Vol.1 - 1 Review
Summary of Studied of Tritium at Toyama University (1956~1981)
Toyasaburo TAKEUCHI
Tritium Research Center, Toyama University Gofuku 3190, Toyama 930, JAPAN
(Received February 24, 1982)
Abstract
The chemical studies of tritium have been continued for 25 years
at the laboratory of physical chemistry Toyama University, since the first
supply of tritium from AERE in 1956. The initial study on tritium was to
establish the measurement of β-ray of tritium by the modification of 2π
counter. Then the isotope effect of tritium for the desorption from nickel
powder was investigated at -183℃ and 120℃. The study was then followed
by the elucidation of the reactivity of adsorption hydrogen on nickel for
the hydrogenation reaction of ethylene adapting the differential isotope
kinetic method.
The simultaneous measurement of tritium and
radioactive carbon 14C was investigated by means of a gas proportional
counter using the energy spectrum of these isotopes. A mixture of tritium
and
14C-carbon dioxide was used as the sample. Two types of
counter tubes of different diameter sizes and two kinds of filling gas,
methane and buthane, were used. It was advantageous for the distinction
between the energy spectrum of tritium and 14C that maximum
range of the β-rays of tritium was shorter than the diameter of the counter
tube. The amounts of both isotopes in the mixed gas could be determined
with an error of 5%, when methane was used as the filling gas and with
in 3% when buthane was used.
The effect of the α-particle irradiation
on the adsorption of tritium on nickel plate and on nickel film prepared
by evaporation was investigated. The change in the amount of adsorbed tritium
was detected by means of autoradiography. The irradiation of α-particles
increased in the case of the nickel plate, but decreased in the case of
the evaporated film. These results were interpreted in terms of the change
in the active sites made of lattice imperfections. The similar studies
were carried out on copper, nickel, and copper-nickel alloys employing
massive metals and evaporated films formed on glass. The results showed
that not only the amount of adsorption of tritium but also the reactivity
of the adsorbed tritium for ethylene were strongly influenced by the irradiation
of α-particles, especially in the range of alloy composition.
The effects of lattice imperfections produced
by 6Li(n,α)3H reaction upon the catalytic activities
in the hydrogenation reaction of ethylene on powdered copper, nickel, and
copper-nickel alloys, which had previously been doped with lithium and
irradiated with thermal neutrons were investigated. In addition, the amount
of tritium taken from these powder was measured by placing it in contact
with normal hydrogen and raising temperature of the powder. The irradiation
of neutrons increased the activities of nickel and copper-nickel by 3-4
times, but did not affect the activity of copper. The dependence of the
amount of tritium upon the composition of the powder was very similar to
that of the catalytic activity, suggesting that the diffusion of tritium
from the interior is the rate-determining step.
The behavior of tritium produced by 6Li(n,α)3H
reaction in the catalytic hydrogenation of ethylene was investigated by
autoradiographs using copper, nickel and copper-nickel alloy plates. These
plates were preliminarily covered with lithium by evaporation and irradiated
with neutrons. The autoradiogrphs given by the striping-film method indicated
that the grain boundaries which were not used in the catalytic reaction
exhibited a much stronger radioactivity due to the tritium than did the
grain; on the other hand, these which were used in the catalytic reaction
behaved in just the opposite way. The electron-microscope autoradiographs
indicated that tritium accumulated preferentially on the step edges of
the slip-band of the crystal. The electron micrographs indicated numerous
micro-holes which would correspond “depleted zone”, an unstable intermediate
stage in the formation of displacement spikes and thermal spikes.
The chemical behavior of dissolved tritium
in iron, copper, and iron-copper sheets in the Fisher-Tropsch reaction
was investigated. The amount of preadsorbed tritium on the surface of iron
and iron-copper sheets markedly increased, about 10 times, due to the addition
of carbon monoxide to the surface. The dissolution of tritium in these
sheets prevented by preadsorbed carbon monoxide.
The ability of trapping of tritium by silica
and alumina which were preliminarily doped with lithium and irradiated
with thermal neutrons and the removal of tritium from these materials by
the reaction with ethylene were investigated. Tritium formed in alumina
was not liberated by the elevation of temperature to 350℃. Tritium in
silica was very slightly liberated at above 250℃. Tritium in silica removed
in the form of tritiated ethane at 300℃ and that in alumina at 100℃.
The doping of 10℃ nickel to alumina and silica promoted the liberation
of tritium gas and the formation of tritiated compounds.
The enrichment of tritium in water by means
of the reaction of tritiated water with Raney-Ni alloy was investigated.
Tritiated water was contacted with the alloy in the presence of sodium
hydroxide, then the temperature was stepwisely raised to 1000℃. It was
found that the concentration of tritium in hydrogen gas released from the
sample was very low at the temperature range from 20℃ to 300℃, and that
hydrogen gas contains 6 times higher level tritium was generated at about
600℃
.