Author: Judy Haar : Posted to Decoded Science on January 2, 2012
Proposed as the energy market’s silver bullet, nuclear power would meet all the worlds needs for increased energy demands with little pollution or fear of accidents, right? Actually, we know that this isn’t true. Light water reactors, which provide the bulk of our nuclear capacity, are notoriously inefficient. Couple this with concerns about waste and nuclear safety, the present day problems loom large. So, what does the future bring for nuclear power? As Robert Kennedy told us, "The future is not a gift. It is an achievement."
It all started about 60 years ago in Idaho. The military was anxious to get up and running with a new power source for their submarine fleet, and the light water reactor (LWR) was obvious for the next step in power generation. At the time, it was easier to take an already-existing military design and scale it up for commercial use. Since then, nuclear power plant design has evolved through four distinct design generations.
The First Generation (1950 -1970) included prototypes and first designs.
The Second Generation (1970 – 2030) included currently operating plants.
The Third Generation (2000 – on) includes improvements and retrofits to current plants.
The Fourth Generation (2030 – on) will include new and advanced nuclear plant designs.
Today, operating reactors are typically LWR’s of the second or third generation. The fourth generation or
Generation IV nuclear reactors are now on the drawing board and in a testing phase. Gen IV reactors are not your garden variety, everyday LWR.
There are two types of LWR: boiling water reactors (BWR) and pressurized water reactors (PWR). Both use water passed through the core, where it is heated. In the BWR, the water turns to steam that drives the turbines and produces electricity. In the PWR, the water is heated by the core and is kept under pressure so it remains liquid. The heated water is then passed through a heat exchanger which produces steam and drives the turbines
Will nuclear power ever be safe? There are risks in everything we do. But realistically, when you split an atom, there is risk, and the future of nuclear power research understands this. Initiated in 2000, the
Generation IV International Forum (GIF) was created to represent the governments of 13 countries where nuclear power is, or will be, significant. The charter is intended to participate in the development of the goals and design of reactor technologies for the future, thus, Gen IV. Goals recently developed through the GIF, of which the United States is a member, focus in broad areas such as: sustainability, economics, safety, reliability, proliferation resistance and physical protection.
Nuclear Sustainability: Produce sustainable energy that meets clean air objectives, and offers long-term availability and effective fuel utilization.
Nuclear Economics: Provide a clear life-cycle cost advantage and financial risk comparable to other energy producers.
Nuclear Safety and Reliability: Excel with a low likelihood of reactor core damage, and eliminate the need for offsite emergency response.
Nuclear Proliferation Resistance and Physical Protection: Obtain the objective of least desirable route for production of weapon-usable material and increased physical protection.
Among these important standards provided by the GIF, other design features are analyzed such as passive safety systems (not power initiated) and higher core efficiencies.
Gen IV reactors will definitely deviate from current LWR technology. Many will not use water, but elements such as helium, fluoride salt, or liquid sodium as a coolant, with sizes ranging from 150 to 1500 MWe. At least four of the systems already have significant operating experience. In addition, expanded uses for the Gen IV might include sea water desalination and process heat production. Based upon safety, environmental concerns, resistance to diversion of weapons grade materials, waste production and cost-effective solutions, the GIF has initially selected six supported designs. A very brief discussion follows for each:
Gas-cooled fast reactor (GFR): This reactor is high efficiency, and helium is used as the coolant instead of water, with an outlet temperature of 850 degrees Celsius, much higher then the Gen III.
LWR design: The core material of this reactor holds the potential of excellent retention of fission products and minimizes the production of long lived radioactive waste.
Lead-cooled fast reactor (LFR): This rector has inherent safety due to the use of un-reactive molten metal as the coolant, and natural primary coolant circulation. This reactor design, for the core, can use depleted uranium or thorium fuel matrices and burn actinides from LWR spent fuel.
Molten salt reactor (MSR): This reactor embodies liquid fuel. The uranium is dissolved in a sodium fluoride salt coolant which circulates through a graphite core. The positive side of the MSR technology is no spent fuel, continuous fission products removal, no fuel fabrication, and minimization of radiotoxic nuclear waste.
Sodium-cooled fast reactor (SFR): With 390 reactor-years of experience in sodium-cooled reactors over five decades, the SFR uses liquid sodium as the coolant. Core options for the SFR include depleted uranium.
Supercritical water-cooled reactor (SCWR): A high temperature, high pressure water-cooled reactor with a single phase coolant, supercritical water directly drives the turbines, and translates into improved economics.
This reactor’s core is enriched uranium oxide.
Very high-temperature gas reactor (VHTR): These are graphite-moderated, helium-cooled reactors with substantial experience. Heat removal is passive. The core can be blocks or pebble bed. This reactor design has potential of low operation and maintenance costs, modular construction, and passive safety.
The closest to commercial use is a small pebble bed reactor under development in China. Its uranium fuel is encased in tennis-sized balls called pebbles, where the fuel doesn’t get hot enough to melt.
New power plants are designed with passive safety systems that do not depend on action such as operator action or a pump turning on to circulate coolant through the core to prevent melting. Nuclear power plant vendors such as Westinghouse have designed their Advanced Passive 1000 (AP1000), for example, and are halfway through construction of several of these reactors. GE is developing modular passive reactors with their own safer designs.
When it comes to nuclear reactors, some think smaller is better; by reducing the output and size in-half, all cooling can be handled by simple gravity flow through natural convection. Smaller reactors cost less, are built faster and produce less spent fuel. And finally, there is fusion. The technology for this panacea for nuclear energy, however, is still around fifty years out.
http://www.decodedscience.com/is-nuclear-power-in-your-future/8910
= = = = = = = = = = = = = = = = = = = = = = = = = = =
Note by the blog author
The above article refers to modernized versions of convention fission power – radioactive rods moved close together to generate heat. The nuclear future may be through laser-powered implosion through fusion or, as a very remote possibility, by the conversion of one element (like nickel) to a simpler element (copper) in a manner which releases enormous energy. The fusion and elemental methods do not involve large quantities of heavy metal waste that has an enormous half-life as radioactive waste.
Proposed as the energy market’s silver bullet, nuclear power would meet all the worlds needs for increased energy demands with little pollution or fear of accidents, right? Actually, we know that this isn’t true. Light water reactors, which provide the bulk of our nuclear capacity, are notoriously inefficient. Couple this with concerns about waste and nuclear safety, the present day problems loom large. So, what does the future bring for nuclear power? As Robert Kennedy told us, "The future is not a gift. It is an achievement."
Nuclear Power: In the Beginning?
It all started about 60 years ago in Idaho. The military was anxious to get up and running with a new power source for their submarine fleet, and the light water reactor (LWR) was obvious for the next step in power generation. At the time, it was easier to take an already-existing military design and scale it up for commercial use. Since then, nuclear power plant design has evolved through four distinct design generations.
The First Generation (1950 -1970) included prototypes and first designs.
The Second Generation (1970 – 2030) included currently operating plants.
The Third Generation (2000 – on) includes improvements and retrofits to current plants.
The Fourth Generation (2030 – on) will include new and advanced nuclear plant designs.
Today, operating reactors are typically LWR’s of the second or third generation. The fourth generation or
Generation IV nuclear reactors are now on the drawing board and in a testing phase. Gen IV reactors are not your garden variety, everyday LWR.
Light Water Reactors
There are two types of LWR: boiling water reactors (BWR) and pressurized water reactors (PWR). Both use water passed through the core, where it is heated. In the BWR, the water turns to steam that drives the turbines and produces electricity. In the PWR, the water is heated by the core and is kept under pressure so it remains liquid. The heated water is then passed through a heat exchanger which produces steam and drives the turbines
Nuclear Technology: What are the New Goals?
Will nuclear power ever be safe? There are risks in everything we do. But realistically, when you split an atom, there is risk, and the future of nuclear power research understands this. Initiated in 2000, the
Generation IV International Forum (GIF) was created to represent the governments of 13 countries where nuclear power is, or will be, significant. The charter is intended to participate in the development of the goals and design of reactor technologies for the future, thus, Gen IV. Goals recently developed through the GIF, of which the United States is a member, focus in broad areas such as: sustainability, economics, safety, reliability, proliferation resistance and physical protection.
Nuclear Sustainability: Produce sustainable energy that meets clean air objectives, and offers long-term availability and effective fuel utilization.
Nuclear Economics: Provide a clear life-cycle cost advantage and financial risk comparable to other energy producers.
Nuclear Safety and Reliability: Excel with a low likelihood of reactor core damage, and eliminate the need for offsite emergency response.
Nuclear Proliferation Resistance and Physical Protection: Obtain the objective of least desirable route for production of weapon-usable material and increased physical protection.
Among these important standards provided by the GIF, other design features are analyzed such as passive safety systems (not power initiated) and higher core efficiencies.
Generation IV Nuclear Power
Gen IV reactors will definitely deviate from current LWR technology. Many will not use water, but elements such as helium, fluoride salt, or liquid sodium as a coolant, with sizes ranging from 150 to 1500 MWe. At least four of the systems already have significant operating experience. In addition, expanded uses for the Gen IV might include sea water desalination and process heat production. Based upon safety, environmental concerns, resistance to diversion of weapons grade materials, waste production and cost-effective solutions, the GIF has initially selected six supported designs. A very brief discussion follows for each:
Gas-cooled fast reactor (GFR): This reactor is high efficiency, and helium is used as the coolant instead of water, with an outlet temperature of 850 degrees Celsius, much higher then the Gen III.
LWR design: The core material of this reactor holds the potential of excellent retention of fission products and minimizes the production of long lived radioactive waste.
Lead-cooled fast reactor (LFR): This rector has inherent safety due to the use of un-reactive molten metal as the coolant, and natural primary coolant circulation. This reactor design, for the core, can use depleted uranium or thorium fuel matrices and burn actinides from LWR spent fuel.
Molten salt reactor (MSR): This reactor embodies liquid fuel. The uranium is dissolved in a sodium fluoride salt coolant which circulates through a graphite core. The positive side of the MSR technology is no spent fuel, continuous fission products removal, no fuel fabrication, and minimization of radiotoxic nuclear waste.
Sodium-cooled fast reactor (SFR): With 390 reactor-years of experience in sodium-cooled reactors over five decades, the SFR uses liquid sodium as the coolant. Core options for the SFR include depleted uranium.
Supercritical water-cooled reactor (SCWR): A high temperature, high pressure water-cooled reactor with a single phase coolant, supercritical water directly drives the turbines, and translates into improved economics.
This reactor’s core is enriched uranium oxide.
Very high-temperature gas reactor (VHTR): These are graphite-moderated, helium-cooled reactors with substantial experience. Heat removal is passive. The core can be blocks or pebble bed. This reactor design has potential of low operation and maintenance costs, modular construction, and passive safety.
The closest to commercial use is a small pebble bed reactor under development in China. Its uranium fuel is encased in tennis-sized balls called pebbles, where the fuel doesn’t get hot enough to melt.
Nuclear Future: Even More is Happening Now
New power plants are designed with passive safety systems that do not depend on action such as operator action or a pump turning on to circulate coolant through the core to prevent melting. Nuclear power plant vendors such as Westinghouse have designed their Advanced Passive 1000 (AP1000), for example, and are halfway through construction of several of these reactors. GE is developing modular passive reactors with their own safer designs.
When it comes to nuclear reactors, some think smaller is better; by reducing the output and size in-half, all cooling can be handled by simple gravity flow through natural convection. Smaller reactors cost less, are built faster and produce less spent fuel. And finally, there is fusion. The technology for this panacea for nuclear energy, however, is still around fifty years out.
http://www.decodedscience.com/is-nuclear-power-in-your-future/8910
= = = = = = = = = = = = = = = = = = = = = = = = = = =
Note by the blog author
The above article refers to modernized versions of convention fission power – radioactive rods moved close together to generate heat. The nuclear future may be through laser-powered implosion through fusion or, as a very remote possibility, by the conversion of one element (like nickel) to a simpler element (copper) in a manner which releases enormous energy. The fusion and elemental methods do not involve large quantities of heavy metal waste that has an enormous half-life as radioactive waste.
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