This report investigates a controlled reduction process (CRP) of triuraniumoctoxide (U3O8) powder into a hyperstoichiometric uranium dioxide (UO2+x)powder that could be mixed with the fresh uranium dioxide (UO2) powderwithout decreasing its sinterability. Before the CRP could be performed, scrapUO2 pellets were oxidized into U3O8 powder which was then reduced. Fiveversions of the CRP process were performed with different parameters. Thecharacteristics of the resulting CRP powders were investigated through X-raydiffraction (XRD), scanning electron microscope (SEM), and thermogravimetricanalysis (TGA). The powders were mixed with fresh UO2 powder, pressed andsintered to pellets. The density of the pellets was investigated, as was theirsurface through SEM.The results indicate that CRP powders with x below 0.25 had higher finalpellet density, suggesting that there is a benefit of reducing the U3O8 powder tothe fluorite crystal structure before mixing with the fresh UO2 powder. Furtherinvestigation and optimisation of the process is necessary, however its futureimplementation could lead to an increase in the weight fraction of recycledscrap material above the current 9 wt% maximum, among other benefits. / Denna rapport undersöker en kontrollerad reduktionsprocess (CRP) avtriuranoktoxid (U3O8) pulver till ett hyper-stökiometriskt urandioxid (UO2+x)pulver. Detta kan blandas med färskt urandioxid (UO2) pulver utan att minskadess sinterbarhet. Innan CRP kunde utföras oxiderades UO2-skrotkutsar tillU3O8-pulver som sedan reducerades. CRP-processen upprepades fem gångermed olika parametrar. Egenskaperna hos de resulterande CRP-pulvren undersöktesgenom röntgendiffraktion (XRD), svepelektronmikroskop (SEM) ochtermogravimetrisk analys (TGA). Pulvren blandades med färskt UO2-pulver,pressades och sintrades till kutsar. Kutsarnas densitet undersöktes, liksomderas yta med SEM.Resultaten indikerar att CRP-pulver med x under 0,25 hade högre slutligkutsdensitet, vilket tyder på att densiteten hos sintrade kutsar blir högre närU3O8-pulvret reduceras till fluoritkristallstruktur innan det blandas med detfärska UO2-pulvret. Vidare undersökning och optimering av processen ärnödvändig, men dess framtida implementering skulle kunna leda till en ökningav viktfraktionen av återvunnet skrotmaterial som används vid kutsfabrikation,bland andra fördelar.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-347040 |
| Date | January 2024 |
| Creators | Dickman Ekvall, Matilda |
| Publisher | KTH, Fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | TRITA-SCI-GRU ; 2024:062 |
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