Microstructure of irradiated SBR MOX fuel and its relationship to fission gas release

Predicting the probability for fission gas resolution into uranium dioxide

“…As the fuel ages, these fission gas bubbles accumulate in the interior of fuel grains and in larger inter-granular bubbles [7][8][9][10][11][12]. The presence of the bubbles leads to changes in the fuel microstructure [2,[13][14][15][16][17][18][19][20] and a corresponding degradation of the material properties of the fuel [13,14,[17][18][19][20][21][22][23]. Additionally, at high burnup, the linkage of inter-granular bubbles [8,[21][22][23][24][25][26][27][28][29][30] leads to the release of fission gas to the fuel-clad gap.…”

Development of the Enigma Fuel Performance Code for Whole Core Analysis and Dry Storage Assessments

“…KEYWORDS : Fuel Performance, ENIGMA UK Sizewell B PWR and the Finnish Loviisa VVER-440 reactor, and mixed oxide (MOX) fuel in the Swiss Beznau-1 PWR. ENIGMA is also used for analysis of experimental and commercial irradiations [9][10][11][12][13][14][15], for assessment of fuel behaviour during interim storage (see Section 4), to perform feasibility studies for future irradiation scenarios [16], to support fuel manufacturing [11,14,15], and to investigate fuel failures or other fuel performance related problems [17].…”

Ceramography Analysis of Mox Fuel Rods After an Irradiation Test

“…Most of the fission reactions occur within the Pu spots where the metallic precipitates and the fission gas bubbles exist as a consequence of high burn-up. As fission products accumulate within the spot, a portion of them migrate to the surrounding matrix by athermal processes such as recoil and knockout [10][11][12]. The high density of the small pores forms a ring around the spot that becomes visible in the polished fuel cross section [12].…”

“…Pores larger than 4 µm were distributed at the fuel center of rod 6. According to the review of post irradiation results for OCOM and MIMAS MOX fuel [11], the fission gas bubble size within the Pu spots varies with radial position; the bubbles at the Pu spot in the cooler peripheral region are generally smaller than in the central region where a few large pores with several micron-sized are often observed. In a peripheral Pu spot of MIMAS MOX fuel with an average burnup of 63MWd/kgHM, the bubble sizes ranged between 1µm and 8µm in diameter [12].…”