Evaluation of micro-homogeneity in plutonium based nuclear reactor fuel pellets by alpha-autoradiography technique

Survey of U.S. Research Reactor Auxiliary Facilities Used for Material Testing and Basic Neutron Science

“…[13] [14] However, this method has shown great promise for determining high concentration regions of alphaemitting Pu and U isotopes in MOX fuels, with increases in sensitivity being achieved by using UV-Vis and photoluminescence spectrophotometry on a CR-39 polymer radiograph. [15,16,17,18,19,20] This is particularly important for quality control, as heavy-metal diffusion during the sintering process often leads to the formation of agglomerates in fuel pellets. This can lead to hotspots during irradiation, ultimately leading to a smaller burnup potential.…”

Evaluation of compositional micro-homogeneity in MOX fuels using lab based μ-XRF spectrometry

“…But unlike UO 2 pellets, in MOX fuel pellets the evaluation of microhomogeneity (homogeneity at the micron level) aer their fabrication is an additional important step in the quality control of these fuels. [4][5][6] A homogeneous distribution of actinides in the pellets is required for the efficient and satisfactory performance of the fuel as well as from the safety point of view during the reactor's operation. Since the fabrication of MOX pellets involves mechanical mixing of the individual oxide powders, inhomogeneity due to agglomeration of a particular oxide is inevitable.…”

“…In Pu bearing fuels, alpha autoradiography or gamma autoradiography is used for monitoring the inhomogeneous distribution of Pu in MOX fuel pellets. 5,6,13 But these techniques are used mainly to locate and identify the a or g emitting radioisotopes. 13 Alpha autoradiography can be used for quantitative estimation of ThO 2 and UO 2 content in sintered MOX pellets, but due to the low specic alpha activity of natural U and Th, getting sufficient alpha track density (109 tracks per cm 2 ) may require up to 10 days of lm exposure.…”

“…Further, if the agglomerate is not dense enough, this method cannot distinguish its boundary or the size of these agglomerates/hot spots very accurately. 5 Other techniques which are used for the micro-homogeneity studies are Electron Probe Micro Analysis (EPMA) and Secondary Electron Microscopy (SEM). 15,16 But these techniques are very expensive and require the surface to be coated with some metal to make it conductive.…”