Behavior of nuclear fuel during a reactor accident
Work in this area is often very expensive to conduct, and so has often been performed on a collaborative basis between groups of countries, usually under the aegis of the Organisation for Economic Co-operation and Development's Committee on the Safety of Nuclear Installations (CSNI).During use the amount of gas inside the fuel pin can increase because of the formation of noble gases (krypton and xenon) by the fission process.As the fuel pin is sealed the pressure of the gas will increase (PV = nRT) and it is possible to deform and burst the cladding.[2] The common failure process of fuel in the water-cooled reactors is a transition to film boiling and subsequent ignition of zirconium cladding in the steam.The effects of the intense hot hydrogen reaction product flow on the fuel pellets and on the bundle's wall well represented on the sidebar picture.The swelling of the fuel pellet can cause pellet-cladding interaction when it thermally expands to the inside of the cladding tubing.The zirconium chemically reacts to the water flowing around it as coolant, forming a protective oxide on the surface of the cladding.To mitigate this hydrazine and hydrogen are injected into a BWR or PWR primary cooling circuit as corrosion inhibitors to adjust the redox properties of the system.At distance x from the center the temperature (Tx) is described by the equation where ρ is the power density (W m−3) and Kf is the thermal conductivity.Tx = TRim + ρ (rpellet² – x²) (4 Kf)−1 To explain this for a series of fuel pellets being used with a rim temperature of 200 °C (typical for a BWR) with different diameters and power densities of 250 Wm−3 have been modeled using the above equation.It is likely that the maths used for these calculations would be used to explain how electrical fuses function and also it could be used to predict the centerline temperature in any system where heat is released throughout a cylinder shaped object.As a result, if the zircaloy tubes holding the pellet are broken then a greater release of radioactive caesium from the fuel will occur.It is clear that the volatile iodine and xenon isotopes have minutes in which they can diffuse out of the pellet and into the gap between the fuel and the cladding.[16] The following fuel is particles of solid solution of urania in yttria-stabilized zirconia dispersed in alumina which had burnt up to 105 GW-days per cubic meter.The physical and chemical forms of the release included gases, aerosols and finely fragmented solid fuel.[20] This mobility has been more evident in reprocessing, with related releases of ruthenium, the most recent being the airborne radioactivity increase in Europe in autumn 2017, as with the ionizing radiation environment of spent fuel and the presence of oxygen, radiolysis-reactions can generate the volatile compound ruthenium(VIII) oxide, which has a boiling point of approximately 40 °C (104 °F) and is a strong oxidizer, reacting with virtually any fuel/hydrocarbon, that are used in PUREX.[4] Fuel was heated in the Knudsen cell both with and without preoxidation in oxygen at c 650 K. It was found even for the noble gases that a high temperature was required to liberate them from the uranium oxide solid.[23] In France a facility exists in which a fuel melting incident can be made to happen under strictly controlled conditions.[26][27] The Loss of Fluid Tests (LOFT) were an early attempt to scope the response of real nuclear fuel to conditions under a loss-of-coolant accident, funded by USNRC.The original intention (1963–1975) was to study only one or two major (large break) LOCA, since these had been the main concern of US 'rule-making' hearings in the late 1960s and early 1970s.38 LOFT tests were eventually performed and their scope was broadened to study a wide spectrum of breach sizes.A NEA/OECD report was written on the subject in 2000 which states that a steam explosion caused by contact of corium with water has four stages.The solid can be described as Fuel Containing Mass, it is a mixture of sand, zirconium and uranium dioxide which had been heated at a very high temperature[34] until it has melted.Uranium dioxide films can be deposited by reactive sputtering using an argon and oxygen mixture at a low pressure.
uranium dioxidenuclear fuelnuclear reactoraccidentOrganisation for Economic Co-operation and Development'sCommittee on the Safety of Nuclear Installationscladdingheliumnoble gaseskryptonLoss-of-coolant accidentThree Mile IslandChernobylpressurecorrosionirradiationzirconium alloybrittleNuclear Safety Research Reactorductilebrittle fracturehydridedrutheniumcaesiumspent fuel pooltemperaturethermocouplesnucleationcritical heat fluxheat transferfilm boilingChalk River Laboratoriesspent nuclear fuel shipping caskZirconiumstress corrosion crackingiodinefission productzircaloycarbon dioxidegraphitemoderatedmagnoxmoleculecarboncarbon monoxideradiationradiolysishydrogen peroxideoxygenhydrazinehydrogencorrosion inhibitorszirconium oxidezirconiaexpands on heatingthermal stressPhD thesisRoyal Institute of TechnologyStockholmSwedenequationthermal conductivitydiameterspower densityfission productsneutron activationthermal neutronssolid solutionuraniayttria-stabilized zirconiaspinelaluminaneutron activatedburnt upscanning electron microscopeneodymiumnanoparticlesSCRAMeddecay heatInternational Atomic Energy Agencyphysicalchemicalaerosolsairborne radioactivity increase in Europe in autumn 2017ionizing radiationspent fuelruthenium(VIII) oxidehydrocarbonburnupKnudsen cellIdaho National LaboratoryNUREG-1150Nuclear powersteam explosioncoriumpressure waveZND detonation wavezirconium dioxidecrucibleGermanythermiteconcretepressure vesselcontainment buildingsiliconesilicatezirconium silicateAC impedance spectroscopyelectrochemistanaerobicsacrificial anodeBibcodeWayback MachineAustriaNuclear technologyOutlineChemistryEngineeringPhysicsAtomic nucleusFissionFusionionizingbrakingTritiumDeuterium