Development of an Ultra-Pure, Carrier-Free (209)Po Solution Standard.

Area of Science:

• Nuclear physics and metrology.
• Radiochemistry and analytical chemistry.

Background:

• Accurate standardization of radionuclides is crucial for various scientific and industrial applications.
• Previous standards for polonium-209 (209Po) were issued in 1994.
• Advancements in measurement techniques necessitate updated standards.

Purpose of the Study:

• To prepare and standardize ultra-pure, carrier-free polonium-209 (209Po) solution standards.
• To establish a new Standard Reference Material (SRM 4326a) for the massic alpha-particle emission rate of 209Po.
• To provide a reliable standard for accurate alpha spectrometry and related applications.

Main Methods:

• Preparation of ultra-pure, carrier-free 209Po solutions in dilute HCl.
• Standardization using 4π alpha liquid scintillation (LS) spectrometry with two distinct LS counting systems.
• Implementation of a unique spectral analysis procedure to account for low-energy conversion electrons and electron-capture decay branches.
• Spectroscopic impurity analyses to ensure radionuclidic purity.

Main Results:

• Successfully prepared and standardized 209Po solution standards with a certified massic alpha-particle emission rate of (39.01 ± 0.18) s⁻¹g⁻¹ as of December 1, 2013.
• The new standards (SRM 4326a) replace the previous SRM 4326.
• No significant photon-emitting or alpha-emitting radionuclidic impurities were detected; the activity ratio of 208Po/209Po was less than 10⁻⁷.

Conclusions:

• The new 209Po standards provide a highly accurate and reliable reference for massic alpha-particle emission rate measurements.
• The revised standardization methodology ensures improved accuracy and accounts for complex decay characteristics.
• These standards are essential for maintaining metrological traceability in nuclear science and applications.