Reactor design description and development status of BWR

The BWR 90 standard plant design of ABB Atom represents an evolution of the design of its successllil predecessor, the BWR 75, with a number of design modifications, improvements and supplements that address new licensing requirements and aim at meeting utility needs for increased public safety, investment protection, lowered cost, and ease of operation and maintenance. 

The BWR 90 design is characterized by the use of internal recirculation pumps, fine motion control rod drives, a prestressed concrete containment, and extensive redundancy and separation of safety-related systems in the same way as the BWR 75 design that was developed in the 1970s. The modifications are mostly moderate and they have been made to adapt to updating technologies, new safety requirements and to achieve cost savings. 

The net electrical output of the smallest BWR 90 version amounts to 830 MWe at a coastal site with very cold circulating water ( 5°C) at sites with warmer circulating water the output will be lower - a typical low value of 700-720 MWe puts it in the upper range of SMRs. For that reason, a description of the smallest BWR 90 version has been included in this SMR report. 

In line with the strong preferences given to proven design features and solutions in the development work, - an approach that was firmly supported by TVO, - it is easily concluded that the design of the reactor has changed very little, and that the nuclear island as a whole has not been changed much. 

Some of the special features of the BWR 90 are reviewed briefly below. 

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