ORNL-2106 - the Molten Salt Energy Technologies Web Site

ANP PROJECT PROGRESS REPORT
a 2.32-Mev alpha particle is given off and that in
the remaining 7% a 2.8-Mev alpha particle is given
off.ll The heating from beta decay resulting from
neutron captures in copper was calculated, and it
was found to be negligible compared with the
a Ipha-part ic le heating.
The gamma-ray heating resulting from the
emission of decay gamma radiation in the heat
exchanger was calculated on the basis of slab
geometry by using Eq. 6 for each energy group.
The spectrum of gamma rays was divided into the
seven energy groups given in ref. 3, with average
energies of 0.5, 1, 2, 4, 6, 8, and 10 MeV. The
buildup factor for the heat exchanger was used
for each energy group. The total heating at
various points was calculated by summing over
the contributions of each energy group.
The source strength of the gamma rays resulting
from inelastic neutron scattering in the beryllium
reflector was also calculated. These sources are
appreciable only in the first 9 cm of beryllium.
However, their contributions to the heating in the
regions around the heat exchanger are small
compared with those of the beryllium capture
gamma-ray sources. The reason for this is that
the gamma rays from inelastic scattering were
taken to be I-Mev gamma rays, which are at-
tenuated much more strongly by the beryllium than
are the bMev capture gamma rays. In addition
the total source strength of the gamma rays from
inelastic neutron scattering is much smaller than
that of the capture gamma rays because of the
volumes of beryllium involved in each.
The source strength of the capture gamma rays
resulting from delayed neutron captures was
calculated by assuming that 50% of the delayed
neutrons were given off in the heat exchanger and
that all these neutrons were captured in the
neighborhood of the heat exchanger. By assuming
that an &Mev gamma ray was given off for each
capture, the average source strength per unit
volume was found to be small as compared with
the other sources in this region.
The capture gamma-ray sources in the copper
were calculated in the same general way that the
alpha-particle heating in the copper was calcu-
lated, with the source converted to a surface
source of gamma rays. In itself this is not an
insignificant source, but the heating resulting
from this source would be only about 2% of the
total from all the sources considered here.
34
The gamma.rays resulting from inelastic neutron
scattering in the core shells were calculated by
using the Curtiss-Wright multigroup fluxes5 and
an inelastic microscopic cross section of 1.5
barns (ref. 13) for the constituents of Inconel.
It was assumed thaf a 2-Mev gamma ray was given
off for each inelastic collision. The results
gave a source strength of about 10% of that
resulting from the capture gamma rays in these
shells.
As has already been remarked, the capture
gamma rays in the island core shell were neglected
because of the shielding properties of the fuel.
Where it has not been stated otherwise, the
dimensions used in these calculations were those
from ref. 1 for the equatorial plane of the reactor.
RADIATION HEATING IN VARIOUS REGIONS
OFTHENORTHHEAD
H. W. Bertini D. L. Platus14
Calculations of the radiation heating to be
ex cted in various regions in the north head of
the ART were undertaken in order to supply
pt numbers from which thermal-stress calculations
could be made. Because of the complexity and
the time that would be involved in calculating
accurately the heating in all the regions of the
north head, it was decided to make preliminary
estimates of the deposition rates. More accurate
values calculated for other regions of the reactor
were used as guides. In all cases the tendency
was to overestimate the heating. These estimates
can be used to identify the thermal-stress
problems, and where the calculated thermal
stresses are marginal, the heating will be recalculated,
Calculations were made of the heat-deposition
rate in a slab of lnconel bounded on one side by
an infinite fuel region containing the sources of
radiation. This heat-generation rate was used in
all regions in the north head which are bounded by
finite fuel volumes,
The heat-deposition rates in a slab of lnconel
bounded on one side by slabs of sodium of various
thicknesses were calculated, and the results were
extrapolated and interpolated to obtain the heat-
generation rates in the lnconel regions of the north
13H. Le Taylor, 0. Lonsio, and T. W. Bonner, Pkys.
Rev. 100, 174 (1955).
assignment from USAF.
LI
8
e-
c
.
.
t
c
9