  We present a high-resolution spectroscopic analysis of the bright (V=11.7),
extreme halo giant CS31082-001 ([Fe/H] = -2.9), obtained in an ESO-VLT Large
Programme dedicated to very metal-poor stars. We find CS31082-001 to be
extremely rich in r-process elements, comparable in this respect only to the
similarly metal-poor, but carbon-enriched, giant CS22892-052. As a result of
the extreme overabundance of the heaviest r-process elements, and negligible
blending from CH and CN molecular lines, a reliable measurement is obtained of
the U II line at 386 nm, for the first time in a halo star, along with numerous
lines of Th II, as well as lines of 25 other r-process elements. Abundance
estimates for a total of 43 elements are reported in CS31082-001, almost half
of the entire periodic table. All elements with 56 \leq Z \leq 72 follow the
Solar r-element pattern, reduced by about 1.25 dex ([r/Fe]=+1.7 dex, a factor
50). Pb, in contrast, seems to be below the shifted Solar r-process
distribution, possibly indicating an error in the latter, while thorium is more
enhanced than the lighter nuclides. Thus, while a universal production ratio
for the r-process elements seems to hold in the interval 56 \leq Z \leq 72, it
breaks down in the actinide region. When available, the U/Th is thus preferable
to Th/Eu for radioactive dating: (i) because of its faster decay rate and
smaller sensitivity to observational errors, and (ii) because the inital
production ratio of the neighboring nuclides 238U and 232Th is more robustly
predicted than the 151Eu/232Th ratio. Our current best estimate for the age of
CS31082-001 is 14.0+/-2.4 Gyr.
