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Boiling Water Reactor

Boiling Water Reactor. Kevin Burgee Janiqua Melton Alexander Basterash. What it is. A type of light water nuclear reactor used for the generation of electrical power It is the second most common type of electricity-generating nuclear reactor after the PWR (Pressurized Water Reactor).

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Boiling Water Reactor

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  1. Boiling Water Reactor Kevin Burgee Janiqua Melton Alexander Basterash

  2. What it is • A type of light water nuclear reactor used for the generation of electrical power • It is the second most common type of electricity-generating nuclear reactor after the PWR (Pressurized Water Reactor)

  3. BWR vs PWR BWR PWR The reactor core heats water (does not boil) then exchanges heat with a lower pressure water system which then turns to steam to drive a steam turbine • The reactor core heats water, which turns to steam and then drives a steam turbine

  4. -Uses mineralized water as a cooler and neutron moderator -Heat is produced by nuclear fission in the reactor core, causing the water to boil and produce steam -Steam is used directly to drive a turbine after which it is cooled in a condenser and turned back to liquid water -It is then returned to the reactor to complete the loop

  5. Control System • Changed by two ways • Inserting or withdrawing control rods • Changing the water flow through the reactor core • Positioning control rods is the standard way of controlling power when starting up a BWR • As control rods are withdrawn, neutron absorption decreases in the control material and increases in the fuel, so reactor power increases • As control rods are inserted, neutron absorption increases in the control material and decreases in the fuel, so reactor power decreases

  6. Control by Flow of Water • As flow of water through the core is increased, steam bubbles are more quickly removed, amount of water in the core increases, neutron moderation increases • More neutrons are slowed down to be absorbed by the fuel, and reactor power increases • As flow of water through the core is decreased, steam voids remain longer in the core, the amount of liquid water in the core decreases, neutron moderation decreases • Fewer neutrons are slowed down to be absorbed by the fuel, and the power decreases

  7. Advantages • The reactor vessel works at substantially lower pressure levels (75 atm) compared to a PWR (158 atm) • Pressure vessel is subject to less irradiation compared to a PWR, so it does not become as brittle with age • Operates at lower nuclear fuel temperature • Fewer components due to no steam generator or pressure vessel

  8. Size • A BWR fuel assembly comprises 74-100 fuel rods • There are approximately 800 assemblies in a reactor core • This holds up to about 140 tons of uranium • The number of fuel assemblies is based on the desired power output, reactor core size, and reactor power density

  9. Steam Turbine • Steam produced in the reactor core passes through steam separators and dryer plates above the core, then goes directly to the turbine • The water contains traces of radionuclides so the turbine must be shielded during operation and radiological protection must be provided during maintenance

  10. Different Variations • Early series • BWR/1-BWR/6 • Advanced Boiling Water Reactor (ABWR) • Simplified Boiling Water Reactor (SBWR) • Economic Simplified Boiling Water Reactor (ESBWR)

  11. BWR/1-BWR/6 • The first, General Electric, series of BWRs evolved though 6 design phases • BWR/4s, BWR/5s, and BWR/6 are the most common types in service today BWR/4

  12. Advanced Boiling Water Reactor • Developed in the late 1980s • Uses advanced technologies such as: computer control, plant automation, in-core pumping, and nuclear safety • Power output of 1350 MWe (megawatt electrical) per reactor • Lowered probability of core damage

  13. ABWR

  14. Simplified Boiling Water Reactor • Produces 600 Mwe per reactor • Used “passive safety” design principles • Rather than requiring active systems, such as emergency injection pumps, to keep the reactor in safety margins, was instead designed to return to a safe state solely through operation of natural forces • Ex. If the reactor got too hot, a system would release soluble neutron absorbers or materials that greatly hamper a chain reaction of absorbing neutrons. This would then bring the reaction to a near stop

  15. Economic Simplified Boiling Water Reactor • Output of 1,600 Mwe per reactor • Has the features of an ABWR with the distinctive safety features of the SBWR • Has been advertised as having a core damage probability of only 3×10−8 core damage events per reactor-year • This means there would need to be 3 million ESBWRs operating before one would expect a single core-damaging event during their 100-year lifetimes

  16. ESBWR

  17. Disadvantages • Contamination of turbine by short-lived activation products (Nitrogen-16) • An unmodified Mark-1 containment can allow some degree of radioactive release to occur

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