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2020:08 Identifying Radiologically Important ESS-Specific Radionuclides and Relevant Detection Methods

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2020:08 Identifying Radiologically Important ESS-Specific Radionuclides and Relevant Detection Methods Research Identifying radiologically important ESS-specific radionuclides and relevant detection methods 2020:08 Authors: Kristina Eriksson Stenstrm, Vytenis Barkauskas, Guillaume Pedehontaa-Hiaa, Charlotta Nilsson, Christopher Rääf, Hanna Holstein, Sren Mattsson, Johan Martinsson, Mattias Jnsson, Christian Bernhardsson Lunds universitet, Lund Report number: 2020:08 ISSN: 2000-0456 Available at: www.ssm.se SSM 2020:08 SSM perspective Background The European Spallation Source (ESS) facility is under construction in Lund, Sweden. High-energy protons will be accelerated in a linear accel- erator and generate neutrons when hitting a rotating target of tungsten. This spallation process will also generate a wide range of diferent radio- active by-products of which a small part will be released to the environ- ment during normal operation. Furthermore, in case of an accident scenario, gases and aerosols might be released from the tungsten target. Emissions from ESS, both during normal operation or in case of an acci- dent, will difer in radionuclide composition to the environment from those activities with ionising radiation that we have experience from in Sweden today. Thus, the Swedish Radiation Safety Authority has found it of great importance to support the possibilities to increase the knowl- edge about measurement and analysis of ESS-specifc radionuclides that could be useful in the environmental monitoring program when the ESS facility starts to generate neutrons in a few years. Results Based on an extensive literature review of ESS-relevant radionuclides the authors concluded that radionuclide production in particle accelerators is well known, while experience with tungsten targets is very limited. The authors showed a good agreement with results of others, except for 148 Gd, and that the calculated radionuclide composition is sensitive to the nuclear interaction models used by developing an independent simplifed model of the ESS target sector for the calculations of radionu- clide production in the ESS target. In this report, suggestions of detection techniques of the most relevant ESS-specifc radionuclides in environmental samples are given based on a literature review. Liquid scintillation counting (LSC) is suggested as a suitable technique e.g. for the beta emitters 3H, 14 C, 35S, 31 P and 33P. Alpha spectrometry is seemed promising for the analysis of alpha-emit- ting lanthanides, in particular for 148 Gd. Among the many types of mass spectrometry techniques, inductively coupled plasma mass spectrometry (ICP-MS) and accelerator mass spectrometry (AMS) are seemed to be the most suitable mass spectrometry techniques for the analysis of long- lived ESS radionuclides in environmental samples (e.g. 243Am and possi- bly lanthanides for ICP-MS and 10Be, 14 C, 32Si, 36Cl, 60Fe and 129I for AMS). Furthermore, this report includes performed experimental parts related to initiation of radioactivity measurements of aerosols at Lund’s Univer- sity, mapping of environmental tritium in the Lund area, and performing a baseline study of the tritium content in urine for persons presently living or working in Lund. This project has resulted in two scientifc publications entitled Prediction of radionuclide production in European Spallation Source target using FLUKA (Nuclear Instruments and Methods in Physics Research B) and Tritium in urine from members of the general public and occupationally exposed workers in SSM 2020:08 Lund, Sweden, prior to operation of the European Spallation Source (Journal of Environmental Radioactivity). Relevance This report gives insight into techniques useful for measurement and analysis of ESS-specifc radionuclides and presents results that are of interest in SSM’s regulatory supervision of the licensee ESS. Need for further research Initially, it should be mentioned that the licensee ESS has a responsi- bility to develop an environmental monitoring program near the ESS facility. This includes ensuring the development of the measurement methods that are identifed as necessary and to carry out and follow up the monitoring program. However, it could still be of interest for SSM to give future further support to scientifc research on development on specifc techniques enabling quantifcation of ESS-specifc nuclides like alpha-emitting lanthanides in various samples (148 Gd) and radionuclides that are rarely studied and presently in lack of any analytical method. Furthermore, development of an extraction procedure for subsequent LSC analyse of relevant beta emitters in environmental samples (and in urine) could also be of interest for future research projects especially if it could be connected to the annual follow-ups of urine content of the general public. Project information Contact person SSM: Peter Frisk Reference: SSM 2018-1636 / 703 0237-00 SSM 2020:08 Authors: Kristina Eriksson Stenström, Vytenis Barkauskas,Guillaume Pedehontaa-Hiaa, Charlotta Nilsson, Christopher Rääf, Hanna Holstein, Sören Mattsson, Johan Martinsson, Mattias Jönsson, Christian Bernhardsson Lunds universitet, Lund 2020:08 Identifying radiologically important ESS-specific radionuclides and relevant detection methods Date: June 2020 Report number: 2020:08 ISSN: 2000-0456 Available at www.stralsakerhetsmyndigheten.se This report concerns a study which has been conducted for the Swedish Radiation Safety Authority, SSM. The conclusions and view- points presented in the report are those of the author/authors and do not necessarily coincide with those of the SSM. SSM 2020:08 Identifying radiologically important ESS‐specific radionuclides and relevant detection methods Kristina Eriksson Stenstrm1, Vytenis Barkauskas1, Guillaume Pedehontaa‐ Hiaa2,1, Charlotta Nilsson1, Christopher Rääf2, Hanna Holstein2, Sren Mattsson2, Johan Martinsson2, Mattias Jnsson2, Christian Bernhardsson2 1Lund University, Department of Physics, Division of Nuclear Physics 2Lund University, Department of Translational Medicine, Medical Radiation Physics, Malm i Summary The European Spallation Source (ESS) is under construction in the outskirts of Lund in southern Sweden. When ESS has entered the operational phase in a few years, an intense beam of high-energy protons will not only produce the desired spallation neutrons from a large target of tungsten, but a substantial number of different radioactive by-products will also be generated. A small part of these will be released to the environment during normal operation. During an accident scenario, a wide range of gases and aerosols may be released from the tungsten target. The palette of radionuclides generated in the ESS target will differ from that of e.g. medical cyclotrons or nuclear power plants, thus presenting new challenges e.g. in the required environmental monitoring to ensure that dose limits to the public are not exceeded. This project (SSM2018-1636), financed by the Swedish Radiation Safety Authority (SSM), aimed to strengthen competence at Lund University for measurement and analysis of ESS-specific radionuclides. First, an extensive literature review, including modelling as well as experimental analyses, of ESS- relevant radionuclides was performed. We found that radionuclide production in particle accelerators is well-known, while experience with tungsten targets is very limited. As a second part of the project, an independent simplified model of the ESS target sector for the calculations of radionuclide production in the ESS tungsten target was developed using the FLUKA code. We conclude that we have a fairly good agreement with results of other authors, except for 148Gd, and that the calculated radionuclide composition is sensitive to the nuclear interaction models used. In the third part of the project, known environmental measurement technologies for various ESS-relevant radionuclides were reviewed, focussing on pure difficult-to-measure alpha- and beta-emitters. Liquid scintillation counting (LSC) is a suitable technique e.g. for the important beta emitters 3H, 14C, 35S, 31P and 33P. Several ESS radionuclides of relevance for dose estimates have never been investigated by environmental analytical techniques, due to their absence in the normal environment. Alpha spectrometry seems promising for the analysis of alpha-emitting lanthanides, in particular for 148Gd. Among the many types of mass spectrometry techniques, ICP-MS (inductively coupled plasma mass spectrometry) and AMS (accelerator mass spectrometry) seem to be the most suitable for the analysis of long-lived ESS radionuclides in environmental samples (e.g. 243Am and possibly lanthanides for ICP-MS and 10Be, 14C, 32Si, 36Cl, 60Fe and 129I for AMS). Three experimental parts were performed during the project, related to initiation of radioactivity measurements of aerosols at Lund University, mapping of environmental tritium in the Lund area, and establishment of a method to measure tritium in urine followed by a study of tritium in persons presently living or working in Lund. Aerosols were collected at a rural background station (Hyltemossa near Perstorp, northern Skåne) using a high-volume aerosol sampler with automatic ii filter change (DHA-80, Digitel). Gamma spectrometry measurements of 7Be agreed rather well with results from a nearby air monitoring station (SSM/FOI). Tritium (radioactive hydrogen) is expected to dominate the source term from the ESS target station to the environment. We have performed several investigations to monitor the current situation of tritium in Lund using LSC: the matrices investigated included air humidity, precipitation,
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