Kokendwaterreactor

Kokendwaterreactor, or boiling water reactor (BWR), is a type of light-water nuclear reactor used for electricity generation. In a BWR, water serves as both coolant and neutron moderator. The reactor core’s heat boils the water inside the reactor vessel, producing steam directly within the primary loop. This steam drives the turbine connected to a generator, and the condensed steam is returned to the reactor as feedwater. Unlike a pressurized water reactor, the steam is generated in the reactor vessel and sent directly to the turbine, forming a single closed loop.

Key components include the reactor pressure vessel with the fuel assemblies, control rods that can be inserted from above to regulate reactivity, and a recirculation system that adjusts water flow and the amount of boiling to control power. The steam leaves the core, passes through moisture separators and dryers, and then drives the turbine before being condensed. Typical operating conditions are around 70 bar of pressure with outlet temperatures near 280°C, giving thermal efficiencies in the low to mid 30s percent.

Safety and design have evolved since the 1950s and 1960s, with General Electric developing early BWR designs and subsequent generations improving containment, instrumentation, and safety systems. Notable examples of BWRs include Dresden Unit 1 in the United States and the Fukushima Daiichi units in Japan. The Fukushima accident highlighted vulnerabilities related to loss of cooling and hydrogen buildup, prompting enhancements in safety measures such as hydrogen management, backup power, and containment robustness.

Advantages of the BWR design include a simpler primary circuit with fewer heat exchangers and a more compact layout. Disadvantages include higher radioactivity levels in the turbine and associated systems, and greater complexity in managing radiolysis byproducts and hydrogen in some scenarios.