ORNL-4191 - the Molten Salt Energy Technologies Web Site

I
212
PHOTO 88994
Fig. 17.2. Apparatus for Measuring the Helium Permeability of Graphite Cylinders; It Is Used with a Standord
Leak Detector.
17.3 GAS IMPREGNATION OF MSBR GRAPHITES
H. Beutler
We are exploring the feasibility of impregnating
graphites with pyrocarbon to reduce the permeation
of gaseous fission products into graphite components
of the MSBR core. It has been estimated
that the permeability should be reduced to below
cm2/sec (for helium) to prevent diffusion of
fission products effectively. So far, we have
carried out a number of exploratory experiments
which demonstrate that this objective can be attained
with a gas-phase impregnation technique.
Gas impregnation of graphite for a similar pur-
pose has been studied by Watt et ai. ' They found
that the gas permeability could be effectively re-
duced by passing hydrocarbon vapors
zene) in a nitrogen carrier gas over gr
mens at 1472 to 1652°F. The process relied
entirely on diffusion to carry react
pores, and there was no need for a
entia1 across the specimen. With benzene as a
reactant, temperatures near 1382" F were required
mum penetration. Above 1472OF, a defi-
nite concentration of deposit on or near the surface
'W. Watt et a1 , Nucl Power 4, 86 (1959).