In the frame of the development of Generation IV Lead-cooled Fast Reactors (LFR), the interaction between fuel and reactor coolant is essential for safety issues evaluations, for example in case of a pin breach. Therefore, interaction tests between a selection of fission product oxides, coming from the fission of uranium-plutonium mixed oxide (MOX), and molten lead have been performed. The oxides have been chosen on the basis of the precedent literature and previous experiments conducted and are, namely, lanthanum, cerium, iron and strontium oxides. Two parameters were studied, the interaction temperature (500-550°C and 750°C) and the duration of the interaction (from 2 hours up to 6 hours). In the experiments, about 5 grams of lead wire were placed in contact with a fission oxide pellet inside a test tube positioned in a furnace under inert atmosphere at a temperature above the melting temperature of the lead (327.4°C). After several hours of interaction in a closed environment, the pellet integrity was preserved in all cases. However, experiments were followed by macroscopic and qualitative analysis. Macroscopic analysis showed the apparent absence of interaction between the two compounds; the only change was in the colour of the iron oxide. With the qualitative analysis, through X-ray diffraction (XRD), the characterization of the interface surface of the oxide pellet has been performed in order to find the presence of compounds deriving from the interaction of the starting ones. Whatever the conditions, neither interaction compounds (crystalline or amorphous) nor lead diffusion into the surface regions of the oxide pellets has been detected. Therefore, from the collected data, the only visible result is the underwent of a sintering process of the oxide pellet, namely pressing and thermal treatment. A further attempt is done with a Differential Scanning Calorimetry (DSC) analysis, in an aluminium crucible are placed very small pieces of lead wire and oxide powder in 2:1 ratio. The only temperature investigated is 550°C because of instrumentation limits. Also SEM-EDS analysis on pure and scratched oxide powders is performed to obtain a map and a quantitative elemental analysis. However, also in these cases the absence of chemical interaction between the compounds is confirmed. Further developments are expected to be achieved in this field changing the various parameters involved in this kind of experiments.
Nell'ambito dello sviluppo dei reattori di quarta generazione raffreddati al piombo l'interazione tra il carburante e il refrigerante del reattore è indispensabile per effettuare valutazioni riguardo a questioni di sicurezza, ad esempio in caso di fessurazione di un elemento di combustibile. Pertanto, sono stati eseguiti test di interazione tra una selezione di ossidi di prodotti di fissione, provenienti dalla fissione dell'ossido misto di uranio-plutonio (MOX), e del piombo fuso. Gli ossidi sono stati selezionati sulla base della letteratura precedente e dei precedenti esperimenti condotti e sono, in particolare, lantanio, cerio, ferro e stronzio. Sono stati studiati due parametri, la temperatura di interazione (500-550°C e 750°C) e la durata dell'interazione (da 2 fino a 6 ore). Negli esperimenti sono stati messi a contatto circa 5 g di filo di piombo e una pastiglia di ossido, preparate mediante l’utilizzo di una pressa manuale, all'interno di una provetta posizionata in un forno contenuto in atmosfera inerte ad una temperatura superiore alla temperatura di fusione del piombo. Si è potuto notare che, dopo diverse ore di interazione, l'integrità della pastiglia è stata conservata in tutti i casi. Tuttavia, gli esperimenti sono stati seguiti da analisi macroscopiche e qualitative. L'analisi macroscopica ha mostrato l'apparente assenza di interazione tra i due composti. È stata poi eseguita la caratterizzazione della superficie all’interfaccia della pastiglia di ossido tramite la diffrazione a raggi X (XRD), al fine di individuare la presenza di composti derivanti dall'interazione di quelli iniziali. Tuttavia, non sono stati rilevati composti di interazione (cristallini o amorfi) né diffusione di piombo nelle regioni superficiali della pastiglia di ossido. Pertanto, dai dati raccolti, l'unico risultato visibile è che la pastiglia è sottoposta ad un processo di sinterizzazione. È stato fatto un ulteriore tentativo con un'analisi DSC (Differential Scanning Calorimetry) una SEM-EDX. Nella prima in un crogiolo di alluminio vengono posti piccoli pezzi di filo di piombo e polvere dell'ossido in diversi rapporti e portati a 550 °C. Nella seconda veine mappata la superficie e condotta un’analisi elementare. Tuttavia, anche in questo caso è confermata l'assenza di interazione chimica tra i composti. Si prevede che in questo campo ci possano essere ulteriori sviluppi cambiando i vari parametri coinvolti in questo tipo di esperimenti.
Experimental study on oxides and molten lead simulating fuel-coolant chemical interaction within lead-cooled fast reactors
DE LUCA, LINDA
2016/2017
Abstract
In the frame of the development of Generation IV Lead-cooled Fast Reactors (LFR), the interaction between fuel and reactor coolant is essential for safety issues evaluations, for example in case of a pin breach. Therefore, interaction tests between a selection of fission product oxides, coming from the fission of uranium-plutonium mixed oxide (MOX), and molten lead have been performed. The oxides have been chosen on the basis of the precedent literature and previous experiments conducted and are, namely, lanthanum, cerium, iron and strontium oxides. Two parameters were studied, the interaction temperature (500-550°C and 750°C) and the duration of the interaction (from 2 hours up to 6 hours). In the experiments, about 5 grams of lead wire were placed in contact with a fission oxide pellet inside a test tube positioned in a furnace under inert atmosphere at a temperature above the melting temperature of the lead (327.4°C). After several hours of interaction in a closed environment, the pellet integrity was preserved in all cases. However, experiments were followed by macroscopic and qualitative analysis. Macroscopic analysis showed the apparent absence of interaction between the two compounds; the only change was in the colour of the iron oxide. With the qualitative analysis, through X-ray diffraction (XRD), the characterization of the interface surface of the oxide pellet has been performed in order to find the presence of compounds deriving from the interaction of the starting ones. Whatever the conditions, neither interaction compounds (crystalline or amorphous) nor lead diffusion into the surface regions of the oxide pellets has been detected. Therefore, from the collected data, the only visible result is the underwent of a sintering process of the oxide pellet, namely pressing and thermal treatment. A further attempt is done with a Differential Scanning Calorimetry (DSC) analysis, in an aluminium crucible are placed very small pieces of lead wire and oxide powder in 2:1 ratio. The only temperature investigated is 550°C because of instrumentation limits. Also SEM-EDS analysis on pure and scratched oxide powders is performed to obtain a map and a quantitative elemental analysis. However, also in these cases the absence of chemical interaction between the compounds is confirmed. Further developments are expected to be achieved in this field changing the various parameters involved in this kind of experiments.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/136891