ORNL-4191 - the Molten Salt Energy Technologies Web Site

17.1 MATERIALS PROCURE
ANDPROPERTY EVALUATION
wl. H. Cook
The procurement and evaluation of potential
grades of graphite for the MSBR remain largely
limited to experimental grades of graphite. Generally,
most of these were not fabricated specifically
for MSBR requirements. Consequently, they
tend to have pore entrance diameters larger than
the specified 1 /L and gas permeabiliti-es greater
than the desired cm2/sec €or helium. Other
properties are reasonably good. The latest graphites,
discussed below, fall into these classifications.
Precursory examinations of five experimental and
two specialty grades of isotropic graphite have
been made using 0.125-in.-diam by l.OOO-in.-long
specimens machined from stock and tested in a
mercury porosimeter. 'The pore entrance diameter
distributions are suinmarized in Fig. 17.1. The insets
on each plot give the grade designation, the
bulk density, and accessible porosity of the specimens
tested. The data indicate trends rather than
absolute values for each grade.
Grades .4XT;-SQBG and H-315A are the specialty
grades, and the others are experimental grades.
Grade AXF-5QHG is an impregnated version of
grade AXF (previous designation, EP-1924), which
looked promising in previous tests in that the entrance
diameters of most pores were less than 1 p.
The specimens for giade AXF-SQ'CX, 1-1, and
16-1 (Fig. 17.1) were taken perpendicular and specimens
1.-4 and 16-4 were taken parallel with the
4 x 6 in. plane of two different plates, each 1'; x
4 x 6 in. Individual results on these were plotted
to show the variations of properties. The pore
...................
'W. 11, Cook, MSR Program Semiann Pro& Hept. Feb.
28, 1967, ORNL-4119, pp~ 108-10.
208
sizes of the impregnated materials vary more than
those of the base stock but are around the 1-/L size
sought. It would be desirable for the pore entrance
diameters to be smaller and more uniformly distributed.
The impregnation of the base stock reduced
its accessible porosity approxiinately 30%.
The experimental grade H17-'1'174 has a pore
distribution similar to that of grade AXF-SQBG.
Grades II-335, -336, -337, and -338 were small
samples of isotropic graphite that had been impregnated
and the impregnate graphitized. Grade
H-315A was the base stock impregnated to make
grade €3-335. The similar pore size distributions
of H-315A and H-335 illustrate again the wellknown
fact that graphite with pore entrance diameters
greater than 1 p is not changed much by conventional
iinpregnatjon techniques. 2.3 The plot
for II-315A is an average of measurements on four
specimens machined from different locations of a
4' 1i1 ,-in.-OD x 3'/,-in.-IU x 11'2-in. pipe section;
the uniformity of the spectrum of pore entrance
diameters was good.
'The three materials H-336, -337, and -338 appear
to have been made from base stocks with pore
spectra similar to that of H-315A. The accessible
porosities measured for H-337 and -338 are relatively
low for the small size of test specimens.
used .
Some mechanical properties, specific resistivities,
and gas perrneabilities ai2 given in Table
17.1 for H-315A and -335 through -338. The mzchanical
properties and specific resistivities of
these grades are satisfactory for MSHR graphite.
The gas permeabilities are high relative to those
sought but seem to be typical for grades of graphite
2W. P. Eatherly et al., Proc. U.N. Intern. Conf.
Peaceful Uses At. Energy, 2nd, Geneva. 1958 7, 389.-
401 (1958).
3W. Watt, R. L. Bickerman, and L, W. Graham, Engi-
neering 189, 110-1 1 (January 1960).