ORNL-1771 - Oak Ridge National Laboratory

ANP QUr4RTERLY PROGRESS REPORT
Additional irradiations of lnconel capsules con-
taining fluoride fuels were carried out in the MTR.
Only one capsule containing a UF3-bearing fuel
has been examined, and it shows no corrosion.
This is in contrast to the capsules containing
UF,-benring fuel in which minor increases in
penetration have at times been observed in the
irradiated specimens as compared with the out-of-
pile controls. However, it should be eniiphasized
that even in the UF4-bearing capsules, the ap-
pearance of small deviations from the controls
could be due to experimental difficulties,
Inspection of the previously described LlTR in-
pile circulating-fuel loop, which failed prior to the
startup, disclosed that the failure was caused by a
break in the weld connecting the pump discharge
nipple to the fuel line. Design revisions and
refabrication of some components are in progress.
Developmental work continued on a smaller loop
for operation in an LlTR A-piece. Work on a loop
for insertion in the MTR is described in Sec. 3,
I 1
Experimenta I Reactor Engineering. ”
Development of equipment continued for in-pile
stress-corrosion tests on lnconel in contact with
fluoride mixtures, and testing of the MTR tensile-
creep rig neared completion. Detailed examination
was completed of an lnconel loop in which sodium
was circulated at high temperature in the ORNL
Graphite Reactor, and no evidence of radiation-
induced corrosion was found in the Inconel.
Metal lographic examinntions were carried out in
the hot cells on irradiated fuel plates for the
Prutt & Vhitney Aircraft Division, and studies were
made on anneal ing-out of fiss ion-fragment dorncsge.
Work continued on examination of wire and multiple-
plate type units for GE-ANP.
MfR STATIC CORROSION TESTS
W. E. Browning G. W. Keilholtz
Solid State Division
A new series of capsules was irradiated in the
MTR to compare NaF-ZrF, fuels containing LJF,
with those containing WF,. The property to be
compared is the effect of fission on static eor-
134
J. B. Tricc
Solid State Division
A. J. Miller
ANI‘ Proiect
rosion of lnconel by the fuels at 1500OF. The
series includes five capsules containing 1.79
mole 76 UF,, 49.3 mole % ZrF,, and 48.9 mole %
NirF and five capsules containing 1.74 mole %
UF, 48.2 mole % ZrF,, and 50.1 mole 96 NaF.
Analyses are being run to confirm the purity of the
UF, with respect to UF, contamination. For
every capsule, there will be an out-of-pile control
capsule. Each fuel generates 1100 w/cm3 in the
A-38 position in the MTR.
Six capsules have been irradiated for the speci-
fied two-week period. Five have been received
at ORNL after irradiation; three of them have been
opened and two have been examined -- one con-
taining UF, and one containing UF,. Both capsules
had been irradiated with the metal-liquid interface
at 1500 k SOOF. The UF3-bearing capsule had
experienced one temperature excursion to 1660 t
5OoF for less than 30 sec, but the temperature of
the UF,-beariiig capsule never exceeded 1550 5
50‘F. The fuel in each capsule was frozen two or
three times during its history. No evidence of
corrosion or film could $e seen in the UF,-bearing
Inconel capsule, There was subsurface void
formation in the UF4-bearing lnconel capsule to a
depth of about 2 mils. No intergranular corrosion
or concentration of voids at the grain boundaries
wos evident.
Analytical samples of the irradiated fuel were
taken with two sizes of drills. Theuranium concen-
trations in the central and outer samples were
identical, within experimental error (13%), and were
of the value expected after burnup correction.
Analyses for iron, chromium, and nickel gave the
following results: Fe, 0.03 to 0.14 wt %; Ni, 0.01
to 0.05 wt %; Cr, less than IOe4 wt %. There were
no significant differences in the final iron, nickel,
and chromium compositions between the two cap-
sules. Analyses of the unirradiated fuels have
not been completed.
It would be unwise to draw conclusions on the
basis of only one pair of samples; however, if
these first results arc confirmed in future capsules,
[IF, fuels may be considered quite desirable as
far as radiation-indiiced corrosion is concerned.