August 13, 2019 Two (IAEA) fellows visited the Nuclear Metrology Group at NPL from VUJE in Slovakia for one week, to receive training on measurement of decommissioning wastes, focusing on various solid matrices and iodine-129. During their visit, training was given on dissolution of solid samples, chemical separation to isolate iodine from interfering radionuclides, and measurement considerations using both decay counting and mass spectrometric techniques. The visit made use of procedures developed as part of MetroDecomII, namely dissolution of complex sample matrices using automated borate fusion, and online reaction-cell separation of interferences using ICP-MS/MS to reduce reliance on offline chemical separation. There was also a site visit to the University of Southampton, where a joint-funded PhD student with NPL has developed a novel method for selective extraction and mass spectrometric measurement of iodine-129 in a range of sample matrices, offering a rapid alternative to time-consuming multi-stage sample preparation and decay counting measurement. The visit established a new collaboration that may be useful for future bids related to meeting decommissioning challenges, and there is the potential opportunity for an IAEA-funded return visit to VUJE in the summer.