Design features and safety of advanced medium size VVER-type reactor

An advanced medium power reactor with a power up to 640 MWe and heat output up to 250 gcal/h for district heating is being developed in Russia. This reactor named VVER-640 is being designed based on the experience of construction and operation of the Soviet VVER-440 and 1000 reactors. The significant safety enhancement is reached by reasonable combination of the passive and active safety systems, reduction in core power density, use of the double containment, etc. The NPP with the VVER-640 can be located in high-seismic areas. The basic design version is calculated for 9.5 MSK-64 scale number (ground acceleration 0,5 g). The VVER-640 core and vessel have the same dimensions at the VVER-1000 reactors. The average burnup of the discharged fuel is 42 MW.day/t U with the initial enrichment of 3,6%. The control rod worth is sufficient to compensate the power and temperature effects as well as the xenon-135 depoisoning effect without charging additional liquid absorbers into the coolant. Under normal operation conditions the NPP contribution to the equivalent irradiation dose is about 0,1% of the background values. The NPPs with the VVER-640 reactor have the specific consumption of metal and concrete by 1,5-2,0 times lower than of the VVER-440 - based NPPs and other considerably improved economic indices. The construction of the first power unit of the VVER-640 NPP is planed to be completed in the year 2001. (author). 8 figs, 2 tabs