ESIR – Extension of SIR
The ESIR is an extension of the SIR designed to handle radionuclides that cannot be measured using the SIR ionization chambers—specifically, pure beta-particle emitters and certain electron-capture decaying isotopes. The system is based on a liquid scintillation counter and employs the triple-to-double coincidence ratio method. Since its inauguration in 2024, the ESIR has been used to measure a solution of 99Tc and a solution of 147Pm as part of the BIPM.RI(II)-K5 key comparisons.
| Radionuclides covered | 3H, 14C, 35S, 36Cl, 45Ca, 55Fe, 63Ni, 89Sr, 90Sr, 99Tc, 147Pm, 241Am, 241Pu |
| BIPM comparator | Operational |
| Level | Radionuclide dependent |
| Quantity | Bq/g |
| Uncertainty | Aiming for 0.5 % (k = 2) |
| Comparison service identifier | BIPM.RI(II)-K5 |
| Underpins equivalence for... | Radionuclides set out in the MMM |
| Validity | Results remain valid for 15 years |
| Key comparison reference value | Power-moderated weighted mean of results |
Guidance document
CCRI Guidance Document on the CIPM MRA
60Co Pilot Study
Coulon R. and Al., The international reference system for beta-particle emitting radionuclides: Validation through the pilot study CCRI(II)-P1.Co-60, Appl. Rad. Isot., 200, 2023
How to participate
ESIR reporting form
Protocol for BIPM.RI(II)-K5 comparisons
Contact
BIPM Ionizing Radiation Department - Radionuclide Metrology