STAN T. ROSINSKI is program manager technology innovation at the Electric Power Research Institute. He is responsible for incubating technology innovation within EPRI by directing fundamental R&D to accelerate the application of advanced science and technology throughout the electricity enterprise. He is secretary and membership chairman of Committee E10 on Nuclear Technology and Applications and a member of Committee E56 on Nanotechnology.
|TOM J. MULFORD is program manager advanced nuclear technology in the R&D division of the Electric Power Research Institute. In this capacity, he is responsible for the overall technical, administrative and financial management of the ANT program, as well as developing its strategic direction and integration of its activities with the rest of the nuclear power industry.
ASTM International Committee E10 on Nuclear Technology and Applications
ASTM International Committee E10 on Nuclear Technology and Applications is responsible for the development and maintenance of standards relevant to the use of nuclear technology. In this context, it also organizes and conducts technical symposia and workshops intended to promote the advancement of nuclear science and technology and the safe application of nuclear energy in all forms. Committee E10 has created and maintains published standards covering a large range of nuclear procedures, with over 100 standards currently maintained by the following six E10 subcommittees:
• E10.01 on Radiation Processing: Dosimetry and Applications;
• E10.02 on Behavior and Use of Nuclear Structural Materials;
• E10.03 on Radiological Protection for Decontamination
and Decommissioning of Nuclear Facilities and Components;
•E10.05 on Nuclear Radiation Metrology;
• E10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices; and
• E10.08 on Procedures for Neutron Radiation Damage Simulation.
Committee E10 activities encompass nearly all civilian applications of nuclear technology, except those related to the nuclear fuel cycle, which are the responsibility of ASTM Committee C26 on Nuclear Fuel Cycle. Committees E10 and C26 maintain a close working relationship, with many members serving on both committees.
Committee E10 has recently held technical forums to evaluate standardization needs for addressing near-term issues related to the design and development of Generation IV reactors. The committee is positioned to provide standardization support for technology innovation in a reinvigorated nuclear power industry.
Technology Innovation in Nuclear Power Generation
There are over 440 nuclear power reactors around the world. Each is a critical component of the global electricity supply portfolio, accounting for about 17 percent of worldwide generation and 20 percent of the U.S. power supply mix. Given growing concern over the connections between fossil fuel combustion, greenhouse gas emissions and global climate change, these facilities are being looked at in a new light. They generate almost half of the world’s non-emitting electricity today and about 70 percent of emission-free power in the United States.
Scientific consensus indicates that rising atmospheric concentrations of carbon dioxide and other greenhouse gases are changing the Earth’s climate. The world remains committed to the United Nations Framework Convention on Climate Change, which became international law in 1994 and has been consistently reaffirmed by the U.S. government. The ultimate objective of the UNFCCC is to stabilize “greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.”
Stabilizing concentrations poses major challenges. By the end of the 21st century, the global population is likely to be at least 50 percent greater than at present, and the global economy is projected to be many times the size of today’s economy. For society to be on a course toward stabilization by 2100, a much larger energy system must be operating at a much lower carbon intensity.
Innovation in nuclear power generation technologies is needed to maintain and expand the role of this carbon-free energy option in meeting the increasing demand for electricity while achieving global climate policy objectives. New and improved nuclear plant designs, systems, components and regulatory frameworks combined with objective and rigorous technical information are critical for reducing costs and addressing safety, security, waste management and proliferation concerns. The extent to which scientific knowledge and innovative technology can help mitigate these concerns and increase political and public acceptance will determine whether nuclear power remains an important component of domestic and global supply mixes in the carbon-constrained future.
The present use of nuclear technology has evolved over the past 50 years as shown in Figure 1. Generation I reactors were developed in the 1950s and ’60s, while Generation II reactors make up the present U.S. fleet and most nuclear plants in operation elsewhere. There are 104 of these plants operating in the United States today.
In the early years, nuclear technology provided hopes for inexpensive electrical power, but the practical application of this technology in the U.S. utility industry was dimmed by cost overruns, extended outages and expensive repairs. Average cost and construction times dramatically increased due to cumbersome construction and licensing approaches associated with individual, custom-designed plants.
As these baseload units accrued service, however, improved operating and maintenance practices as well as component and material updates have been able to improve the fleet’s average capacity factors of Generation II designs over the past 25 years from about 60 percent to almost 90 percent in the United States. Today, there is increased interest in Generation III plants based on excellent current operating experience, enhanced economics of new designs, a revised licensing process and increased government support.
Generation III and III+ plants are in operation in Japan, and others are under construction or ready to be ordered. Generation IV designs are still on the drawing board and will not be operational before 2020 at the earliest.
By the early 1980s, it was understood that designs for new nuclear reactors needed to be more robust and rugged to support more cost-effective operations over the plant life-cycle and to provide a greater degree of inherent safety. In the mid-1980s, a large U.S. and international utility effort developed the basis for standardized plant designs offering enhanced reliability, economics and safety. This led to evolutionary Generation III designs based on lessons learned from operating experience, improved components and materials, simplified systems, etc. It also yielded Generation III+ designs that incorporate these evolutionary improvements, as well as a new conceptual approach to safety passive safety, as shown in Figure 2.
Generation III+ passive safety designs utilize natural circulation, driven by gravity, to provide backup cooling for the reactor. A similar natural circulation approach is also used to protect the containment from leaking due to excess pressure. By contrast, previous safety system designs relied on electric-driven pumps that may be affected by power loss or the degradation of pump internal components. The passive safety approach makes Generation III+ reactors inherently safer than other designs since no active measures by operators or by mechanical or electrical systems is required. This approach also reduces the amount of equipment and components in the plant, supporting reduced capital, operations and maintenance costs.
The Generation III and III+ plant design initiative has also directly addressed the need to reduce construction times, costs and uncertainties, which together present a substantial economic barrier to new plant deployment. The advanced designs are standardized, eliminating plant-specific customized engineering, and allowing a larger portion of the plant to be built in modules and shipped to the site. Operations and timelines in the factory are typically far more efficient and predictable than in the field, and construction and site preparation work can proceed in parallel. Advanced plants also take advantage of modern design and planning tools such as 4-D visualization technology, which extends conventional, 3-D computer-aided design by adding the fourth dimension of time to the modeling process. Engineers can apply 4-D techniques to simulate plant construction sequences in unprecedented detail. This capability allows them to identify and avoid potential problems and to otherwise optimize sequencing, yielding streamlined schedules that also are more certain and, thus, easier to finance.
In the United States, further economic efficiencies are promised for Generation III and III+ nuclear power plants under an improved reactor licensing process as shown in Figure 3. The new process defined in 10 CFR Part 52 has three separate phases. The early site permit phase allows a company to apply for and obtain approval for a plant site prior to making a final decision on whether or not to actually build on that site. Design certification signifies approval that a specified design meets regulatory safety standards. A combined construction and operating license allows for the construction and subsequent operation of a specified design at a specified location. Public input is encouraged at each of these early steps, prior to construction. Each phase introduces certainty and efficiency to the U.S. regulatory process, especially when compared with the process in place when Generation II nuclear plants were licensed after the plant was built.
Even as U.S. efforts to develop, license and deploy Generation III and III+ plants continue, there is significant R&D under way worldwide to enhance commercial nuclear power plant technology. The Generation IV International Forum is an international collective of countries committed to joint development of the next generation of nuclear technology. They include Argentina, Brazil, Canada, China, European Union nations, Japan, Russia, South Africa, South Korea, Switzerland, and the United States.
In late 2002, GIF members selected six reactor technologies that could expand the options for nuclear energy, augmenting the capabilities of Generation III designs. The technologies were selected on the basis of being clean, safe, efficient and cost-effective means of meeting increased energy demands on a sustainable basis, while being resistant to the diversion of materials for weapons proliferation and secure from terrorist attacks.
Almost all existing nuclear plants in the United States and elsewhere use an open fuel cycle approach. This means that the fuel, once it is discharged from a reactor, is not recycled to claim unspent residual fuel. Use of fast breeder reactor designs combined with reprocessing could close the fuel cycle and extend the usefulness of mined uranium by more than 60 times an important consideration in the case of growing demand for fuel. With proper technology choices, these designs can minimize proliferation concerns. Most of the six systems selected by GIF members employ a closed fuel cycle to maximize the resource base and minimize high-level wastes to be sent to a repository.
Heat transfer system design is another key consideration, as current nuclear plants using water to transfer heat from the reactor to the steam turbine-generator system for electric power production are limited in their efficiency by the temperature of the water and the amount of energy that can be transferred. Of the Generation IV designs being pursued, only one is cooled by light water. The remaining designs are cooled by helium, lead-bismuth, sodium or fluoride salt. Some of these designs will operate at a temperature significantly higher than today’s light water reactors. This provides the possibility for thermochemical or high-temperature electrolysis hydrogen production. Flexibility in the design of these advanced reactors will also support distributed generation or desalination plant applications.
To support and complement R&D activities being pursued by GIF members, the U.S. Department of Energy announced the Global Nuclear Energy Partnership in 2006, which emphasizes the development and use of reprocessing technology for spent nuclear fuel. Through GNEP, the United States will work with other nations to develop new, proliferation-resistant recycling technologies. Additionally, participating nations will develop a fuel services program to help non-fuel-cycle-capable countries enjoy the benefits of abundant, clean, safe and cost-effective nuclear power in exchange for a commitment to forgo their own fuel enrichment and reprocessing activities.
A wide range of energy-economy modeling studies have examined the possible roles of nuclear power and other technologies in achieving economic, environmental and social objectives over the next several decades and beyond. Many of these studies assume the gradual, broadening adoption of efficient, increasingly stringent, market-based restrictions on greenhouse gas emissions. These climate policy restrictions typically take the form of a “carbon price” a monetary value assigned to CO2 emissions that imposes a cost adder on fossil-fuel-based technologies and creates an incentive to reduce emissions.
According to several prominent studies, nuclear power including the continued operation of today’s units as well as accelerated development and deployment of Generation III, III+ and IV plant designs represents a critical element in the world’s technology portfolio for a carbon-constrained future due to economic, fuel security and other reasons. When advanced, cost-competitive nuclear power technologies are deployed, they will account for a significant fraction of gross capacity additions. If nuclear power were to be removed from the generation mix, the cost of meeting climate policy objectives increases, as does vulnerability to global supply and demand imbalances relating to fossil fuels.
Modeling studies also project that the role of electricity in meeting demand for energy services will increase as emissions constraints tighten and carbon prices rise. Advanced nuclear plants and other low- and non-emitting generation technologies will dominate capacity additions. They will eventually replace much of today’s emitting generation systems, and their clean power will displace direct end uses of fossil fuels.
For example, plug-in hybrid vehicles running on batteries charged at night by baseload nuclear plants represent a carbon-free transportation solution. The SuperGrid is another application contemplated for advanced nuclear technologies. This visionary energy system integrates a continental-scale, underground, superconductor-based, hydrogen-cooled transmission spine with advanced nuclear plants and co-located hydrogen production facilities. It would interconnect with existing power and fuel delivery networks, supplying load centers with electricity and hydrogen as needed for diverse applications. The SuperGrid concept is viewed as an energy solution that may be possible by mid-century.
In the meantime, Generation III and III+ plants represent modern, standardized designs that are simpler, more rugged and inherently safer. They offer potential for reduced capital costs and construction times, ease of operations and maintenance, reduced vulnerability to operational upsets, higher availability, longer operating life (minimum of 60 years) and greatly reduced possibility of safety problems. These characteristics in addition to expanding utility interest, the more streamlined U.S. licensing process, increased political support and growing concern about climate change suggest initial U.S. deployment within the next decade and continued overseas deployment. Continued technology innovation, in the form of Generation IV designs and the addressing of safety, resource efficiency, waste management and proliferation concerns, bodes well for nuclear power’s long-term future. //