| 1. |
- Eriksson Stenström, Kristina, et al.
(författare)
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Identifying radiologically important ESS-specific radionuclides and relevant detection methods
- 2020
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Bok (refereegranskat)abstract
- 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 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, pond water, indoor air at one accelerator facility and urine from the general public as well as from persons who may be occupationally exposed to tritium. Environmental tritium was generally very low (<3.4 Bq L-1), with somewhat higher concentration in the springtime than during the rest of the year. Tritium in the vast majority of the 55 urine samples was also very low: only a few exposed workers were found to have up to 11 Bq L-1 in their urine, which still is very low compared to e.g. reactor workers. Suggestions for further actions and work related to measurement and analysis of ESS relevant radionuclides are presented.
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| 2. |
- Hinrichsen, Yvonne, et al.
(författare)
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Influence of the migration of radioactive contaminants in soil, resident occupancy, and variability in contamination on isodose lines for typical Northern European houses
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- In the remedial phase following an accidental radioactive release, it is important that soil decontamination measures are carried out on the areas that contribute most to the radiation dose. In this study, the newly developed concept of isodose lines was applied to the area around typical Swedish dwellings to identify these areas. The influence of the most common building materials in Sweden, wood and brick, and the importance of the positions of doors and windows on the isodose lines were demonstrated for specific positions inside the houses, as well as for the entire house, assuming the residents exhibit typical resident occupancy. Decontamination of the areas within certain isodose lines was shown to result in a greater dose reduction than decontaminating the same area of soil within a certain distance of the house. Furthermore, the impact of vertical migration of the radioactive contaminants in the soil on the isodose lines was studied, showing that the area enclosed by isodose lines decreases over time as the contaminants migrate deeper into the soil. The resulting isodose lines and their change over time are dominated by the downward movement of the contamination in the upper layer of soil. The impact of the variability in contamination on the final isodose lines and their dependence on building materials are demonstrated.
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| 3. |
- Hinrichsen, Yvonne, et al.
(författare)
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Maximizing avertable doses with a minimum amount of waste for remediation of land areas around typical single family houses after radioactive fallout based on Monte Carlo simulations
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322.
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Tidskriftsartikel (refereegranskat)abstract
- The uncontrolled release of long-lived radioactive substances from nuclear accidents can contaminate inhabited land areas. The removal of topsoil is an important method for reducing future radiation exposure but can also generate a large amount of waste that needs safe disposal. To the best of our knowledge, previous studies have determined the optimal depth of topsoil removal but not the size of the area designated for this measure. For this purpose, this study performed Monte Carlo simulations of hypothetical 137Cs surface contamination on various ground areas in a typical northern European suburban area. The goal was to study the size of the areas needed and amount of waste generated to achieve a certain relative and absolute dose reduction. The results showed that removing the topsoil from areas larger than 3000 m2 around the houses in the study neighbourhood results in only marginal reduction in radiation exposure. If, on average, 5 cm of topsoil is removed over 3000 m2, then 150 m3 of waste would be generated. However, in this scenario adjacent properties benefit from each other’s decontamination, leading to a smaller amount of waste for a given reduction in future radiation exposure per inhabitant of these dwellings. Additionally, it was shown that topsoil removal over limited areas has a higher impact on the absolute dose reduction at an observation point inside or outside the houses with higher initial dose.
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| 4. |
- Hinrichsen, Yvonne, et al.
(författare)
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Monte-Carlo simulations of external dose contributions from the surrounding ground areas of residential homes in a typical Northern European suburban area after a radioactive fallout scenario
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The emissions of 137Cs into the environment from the nuclear accidents in Chernobyl in 1986 and Fukushima in 2011 led to the need to decontaminate large areas to avert radiation doses to the population in the affected areas. To be able to perform cost-effective and sustainable remediation, knowledge is needed about how radiation doses can be minimized through optimized interventions such that the greatest possible reduction in radiation dose is obtained with the smallest possible negative impact on the area. Theoretical calculations have been performed to determine how radiation doses in single family houses in a typical Swedish residential suburb arise from a hypothetical 137Cs deposition on the ground. The intention was to highlight how remediation of different parts of the surroundings affects the radiation dose to the residents in a particular property. A Monte Carlo model of the houses and the environment in a suburban area was set up to allow calculations of the dose contributions from different contaminated ground areas such as their own property, neighbouring properties, streets and surrounding recreational areas. Calculations were performed for eleven observation points inside different rooms of the house and one observation point in the garden outside the house, for four houses in the neighbourhood, and for two types of building construction material. The influence of the time spent in different rooms of the house and the contamination of areas surrounding the house was studied. The results show that in general the main dose contribution originates from their own property, but that a significant part (30–80%, depending on the observation point) can come from other areas, showing the importance of considering the surroundings in remediation actions. More detailed analysis of the results showed that the dose contribution from a source region is in general highly dependent on the position of windows in a brick house, whereas for a wooden house the distance to the source region is also of relevance.
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| 5. |
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| 6. |
- Isaksson, Mats, et al.
(författare)
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Stråldosen till boende i nedfallsdrabbade områden: Preliminära uppskattningar efter svenska förhållanden
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Utifrån modeller som tagits fram efter radioekologiska studier av svenska förhållanden utförda efter Tjernobylolyckan 1986 visar preliminära beräkningar att de avstyrda stråldoser som kan åstadkommas med sanering av byggnadshus respektive strikta livsmedelsrestriktioner är relativt lika (ca 25%). En kombination av dessa åtgärder kan teoretiskt sänka den summerade stråldosen med 50% under ett 50-årsperspektiv efter nedfallet. Dessa värden har utgått från en genomsnittlig dosreducerande effekt på 50% av en saneringsinsats på en typisk svensk bostad. I det pågående projektet kommer mer detaljerade studier kring saneringseffektvitetens roll i den avstyrda stråldosen över lång sikt att studeras vidare.
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| 7. |
- Martinsson, Johan, et al.
(författare)
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Decontamination efficiency and waste generation for the decontamination of radioactively contaminated urban and rural environments
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A radioactive fallout following a nuclear accident can result in contamination of large areas of land. In order to protect human health against ionizing radiation, large-scale decontamination that includes multiple sets of clean-up measures may be necessary. Sweden lacks national experience of this type of large-scale decontamination. There are thus great uncertainties in the effect of such a decontamination which is dependent on the efficiency and waste generation of the individual remediation measures. In this report, the results from a literature review of the Japanese experience of decontamination after the nuclear accident in Fukushima-Daiichi, 2011, are highlighted. We show that the Japanese decontamination efficiency was on average about 12 percentage points lower than the decontamination efficiencies listed in reference literature on radioactive material decontamination. Removed contaminated soil is by far the largest contribution to radioactive waste production during decontamination. There is a positive correlation between reduced radiation dose rate and amount of soil removed during decontamination. Over time, however, ecological processes contribute by far the most to reduced radiation dose rates. The results can be an important contribution to current decontamination strategies and valuable for responsible agencies and authorities in the case of nuclear fallout incident.
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| 8. |
- Martinsson, Johan, et al.
(författare)
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Experimental wildfire induced mobility of radiocesium in a boreal forest environment
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 792
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Tidskriftsartikel (refereegranskat)abstract
- Wildfires are expected to increase with warmer climate, which can contribute to the mobility and the resuspension of long-lived and potentially hazardous radionuclides. The release of 137Cs during combustion of dried litter, forest floor organic soil, and peat was investigated in a small-scale experimental set-up. Combustion conditions were varied to simulate different wildfire scenarios, and the fuels were dried organic material collected in a boreal environment of Sweden that was contaminated following the Chernobyl accident in 1986. The combustion-related release of 137Cs to the air was on average 29% of the initial fuel content, while 71% of the initial 137Cs remained in the ashes after the combustion. Peat and forest soil had the highest releases (39% and 37%, respectively), although these numbers should be viewed as potential releases since authentic wildfire combustion of these fuels are usually less effective than observed in these experiments. These results indicates that the 137Cs has migrated downwards in the organic material, which imply potentially significantly more 137Cs emissions in severe wildfires with intense combustion of the organic vertical profile in peatbogs and forests. More 137Cs tended to be released during intense and efficient combustion processes, although no significant differences among combustion intensities were observed. The generated experimental data was used in an emission scenario to investigate the possible range in 137Cs emissions from a wildfire. Our study shows that a severe wildfire in a contaminated area of 10,000 ha could potentially release up to 7 TBq of 137Cs. This is the first laboratory study to investigate 137Cs release upon varying combustion conditions using real fallout contaminated organic material obtained from a boreal environment.
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| 9. |
- Martinsson, Johan, et al.
(författare)
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Influence of variable oxygen concentration on the combustion derived release of radiocesium from boreal soil and peat
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 815
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Tidskriftsartikel (refereegranskat)abstract
- Radiocesium, 137Cs, is one of the most common and dispersed human-made radionuclides. Substantial stocks of 137Cs are stored in organic layers, like soils and peat, as a consequence of nuclear weapons fallout and accidental releases. As climate warming progresses these organic layers are subject to enhanced risks of wildfires, especially in the vast boreal biome of the northern hemisphere. Reemission of 137Cs to the atmosphere is therefore presumed to increase. Here, we experimentally investigated the emissions and redistribution of 137Cs in smoldering fires of boreal soil and peat by varying the oxygen concentration during combustion. For both soil and peat, significantly more 137Cs was released through flaming combustion in 21% O2 (50% and 31%, respectively) compared to smoldering in reduced O2 environments (14% and 8%, respectively). The residual ashes were heavily enriched (>100%) in 137Cs. Hence, after a wildfire induced volatilization of 137Cs, there exists further pathways of 137Cs enriched ash to proliferate in the environment. These results serve as a link between wildfire combustion conditions and the mobility of the 137Cs inventory found in ground fuels of the boreal environment and can be valuable for radiological risk assessments in a warmer and a more nuclear energy reliant world.
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| 10. |
- Rääf, Christopher L., et al.
(författare)
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Time‑dependence of decontamination efficiency after a fallout of gamma‑emitting radionuclides in suburban areas: a theoretical outlook on topsoil removal
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Decontamination of urban areas may be necessary in the case of extensive fallout of radioactive material after a nuclear accident, as removal of contaminated soil and vegetation will significantly reduce doses for the residents in an area affected by fallout. Experience from Japan shows that cleanup operations of urban areas may take years despite investment in ample resources. The time delay between the initial fallout and completion of the decontamination measures allows natural and physical processes to affect the results. The efficiency of the decontamination will therefore depend significantly on time. Radioecological modeling and computer simulation of urban topography with one-story houses were applied in this study to estimate action-influenced time-integrated dose reductions (TDR) of contaminated topsoil removal as a function of time after the fallout. Results indicate that the TDR decreases gradually after the fallout depending on the vertical migration rate of radiocesium and, to some extent, the initial 134Cs/137Cs ratio. Delaying the topsoil removal from 1 to 10 years will result in a TDR decrease by more than a factor of two. Removing the topsoil within one year after fallout results typically in an averted effective dose between 34 and 80 mSv per MBq m− 2 deposition of 137Cs for residents in wooden houses. The corresponding values for residents in brick houses are about 50% lower due to higher shielding. Additional modeling is needed to estimate how age and sex influence the averted detriment to affected cohorts. In addition, more in-depth knowledge of how the efficiency of topsoil removal in practice compares with hypothetical models and the effect of incomplete removal of radiocesium is needed to improve calculations of TDR values.
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