Nuclear Reactors: Generation to Generation
The Key Reactor Factors
Nuclear reactor designs are usually categorized by “generation”; that
is, Generation I, II, III, III+, and IV. The key attributes characterizing the development
and deployment of nuclear power reactors illuminate the essential differences between
the various generations of reactors. The present analysis of existing reactor concepts
focuses on six key reactor attributes:
- Cost-effectiveness. From the customer’s perspective, a nuclear kilowatt-hour
is, aside from its cost, indistinguishable from a renewable or fossil-fired kilowatt-hour.
Nuclear power must therefore be economically competitive. Accounting for the life-cycle
costs actually paid by the retail electricity customer has proven to be far from
trivial and is one of the more controversial elements in the discussion of competing
energy technologies. Fossil-fired power, without carbon controls, sets the market
price today and will likely continue to do so over the next decade. What policies
or initiatives might make nuclear power more competitive with current fossil fuel
prices? How can the prospects for nuclear power plant financing be improved?
- Safety. Several nuclear systems are incorporating passive design features
to ensure the safe operation of nuclear reactors, as compared to active safety systems
requiring intervention by human agents. This is due to a variety of technical and
public policy reasons, including quantitative risk reductions. What safety measures
are proposed for new reactors? Do they maintain or advance current measures?
- Security and nonproliferation. Nuclear power systems must minimize
the risks of nuclear theft and terrorism. Designs that will play on the international
market must also minimize the risks of state-sponsored nuclear weapons proliferation.
Concerns about dual-use technologies (i.e., technologies that were originally developed
for military or other purposes and are now in commercial use) are amplifying this
threat. What designs might mitigate these risks?
- Grid appropriateness.
The capabilities of both the local and national electric grid must match the electric
power a proposed reactor will deliver to the grid. Grid appropriateness is determined
by a combination of nameplate capacity and externalities defined by the extant electrical
grid.1 How does the capacity of the electric
grid impact the financial requirements, long-term economic feasibility, and availability
of a reactor?
- Commercialization roadmap. Historically, the displacement
of a base power source by an alternative source has been an evolutionary process
rather than a sudden, disruptive, and radical shift. Attempting to “push the
envelope” by forcing the shift is typically economically infeasible because
investors are rarely willing to bear, for example, the capital costs associated
with the deployment of alternative technology into the existing grid architecture.
Commercialization roadmaps must therefore include a plausible timeline for deployment.
The current need for near-term readiness (especially in emerging technological powerhouses
such as China, India, and the Republic of Korea) is such that only those technologies
that have either already been tested in the marketplace or are close to commercial
demonstration are likely to be considered. Will modular construction practices streamline
the commercialization of nuclear reactors and reduce the overnight cost burden?
- The fuel cycle. The details of a given reactor’s fuel cycle are critical
elements in determining risk levels for nuclear safety, security, and surety. With
both the front and back ends of the fuel cycle, intrinsic properties of reactor
design couple intimately with externalities such as the possible internationalization
of the front and back end processes.
- The front end. The extent to which a nuclear reactor requires continued refueling
with enriched fresh fuel is a critical factor in determining risk. A related factor
is the extent and manner in which the fuel supply (especially its enrichment and
fabrication) is internationalized. Moving toward reactor design features—
such as high fuel utilization and higher fuel burnup (a measure of how much energy
is extracted from fresh fuel; e.g., deep burn reactor designs are generally ≥
20 percent) and sealed long-life core designs—could significantly reduce such
- Used fuel disposition (the “back end”). Given the institutional
challenges presented by the long-term storage and ultimate disposal of used fuel,
future reactor systems must minimize the amount and toxicity of nuclear waste.
This is an institutional issue, not a short- or intermediate-term safety or
security issue. The use of dry cask storage (typically steel cylinders)—a
proven, safe approach to storing waste—will provide a 60–80 year window
of opportunity in which to conduct a robust, innovative research and development
program on an advanced fuel cycle system.