ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
tank would be shielded fairly well, and it would
be possible for a man to enter the inner tank through
a manhole at the top for inspection or repair work,
even after the tank had been closed and the re-
actor had been run at high power. The water
capacity of the space between the tanks, together
with the water in the reservoir above the inner
tank (approximately 10 ft deep), would be of the
order of 110,000 gal. Boiling of this water would
suffice to carry off all the heat generated by the
fission products for about two days without any
fresh water being supplied to the outer tank. All
the various wires, pipes, tubes, etc. connected to
the reactor and its auxiliaries would pass through
carefully laid-out junction panels such as the one
shown in Fig, 2.7. Such a panel might be installed
II of the tank shown in Fig. 2.6 with a
ight gasketed flanged junction. The
various thermocouples, power wiring, etc. could be
installed on the reactor assembly in the shopand
fitted with Cannon plugs so that they could be
plugged into the panel in a short period of time
after the reactor assembly had been lowered into
position in the test facility. This should minimize
the amount of assembly work required in the field.
The layout investigated as the fourth proposed
installation would involve placing the reactor in-
side a sort of swimming pool with water-tight
thermal insulation surrounding the pressure shell,
lines, and pumps. The lines could then be brought
out the top of the water tank to the instruments
and the heat dumps. In the event of a severe
accident that resulted in a meltdown, there would
be sufficient heat capacity in the water to absorb
the heat from the fission products for some days
before a seriously large amount of water would
have been boiled out of the pool, Such an arrange-
ment could be enclosed, of course, in an air-tight
building. This might not be necessary, but it
seems likely that, in the event of an abrupt melt-
down type of failure, the high heat capacity of the
region inside the thermal insulation might put so
much heat into the water in a very short period of
e that bubbles would boil violently to the
surface and disperse entrained fission products.
After, perhaps, 10 or 15 min, it seems unlikely
that such entrainment would prove to be a problem.
The unshielded reactor assembly will weigh
approximately 10,000 Ib, the lead gamma shield
approximately 30,000 Ib, and the water in the
shield approximately 34,000 Ib. The first two of
34
these items could be handled conveniently with a
20-ton crane, while the borated water could be
pumped in after the rubber tanks had been installed
for the water shield.
An arrangement such as the double-walled tank
shown in Fig. 2.6 should prove to be adequate to
take care of any accident not involving sabotage
or bombing. The same should be true for either
the hemispherical or circular Quonset type of
building. Only the NRTS installation would, be-
cause of the remote location, present a not-too-
serious hazards problem if effectively sabotaged.
To evaluate the merits of each of the installa-
tions considered, an attempt was made to envision
as many accidents as possible that might prove to
be serious during the course of operation of the
ART. The worst natural accident that could be
envisioned would result in a meltdown. The only
source of an explosion that has been envisioned
would be either sabotage or bombing. If the
volatile fission products are removed during the
course of operation, the major hazard to the sur-
rounding area would be from the fission products
that might be dispersed in the course of violent
boiling or from an explosion.
Although in the preliminary hazards analysis
consideration was given to operational hazards,
operational sabotage, fire, earthquake, flood,
windstorm, and bombing, the controlling considera-
tions appeared.to be those associated with a total
reactor tragedy. The total reactor tragedy is con-
sidered here as being an accident in which all the
heat that could possibly be released from the
chemical combination of various materials in the
reactor and associated system would be released,
together with the heat from the fission products
accumulated after extended operation at full power
and the energy released in an extreme nuclear
runaway. The principal hazard associated with an
ultimate reactor catastrophe is the dispersion of
the fission products that would have accumulated
from extended operation at high power. The key
data on these parameters are presented in Table
2.2.
In examining the data on the heat that could be
released from the combustion of various materials
in the reactor installation, it is immediately evi-
dent that if kerosene or another hydrocarbon were
used in place of water in the shield a very large
amount of heat could be released, an amount almost
one hundred times greater than that from any other