The international reference system for beta-particle emitting radionuclides: Validation through the pilot study CCRI(II)-P1.Co-60

The Bureau International des Poids et Mesures (BIPM) is developing a new transfer instrument to extend its centralized services for assessing the international equivalence of radioactive standards to new radionuclides. A liquid scintillation counter using the triple/double coincidence ratio method is being studied and tested in the CCRI(II)-P1.Co-60 pilot study. The pilot study, involving 13 participating laboratories with primary calibration capabilities, validated the approach against the original international reference system based on ionization chambers, which has been in operation since 1976. The results are in agreement and an accuracy suitable for purpose, below 5 x 10-4, is achieved. The pilot study also reveals an issue when impurities emitting low-energy electrons are present in the standard solution, which have a different impact on liquid scintillation counting compared to other primary measurement methods.

Automated summary

The Bureau International des Poids et Mesures (BIPM) is developing a new transfer instrument to evaluate the international equivalence of radioactive standards for new radionuclides. A pilot study involving 13 laboratories validated the approach using a liquid scintillation counter with a triple/double coincidence ratio method. The results achieved an accuracy below 5 x 10-4, suitable for the purpose, and revealed a difference in impact compared to other primary measurement methods when impurities emitting low-energy electrons are present.