ORNL-4191 - the Molten Salt Energy Technologies Web Site

MSRE, details of some of the equipment, and descriptions
of specific problems. The demonstrations
involved the viewing equipment, the remote
cranes, the portable maintenance shield, and some
of the long-handled tools. Practice sessions on
core sample removal and replacement served both to
train personnel and to shake down the equipment.
The planning part of the preparation involved
the writing or updating of step-by-step procedures
fGr each job. These procedures were used to draw
up lists of requiied tools, equipment, and material,
and to estimate time and manpower requirements.
Possible problem areas were recognized €or prior
testing and mockup practice. Before the shutdown
began, the procedures were used to provide information
to the foremen and the working crews.
A large effort was required to put all the physical
equipment into readiness. This meant fabrication
of new equipment; cleaning, maintenance, and
repair of existing equipment; and procurr?rnerit of
some special items. Numerous long-handled tools,
containers €or hot pulls, materials for contamination
control, handling equipment, and devices for
shielding, lighting, and viewing were prepared.
Evaluation of Remote Maintenance After Run 11
The maintenance work during this ::hutdown was
done on a two-crew, two-shift-per-day basis, Al-
though there were drawbacks, such as spreading
more thinly the knowledgeable personnel and lost
motion at shift change, the' work proceeded safely
and smoothly. Radiation levels were about the
sane as at the last shutdown and did not require
any changes in procedure. Some bothersome de-
!ays wete caused by breakdowns of the cranes and
maintenance shield, but the schedule was not
seriously affected. Comments on individual jobs
follow.
Removing and replacing the sample array in the
core was the most difficult task of the shutdown,
involving as it did an extremely intense source
of radiation and contamination. The standpipe
above the reactor access flange contained the
assembly and maintained an inert atmosphere on
it. Before the operation a new charcoal filter
was installed iri the vent line from the standpipe
to prevent iodine releases. The procedure used
previously was changed to minimize the time of
exposure for the uncontained sample within the
stkindpipe and to provide complete containment
37
and shielding during the transfer of the sample
from the standpipe to the shielded carrier. Two
unanticipated situations arose. The bushing which
supports the sample assembly arid which is supposed
to stay locked in position in the vessel
outlet strainer actually came out on the sample
basket. After visually ascertaining that the
strainer was not damaged, a new bushing was
inserted. Ulieri difficulty was encountered later
in obtaining a satisfactory seal while replacing
the reactor access flange, four bolts were replaced,
and all the threads on the nut:; were
cleaned by tapping. This permitted an increase
in gasket loading which eliminated the leak.
Iiemoval, repair, inspection, and replacement of
a control rod drive went smoothly.
The leaking east space cooler was disconnected
through the portable maintenance shield and then
was removed by using the crane, television, and
remotely operated maintenance-shield slide from
the maintenance control rooin. A new unit, reassembled
on the old frame, was reinstalled the same
way without excessive difficulty.
The metallurgical specimens which hang in the
reactor vessel furnace were replaced without difficulty.
The carrier for the core samples was
used to transport the specimens to the hot cell.
'The fresh neutron source was transferred from a
carrier and placed in the source t.ube (,on top of
the original source) without incident..
Visual inspection in the cell was by use of a
periscope, binoculars, and remote television.
Thermocouple junction boxes were tested, and
four thermocouples were plugged into a spare disconnect
box by using long-handled tools through
the maintenance shield.
As a result of the experience during this shutdown,
procedures were reviewed and revised
where desirable, and some tools and equipment
were revised or overhauled. The television camera
mounts were changed for greater flexibility, and
revisions were made to the track and to the roller
and guide bearings on the maintenance shield.
Repair of Sampler-Enricher and Recovery of Latch
After the failure of the sampler-enricher drive
unit, a lead carrier was built, and detailed pro-
cedures for the removal of the delective unit were
prepared and reviewed. The actual removal of
this component was without incident.