ORNL-2106 - the Molten Salt Energy Technologies Web Site

an lnconel shell and a complicated boron-copper
layer. In considering the radiation as seen outside
the shield, this region can be adequately simulated
in the SMC with a shell of Intonel followed by
layers of bora1 to give the proper density in g/cm2,
Calculations are being carried out at Pratt &
Whitney Aircraft to determine the importance of
each region as a source of radiation.
The heat exchanger region just beyond the first
boron curtain affects the crew compartment dose
rate in several ways: (1) it attenuates the radia-
tion from the core and the beryllium; (2) it is a
source of some capture gamma radiation from core
neutrons; and (3) it is a source of delayed neutrons
and fission-productdecay gamma rays. In order
to account for the first two effects, the heat
exchanger region will be mocked up with fused
salts (in the form of NaF and KF) and NaK, as a
homogenized mixture. This will be accomplished
by heating the salt, the NaK, and the can to about
1000°C in an evacuated furnace. The cans will
be placed in two layers to eliminate leakage paths
between the cans. The lnconel in the heat ex-
changer will be split to form two shells around the
salt region. The inner shell will act as the
pressure shell for the SMC. Outside the outer heat
exchanger shell will be the second sodium-cooled
boron curtain, which, like the first curtain, will
be mocked up with boral.
The regular CFRMR pressure shell will follow
the heat exchanger region. It has bee0 proposed
that part of this shell be split off for use in mount-
ing the lead shielding. This section is to be re-
movable to allow the lead shield to be changed
without dismantling the reactor,
The neutron shielding material will be contained
in an aluminum tank. The optimized neutron shield
will be a sphere placed off-center with respect to
the reactor. It is proposed to permit lateral motion
of the neutron shield, while using water as shield
material, to check the present optimization. Later
the shield container is to be sealed in the optimized
position, and neutron shielding materials other
than water can be used.
In order to facilitate the measurements at thhtTSF
the whole reactor and shield system has been de-
signed so that it can be rotated about the vertical
axis.
COMPARISON OF SMC AND CFRMR
An examination of some of the results of the cal-
culations performed by Pratt & Whitney indicates
PERIOD ENDING JUNE 10, 1956
how closely the SMC radiation simulates the
CFRMR. Thermal-neutron captures in the reflector
and the power distribution within the core have
been considered, and the importance of each region
of the reactor as a gamma-ray source is being
investigated.
Neutron Captures in Beryllium
Since approximately 20% of the dose rate in the
crew compartment is expected to originate from
neutron captures in the beryllium, this source is
to be accurately simulated. Figure 5.4.2 shows
the captures that can be expected in the SMC
beryllium with normal water as the coolant in the
core. The lower curve shows the absorptions in
the SMC beryllium when the space between the
fuel plates is completely filled with normal water
and the reactor is operated at room temperature.
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2-09-059-776
CONFIGURATION 160: SPACE BETWEEN FUEL PLATES
FILLED WITH 100 % H20
CONFIGURATION 167: SPACE BETWEEN FUEL PLATES
FILLED WITH 50% H20-50% AI
CONFIGURATION 168: SPACE BETWEEN FUEL PLATES
FILLED WITH 25%H20-75%AI
CONFIGURATION 168A: SPACE BETWEEN FUEL PLATES
FILLED WITH 12.5% H20--87.5% AI
35 40 45 50 55 60 65
SPACE POINTS IN REFLECTOR
Fig. 54.2. Comparison of Neutron Captures in
Beryllium Reflector of SMC for Various Configu-
rations with Neutron Captures in Reflector of
CFRMR.
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