Clean and Environmentally Safe Advanced Reactor
The Clean And Environmentally Safe Advanced Reactor (CAESAR) is a nuclear reactor concept that uses steam as a moderator. Steam's density can be controlled very finely so, according to it's developer Dr. Claudio Filippone, it can be used to fine tune neutron fluxes to ensure that neutrons are moving with an optimal neutron energy profile to split 238U92 nuclei.
The CAESAR reactor design exploits the fact that the fission products and daughter isotopes produced via nuclear reactions also decay to produce additional delayed neutrons. Unlike in conventional fission reactors, where fission occurring in enriched 235U fuel rods moderated by liquid water coolant releases a Maxwellian thermal neutron flux profile, the neutron energy profile from delayed neutrons varies widely. In a conventional reactor, the moderator slows these neutrons down so that they cannot contribute to the 238U reaction; 238U has a comparatively large cross-section for neutrons at high energies.
Dr. Filippone maintains that when steam is used as the moderator, the average neutron speed/energy is increased from that of a liquid water moderated reactor and the delayed neutrons keep going until they hit another nucleus. He claims that the resulting extremely high neutron economy will make it possible to maintain a self-sustaining reaction in fuel rods of pure 238U, once the reactor has been started by enriched fuel.
Skeptics, however point out that it is generally believed that a chain reaction is not possible with 238U. It does undergo induced fission when impacted by an energetic neutron with over 1 MeV of kinetic energy. But the neutrons produced by 238U fission are not, themselves, energetic enough to induce further fissions in 238U. Instead, bombarding 238U with slow neutrons causes it to absorb them (becoming 239U) and decay by beta emission to 239Pu (which is itself fissionable).
The CAESAR Project is headed by Dr. Filippone, who is a nuclear scientist and the Director of the Center for Advanced Energy Concepts at the University of Maryland, College Park.
External links
- The Clean And Environmentally Safe Advanced Reactor (CAESAR) Project
- Hail, Caesar Economist article
- Putting Nuclear Waste to Work Popular Mechanics article from 1998 describing a related reactor design (NPTRE) proposed by Dr. Filippone.
- A Second Caesar to Change the Course of History? Article from University of Maryland newsletter.