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Vitrification Facility Load Lowering Device
Description
Following the vitrification process, at the DOE’s West Valley Demonstration site, the high level waste is placed in storage canisters. A remotely operated crane system is used to handle these canisters. In the event of crane or power failure, it is important that there is a means for the operator to lower a canister so that the crane can be withdrawn for maintenance.
Because of the possible consequences of dropping the load, the lowering operation must be strictly controlled. Given that any power or control is unlikely to be available to the crane during such a failure however, the lowering equipment must be capable of operating in an un-powered state.
The Solution
During concept development Numet researched and tested a variety of passive energy absorbing systems to determine their individual ranges and capacities, however the method chosen has no electrical, pneumatic, hydraulic, stored energy systems or external power.
The system chosen for Numet’s Load Lowering Device incorporates a set of four “inefficient” fan blades. The rotation of the blades regulate the descent of the load being carried through viscous dampening. The descent is started or stopped by the push/pull of a lever from an independently powered, remote manipulator, and the load itself drives the fan blades. The principles of energy absorption vs speed for this type of arrangement provides a reliable non-powered means of lowering canisters of weights varying from 1000 to 6000 pounds, within a narrow controlled speed range of 6 to 12 inches / min. Simple rugged chains, gears and sprockets are used in the design to ensure long and reliable operation in varying environments, without the need for lubrication. Special design consideration was given to the selection of components and materials with a tolerance to a high radiation, and an insensitivity to prolonged periods between use.
Project Responsibility Highlights
Bench testing of energy absorption system concepts
Presentation and demonstration of engineering findings to the client
Complete detailed design, fabrication and assembly to ASME NQA-1 standards
Adherence to crane code design standards
Functional testing and demonstration of completed devices
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