PLENTIFUL ENERGY

inferior to sodium in their thermal/hydraulic properties. Sodium‘s compatibility
with the metals of reactor structures and components is important too, and is a
characteristic not shared by lead and lead alloys. Radioactive corrosion products are
not formed in any significant amount, radiation exposures to plant personnel are
very low, and access for maintenance is easy. Sodium reaction with air or water, its
principal disadvantage, can be easily handled by proper design. Sodium leaks,
principally in the non-radioactive secondary systems but occasionally in the steam
generator systems, in the first-generation demonstration plants were handled as a
practical matter without much difficulty. Easily detected, the resulting smoke or
flame can be extinguished without significant consequences. Major problems
resulted in only one case—the Japanese demonstration plant, MONJU, where antinuclear
campaigning and related political matters extended the shutdown
interminably after the relatively minor cleanup.
We then went on to look at the physics principles underlying breeding, showing
the principles involved in practical design for high breeding. The possible breeding
characteristics of the world‘s principal reactor types were shown. Then,
concentrating on IFR design itself, we showed that fuel pin diameter is the
important variable in determining breeding, in the core, and with this, the way the
thermal, hydraulic and mechanical constraints must be accommodated. Finally, we
discussed the tradeoffs that enter in further balancing the requirements for an
optimum design.
We then turned to the experience with fast reactor development in the past and
examine the various problems and difficulties. Operational experience with fast
reactors has generally been with first-of-a-kind demonstrations in each country as
each took its own path. There have been a variety of difficulties. As with any other
reactor type, or for that matter with any engineered system, there were design
mistakes, component failures, sodium leaks and fires, partial core meltdowns, and
so on.
We contrasted that experience with the thirty years of operation of EBR-II,
which after a few-year initial shakedown period, were faultless. Remarkably easy
operation and its flexibility in carrying out the multitude of experiments it did over
the years attest to its insightful design. For all those years EBR-II acted as a pilot
demonstration of today‘s IFR technology. It could have gone operating indefinitely,
and it provides concrete evidence of the very high level of reliability,
maintainability, operability, and longevity inherent in IFR technology. A sodiumcooled
fast reactor designed along the lines of EBR-II—pool, metallic fuel—can be
a simple, forgiving system, avoiding complexity, and avoiding layers of safety
systems. The operational success of EBR-II clarified the design features that will be
important and desirable in future plants.
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