Kevin Burgee Janiqua Melton Alexander Basterash 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)

BWR vs PWR BWR PWR The reactor core heats water, which turns to steam and then drives a steam turbine 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

-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

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core Positioning control rods is the standard way of controlling power when starting up a BWR As control rods are withdrawn, neutron absorption decreases in the control material and increases in the fuel, so reactor power increases As control rods are inserted, neutron absorption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

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

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

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

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

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

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

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

ABWR

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

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

ESBWR

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