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epoxy used for bonding was EA500, and the pro-
tective coatings (GageKote Nos. 2 and 5) further
assure their stability. A Budd model P.350 strain
mcnsuring device was used to obtain the strain
values.
The metal was removed by a milling cutter,
This machining process eliminated the need to
reiilove the electrical connections to the strain
gages between readings. Thermal effects were
avoided by submerging the specimen in a cutting
fluid solution that was continuously circulated
during machining. To avoid any errors due to the
holders, eccentric clamping was used in order that
the pressure could be easily relieved before read-
ings were taken.
Currently, we are analyzing the results obtained
from the first welds and checking the reproduci-
bility of results with identically prepared speci-
mens.
We intend to study the residual stress distribu-
tion that results from weld:; made by various proc-
esses and from varying parameters within a given
welding process. We initiated the program with
bead-on-plate welds. The investigation will be
expanded to include the effect of multipass welds
in a V-groove joint configuration. Each weld pass
will be deposited under identical welding param-
eters, thus permitting us to study the influence of
joint geometry.
The metal-arc inert-gas process will also be in-
vestigated in order to study the influence of this
mode of filler metal addition on the residual stress
distribution. The effect of postweld heat treatment
on the residual stress level will also be determined
The completion of this program should allow us to
define the welding process, optimum parameters
within that process, and the correct postweld heat
treatment that will minimize the residua1 stress
level in Hastelloy N.
18.6. CORROSION STUDIES
A. P. Litman
We are continuing to study the compatibility of
structural materials with fuels and coolants of
interest to the Molten-Salt Reactor Program. Nat-
ural-circulation loops are used as the standard
test in these studies.
226
Two loops are presently in operation, Nos. 1255
and 1258. One loop, No. 10, has recently completed
its scheduled circulation time; one loop,
No. 12, prematurely plugged recently; and four new
loops, Nos. 13-16, will start. operation a, = test
salts become available. The latter loops will contain
candidate MSBR fuel, blanket, or coolant
salts. Table 18.3 details the service parameters
of these test units.
Loop 12.55, constructed of Hastelloy N and con-
taining a simulated MSRE fuel salt plus 1 mole %
ThF 4, continues to operate without difficulty after
more than 5.4 years. Loop 1258, constructed of
type 304L stainless steel and containing the same
salt as loop 12.55, has logged 4.1 years' circulation
time with only minor changes in flow character-
istics. To examine the corrosive behavior of the
relatively old simulated fuel salt in this loop, ten
fresh stainless steel specimens were placed in the
hot leg last January. A plot of thc weight change
for the new specimens at the hottest point in the
system and a comparison with earlier data as a
function of time are shown in Fig. 18.11. It is
clear that very rapid attack occurs in the first 50
12
5
_ a
N W
E 4
ORNL-DWG 57~11842 ~-~
DATA FOR SPECIMENS DURING LOOP STfiRT-UP 4964
DfiTfi FOR NCW SPEC'NIFV5 1967
- -' LONE 7 1 rnil/yr UNIFORM ATTACK
--A LONC z mi/yr UNIFORM ATTACK
0
1
1000 2000 3000 4000
TlVE (hr)
Fig. 18.11. Weight Change as a Function of Time for
Type 304L Stainless Steel Specimens Exposed at 1250°F
in Loop 1258 Containing LiG-Bef2-ZrFq.UFq-ThF~ (70-
23-5-1-1 mole %),