ORNL-4191 - the Molten Salt Energy Technologies Web Site

Our materials program has been concerned both
with the operation of the MSRE and with the de-
velopment of materials for an advanced MSBR.
'The primary role of the materials program in the
operation of the MSRE has been a surveillance
program in which we follow the property changes of
the MSRE graphite and Hastelloy N as the reactor
operates, We have surveillance facilities in the re-
actor core and on the outside of the core tank.
The successful operation of the MSRE has
strengthened our confidence in the molten-salt re-
16. AA
16.1 GENERAL DESCRIPTION OF THE
SURVEILLANCE FACILITY AND
OBSERVATlONS ON SAMPLES REMOVED
W. H. Cook
terial t
H. E. McCoy J. R. Weir
The effects of the operational environments of the
MSKE on its unclad moderator of grade CGB graphite
and its structural alloy of Hastelloy N continue
to be monitored periodically with surveillance specimens
of these materials. The surveillance assembly,
the general sampling schedule, and the examination
program have been described previously.
The second group of reactor core specimens,
stringer RS2, has been removed from the core after
accumulating peak fast- (E > 0.18 MeV) and thermalneutron
doses of approximately 1 x loz1 and 4 x
lo2 neutrons/cm2 respectively. These specimens
were subjected to a temperature of 1190 +_ 18OF for
5500 hr. The first group of vessel specimens,
'MSR Program Semiann. Progr. Rept. Aug. 31, 1965,
ORNL-3872, pp. 87-92.
196
actor concept, and we have initiated a materials
program in support of an MSBR. In this reactor the
graphite will be a primary structural material, since
it separates the breeder and the fuel salts.
Hastelloy N will be the metallic structural material,
and it will be necessary to develop a joint between
graphite and Hastelloy N. Thus, most of our re.
search effort is concerned with the structural materials,
graphite and Hastelloy N, and the joint between
thcm.
stringer X1, was also removed. The peak thermal-
neutron dose on these is approximately 2.5 x 10''
neutrons/cm2. 'The estimated temperature range on
these specimens was 900 to 1200°F, and the time
at temperature was approximately 11,000 hr. Initial
results of examination of these groups have not re-
vealed any unexpected or serious effects. These
two groups have been replaced with new sets of
specimens which are being exposed in the MSRE
environments together with other groups that were
not sampled at this time.
To review briefly, the reactor core surveillance
specimens consist of both graphite and Hastelloy N
mounted approximately 3 in. away from, and parallel
with, the axial center line of the moderator core.
The reactor vessel specimens are Hastelloy N
mounted approximately 4'5 in. outside the reactor
vessel. The reactor core specimens are exposed to
the molten fluoride fuel, and the reactor vessel
specimens are exposed to the nitrogen-2 to 5 vol %
oxygen atmosphere of the reactor containment cell.
The result is that the current and future irradiation