ORNL-4191 - the Molten Salt Energy Technologies Web Site

198
SPLIT STRAP
SLEEVE BAND
(a) S FLUX
MONITORS
iRS2) REMOVED
ORNL-OlVG 67-10918R
(RS3) INS-IALLED
Fig. 16.1. MSRE Reactor Core Surveillance Specimens. (a) Assenibled detailed plan view and (b) Unassambled.
The RI-2 and RR2 stringers were not disasserrlbled for the removal of RS2 and the installation of RS3 stringers.
effects on the Hastelloy N can be monitored by the
reactor vessel and reactor core specimens respec-
tively. 'The radiation dose on the structural
Hastelloy N, because of its location, is less than
that on the Hastelloy N reactor core specimens (see
Table 16.1). This is a desirable condition of the
surveillance specimens of the MSRE, because
Hastelloy N is more strongly affected by the radia-
tion than is graphite under the MSRE conditions.
'The previous reactor core specimen assembly for
the first sampling had nonnuclear, mechanical dam-
age that broke some of the graphite and bent some
of the Hastelloy N specimens.2 This assembly was
replaced by a slightly modified one, from which the
current sampling was made. * The complete assem-
bly is withdrawn from the reactor in order to remove
any one of the three stringers. This time, the as-
sembly appeared to be in the same condition as it
was prior to its exposure, except that the surfaces
of the I-Iastelloy N specimens had been dulled. One-
third of the assembly, stringer RS2, was removed,
and a new stringer, RS3, vias joined to the other
two stringers (Fig. 16.1). These were returned to
2W. H. Cook, MSR Program Semiann. Progr. Rept. Aug
31, 1966, OKNL-4037, pp. 97---103.
the reactor in a new containment basket, as is our
standard practice. This completed our second
sampling operation, shown as sampling 2 in Table
16.1.
,\
1 he controls for the reactor core specimens, which
are exposed to fuel salt under MSRE conditions except
that the salt is static and there is no tadiation,
were also removed from the controlled test rig.
The typical appearance of the reactor core specimens
and theit controls is shown in Fig. 16.2,
Visually, the graphite, with the exception of a few
salt droplets, appeared unchanged; note that
Hastelloy N tensile specimens are reflected in the
bright surfaces of the graphite (Fig. 16.2~).
The graphite specimens were pinned at their
tongue-and-groove joints within Hastelloy N straps
with 0.030-in.-diam Hastelloy N wire. The movement
of the graphite column of specimens relative
to that of the Hastelloy N tensile specimen rods
was sufficiently difficult to deform the pins in the
reactor core specimens. 'These pins had to be
drilled out during disassembly. The pins of the
control specimens were not deformed, but the control
assembly is less complex, since space limitations
are not as restricted for it as for those in the
reactor. Each control stringer is separate from the