Economic Simplified Boiling Water Reactor
Encyclopedia
The type of nuclear reactor formally known as the Economic Simplified Boiling Water Reactor (ESBWR) is a passively safe generation III+ reactor
derived from the predecessor Simplified Boiling Water Reactor (SBWR) and the Advanced Boiling Water Reactor
(ABWR). All are designs by GE Hitachi Nuclear Energy
(GEH), and are based on previous BWR designs.
(RPV); there are no recirculation pumps and none of the associated piping, power supplies, heat exchangers and instrumentation & controls.
ESBWR’s passive safety systems include a combination of three systems that allow for the efficient transfer of decay heat from the reactor to pools of water outside of containment – the Isolation Condenser System, the Gravity Driven Cooling System, and the Passive Containment Cooling System
. These systems utilize natural circulation based on simple laws of physics to transfer the decay heat outside of containment while maintaining water inventory inside the reactor keeping the nuclear fuel submerged in water and adequately cooled.
In events where the Reactor Coolant Pressure Boundary remains intact, the Isolation Condenser System (ICS) is used to remove decay heat from the reactor and transfer it outside of containment. The ICS system is a closed loop system that connects the reactor pressure vessel to a heat exchanger located in the upper elevation of the reactor building. Steam leaves the reactor through the ICS piping and travels to the ICS heat exchangers which are submerged in a large pool. The steam is condensed in the heat exchangers and the heavier condensate then flows back down to the reactor to complete the cooling loop. Reactor coolant is recycled through this flow path to provide continuous cooling and makeup water to the reactor core.
In cases where the Reactor Coolant Pressure Boundary does not remain intact and water inventory in the core is being lost, the Passive Containment Cooling System (PCCS) and Gravity Driven Cooling System (GDCS) work in concert to maintain water level in the core and remove decay heat from the reactor and transfer it outside of containment.
If water level inside the reactor pressure vessel drops to a pre-determined level due to the loss of water inventory, the reactor is depressurized and the GDCS is initiated. It consists of large pools of water inside containment above the reactor which are connected to the reactor pressure vessel. When the GDCS system is initiated, gravity forces water to flow down from the pools into the reactor. The pools are sized to provide sufficient makeup water to maintain water level above the top of the nuclear fuel. After the reactor has been depressurized, the decay heat is transferred to containment as water inside the reactor boils and exits the reactor pressure vessel into containment in the form of steam.
The PCCS system consists of a set of heat exchangers located in the upper portion of the Reactor Building. The steam from the reactor rises through containment to the PCCS heat exchangers where the steam is condensed. The condensate then drains from the PCCS heat exchangers back to the GDCS pools where it completes the cycle and drains back to the reactor pressure vessel.
Both the ICS and PCCS heat exchangers are submerged in a pool of water large enough to provide 72 hours of reactor decay heat removal capability. The pool is vented to the atmosphere and is located outside of containment. The combination of these features allows the pool to be refilled easily with low pressure makeup water and pre-piped connections.
The reactor core is shorter than in conventional BWR plants to reduce the pressure drop over the fuel, thereby enabling natural circulation. There are 1,132 fuel rod bundles and the thermal power is 4,500 MWth in the standardized SBWR. The nominal summertime output is rated at 1,575-1,600 MWe, yielding an overall plant Carnot efficiency of approximately 35%.
In case of an accident, the ESBWR can remain in a safe, stable state for 72 hours without any operator action or alternating current (AC) power supply. Below the vessel, there is a piping structure which allows for cooling of the core during a very severe accident. These pipes facilitate cooling above and below the molten core with water. GEH’s Probabilistic Risk Analysis indicates that a core damage event would occur no more often than once in 59 million years.
Generation III reactor
A generation III reactor is a development of any of the generation II nuclear reactor designs incorporating evolutionary improvements in design developed during the lifetime of the generation II reactor designs...
derived from the predecessor Simplified Boiling Water Reactor (SBWR) and the Advanced Boiling Water Reactor
Advanced Boiling Water Reactor
The Advanced Boiling Water Reactor is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy and Toshiba...
(ABWR). All are designs by GE Hitachi Nuclear Energy
GE Hitachi Nuclear Energy
GE Hitachi Nuclear Energy is a provider of advanced reactors and nuclear services. It is located in Wilmington, N.C.. Established in June 2007, GEH is a global nuclear alliance created by General Electric and Hitachi...
(GEH), and are based on previous BWR designs.
Passive safety system
The passive safety systems in an ESBWR operate without using pumps whatsoever, thereby further increasing design safety integrity and reliability, while simultaneously reducing overall reactor cost. It also uses natural circulation for coolant recirculation within the reactor pressure vesselReactor vessel
In a nuclear power plant, the reactor vessel is a pressure vessel containing the Nuclear reactor coolant and reactor core.Not all power reactors have a reactor vessel. Power reactors are generally classified by the type of coolant rather than by the configuration of the reactor vessel used to...
(RPV); there are no recirculation pumps and none of the associated piping, power supplies, heat exchangers and instrumentation & controls.
ESBWR’s passive safety systems include a combination of three systems that allow for the efficient transfer of decay heat from the reactor to pools of water outside of containment – the Isolation Condenser System, the Gravity Driven Cooling System, and the Passive Containment Cooling System
Boiling water reactor safety systems
Boiling water reactor safety systems are nuclear safety systems constructed within boiling water reactors in order to prevent or mitigate environmental and health hazards in the event of accident or natural disaster....
. These systems utilize natural circulation based on simple laws of physics to transfer the decay heat outside of containment while maintaining water inventory inside the reactor keeping the nuclear fuel submerged in water and adequately cooled.
In events where the Reactor Coolant Pressure Boundary remains intact, the Isolation Condenser System (ICS) is used to remove decay heat from the reactor and transfer it outside of containment. The ICS system is a closed loop system that connects the reactor pressure vessel to a heat exchanger located in the upper elevation of the reactor building. Steam leaves the reactor through the ICS piping and travels to the ICS heat exchangers which are submerged in a large pool. The steam is condensed in the heat exchangers and the heavier condensate then flows back down to the reactor to complete the cooling loop. Reactor coolant is recycled through this flow path to provide continuous cooling and makeup water to the reactor core.
In cases where the Reactor Coolant Pressure Boundary does not remain intact and water inventory in the core is being lost, the Passive Containment Cooling System (PCCS) and Gravity Driven Cooling System (GDCS) work in concert to maintain water level in the core and remove decay heat from the reactor and transfer it outside of containment.
If water level inside the reactor pressure vessel drops to a pre-determined level due to the loss of water inventory, the reactor is depressurized and the GDCS is initiated. It consists of large pools of water inside containment above the reactor which are connected to the reactor pressure vessel. When the GDCS system is initiated, gravity forces water to flow down from the pools into the reactor. The pools are sized to provide sufficient makeup water to maintain water level above the top of the nuclear fuel. After the reactor has been depressurized, the decay heat is transferred to containment as water inside the reactor boils and exits the reactor pressure vessel into containment in the form of steam.
The PCCS system consists of a set of heat exchangers located in the upper portion of the Reactor Building. The steam from the reactor rises through containment to the PCCS heat exchangers where the steam is condensed. The condensate then drains from the PCCS heat exchangers back to the GDCS pools where it completes the cycle and drains back to the reactor pressure vessel.
Both the ICS and PCCS heat exchangers are submerged in a pool of water large enough to provide 72 hours of reactor decay heat removal capability. The pool is vented to the atmosphere and is located outside of containment. The combination of these features allows the pool to be refilled easily with low pressure makeup water and pre-piped connections.
The reactor core is shorter than in conventional BWR plants to reduce the pressure drop over the fuel, thereby enabling natural circulation. There are 1,132 fuel rod bundles and the thermal power is 4,500 MWth in the standardized SBWR. The nominal summertime output is rated at 1,575-1,600 MWe, yielding an overall plant Carnot efficiency of approximately 35%.
In case of an accident, the ESBWR can remain in a safe, stable state for 72 hours without any operator action or alternating current (AC) power supply. Below the vessel, there is a piping structure which allows for cooling of the core during a very severe accident. These pipes facilitate cooling above and below the molten core with water. GEH’s Probabilistic Risk Analysis indicates that a core damage event would occur no more often than once in 59 million years.
NRC design review process
The ESBWR received a positive Safety Evaluation Report and Final Design Approval on March 9, 2011. On June 7, 2011, the NRC completed its public comment period. Final design certification is set for the fall of 2011.See also
- Nuclear powerNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
- Nuclear safety in the U.S.
- Economics of new nuclear power plantsEconomics of new nuclear power plantsThe economics of new nuclear power plants is a controversial subject, since there are diverging views on this topic, and multi-billion dollar investments ride on the choice of an energy source...
- Boiling Water ReactorBoiling water reactorThe boiling water reactor 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 pressurized water reactor , also a type of light water nuclear reactor...
- Generation III reactorGeneration III reactorA generation III reactor is a development of any of the generation II nuclear reactor designs incorporating evolutionary improvements in design developed during the lifetime of the generation II reactor designs...
- Nuclear Power 2010 ProgramNuclear Power 2010 ProgramThe "Nuclear Power 2010 Program" was unveiled by the U.S. Secretary of Energy Spencer Abraham on February 14, 2002 as one means towards addressing the expected need for new power plants...
- ABWR
- AP1000
External links
- POWER magazine article on the ESBWR
- NRC ESBWR Overview page
- ESBWR Probabilistic Risk Assessment
- ESBWR Design Control Document, Rev. 9
- GE Energy ESBWR website
- Pictures of ESBWR design
- Design overview published in ANS Nuclear News (2006).