Reduced Pressure Principle Backflow Preventer Evaluation and Use at Oak Ridge National Laboratory

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Abstract
The necessity for prudent conservation of potable water, the need for protecting water supplies from contamination, and the increased cost of dual water distribution systems serving an expanding nuclear complex, generated an interest at Oak Ridge National Laboratory in the reduced pressure principle backflow preventer. This device, despite its advantages of economy and convenience, has been only partially accepted as a substitute for air-gap separation in preventing pollution of potable water. Previous tests generally reported dynamic or maltreatment conditions. To provide additional assurance of the safety of the device, a reduced pressure principle backflow preventer was tested under 5 different conditions. A solution of manganese and potassium nitrates was used as a nonradioactive tracer. Activation and radiochemical analyses having a sensitivity of -0.2 parts per billion of manganese proved there was no detectable backflow from the discharge side to the supply side. Potassium analyses also showed no detectable backflow, but with a lesser sensitivity. The "Protection Factor" (PF) for the device is defined as: [image] The minimum protection factor proven in these tests based upon the limit of sensitivity of manganese analysis is 6.5 X 108. This factor provides a rational basis for installation where the concentration of radioactivity or other contaminant can be estimated, measured or limited. Criteria for RPPBP installations at ORNL include purchase specifications, inspection requirements, approvals required for use in 3 levels of hazard, installation requirements and maintenance considerations.

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