial charge core and the core characteristics in the start-up operation are reported. It was confirmed that the good core characteristics as expected can be obtained. (K.I.)