Word: thorium
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...technique the geologists used was based on another sort of radioactive decay. Organisms contain traces of uranium, which degrades into thorium. The rate of decay is known, and by measuring the relative amounts of the two substances in a sample, age can be accurately calculated...
...this case, samples came from a coral reef off Barbados. Carbon 14 and uranium-thorium dating largely agreed for pieces of coral up to about 9,000 years old. But for older pieces the findings diverged, with a maximum disparity of 3,500 years for coral about 20,000 years...
...scientists assume that the uranium-thorium tests were right and the carbon 14 tests wrong? For one thing, the carbon datings pointed to the strange conclusion that ice ages, thought to be related to changes in the earth's orbit around the sun, have mysteriously lagged behind those changes by a few thousand years. But uranium-thorium dating shows no such lag. Moreover, carbon 14 levels in the air -- and thus the amount ingested by organisms -- are known to vary over time, and that can affect the results of carbon dating...
During private talks in the gold-carpeted presidential office in Brasilia's Planalto Palace, both leaders touched only briefly on the issues that divide them. Carter urged Brazilians to consider fueling their nuclear reactors with thorium rather than uranium. Reason: uranium-fueled reactors produce more plutonium that can readily be used in nuclear weapons than thorium-fueled reactors would produce. But Geisel seemed unpersuaded, and Carter did not press the matter. "What would it accomplish?" asked a top White House aide. "Neither side is going to change, so we might as well spend our time discussing things of mutual...
...increase the danger of atomic-weapons proliferation. The Administration also considers the project too costly for current needs. The likely compromise: if Congress abandons the Clinch River project, as Carter wants, the Administration will agree to bankroll another, more advanced, large demonstration breeder that would use "safe" fuels like thorium instead of plutonium...