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|Title:||EFFECTS OF HELIUM BUILD-UP ON NUCLEAR FUEL EVOLUTION DURING STORAGE|
|Authors:||RONDINELLA Vincenzo; WISS Thierry; MAUGERI E.; COLLE Jean-Yves|
|Citation:||Proceedings IHLRWMC 2011 p. 230 - 233|
|Publisher:||American Nuclear Society|
|JRC Publication N°:||JRC67161|
|Type:||Contributions to Conferences|
|Abstract:||The evolution during storage of properties relevant for safe handling/processing of high specific alpha-activity fuels and wasteforms is strongly affected by the build-up of alpha-decay damage and helium. This paper describes the alteration of properties, such as hardness, lattice parameter swelling, thermal diffusivity, monitored as a function of time, hence of accumulated damage, on various irradiated and unirradiated compounds. The integral over time of the alpha-decay effects accumulated under accelerated conditions (high specific alpha-activity) can simulate the effects of long storage times in fuels and waste forms. Experiments combining annealing studies using calorimetry techniques and He-release as a function of temperature with microstructure examination using transmission electron microscopy are performed to investigate the correlation among the annealing of defects in the microstructure, the release behavior of He, and the heat effects associated with these processes in the material. Discrete property recovery stages were identified between ~500 and ~1400 K, corresponding to the mobility of various types of defects and to a He release stage. The energy associated with these annealing steps was determined. The materials studied include LWR UO2 and MOX, and minor actinide-containing mixed oxide fuel irradiated in fast reactor. The investigation on irradiated fuel is complemented by studies on alpha-doped UO2 and ceramic matrix materials, and on natural analogues. This allows assessing the superimposition of alpha-decay effects occurring during storage at relatively low temperature on the fuel alterations occurring during in-pile irradiation. Comparative analysis of spent fuel and alpha-doped materials also allows assessing the relevance of dose rate effects on the property evolution under accelerated He/decay damage accumulation regimes. The final goal of these studies is to assess the mechanical integrity of nuclear and high level waste forms during storage in view of further handling/processing.|
|JRC Institute:||Institute for Transuranium Elements|
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