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1	Modellering, simulering och analys av kärnreaktorn BWRX-300 Backlund, Erik January 2023 (has links) The demand for fossil-free energy production is rising due to electrification and increased consumption in the energy system. There are also multiple climate goals to reach, to preserve the possibilities of a sustainable future. A response to this is the BWRX-300, a natural circulation boiling water small modular reactor (SMR) concept developed by GE Hitachi Nuclear Energy. It is currently at the forefront of study for many power utility companies around the world. For decision making it is of interest to investigate the capabilities of new facilities. This Master Thesis work's aim is to study the BWRX-300 reactor's feasibility together with evaluating and optimizing its performance using the core simulation softwares Casmo5 and Simulate5. This is carried out by first verifying Simulate5's natural circulation capabilities by modifying an existing forced-circulation reactor to natural circulation, then comparing simulation results to real world data. Next a comprehensive model of the BWRX-300 reactor pressure vessel is modelled and validated. Equilibrium cores for 12- and 24-month cycle lengths are then simulated where key reactor performance metrics such as fuel economy, safety margins, axial profiles (of voids and pressure drop) and reactor characteristics are extracted. The effect of different fuel assembly designs in the BWRX-300 reactor core is investigated to find first core design optimums. Furthermore the decay heat removal system in the BWRX-300 is investigated. Lastly the results are used to evaluate the optimal operating mode given the current and future more dynamic projected state of the energy system. The results show that there are no real technical difficulties while operating the BWRX-300 reactor for 12 or 24 months. The decay heat removal system and core flow characteristics provide abundant coolant flow to maintain long term fuel integrity during both normal and abnormal operation modes. More or less routine core design optimization work is required to obtain sufficient safety margins and improve fuel economy. It is observed that the smaller reactor core requires an increase in average fuel enrichment to maintain criticality throughout the cycle, potentially creating an incentive to raise the current licensing limit. However it is deemed possible to avoid this by conducting further fuel design optimization work. Kärnkraft SMR små modulära reaktorer liten modulär reaktor kärnreaktor BWR BWRX-300 självcirkulation passiv säkerhet GE Hitachi cykellängd härddesign nukleär design Simulate5 GNF2 kärnbränsle reaktormodell Energy Engineering Energiteknik Energy Systems Energisystem
2	Förbättrade effektmarginaler med radiell anrikningsfördelning för PWR-bränsle / Improved peaking factors with radial enrichment distribution för PWR fuel assembly Åkerman, Mattias January 2016 (has links) In recent years, the enthalpy raise hot channel factor limit has decreased significantly due to the power upgrade of Ringhals 4 and the use of shielding fuel assemblies. The shielding fuel assemblies task are to reduce the neutron leakage to the reactor vessel and in that way extend the reactor lifetime. This is achieved by replacing a few fuel rods with steel rods. Experiences from the last fuel cycles show that the core design procedure has been hampered because of this and that it’s hard to stay under the design limit. A way to overcome this problem and to improve the fuel economy is to introduce the use of radial enrichment distribution in the fuel assembly. This master thesis shows, through a case study of three fuel cycles at Ringhals 4, that the internal peaking factor can be improved by roughly 2–3 % and that the maximum enthalpy raise hot channel factor can be improved by about 2.0–2.5 % if the fuel assemblies contain three different levels of enrichments instead of currently one. This can be achieved without any noticeable decrease in cycle length. / Genom en fallstudie av tre driftcykler för Ringhals 4 visar den här rapporten att max FΔH under cykeln kan sänkas med 2,0–2,5 % om bränsleknippena radiellt anrikningsoptimeras med minst tre delanrikningar. Totalt under cykeln kan FΔH sänkas med upp till 4 %. Om radiell anrikningsoptimering införs för Vattenfalls PWR:er skulle arbetet med att designa härdarna förenklas och utrymme ges för att ladda reaktorerna på ett mer ekonomiskt sätt. Ringhals 4 PWR fuel rod fuel assembly shielding fuel assembly reactor core reactor cycle burnable absorber peaking factor internal peaking factor enthalpy raise hot channel factor radial enrichment distribution enrichment optimization CASMO SIMULATE XIMAGE Ringhals 4 PWR bränslestav bränsleknippe skärmande knippen reaktorhärd reaktorcykel brännbar absorbator intern effektformfaktor radiell effektformfaktor effektmarginal radiell anrikningsfördelning anrikningsoptimering bränsledesign härddesign CASMO SIMULATE XIMAGE

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Modellering, simulering och analys av kärnreaktorn BWRX-300

Förbättrade effektmarginaler med radiell anrikningsfördelning för PWR-bränsle / Improved peaking factors with radial enrichment distribution för PWR fuel assembly