ORNL-2106 - the Molten Salt Energy Technologies Web Site

ANP PROJECT PROGRESS REPORT
Fig. 3.2.1. Specimens of lnconel Joints Brazed with the 70% Ni-13% Ge-11% Crd% Si Brazing Alloy
and Exposed for 500 hr to the Fuel Mixture (No. 44) NaF-ZrF,-UF, (53.5-40-6.5 mole se) in the Hot Leg
of an lnconel Thermal-Convection Loop. (a) Joint located in coolest (145OOF) portion of hot leg. (b)
I
Joint located in hottest (1500OF) portion of hot leg. Etched with 10% oxalic acid: 150X. Reduced 19%.
was found in the cold leg of the loop that circu-
lated the fuel mixture. Spectrographic analyses
of these crystals showed strong lines for chromium
and nickel and weak lines for iron. There was
no evidence of mass transfer in the loop that
circulated NaK.
The brazing alloy showed good corrosion resist-
ance to NaK, as shown in Fig. 3.2.2, but large
cracks which extended to a depth of one-half the
tube wall thickness were found in some of the
brazed joints, Fig. 3.2.3. It is not known whether
these cracks were caused by thermal stresses or
shrinkage. Analysis of the NaK after the test
showed 1160 ppm of oxygen. This is admittedly
high, but no efforts were made to purify the NaK
which was received in container lots.
A third lnconel thermal-convection loop was
operated for 500 hr in which the hot leg contained
lnconel inserts brazed with the 82% Au-18% Ni
brazing alloy. The fluid circulated was the fuel
mixture (No. 30) NaF-ZrF,-UF, (50-46-4 mole %).
The hot and cold legs were maintained at tempera-
tures of 1500 and 1175OF, respectively. Micro-
142
scopic examination of samples from each brazed
joint showed the attack on the QIIOY to average
about 8 mils, with a maximum depth of 10 mils.
Tests were also conducted on a series of buttons
of Coast Metals brazing alloy No. 52 (89% Ni-
5% Si-4% 8-294 Fe), which were exposed in see-
saw apparatus to NaK (56-44 wt %) and to the
fuel mixture (No. 44) NaF-ZrF,-UF, (53.5-40-6.5
mole %). Since previous tests of this alloy showed
depletion of the second phase at the exposed
edge,l these tests were conducted to determine
whether the high-cross-section boron component
was removed and, if so, whether the removal was
time dependent. The buttons were contained in
nickel tubes with hot-zone temperatures of 1500OF
for both tests and with cold-zone temperatures of
llOO°F in the tests with NaK and 120OOF in the
tests with the fuel mixture. In a11 the tests, the
specimens were retained in the hot zone of the
test capsule. The duration of the exposures to
lD. H. Jansen. ANP Qum. Prog. Rep. Dec. 10, 1955.
ORNL-2012, p 119. Fig. 5.17.