SU-F-BRCD-02: Activity Assay of a Y-90 Microsphere Sample Using a Coincidence Detection System.

Area of Science:

• Nuclear physics and instrumentation
• Radioactive decay analysis
• Metrology and standards

Background:

• Accurate activity determination of Yttrium-90 (Y-90) is crucial for various applications.
• Traditional methods can be limited by spectral interferences, increasing uncertainty.
• Internal pair production branching ratios provide a new avenue for precise Y-90 assay.

Purpose of the Study:

• To spectroscopically assay Y-90 microsphere activity using a novel coincidence detection system (CDS).
• To leverage a newly determined, low-uncertainty branching ratio for Y-90 internal pair production.
• To validate the CDS performance against a NIST Y-90 standard.

Main Methods:

• A coincidence detection system (CDS) pairing a HPGe detector with a NaI detector was employed.
• Electronic filtering of the bremsstrahlung continuum was achieved by gating HPGe signals with coincidence signals.
• Efficiency calibration and geometric characterization were performed, and pulsers corrected for counting losses.

Main Results:

• The CDS accurately determined the activity of a NIST Y-90 standard within 2.6%, consistent with measurement uncertainty.
• The Y-90 microsphere sample activity was measured as 3.72 GBq ± 1.9%.
• This result was 19% higher than the manufacturer's stated activity, exceeding their uncertainty margin.

Conclusions:

• The validated CDS accurately determines Y-90 source activity.
• The system's application was successfully extended to assay Y-90 microsphere samples.
• Discrepancies with manufacturer data highlight the importance of independent verification.