The existence and viability of nuclear power have been at the center of debate for several decades due to the inherent safety risks. Disasters such as Three Mile Island (1979), Chernobyl (1986), and Fukushima Daichii (2011) have resulted in severe consequences but have also led to higher safety standards and precautionary measures within the nuclear industry. This process of learning from past accidents and incidents, commonly known as experience feedback, has played a significant role in improving nuclear power safety. This Master thesis aims to investigate how Forsmarks Kraftgrupp (FKA) utilizes experience feedback and how they could draw insights from other industries to achieve best practices. The research questions involve conducting a current analysis of FKA's experience feedback process, exploring how representatives from transportation-, defense-, and pharmaceutical industries handle experience feedback, and providing recommendations to FKA based on benchmarking with these external industries. Using the Functional Resonance Analysis Method (FRAM) model, the study identified best practices in experience feedback through a comparison with the other organizations involved. The results indicate that to foster a strong reporting culture, clear guidelines and support from top management are crucial. A digital tool for incident and case management is essential to support and streamline experience feedback. This tool should be user-friendly, accessible through mobile applications and web forms, and capable of generating statistics and reports to monitor performance. Promoting a culture of learning is beneficial through diverse methods such as workshops, seminars, web-based training, and informal approaches like knowledge portals. A reform leader and regular managerial meetings can anchor the implementation of lessons learned. External forums facilitate knowledge exchange and learning from other organizations. Proactivity and forward-thinking are fostered through collaborations with stakeholders to broaden perspectives. Mandatory improvement opportunities promote long-term sustainability, while training courses and study circles offer innovative future solutions. By comparing FKA's experience feedback process with organizations from various industries, this research provides recommendations for further development. A crucial conclusion is that FKA should prioritize all four dimensions addressed by the FRAM model: Respond, Monitor, Learn, and Anticipate. Implementing these recommendations will enhance nuclear power safety and contribute to a culture of continuous improvement within the organization.

Nuclear power is an important part of Sweden's energy system and contributes with about 30 % of the supplied electric energy. Interest in new construction is currently high and one type of reactor that may be built is small modular reactors, SMRs. A method that is used to evaluate the safety of a traditional nuclear power plant is the so called probabilistic safety assessment (PSA). An important question is if PSA is applicable to SMRs. This thesis examines differences between a BWRX-300 type SMR and a generic boiling water reactor to investigate if the traditional PSA method is applicable to SMRs and what characteristics that may affect the results.  To investigate the topic, a simplified PSA analysis is carried out at level 1 for five different initiating events: extreme snowfall, loss of cooling accident, loss of main feedwater, loss of offsite power supply and transient. These are then compared to a model of a generic BWR reactor.  The conclusions that emerge from the analysis are that the traditional PSA method can be applied for SMRs of the BWRX-300 type. The features that distinguish the BWRX-300 compared to a generic BWR are mainly that the SMR is smaller in size and power and the influence of the passive safety systems. This results in a lower core damage frequency. Some the areas where the PSA method could be developed for SMRs are the analysis of passive components and passive functions.

<p>I chose to study how the Swedish Air force carries out their work with setting goals for their work to improve flight safety and compare this with how the Swedish nuclear power plant Forsmark performs their work with improving nuclear safety. The study showed that both organisations have a lot to improve on in their ways of how to work. Especially when it comes to engaging the employees in the process, both in letting the employees be a part of coming up with areas to work on and in letting the employees evaluate which progress that has been made. It also showed that both organisations need to improve their methods for evaluating the work that has been done. This is especially important for the Air Force which evaluates on many levels and locations and did not have a set standard for how to conduct the evaluation. Although, Forsmark also needed to improve but on how to conduct the evaluation on more than one level in the organisation, allowing more people into the evaluation process and maybe letting someone not part of the process be a part of the evaluation to see things from a different perspective. Also, Forsmark had goals set which did not have a set time for when to evaluate them, which is another criteria for success.</p>

I chose to study how the Swedish Air force carries out their work with setting goals for their work to improve flight safety and compare this with how the Swedish nuclear power plant Forsmark performs their work with improving nuclear safety. The study showed that both organisations have a lot to improve on in their ways of how to work. Especially when it comes to engaging the employees in the process, both in letting the employees be a part of coming up with areas to work on and in letting the employees evaluate which progress that has been made. It also showed that both organisations need to improve their methods for evaluating the work that has been done. This is especially important for the Air Force which evaluates on many levels and locations and did not have a set standard for how to conduct the evaluation. Although, Forsmark also needed to improve but on how to conduct the evaluation on more than one level in the organisation, allowing more people into the evaluation process and maybe letting someone not part of the process be a part of the evaluation to see things from a different perspective. Also, Forsmark had goals set which did not have a set time for when to evaluate them, which is another criteria for success.

Control room operating crews are a crucial component in maintaining the safety of nuclear power plants. The primary support to operators during disturbances or emergencies are numerous emergency operating procedures. Further support is provided by reoccurring crew training in which the crews practice on handling anticipated disturbances in full-scale simulators. Due to the complexity of nuclear power plants and the small number of previous accidents to learn from, every possible accident scenario cannot be covered by the procedures and hence not trained on in the simulator. This raises the question of how operators can be prepared and able to cope with unexpected events by other means.   This thesis investigates the possibilities of operating crews to act flexibly in situations where stable responses in the form of prescribed actions sequences from procedures cannot be applied. The study is based on the safety research paradigm of resilience engineering and the four cornerstones of resilience; learning, monitoring, anticipating, and responding (Hollnagel, 2011). The meaning and applicability of the resilience cornerstones were examined by interviewing a domain expert at the time employed by the OECD Halden Reactor Project. Subsequently, eight semi-structured interviews with operator training personnel at a Swedish nuclear power plant provided the main data of this study.   This study shows that the resilience cornerstones were applicable to the work of nuclear power plant crews during emergency operations. In addition, the study provides findings regarding which artefacts (e.g. procedures) or crew characteristics (e.g. ways of communicating) support the cornerstone functions. The base thesis is that procedures always shall be used, but in situations where an operator perceives that no procedure is applicable, the crew have an opportunity to discuss the problem to come up with some other solution, i.e. act flexibly. Some trainers argued that the room for flexibility is there when needed, but it is not as certain how much flexibility and what kind of flexibility the operators are given. However, it does not seem like the flexibility, or lack of flexibility, given to operators is in itself the most problematic issue in the preparation of crews for unexpected events. Instead, this study identified several other problems of training and everyday work that could negatively affect crews’ capability to handle unexpected events. On the other hand, the trainers highlighted communication and teamwork to be important when the unexpected strikes and that much focus have been shifted towards such issues in training. Hence this can be claimed to be an important contribution given by the training today in successfully handling unforeseen events.

This project deals with two-phase CFD model validation, a subject which is currently under active research due to its complexity. The goal is to create a model that predicts data profiles to an acceptable degree for a wide array of flow conditions. The applications within the nuclear field would mainly be for safety analysis, e.g. to predict phenomena such as the critical heat flux. The underlying physics were investigated, and simulations were performed of two-phase flow of the coolant R12 using the program OpenFOAM in an attempt to match radial profiles of void fraction, interfacial area concentration, vapour velocity and sauter mean diameter for different flow conditions provided by the DEBORA experiments. The proper set of models was found via sensitivity testing: trying combinations of different models and model coefficients. The effect on the simulation result was investigated, with the models that improved the result kept while the rest were discarded. The main strategy was to find models that accurately predicted the sauter mean diameter, as initial sensitivity tests showed the result to be highly dependent on this parameter. The impact of initial conditions and mesh refinement was also investigated, and a temperature validation study was done. The process was aided by a number of Matlab programs written by the author, to calculate and verify inputs and to post-process the result. A model was found that simulated the subcooled nucleate boiling datasets to an acceptable degree. The model failed to accurately simulate saturated nucleate boiling. / Detta projekt behandlar tvåfas CFD-modellvalidering, ett ämne som fortfarande ärunder aktiv forskning på grund av sin komplexitet. Syftet är att utveckla en modellsom förutser dataprofiler till en acceptabel grad för en mängd olika flödesregimer.Inom kärnkraftsbranchen skulle detta primärt vara applicerbart inom reaktorsäkerhet,t.ex. för att förutse fenomen så som critical heat flux. Den underliggande fysikenundersöktes, och simuleringar genomfördes på tvåfas flöde av kylmedlet R12 med hjälpav programmet OpenFOAM i ett försök att matcha 14 dataprofiler för void fraction,interfacial area, vapour velocity och sauter mean diameter för olika flödesregimertillhandahålla av DEBORA-experimenten.Den rätta uppsättningen modeller fanns via känslighetsanalys, genom att testa olikakombinationer av modeller och modellkoefficienter. Deras effektersimuleringsresultatet undersöktes, och de modeller som förbättrade resultatet behölls,medans resten förkastades. Huvudstrategin var att hitta modeller som förutsåg sautermean diameter, bubblornas medeldiameter, väl, då preliminär känslighetsanalysvisade att resultaten var mycket känsliga på denna parameter. Inflytandet avinitialvillkor och mesh-förfining undersöktes, och en temperaturprofilsvalideringgenomfördes. Till hjälp i processern var ett antal Matlab-program skrivna avförfattaren för att beräkna och verifiera inmatning och behandla och visualiserautdatan. En modell hittades som simulerade underkyld kokning till en acceptabel grad.Modellen misslyckades med att träffsäkert simulera mättad kokning.