silo 3 - U.S. Department of Energy

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Access and Retrieval Strategy for the Silo 3 Project
Document No. 40430-PL-0002, Rev. 1
September 2003
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-. *{n addison, the Excavator Room size allows the storage of end effectors and containers for
oversized material and debris recovered from the Retrieval Bin grating.
4.2 MECHANICAL RETRIEVAL SYSTEM OPERATION
A reinforced concrete frame has been installed on the east silo wall during the project
construction phase. Once sufficient material has been pneumatically removed from behind
the proposed wall opening, the silo wall is cut using a wall saw mounted on a track and
wall sections are removed to allow the Excavator to access the Silo 3 contents. The
cutting operation includes adding a system of braces to stabilize the wall. This allows
flexibility to remove the wall in sections or to continue until the entire opening has been
cut. The extent of wall removal will be determined by the quantity of material present
behind the wall.
Through a combination of pushing, raking, and lifting, the Excavator (EXC-11-5050)
transfers material to the Retrieval Bin (HBN-11-5054). The excavator can also move/
transfer the material under the silo dome man ways, where it is accessible for retrieval
using the vacuum wands. The excavator may also be used to manipulate a vacuum wand
and hose for pneumatic retrieval.
To minimize the likelihood of material collapse, the Silo 3 material is routinely graded to
maintain an adequate angle of repose.
Once the Excavator is in full operation, the water-misting system (on the excavator) may
be employed for one or both of the following functions:
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Dust suppression: During mechanical retrieval, the silo's contents will be disturbed, and
excessive dusting2 in the Excavator Room may result; however, the Excavator is
expected to be operated in a controlled banner to minimize dusting.
Stabilization of working face: As piles of Silo 3 material are created and "groomed,"
water misting may be used as a safe working practice to help establish a stable face.
Water is supplied to the system from a water tank located on the Excavator. Tests have
shown that the Silo 3 material has a significant capacity to absorb moisture, even to the
point of deliquescence. Because the misting system will be used infrequently and the
water introduced is a small fraction of the absorbent capacity of the material, it is
expected that moisture addition will have no deleterious effect on the material-handling
process if controlled properly. Caution must be used to only facilitate crusting of the
material and avoid creating wet areas.
Use of this system will be limited since the dust
can also be removed after settling by vacuuming. Use of the misting system may be very
localized and specific for operator access to the work area.
One operator will control the excavator from the corridor between the Excavator Room
and the Process Building; a viewing window is provided on the Excavator Room wall. The
excavator operator will be guided by viewing through the Excavator Room window and by
'"Excessive dusting" is defined as that degree of atmospheric dusting that interferes with visibility
(both visual and CCTV) in the Excavator Room.
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