Abstract View

Objectives: The overall production pipeline of fluorine-18 labeled radiotracers generate numerous radioactive wastes, both solid and liquid. Managing these wastes is an everyday challenge, constantly balancing regulatory requirements and costs. Here we will present the procedures and methods we developed at the University of Liège for the collection, storage, analysis and classification of nuclear waste from our cyclotron and clinical production facility.

Methods: To ensure proper management of the radioactive wastes, a comprehensive methodology was developed. First, the origin and the nature of the waste is identified to determine the appropriate treatment pathway. Then, according to the previous categorization, the waste is stored for a set decay duration, ranging from tens of hours (typically for liquid effluents) to several years (e.g. for solid cyclotron's wastes). The isotopic composition of the waste is subsequently determined using HPGe gamma spectrometry taking care of considering background noise, detection limits, and measurement geometry; each radiocontaminant is identified from the comparison of its measured energy with a pre-established library and the corresponding activity is calculated.^1,2 Finaly, the measured values are compared to regulatory thresholds to decide whether to discharge/release the waste or keep it in storage for longer; solid waste can be released when their specific activities are below authorized levels, while liquids are discharged via conventional pathways when activity levels comply with discharge limits or are below detection thresholds.³

Figure 1. Setup for HPGe measurements of solid (A) and liquid (B) radioactive wastes.

Results: The adequacy of the developed method was tested on both solid (50 kg) and liquid (200 L) wastes that had spent up to 20 years in storage. Amongst these, we determined that 95% of solid wastes could be released after 15 years in storage. The remaining 5% consist of activated metal components from cyclotron maintenance or target systems. As for liquids, 100% were found to have activity levels below detection or discharge limits after an average of 9 months in storage and were discarded through conventional ways.

Conclusion: The developed methodology provides a robust framework for managing solid and liquid radioactive waste in line with regulatory requirements. Based on a combination of experimental characterization and controlled decay, it ensures safe and optimized waste management whilst limiting environmental impact and costs associated with systematic nuclear waste disposal. The integration of regular measurement campaigns and the adaptability of waste streams to evolving activities further guarantee the sustainability and efficiency of the waste management system. This framework is transferable to other production centers with similar regulatory constraints.

References

¹ Phys. Atom. Nuclei 83, 1732–1737 (2020).

² Appl. Rad. and Isotopes 67, Pages 248-255 (2009).

³ Belgian Royal Decree of 20 July 2001 (RGPRI), Annex IB and III