3. Boiling Water Reactors - Chapter 3 BOILING WATER...

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Chapter 3 BOILING WATER REACTORS © M. Ragheb 11/2/2008 3.1 INTRODUCTION Boiling Water Reactors (BWRs) operate at a reactor vessel pressure of 1,040 psia, a value considerably lower at almost one half that the operating pressure of PWRs at 2250 psia. Their nuclear steam supply system is different than PWRs in that the steam is produced within the core and is directly fed to the turbine-generator plant. This system uses a direct cycle as opposed to the indirect cycles used in other nuclear power plants. BWRs are the most commonly deployed design after the PWR design. The Clinton BWR plant using an artificial cooling late in Central Illinois, USA is shown in Fig. 1. Fig. 1: The Clinton Boiling Water Reactor with its cooling lake in Central Illinois, USA. 3.2 BOILING WATER REACTOR POWER CYCLE Boiling Water reactors with a direct cycle offer the capital cost advantage of eliminating the need for steam generators and a pressurizer. Another feature is the heat transfer in the core is mostly by latent heat as opposed to sensible heat in other power plants. This results in smaller flow rates and pumping energy needs. These advantages are countered by the presence of the short-lived isotope N 16 in the turbine plant area. Nitrogen 16 has a half-life of 7.1 seconds with beta emissions at energies of 4.3
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