Separation and Measurement of

Separation and Measurement of
Ra-226 in Water Samples
Using Scintillation Disk Technology

Joy I. Stoleson* and David C. Seely**

*Braun Intertec, Minneapolis, MN

**3M Filtration Products, St. Paul, MN

The main objective of this research is to find a quick and reliable means of sampling and analyzing ground and surface water samples for radionuclide activity without the need to transport potentially hazardous samples back to a laboratory. The DOE’s Characterization, Monitoring, and Sensor Technology (CMST) program is supporting 3M’s application of solid phase extraction (SPE) disk technology to field analysis needs. For this to be a success, it needs to satisfy several requirements. Separation and measurement of the target radioisotope needs to be done at the sampling site in the field, and the sampling technique and analysis needs to be sensitive to low levels of activity (<100 pCi).

This paper describes the theory and practice of a field sampling scintillation technique for the separation and measurement of Ra-226 in aqueous matrices. Currently, 3M makes a product, the EmporeÔ Radium Rad disk, which selectively adsorbs radium from aqueous samples, thereby eliminating the need for lengthy laboratory separation methods. Altering the EmporeÔ disk formula, an inorganic scintillant (silver-doped zinc sulfide) was incorporated to create a ‘scintillating disk’. When a radium ‘scintillating disk’ is loaded with 1 to 4 liters of sample, the Ra-226 present in the sample is adsorbed and interacts with the zinc sulfide inside the disk. Light photons that are emitted during this interaction can then be counted with a portable counter. Counting efficiency remains high due to the incorporation of the radium absorber and scintillator in one disk, (resulting in minimal air space through which the alpha particles have to travel.)

The advantages and challenges faced by this sampling/analysis technique will be discussed, along with properties of the scintillation disk technology, as it regards to light/dark adaptation, sensitivity and practical handling issues.