01 How It Works
Unlike PWRs, BWRs allow the coolant water to boil inside the reactor pressure vessel at about 75 bar. The steam produced goes directly to the turbine without a steam generator, making the design simpler and cheaper. The tradeoff is that the turbine becomes slightly radioactive (short-lived N-16) during operation, requiring shielding. Power is controlled by adjusting coolant flow and recirculation pump speed.
02 Pros & Cons
โ Advantages
- Simpler design - no steam generators or pressuriser
- Lower operating pressure than PWR
- Direct steam cycle - more efficient energy transfer
- Good load-following capability
โ Disadvantages
- Turbine becomes mildly radioactive
- Boiling instability can be a control challenge
- Larger reactor vessel than PWR for same power
- Three Fukushima reactors were Mark I BWRs
03 Specifications
THERMAL EFFICIENCY~34%
OPERATING TEMP~285ยฐC
PRESSURE~75 bar
FUELEnriched UOโ (2โ4%)
FUELEnriched UOโ (2โ4%)
COUNTRIESUSA, Japan, Sweden, Germany, Finland
04 Did You Know?
The Fukushima Daiichi reactors were all BWRs. General Electric designed the Mark I containment used there - later criticised for its small volume.