HRE (Homogeneous Reactor Experiments)


We think of Nuclear Reactors as being extremely complex and difficult to control devices. It must be remembered that there are over 900 possible nuclear reactors! Of the 900 possiblities, we use primarily 2; Boiling Water Reactors (BWRs) and Pressurized Water Reactors (PWRs), which are examples of "Hetrogenous" reactors; the fuel and moderator/coolant are separate and fixed. The HRE was a scaled up version of Los Alamos National Laboratory's (LANL) LOPO and SUPO Aqueous Homogeneous Reactors built at Oak Ridge National Laboratory (ORNL).

Aqueous Homogenous Reactors are what their name suggests; water in which soluble nuclear salts (usually uranium sulfate or uranium nitrate) have been dissolved in water. Thus the fuel is also the coolant and the moderator, thus the name "Homogenous" ('mixed together') The water can be either "Heavy Water" (water enriched in naturally occuring deuterium [the second isotope of hydrogen, with 1 proton & 2 neutrons]; a deuteron occurs in 1 out of 6400 atoms of hydrogen.) or ordinary water, both which are very pure. A heavy water aquous homogenous reactor can achieve criticality (turn on) with ordinary, un-enriched uranium dissolved as uranium sulfate! Thus, no enrichment is needed for this reactor, as is also the case with the first graphite reactors (the "graphite piles" - you can go visit the oldest remaining Graphite Reactor which was used during World War II to produce the plutonium at Oak Ridge National Laboratory, near Knoxville, Tennesse, USA. It has been declared a "National Historical Site" & is open to the public.).

Aqueous Homogenous reactors, sometimes also called "Water Boilers", as they seemed to be boiling their water, but the bubbles coming out are hydrogen and oxygen as the radiation, and especially the fission particles, rip apart (dissociate) the water into its constituent gases, were widely used as research reactors as they have very high neutron fluxes and their safety and ease of control (they were self-controlling!) were added pluses. Corrosion is their biggest problem, especially at high temperatures.

Their most interesting feature to me is the Heavy Water versions have the lowest specific fuel requirements (least amount of nuclear fuel is required to start them;). Even in ordinary water versions less than 1 pound (454 grams) of Plutonium-239 or Uranium-233 is needed for operation! Neutron economy in the heavy water versions is the highest of all reactors. Their self-controlling features and ability to handle very large increases in reactivity {e.g., the 'Kinetic Energy Experiments' at Santa Susana, California where they took high value control rods, ~19 dollars worth, & flung them out as fast as a big spring could (milliseconds!). Energy output shot up from ~100 watts to over 1000000 million with NO PROBLEMS!} make them unique among reactors, and possibly the safest. Should methods and/or materials be developed to solve their difficult corrosion problems, they would be excellent breeders of Uranium-233 fuels from Thorium, and also be incapable of net, or bomb grade, plutonium production.

Oak Ridge National Laboratory (ORNL) account of their work on Aqueous Homogenous Reactors {see the section, " HOMOGENEOUS REACTOR".



Copyright © Bruce Hoglund, 1997

The above was written and created by Bruce Hoglund <>, © 1997

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