Advanced Construction of Compact Containment BWR

Abstract

The reactor concept considered in this paper has a mid/small power output, a compact containment and a simplified BWR configuration with comprehensive safety features. Compact Containment BWR (CCR) is being developed with matured BWR technologies together with innovative systems/components, will provide attractiveness for the energy market in the world due to its flexibility in energy demands as well as in site conditions, its high potential in reducing investment risk and its safety feature facilitating public acceptance. The flexibility is achieved by CCR’s mid/small power output of 400 MWe class and capability of long operating cycle (refueling intervals). The high investment potential is expected from CCR’s simplification/innovation in design such as natural circulation core cooling with the bottom located short core, top mounted upper entry control rod drives (CRDs) with ring-type dryers and simplified safety system with high pressure resistible primary containment vessel (PCV) concept. The natural circulation core eliminates recirculation pumps as well as needs for maintenance of such pumps. The top mounted upper entry CRDs enable the bottom located short core in RPV. The safety feature mainly consists of large water inventory above the core without large penetration below the top of the core, passive cooling system by isolation condenser (IC), high pressure resistible PCV and in-vessel retention (IVR) capability. The large inventory increases the system response time in case of design base accidents including loss of coolant accidents. The IC suppresses PCV pressure by steam condensation without any AC power. Cooling the molten core inside the RPV if the core should be damaged by loss of core coolability could attain the IVR. CCR’s specific self-standing steel high pressure resistible PCV is designed to contain minimum piping and valves inside with reactor pressure vessel (RPV), only 13m in diameter and 24m in height. This compact PCV makes it possible to fabricate and perform pressure-test at the factory and transport to the construction-site as a module. Basing on CCR design concept of simplification and compact, reactor building layout design has been carried out. Layout design has been performed taking into account module construction, reduced system and components and compact PCV. As a result, CCR’s reactor building, specific volume to power output value is almost equal to ABWR one. Module fabrication and construction method is promising technology from the points of construction duration shortening and construction cost reduction. Electrical equipment are piled up to multi-layer and connected and tested at the factory and transported to the construction-site in one module. Other equipment rooms and areas are also built into the various pre-fabricated module types in CCR construction. The construction of the CCR by the large module is planned to achieve only 24-month construction period from bedrock inspection to commercial operation. The CCR has possibilities of attaining both economical and safe small reactor by simplified system and compact PCV technologies with advanced construction.