Antinuclear

Australian news, and some related international items

Thorium nuclear reactors pose the same weapons proliferation and safety problems, and mining pollution problems – as uranium nuclear reactors.

Is the thorium-fueled “Molten Salt reactor a proven technology?

The first thorium-fueled molten salt reactor ever built was intended to power an aircraft engine in a long-range strategic bomber armed with nuclear weapons. Despite massive expenditures, the project proved unviable as well as prohibitively costly and was ultimately cancelled by President Kennedy. However, the Oak Ridge team responsible for the aircraft engine reactor project, under the direction of Alvin Weinberg, was allowed to conduct a further thorium-fuelled molten salt reactor experiment for a period of four years, from 1965 to 1969. At the beginning, only U-235 was used; soon afterwards, a smaller amount of U-233 was used.

During its four years of operation under experimental conditions, the Oak Ridge molten salt reactor experienced over 250 shutdowns, most of them completely unplanned.  The molten-salt thorium fuelled experience of 52 years ago at Oak Ridge – the only such experience available to date – consumed about one quarter of the total budget of the entire Oak Ridge nuclear complex. It is difficult to understand how anyone could construe this experiment as demonstrating that such a technology would be viable in a commercial environment.

There are, at the present time, no thorium reactors operating anywhere in the world.

Summary (Thorium Reactors)

It appears that thorium-fuelled reactors pose the same kinds of problems, qualitatively speaking, that afflict existing nuclear reactors. Problems associated with the long-term management of nuclear waste, and the potential for proliferating nuclear weapons, are not fundamentally different even though the detailed considerations are by no means identical.

Since a nuclear reactor accident will have off-site consequences only due to the unintended release of high-level nuclear waste materials into the environment, there is no qualitative difference there either.  Thorium reactors pose the same risk of reactor accident risks as in the case of a comparable non-thorium reactor.

The “Front End” of the Nuclear Fuel Chain

So much for the “back end” of the fuel chain, but what about the “front end”? What about the dangers and environmental consequences associated with mining a radioactive ore body to obtain the uranium or thorium needed to sustain a uranium-based or thorium-based reactor system?

Thorium versus Uranium

Uranium and thorium are naturally occurring heavy metals, both discovered a couple of centuries ago. Uranium was identified in 1789. It was named after the planet Uranus, that was discovered just 8 years earlier. Thorium was identified in 1828. It was named after Thor, the Norse god of thunder.

In 1896, Henri Becquerel accidentally discovered radioactivity. He found that rocks containing either uranium or thorium give off a kind of invisible penetrating light (gamma radiation) that can expose photographic plates even if they are wrapped in thick black paper.

In 1898, Marie Curie discovered that when uranium ore is crushed and the uranium itself is extracted, it is indeed found to be a radioactive substance, but the crushed rock contains much more radioactivity (5 to 7 times more) than the uranium itself. She identified two new elements in the crushed rock, radium and polonium – both radioactive and highly dangerous – and won two Nobel Prizes, one in Physics and one in Chemistry. 

The radioactive properties of both radium and thorium were used in medical treatments prior to the discovery of fission in 1939. Because of the extraordinary damage done to living tissues by atomic radiation (a fact that was observed before the advent of the twentieth century) these radioactive materials derived from natural sources were used to shrink cancerous tumours and to destroy ringworm infections in the scalps of young children. It was later observed that while acute doses of atomic radiation can indeed kill malignant as well as benign growths, atomic radiation can also cause latent cancers that will not appear until decades later, even at chronic low dose radiation levels that cause no immediately perceptible biological damage.

Uranium Mining and Mill Tailings

It turns out that 85 percent of the radioactivity in uranium ore is found in the pulverized residues after uranium is extracted, as a result of many natural radioactive byproducts of uranium called “decay products” or “progeny” that are left behind. They include radioactive isotopes of lead, bismuth, polonium, radium, radon gas, and others. Uranium mining is dangerous mainly because of the harmful effects of these radioactive byproducts, which are invariably discarded in the voluminous sand-like tailings left over from milling the ore. All of these radioactive decay products are much more radioactive and much more biologically damaging than uranium itself.

Thorium Mining and Mill Tailings

Thorium is estimated to be about three to four times more plentiful than uranium. Like uranium, it also produces radioactive “decay products” or “progeny” – including additional radioactive isotopes of lead, bismuth, polonium, radium, radon gas, thallium, and others. These radioactive byproducts are discarded in the mill tailings when thorium ore is milled. See

www.ccnr.org/Th-232_decay_chain.png .

Most of the naturally-occurring radioactivity found in the soil and rocks of planet Earth are due to the two primordial radioactive elements, uranium and thorium, and their many decay products. There is one additional primordial radioactive element, potassium-40, but it has no radioactive decay products and so contributes much less to the natural radioactive inventory.

Gordon Edwards.

P.S. I have written about thorium as a nuclear fuel several times before, beginning in 1978.

See www.ccnr.org/AECL_plute.html  ;  www.ccnr.org/aecl_plute_seminar.html ;

www.ccnr.org/think_about_thorium.pdf ;  and  www.ccnr.org/Thorium_Reactors.html

December 27, 2021 - Posted by | Uncategorized

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