Boiling water reactor core design

FIG. 19.13. Design of a boiling water reactor core system, ABB-Atom, Sweden. 

The basic design of most nuclear reactors is similar, but several types of reactors are used throughout the world. In the United States most reactors use plain water as the coolant. Reactors using ordinary water are called light water reactors. Light water reactors can be pressurized to approximately 150 atmospheres to keep the primary coolant in the liquid phase at temperatures of approximately 300°C. The heat from the pressurized water is used to heat secondary water to generate steam. In a boiling water reactor, water in the core is allowed to boil. The steam produced powers the turbines directly. Heavy water reactors use water in... 

The design of the Simplified Boiling Water Reactor (SBWR) represents a complete design fijr a nominal 600 MWe power plant. The rated thoina] output of the reactor core is 2000 MWt, and the rated NSSS thermal output is 1996.1 MWth. The SBWR incorporates innovative, yet proven, concq>ts to fiirther amplify an inherently simple direct cycle nuclear plant. The features selected are all proven concepts in large nuclear power plants. 

The reactor could be designed, built and operated as a boiling water reactor (BWR), a pressurized water reactor (PWR) or a direct-flow system with superheated steam at the core outlet. The latter offers the potential for having a steam cycle thermal efficiency of about 43%, which could decrease the capital costs per kW(e) by nearly one-third. The present short description is based on the data for a BWR version of the AFPR. 

The PBWFR is designed to generate electricity. The cycle type is direct and the system pressure is the same as in conventional boiling water reactors (BWRs), see Fig. XXVII-2. Steam is generated in the chimneys in direct contact with hot Pb-Bi coolant above the core. There are no steam generators and intermediate heat transport systems. 

The two light water reactors (LWRs) are the pressurized water reactor (PWR) and the boiling water reactor (BWR). The systems are similar in that both employ light water as both moderator and coolant, which necessitates the use of fuel enriched to about 2.0 %-2.5 % due to the appreciable neutron absorption of the water in the core. They are also alike in that in both cases the core is enclosed within a single large steel pressure vessel (see Fig. 7,1). The distinction between the two designs is also illustrated in the figure. In the... 

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