Helium/solid powder O-ring leakage correlation experiments using a radiotracer Page: 3 of 7
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-2-
detection. Figure 1 shows a typical test fixture, further described in
Reference 1. The primary 0-ring seal (supplied by PNC) is the only barrier
between the central chamber and the test cavity. The valves, filters and
other plumbing connect with either the central chamber or test cavity and
are used for measuring pretest He leak rates, controlling pressure, intro-
duction of tracer to the central chamber and for post-test sampling of the
test cavity.
Tracer
The previous experiments used depleted U02 powder, > 95 % by count 0.2
to 2.0 pm. diameter, as a surrogate for the PNC mixed oxide fuel powder
(nominal size 2 to 3 pm). The experiments reported here use the same
U02 powder neutron activated by reactor irradiation to convert a small
fraction of the 238U atoms to 239Np (t1/2 = 2.35 days) by the reaction
238 239 _ S~ 239 ~ 239
U(ny) Ut/2 23.5 min. Np t1/2 = 2.35 days Pu...
The 239Np produced is trapped in the U02 particles and is a radioactive tag
for the U02. Each test used 1 gram of U02 activated to a 239Np activity
of 1 x 108 to 2 x 108 Bq.
Test Routine
Each fixture has its He leak rate measured and is then taken to the test
temperature. The U02 holder, isolated by valves V7 and V8, is removed,
filled with tracer and reinstalled. The test is started by opening valve
V8 and then V7 to introduce tracer and He (at test pressure) to the
previously evacuated central chamber. A vibrator agitates the fixture
during the test and thermocouples monitor temperature.
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Bild, R. W.; Leisher, W. B.; Weissman, S. H. & Seya, M. Helium/solid powder O-ring leakage correlation experiments using a radiotracer, report, January 1, 1984; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1053334/m1/3/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.