Characterization of pyrocarbon coatings of HTGR fuel particles by inert gas intrusion [electronic resource].

Published: Oak Ridge, Tenn. : Oak Ridge National Laboratory, 1979.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description: Pages: 46 : digital, PDF file
Additional Creators: Oak Ridge National Laboratory and United States. Department of Energy. Office of Scientific and Technical Information

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Summary

Biso fuel particles used in the HTGR have a pyrocarbon coating designed to retain fission gases during reactor operation. The inert gas permeability of the pyrocarbon coating is variable and a measure of it is an important clue to fuel performance. A method was developed to measure the permeability of pyrocarbon coatings by intrusion of light inert gases. The mole quantity of neon and helium entering the fuel particle at elevated temperature (1375/sup 0/C for 1 h) from an equimolar mixture is determined by mass spectrometry after breaking the particle. The ratio of the two gases constitutes a useful measure of the pyrocarbon coating permeability. Activation energies for intrusion of helium, neon, and argon show a sharp increase with atomic number. Pyrocarbon coatings have a measurable permeability for krypton only at very high temperatures and only then in the more permeable coatings. Neutron irradiation reduced the permeability of the pyrocarbon coatings on inert kernels. Neon and helium ratios measured on hundreds of fuel particle batches ranged from 0.03 to greater than 1.0, and we estimate that a pyrocarbon with neon-helium ratio below 0.30 or 0.35 will be gastight under HTGR operating conditions.

Report Numbers

E 1.99:ornl/tm-6819
ornl/tm-6819

Subject(s)

Note

Published through SciTech Connect.
09/01/1979.
"ornl/tm-6819"
Morgan, C.S.

Funding Information

W-7405-ENG-26

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