joints and crevices should be caulked or sealed to prevent the accumulation of
contaminated materials at inaccessible locations. The use of hazardous
material should be minimized to preclude the generation of mixed waste.
The following sections address design features that should be considered for
radioactive and hazardous materials processing and handling facilities.
Equipment Selection and Location . Equipment and configurations should be
selected that preclude, to the extent practicable, the accumulation of
radioactive or other hazardous materials at curves, turns, and joints in the
piping, especially in hard-to-reach or inaccessible locations. The design should
avoid the use of built-in crud traps, such as flanged couplings, dead legs, etc.
Construction materials and surface finishes should be considered to minimize
porosity, crevices, rough machine marks, etc., to limit the possibility of tightly
adherent contamination and to facilitate ease of decontamination. An example
of this is electro-polished stainless steel liners.
Localized liquid transfer systems should be considered that avoid long runs of
contaminated piping to the extent practical, with special attention to the design
features necessary to maintain the integrity of joints in buried pipelines. Local
processing (solidification) of liquid wastes should be considered when
designing piping and liquid disposal systems.
The design should provide for full draining of contaminated piping systems by
including the installation of low-point drains, pump drains, tank vent systems,
and drain systems, and the elimination of dead legs between valves in system
designs. A valuable tool in this design effort would be a 3-D computer-assisted
design and drafting system to confirm that all low points can be drained and
that dead legs are not designed into the system.
The design should allow access for easier dismantlement, cut-up
(segmentation), removal, and packaging of contaminated equipment from the
facility. Modular process equipment packages lend themselves well to this
approach. The design should minimize pipe spring due to residual stress.