ORNL-4191 - the Molten Salt Energy Technologies Web Site

The retrieval of the sample latch would have
been facilitated had it been magnetic. Therefore,
f.he replacement latch was made of magnetic typte
430 stainless steel instead of type 304 stainless
steel. Another change in the replacement unit
was the addition of a sleeve to bridge the 2-in.
gap between the cable drive reel and the floor
of the drive compartment. This wi11 prevent the
cable from escaping into this compartment if it
meets resistance while being unreeled.
As explajried on p. E, the detached capsule is
positively confined by the baffle so that it cannot.
escape. Swirl velocities observed in the bowl of
the prototype salt pump were less than 0.1 fps,
indicating that continual movement of the loose
capsule is very unlikely. Nor should the capsule
corrode. The body of the capsule is copper, and
the cap is mild steel with a thin nickel plating
that probably leaves some ferrous metal exposed.
On exposure to t.he molten salt, the copper-ironnickel
assemblage in contact with the chromiumcontaining
Hastelloy of the baffle and lower head
will temporaiily constitute an electrochemical
cell, in which Cr0 from the Wastelloy surfaces
will be oxidized to + Cr2 and reduced once again
to Cro metal on the capsule surface. This reaction
slows down as the chromium activity in the
capsule surface approaches that of the Hastelloy
surfaces. Eventually the transfer diminishes to
the rate at which the chromium can diffuse into
the capsule metal. 'The amount of chromium that
can be transferred in this way will have negligible
effect on nearby Hastelloy surfaces. The conclusion
is, therefore, that no ill effects will result
from the presence of the capsule in the pump
bowl.
Coolant Sampler. - During this report period,
seven 10-g samples were isolated from the coolant
salt pump, bringing the total with this sampler to
60. There were no operating difficulties and no
maintenance was required.
Fuel Processing Sampler. - The shielding
around the fuel processing sampler was finished,
complet-ing the installation of this sampler. The
nylon guide in the removal area and the manipula-
tor arm were subsequently removed for use in the
fuel sampler. Other spares are now on hand but
will not be installed until near time for use of the
processing facility.
33
Containment
I?. 11. Harley R. c. Steffy
Secondary Containment. -- During run 11, the
containment cell inleakage was measured to be
cu 10 scf/day with the cell at .- 2 psig. This de-
termination was made by monitoring the cell pres-
sure with the Hook gage (a sophisticated water
manometer) and by measuring ,711 known purges
into and out of the containment cell. The cell
ptessure arid system purges remained virtuaIly
constant, with small pressure oscillations occur-
ring as the outside temperature fluctuated. Thesc
oscillations were particularly not iceable during
the colder months.
Between May 16 and June 13, an extensive
contaitirrient check was made. Thirteen block
valves out of a total of 160 were found to be
leaking and were repaired. Five were instrument
air block valves, three were in the cover-gas
{helium) system, and five were in the treatedwater
syst.em. The most common cause of leakage
was aging elastomer O-rings; a few, however,
had scale, metal filings, or dirt on the seating
surfaces. None of the valves leaked excessively,
and seven of them are backed by a closed system.
Two others are in use .:0.1"/, of the time arid are
normally backed by closed hand valves.
At the beginning of run 12, the secondary con-
tainment vessel leakage was checked with t.he
containment cell at 20 psig. At this pressure the
cell leaked only "u 28 scf/day. The cell was then
evacuat.ed to - 2 psig, and reactor filling opera-
tions were started.
As during earlier runs, there was a water leak
in the cell during tun 12 (this leak is discussed
later iri the section). As a result of the water
leak the first determinations placed the cell
leak rate at -270 scf/day. However, as soon as
the cell air became saturated, the indicated leak
rate dropped to t20 scf/day. This took only
about seven days. For the major part of run 12,
the indicated cell leak rate remained essentially
constant at ^' 14 scf/day..
For both runs 11 and 12, the (:ell leak rate
values were well below the 85 scf/day permissible
(extrapolated from accident conditions at a 39-
psig cell pressure).