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The 30th meeting of the Consultative Committee for Ionizing Radiation Section II, “Measurement of Radionuclides,” was held at the BIPM headquarters in Sèvres, France, from 3 to 5 November 2025. The meeting was hybrid, with 24 participating in person and 13 online. The 37 participants represented national metrology institutes (NMIs), designated institutes (DIs), and international organizations.

The first session was held jointly with the Key Comparison Working Group [KCWG(II)] and reviewed the status of ongoing and completed key and supplementary comparisons, including approval of the final report of CCRI(II)-K2.Tc‑99. The rolling 10‑year comparison plan for the years 2025–2028 was updated, and the Committee endorsed new key comparisons of Cr‑51 (to be piloted by POLATOM in early 2026) and Am‑241 (piloted by ENEA in early 2027). In addition, a SIM regional comparison of Ac‑225 (piloted by NRC Canada) was agreed for summer 2026.

The Extended SIR (ESIR) has expanded its protocol to include H‑3 and Cl‑36. The SIR, after 50 years of service, will be progressively move to the “SIR 2.0” with improved capabilities for lower‑activity measurements and able to accommodate gaseous samples. The SIRTI continues to support on‑site and remote comparisons, having conducted 20 exercises at 16 NMIs since 2009.

Updates from the working groups including the finalization of the “Criteria for a RMO SIRTI” document and modifications to the Measurement Methods Matrix by the KCWG(II). The CCRI RTQI Working Group organized a workshop on alpha‑emitting therapeutic radionuclides, and is collaborating with the IAEA on a Good Practice Guide to support clinical users. The Communications Working Group has held 12 webinars attracting over 1,700 attendees. The CCRI(II)-MS Task Group continues to promote mass spectrometry for long‑lived radionuclides, having held a workshop earlier in the year (at the NPL).

To improve global comparability of measurements, CCRI(II) agreed to form a Task Group on the development of RMO‑SIRTIs. Chaired by Raphael Galea (NRC, Canada) and working in coordination with the ICRM, this Task Group will include members from the BIPM and each RMO. The Committee also welcomed a proposal for a supplementary comparison of digital data analysis algorithms. Technical aspects will be discussed within the ICRM RMT Working Group, and the comparison will be returned to CCRI(II) when ready to be run, with the BIPM serving as pilot laboratory.

The Committee adopted several other resolutions, recommending that the CCRI‑DT‑TG become a formal Working Group (CCRI‑DT‑WG) and that the JCRB review process on the KCDB 3.0 be aligned with the RMO review to allow multiple comment rounds. The CCRI(II)‑MS Task Group on mass spectrometry will continue until the next Section II meeting in 2027 when it maybe be proposed to become a working group.

CTBTO was welcomed as an official liaison organization to CCRI(II). The meeting also noted the handover of the Chairmanship from Dr Lisa Karam (NIST, USA) to Dr Haoran Liu (NIM, China). The next CCRI(II) meeting is tentatively planned for May 2027, likely to be held in Brazil immediately before or after the ICRM conference.

This meeting was directly followed by the CCRI(II) Workshop on “Future of Radionuclide Metrology and CCRI(II): Meeting Evolving Applications at Near-Trace Levels” on the afternoon of November 5th.