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Merging Two Technologies (file A09)

by Ludwik Kowalski, Sylvie Leray and David Whittal

According to (9) the idea of using spallation neutrons for fabrication of 239Pu from 238U was explored in the USA as early as 1949 but the project was abandoned several years later and the Savannah River reactor was used to accomplish the task. This was during the Cold War period and the purpose was to produce, rather than to destroy, plutonium. Similar ideas emerged in 1952 in Canada (10). The Canadian proposal eventually led to a suggestion that heat produced in a target could be collected and used to generate electricity (11). The next step along this line of reasoning was to combine a target with a reactor where heat and neutrons are utilized to maximize the output. One proposal of that kind, the project PHOENIX, was developed at Brookhaven National Laboratory (12).

More recent proposals are also based on the idea that reactors and accelerators should work together as matched hybrid systems but each proposal offers a unique innovative way of accomplishing the task. New hybrid systems are now being promoted in the Los Alamos National Laboratory, USA (13,14), CERN, Switzerland (15,16,17) and in Japan's Atomic Energy Research Institute (18,19). The European Organization for Nuclear Research, known by its French acronym, CERN, is a large international center whose main mission has always been fundamental research based on large accelerators. In 1993 one of its leading scientists, the Nobel Prize Laureate Carlo Rubbia, decided to focus his efforts on a practically oriented mission. A group of accelerator and reactor experts, from several European countries, work with him on that project.

Powerful accelerators of protons (nominally 1000 MeV and 100 mA) will have to be designed to drive large hybrid systems. An existing low current accelerator (providing protons between 200 and 1600 MeV) is now being used at the Laboratoire National Saturne, France, to measure the probabilities of production of spallation neutrons in various materials (20). These data will be needed to design reliable computer simulation codes for the optimalization of hybrid systems. Several other investigatory experiments are currently conducted to collect data on various aspects of new technology. For the time being each team of designers wants to build a small scale system and to show that its performance agrees with what was anticipated. Only then can they ask for the large financial investments necessary to build industrial devices. The projects are being discussed and are often modified to accommodate new ideas. One such idea is to use thorium, rather than uranium, is a source of blanket fuel. The advantages of thorium are outlined in the appendix. The accelerator-reactor technology, existing only in the form of proposals, may become reality in the near future.

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