Nuclear Reactors: Generation to Generation

The Key Reactor Factors

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Stephen M. Goldberg and Robert Rosner
Global Nuclear Future

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:

  1. 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?
  2. 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?
  3. 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?
  4. 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?
  5. 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?
  6. 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.

a. 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 risks.

b. 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.


  • 1Some of the externalities include: (1) remote areas requiring localized power centers to avoid long and expensive transmission lines; (2) geography and demography constraints that are best suited to low- and mid-size urban and power needing areas fairly scattered, rather than concentrated in a few “mega centers” and; (3) financial capabilities that preclude raising the several billions dollars capital investment required by larger plants.