⁶⁸(Ge+Ga) activity standardization by 4πβ(LS)-γ(NaI(Tl)) anticoincidence counting measurements

Area of Science:

• Nuclear Metrology
• Radiochemistry
• Applied Physics

Background:

• Accurate standardization of radioactive sources is crucial for various applications, including medical imaging and research.
• International key comparisons ensure consistency and comparability of measurement standards globally.
• The National Institute of Ionizing Radiation Metrology (LNMRI) in Brazil participates in key comparisons to validate its metrological capabilities.

Purpose of the Study:

• To standardize a ⁶⁸(Ge+Ga) solution at LNMRI as part of the international key comparison CCRI(II)-K2.Ge-68.
• To validate the primary 4πβ(LS)-γ(NaI(Tl)) anticoincidence method through independent measurements.
• To assess the metrological capabilities of LNMRI in radionuclide standardization.

Main Methods:

• Standardization of ⁶⁸(Ge+Ga) activity concentration using the 4πβ(LS)-γ(NaI(Tl)) anticoincidence method with live-time and extended dead-time.
• Validation measurements using 4πβ(LS)-γ(NaI(Tl)) coincidence counting.
• Validation measurements using liquid scintillation counting with the Triple to Double Coincidence Ratio (TDCR) method.

Main Results:

• The activity concentration values obtained by coincidence and TDCR methods showed deviations of 1.7% and 0.63%, respectively, from the anticoincidence result.
• These deviations were within the experimental evaluated uncertainties at a 95% confidence level (k=2).
• Combined relative standard uncertainties were 0.65% (anticoincidence), 0.70% (coincidence), and 0.53% (TDCR), demonstrating high precision.

Conclusions:

• The 4πβ(LS)-γ(NaI(Tl)) anticoincidence method at LNMRI is reliable for standardizing ⁶⁸(Ge+Ga) solutions.
• The results are consistent with international standards and previous findings, confirming LNMRI's metrological competence.
• The study successfully contributed to the international key comparison, reinforcing global traceability in radioactivity measurements.