A BWR operates on the principle of a direct power cycle. Water passing through the core is allowed to boil at an intermediate pressure level. The saturated steam that exits the core region is transported through a series of separators and dryers located within the reactor vessel that promote a superheated state. The superheated water vapour is then used as the working fluid to turn the steam turbine.
Pros:
- Simpler plumbing reduces costs
- Power levels can be increased simply by speeding up the jet pumps, giving less boiled water and more moderation. Thus, load-following is simple and easy.
- Very much operating experience has been accumulated and the designs and procedures have been largely optimized.
Cons:
- With liquid and gaseous water in the system, many weird transients are possible, making safety analysis difficult
- Primary coolant is in direct contact with turbines, so if a fuel rod had a leak, radioactive material could be placed on the turbine. This complicates maintenance as the staff must be dressed for radioactive environments.
- Can’t breed new fuel — susceptible to “uranium shortage”
- Does not typically perform well in station blackout events, as in Fukushima.
