KYT SURFACE:Complementary Considerations in Assessing Performance of a Landfill-Type Near Surface Repository

Design basis and performance targets for a landfill type near surface repository have been examined as part of the KYT2022 SURFACE project, as well as the differences between a near surface repository and a landfill for hazardous waste landfill. The main difference comes from legislation and from ensuring passive safety for the repository after closure. The effect of site conditions on the engineered barriers was studied from the perspective of low temperatures during winter in Finland. Numerical modelling shows that freezing of some or all of the engineered barriers in the cover layer can take place during a cold winter, especially in a situation when there is lack of sufficient snow coverage that would provide insulation. In normal and hazardous waste landfills, the frost shall not penetrate to the level of the mineral sealing layer. This leads to a recommendation of performing site and design specific numerical modelling on the frost penetration and, based on the results, considering cover top layer thicknesses that are more than the typical minimum 1 m used in normal and hazardous waste landfills. The potential impacts of post closure forestation also supports use of a thicker top layer to avoid puncture of synthetic liners by tree roots.Limiting water inflow into the repository through the cover layer was identified as one of the key factors in ensuring long-term and passive safety for the near surface repository. This can be done by combining water tight synthetic liners with a mineral sealing layer. Limiting water flow to the repository decreases the quantity of formed leachates and can slow the generation of landfill gas.The need for gas management systems depends on the rate at which gas is generated in the waste. In order to minimize gas generation from soft waste pallets containing organic waste, placing this waste into metallic packages was reviewed as an option. This would also enhance the mechanical stability of the repository. Performance of the drainage systems at the foundation structure and collection and handling leachate waters was also assessed as part of this work. Some of the drainage is in any case needed for preventing accumulation of leachate water in the bottom of the repository. However, the effect of the drainage and leachate water collection system for post closure safety requires further considerations. If the cover layer works as expected and the waste is not in direct contact with the water, the generation of leachate water should be minimal.Final recommendations concerning the design of the landfill type near surface repository will be summarised in 2022 including the analysis of results from KYT2022 SURFACE tasks 1 (radionuclide migration) and 3 (steel corrosion and microbial activity) on the repository design recommendations

Waste Management of Small Modular Nuclear Reactors in Finland

Small modular nuclear reactors (SMRs) represent advanced technology in nuclear energy aim-ing to produce low carbon energy at smaller unit size and enhanced passive safety in compar-ison to traditional nuclear power plants (NPPs). The management of spent nuclear fuel (SNF) and low- and intermediate-level waste (LILW) from SMRs is an issue that needs to be resolved as part of any deployment of SMR technology in Finland. Currently, spent nuclear fuel from NPPs in Finland is planned to be disposed in the ONKALO® deep geological repository applying the KBS-3V disposal concept. This concept should be applicable for spent fuel from SMRs using light-water reactor (LWR) technology. However, there are some differences in the waste forms, most obviously the length of the fuel assemblies, but also in the spent fuel characteristics that need to be considered in the further development of the concept for spent fuel from SMRs. Preliminary 2D calculations were made with the continuous-energy Monte Carlo code Serpent to compare the spent fuel characteristics from two example LWR-SMRs to spent nuclear fuel from currently operating NPPs in Finland. In one example case, a NuScale Power ModuleTM was considered as it is one of the most advanced LWR-SMRs in the world. The other example case is an SMR planned in Finland for district heating purposes. The main differences between the SMR and NPP spent fuels are linked to lower burnups in the SMRs. Lower discharge burnups are to be studied further from the point of view of criticality safety at disposal. Other-wise, the lower average discharge burnup of these SMR fuel types, in principle, generally tends to make the handling of spent fuel assemblies less demanding with respect to the decay heat and ionizing radiation emitted from the assembly. However, rigorous calculation of the dose rates would require 3D calculations to determine the axial burnup distribution within a fuel as-sembly, which was outside the scope of this study. Published studies indicate that possibly larger masses (per GWe-year) of SNF and other HLW and larger volumes (per GWe-year) of LLW will be produced in a LW-SMR compared to a large NPP. However, because of the lower decay heat in the SMR SF (due to the lower burnup), less excavated volume and, consequently, less clay-based filling material (deposition tunnel back-fill) may be needed in a repository. Depending on the number of SMR units located at sites in Finland, the amounts of spent fuel and other waste streams can be relatively small so that a centralised waste management facility and repository could be the most feasible option for processing and disposal of all the nuclear waste. Alternatively, the wastes can be disposed of locally (near SMR sites in smaller facilities) or a hybrid model, where, e.g., only SNF is disposed centrally, could be considered. These alternatives will depend strongly on the ownership structure of the SMRs deployed in Finland. Local stakeholder and public opinion will be very important as well. Other issues, such as ge-ological suitability of the SMR sites for disposal, transport and interim storage will need to be assessed. In terms of final disposal of SNF from LWR-SMRs, the only currently available option is the KBS-3V concept, especially considering the state of the licencing process for this concept in Finland. Deep borehole disposal represents an intriguing, particularly in the case of local disposal for relatively small amounts of waste, but not yet fully developed alternative. The suitability of deep borehole disposal in the crystalline rock conditions prevailing in Finland will be studied in the next phase of the project. Spent fuel from non-LWR SMRs, i.e., high-temperature-gas-cooled, fast neutron-spectrum and molten salt-type SMRs, was also discussed briefly. Challenges were identified in the pre-treat-ments needed for SNF from these reactors prior to disposal including lack of suitable facilities in Finland and potential proliferation issues. In some cases, e.g., reactors with graphite mod-erators, the disposal of the LILW waste streams was considered problematic as the current methodologies in use in Finland for disposal of LILW would not be applicable. More extensive studies would be required to specifically identify the waste streams from non-LWR SMRs and how the waste characteristics would need to be taken into account for disposal

Mechanisms Governing 90Sr Removal and Remobilisation in a VLLW Surface Disposal Concept

Flow-through columns were used to assess potential long-term trends in 90Sr biogeochemistry and transport in a Finnish near-surface very low-level waste (VLLW) repository concept. Experiments simulated the effects of water intrusion and flow through the repository barrier and backfill materials, examining impacts on 90Sr migration. Artificial rainwater containing 2.0 mg/L stable Sr (as a proxy for 90Sr) was pumped through column systems that had varying compositions from a matrix of rock flour (backfill material), bentonite (backfill/sealing material), and carbon steel (waste encapsulation material), for 295 days. Effluent geochemistry was monitored throughout. Sr retention behaviour in all column systems was broadly similar. Sr removal from influent rainwater was marked (~95% removed) at the beginning of the experiments, and this degree of removal was maintained for 20 days. Thereafter, Sr concentrations in the effluents began to rise, reaching ~2 mg/L by 295 days. Further, 56%–67% of added Sr was retained in the repository materials over the 295-day reaction period. Analysis of the effluents indicated that colloids did not form; as such, Sr output was likely to be aqueous Sr2+. Upon completion of the experiment, solid-associated Sr distribution and speciation in the columns were assessed through column sectioning and post-mortem analyses, which encompassed the following: total acid digests, sequential extractions, and XAS analysis. The total acid digests and sequential extractions showed that Sr was evenly distributed throughout the columns and that the majority (68%–87%) of solid-associated Sr was in the exchangeable fraction (MgCl2). This suggested that a major part of the solid-phase Sr was weakly bound to the column materials via outer-sphere sorption. Interestingly, a smaller amount of Sr (7%–23%) could only be extracted by aqua regia, suggesting that a proportion of Sr may bind more strongly to the barrier materials. XAS analysis of select samples confirmed that the dominant Sr phase was sorbed to the rock flour and bentonite, but not corroded carbon steel. Columns were also subject to remobilisation experiments using artificial rain- and seawater without added Sr. While rainwater remobilised Sr slowly, high-ionic strength seawater remobilised Sr at much higher rates in the systems containing bentonite. Interestingly, Sr was well retained in the rock flour-only system following rain and seawater intrusion. Overall, the results indicate that the column materials provide reactive surfaces for Sr removal should it be released from waste packages; however, the backfill and barrier materials have limited retention capacity, and the dominant sorption interaction is relatively weak. The safety case for the shallow disposal of radioactive waste should consider the possibility of seawater intrusion and that the bentonite-bound Sr was significantly more susceptible to remobilisation following seawater, despite retaining slightly more Sr during sorption experiments

KAVIOIDEN KOPSETTA JA IKUISTETTUJA HETKIÄ - Hevostoiminnan ja valokuvauksen menetelmäkansio lastensuojeluyksikön työntekijöille

Tämän opinnäytetyön tarkoituksena on tuottaa tietoa valokuvauksen ja hevostoiminnan menetelmästä lastensuojelun sijaishuollossa. Opinnäytetyön tavoitteena on antaa työntekijöille valmiita harjoitteita menetelmien käyttöön, jota tukee koottu tietoperusta. Nämä menetelmät ja koottu tietoperusta löytyy menetelmäkansiosta. Opinnäytetyön toimeksiantajana toimii yksityinen lastensuojeluyksikkö Pohjois- Karjalassa ja opinnäytetyön aihe syntyi toimeksiantajan tarpeesta. Opinnäytetyö toteutettiin toiminnallisena opinnäytetyönä, joka sisältää neljä hevostoiminnan ja neljä valokuvauksen menetelmää lastensuojelun sijaishuollon työn tueksi. Menetelmät pohjautuvat lastensuojelun, sosiaalipedagogiikan ja Green Caren viitekehyksiin. Osallistujien palautteen ja ohjaajien havainnoinnin perusteella voidaan todeta, että harjoitteet tukivat työskentelyä lasten kanssa, sekä vastasivat lapsille asetettuja tavoitteita. Harjoitteet koettiin mielekkäiksi ja hyödyllisiksi. Opinnäytetyötä voisi jatkossa kehittää siten, että muihin lastensuojeluyksikössä käytettäviin menetelmiin kehitettäisiin vastaavat menetelmäkansiot.The purpose of this thesis is to produce information of photography and equine assisted methods in child welfare surrogate care. The aim of the thesis is to give the employees ready exercises for the use of methods supported by the compiled knowledge base. These methods and assembled framework can be found in the method folder. Employer of the thesis is private child welfare unit in the North Karelia. Subject of the thesis came from employer’s needs and was fulfilled as a functional thesis. It includes four equine assisted activity and four photographic methods to support work at the child welfare unit. The methods are based on a framework of child welfare, social pedagogy and Green Care. Based on the feedback from the participants and the observations of the instructors, it can be concluded that the exercises supported the work with the children and correlated the goals which was set for the child. The exercises experienced meaningful and useful. As a suggestion for further research we propose that by developing corresponding method folders for the other methods which is used in the child welfare unit