Helium Release Behavior of Aged Titanium Tritides Page: 3 of 7
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The Ti used in this experiment was specially manufactured by Ergenics, Inc., and
consisted of large particles of x to y mesh size. The samples were placed in stainless
steel test cells equipped with stainless steel Nupro valves using Cajon VCR connections.
In some cases, the particle size had to be reduced by fracturing the chunks in order to get
the sample to pass through the VCR weld gland. The sample was loaded with a 50/50
mix of D/T isotopes, and allowed to age. At that point the sample was mounted on a
Sievert's apparatus equipped with MKS 10000 torr Baratron pressure sensors for these
studies. Gas grab samples were collected and analyzed for isotope and 3He content at
appropriate points during experimentation. The test cell was not equipped with any
method to directly measure sample temperature internally. Temperature measurement
was accomplished by attaching a Type K thermocouple to the exterior of the cell near
where the Ti was located. Isotope exchange experiments used commercial high-purity
Results and Discussion
The Ti sample was loaded with a 50/50 D/T mix and the final loading (D+T)/M (= Q/M )
was 1.8., where it is assumed that all hydrogen isotopes were eventually absorbed by the
Ti leaving a very low overpressure. After storage for 6.46 years (half-life of T is 12.6
years), the Ti sample was found to have a small amount of gas overpressure which was
analyzed and found to be 100% 3He. The sample then was thermally desorbed and
results are show as a time plot in Figure 1, where two peaks are evident. Three grab
samples were taken during this experiment (indicated by the asterisks in the Figure). The
first was acquired on the early part of the first peak, the second was collected at the
minimum between the peaks, and the third at the very end of the experiment. Mass
spectrometric analysis of the samples showed that the first sample was 1.53% 3He and
98.0% hydrogen isotopes (41.4% T). The second sample was 1.12% 3He and 98.9%
hydrogen isotopes (41.5% T), indicating a slight dilution of the 3He. The third sample
however was 42.3% 3He and 57.2% hydrogen (41.5% T), which defines the second peak
as being due to 3He evolution. Initial He/M ratio was 0.28, and the location of the He
peak maximum is roughly consistent with , where a 30 at% He content produced an
initial peak at ~850K and a 22 at% He content produced an initial peak at ~1050K. Gas
evolution was still increasing when the temperature stabilized at -923K, the upper limit
for that run.
The sample was isolated at that point and the small residual hydrogen isotopes found in
the -25cc test cell gas space were allowed to reabsorb. Subsequently a second thermal
desorption was undertaken, with very little pressure being developed, with 28.2% being
3He. Computations based on the calibrated system volumes, temperatures, and pressures
indicated that the He/Pd ratio had decreased from 0.28 to 0.05 in the first desorption. The
second desorption further released approximately 0.005 He/Pd units, but that number is
the approximate experimental error. Final Q/Ti ratio was computed to be 0.97. The
sample was reloaded with deuterium and desorbed. The third desorption was computed
to reduce to He/Ti ratio to approximately zero, but some small amounts of He were still
observed in the next (fourth) desorption's offgas.
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SHANAHAN, KIRKL. Helium Release Behavior of Aged Titanium Tritides, article, July 27, 2004; South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc785112/m1/3/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.