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