Obtaining samples of high-level waste created during the reprocessing of spent nuclear fuels presents unique challenges. Generally, high-level waste is stored in tanks with limited access to decrease the potential for radiation exposure to personnel. Samples must be obtained remotely because of the high radiation dose from the bulk material and the samples; samples require shielding nbsp;nbsp;nbsp;for handling, transport, and storage. The quantity of sample that can be obtained and transported is nbsp;nbsp;nbsp;small due to the hazardous nature of the samples as well as their high radiation dose.
Many high-level wastes have been treated to remove strontium (Sr) or cesium (Cs), or both, underwent liquid volume reductions through forced evaporation or have been pH modified, or both, to decrease corrosion of the tanks. These processes, as well as waste streams added from multiple process plant operations, often resulted in precipitation, and produced multiphase wastes that are heterogeneous. Evaporation of water from waste with significant dissolved salts concentrations has occurred in some tanks due to the high heat load associated with the high-level waste and by intentional evaporative processing, resulting in the formation of a saltcake or crusts, or both. Organic layers exist in some waste tanks, creating additional heterogeneity in the wastes.
Due to these extraordinary challenges, substantial effort in research and development has been expended to develop techniques to provide grab samples of the contents of the high-level waste tanks. A summary of the primary techniques used to obtain samples from high-level waste tanks is provided in Table 1. These techniques will be summarized in this guideline with the assumption that the tank headspace is adequately ventilated during sampling.
Technique | Material Type | Notes | ||
Solid | Slurry | Liquid | ||
HAST in-tank needle orifice | X | Orifice as part of Reverse-Flow Diverter (RFD) | ||
Bottle on a String | X | X | Dip sample | |
Vacuum Pump | X | X | ||
Auger | X | X | Only high viscosity slurries | |
Sample Cup | X | X | Manual system used at Savannah River Site to obtain salt-cake samples and hard sludges that don’t slump. | |
Core Drilling Rotary Mode (Hanford Sampler) | X | X |
ASTM C1751-11 Referenced Document
ASTM C1751-11 history
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