GE BWR
's BWR product line of Boiling Water Reactors represents the designs of a relatively large percentage of the commercial fission reactors around the world.
History
The progenitor of the BWR line was the 5 MW Vallecitos Boiling Water Reactor, brought online in October 1957.BWR-1
- BWR Type 1 : In 1955 GE developed their original VBWR design into the 197 MW Dresden 1 reactor, embodying the first iteration of GE's BWR/1 design. Dresden 1 used forced circulation and a unique dual cycle heat transfer design that proved to be uneconomical. GE further developed the BWR-1 design with the 70 MW Big Rock Point reactor, which used the more economical direct cycle method of heat transfer, but disposed with the external recirculation pumps in favor of natural circulation. The 65 MW Humboldt Bay reactor followed Big Rock Point, returning to the more efficient forced circulation method. These experimental designs used fuel rod bundles in 6×6, 7×7, 8×8, 9×9, 11×11, and 12×12 configurations, but GE's 9×9 bundle later used in BWR/2–6 reactors is different from the one used in the BWR/1 era. The BWR/1 was the first BWR design with internal steam separation. It also had an isolation condenser, and pressure suppression containment.
BWR-2
- BWR Type 2 : Introduced in 1963, >500 MW, typically around 650 MW gross. Included a large direct cycle. 5 recirculation loops, variable speed external recirculation pumps. This design, as well as the BWR/3–6, would all later be classified as Generation II reactors for their increased scale, improved safety features, commercial viability, profitability, and long lifetime.
BWR-3
- BWR Type 3 : Introduced in 1965, 800 MW. First use of internal jet pumps. 2 recirculation loops, variable speed recirculation pumps. Improved ECCS spray and flood, improved feedwater spargers. Monticello and Pilgrim 1 had significantly lower power ratings despite also being classified as BWR/3 models.
BWR-4
- BWR Type 4 : Introduced in 1966, 1100 MW. Largely similar to the BWR/3 in design with an identical recirculation system, but power density was increased by 20%. Available with either Mark I or Mark II containment.
BWR-5
- BWR Type 5 : Introduced in 1969, 1100 MW. Same number of loops & jet pumps, but the jet pumps were upgraded to a five nozzle design. Variable speed pumps were replaced with two-speed pumps, and a flow control valve was added to each loop for use in regulating recirculation flow. Improved ECCS valve flow control. Only available with Mark II containment.
BWR-6
- BWR Type 6 : Introduced in 1972, available in configurations ranging from 600–1400 MW. Transitioned from 7×7 to 8×8 fuel bundle with longer and thinner fuel rods that fit within the same external footprint as the previous 7×7 fuel bundle, reduced fuel duty, improved compact jet pumps with higher circulation capacity, increased capacity of the steam separators and dryers, increased fuel capacity, increased output, improved ECCS, introduced an option for a compact control room, and introduced a solid-state nuclear system protection system option. First and only model available with Mark III containment.
ABWR
- ABWR: Higher safety margins, no external recirculation loops, reactor internal pumps. It also has fine motion control rod drives.
ESBWR
- ESBWR: Passive safety, natural circulation, 1600 MW. It has a gravity flooder, isolation condenser, and passive containment cooling.
Fuel Rod Bundles
GE-2
- 7x7 fuel bundle.
GE-3
- Improved 7x7 fuel bundle with 49 fuel rods, one of which is segmented.
GE-4
- 8x8 fuel bundle with 63 fuel rods and 1 water rod.
GE-5
- Retrofit 8x8 fuel bundle Prepressurized and Barrier fuel bundles containing 62 and two water rods.
GE-6 & 7
- Prepressurized at 3ATM with helium with a Barrier
GE-8
- 8x8 fuel bundle with 58 to 62 fuel rods and 2-6 water rods. Prepressurized at 5ATM with helium.
GE-9
Containment
Mark I
A drywell containment building which resembles an inverted lightbulb above the wetwell which is a steel torus containing water.Mark II
Described as an "over-under" configuration with the drywell forming a truncated cone on a concrete slab. Below is a cylindrical suppression chamber made of concrete rather than just sheet metal.Mark III
The GE Mark III Containment-system is a single barrier pressure containment and multi-barrier fission containment system, consisting of the containment vessel plus associated dry- and wetwell, the external shield building of it, the auxiliary building and the fuel building, all of which are normally kept at negative pressure which prevents the egress of fission products.Features of the containment :
- Improved seismic response
- Lower pressure containment design, but significant larger volume than Mark I and II
- Improved pipe whip design
- Combines the dry containment with the typical BWR-pressure suppression type containment
Advantages
- One advantage of the BWR design is improved load-following by virtue of control rod manipulation combined with changing the recirculation flow rate. The integration of the turbine pressure regulator and control system with the recirculation flow control system allows automatic power changes of up to 25% of rated power without altering control rod settings.
- Bottom entry bottom mounted control rods allow refueling without removal of the control rods and drives, while also allowing drive testing with an open vessel prior to fuel loading.
- BWR allow lower primary coolant flow than PWR.
- Jet pumps internal to the reactor vessel provide 2/3rds of the recirculation flow allowing the external recirculation flow loop to be small and compact compared to contemporary PWR designs.
- Under loss of coolant jet pumps provide 10% power similar to boilers.
- BWR designs operate constantly at about half the primary system pressure of PWR designs while producing the same quantity and quality of steam in a compact system: 1020 psi reactor vessel pressure, and 288 °C temperature for BWR which is lower than 2240 psi and 326 °C for PWR.
- Steam is generated in the reactor pressure vessel in a BWR, whereas it is generated in the steam generator on a second loop in a PWR.
- BWR allows for bulk boiling while PWR doesn't.
Disadvantages
- Steam generated in a BWR contains trace amounts of radioactive materials, as a result, large portions of the Turbine Building are compartmentalized to prevent radiation exposure to workers. PWR Turbine Buildings, on the other hand, are essentially the same as a fossil fuel power plant's Turbine Building with all equipment accessible at all times.