GENEVA - It's high time for the nuclear industry to overhaul its conventional technology and shift to radically different reactor designs based on thorium fuel, a Nobel Prize winning physicist said.
Carlo Rubbia, a former director of the CERN laboratory who shared the 1984 Nobel Prize in Physics, described thorium as having "absolute pre-eminence" over all other fuels including fossil fuels and uranium, the metallic element that has driven reactors since nuclear first started powering public grids in 1956.
"In order to be vigorously continued, nuclear power must be profoundly modified," Rubbia said at the Thorium Energy Conference 2013, held on the CERN campus here last week.
Rubbia pointed out that thorium leaves less long-lived waste than uranium, is far more plentiful and is resistant to weapons proliferation, as I reported on my Weinberg blog. He also noted that thorium is effective at safely breeding more fuel, and that it has a much higher energy content than uranium or fossil fuels (see chart below), a characteristic that he said gives it "absolute pre-eminence...as a source of energy."
Proponents of thorium disagree over the reactor technology that is best suited to optimize its characteristics. Unlike uranium, thorium is not "fissile," so it needs to be coaxed into a reaction.
Rubbia, a particle physicist, favors a method that would bombard thorium with neutrons freed from a source hit by protons from a particle accelerator. Advocates of that approach claim it is highly safe because the thorium would not sustain a chain reaction and operators could stop the reactions by simply switching off the accelerator. Operators could also vary a reactors' energy output by modifying the particle beam.
Critics say that the accelerator method - Rubbia invented one called the "energy amplifier" - is too unwieldy and unreliable.
Other experts prefer mixing thorium with a starter of uranium isotopes to kick off chain reactions, in alternative reactor designs such as molten salt reactors (MSRs) and pebble bed reactors (PBRs). Still others, such as Norway's Thor Energy, prefer putting thorium into conventional reactors. Some nuclear scientists believe that alternative reactors like MSRs, PBRs and another type called a fast reactor could offer significant advantages over conventional reactors even if they run uranium.
Thorium's supporters include former United Nations chief weapons inspector Hans Blix, who also spoke at the conference, praising thorium's proliferation reduction.
Rubbia, the particle physicist, said that thorium could help reverse nuclear's tarnished image in a post-Fukushima world, and that the planet will need it as a low carbon energy source - a job often ascribed to renewables like wind and solar.
"A distinction between renewable and not renewable energy is academic," he said.
Rubbia shared his 1984 Nobel Prize with Simon van der Meer for discovering the W and Z bosons. He currently works with the Gran Sasso National Laboratory in Italy and with the Institute for Advanced Sustainability Studies in Potsdam, Germany. He previously ran ENEA, an Italian energy and technology agency where he promoted solar thermal power.
Italy's President Giorgio Napolitano recently named Rubbia as a senator for life.
Photo of Carlo Rubbia is by Mark Halper
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