• Nuclear Engineering and Technology
• /
• v.53 no.5
• /
• pp.1569-1579
• /
• 2021

This study aims to provide microstructural characterization for the matrix graphite which molten salt reactors (MSRs) use, and improve resistance to molten salt infiltration of the matrix graphite for fuel elements. Mesocarbon microbeads (MCMB) densified matrix graphite A3-3 (MDG) was prepared by a quasi-isostatic pressure process. After densification by MCMBs with average particle sizes of 2, 10, and 16 ㎛, the pore diameter of A3-3 decreased from 924 nm to 484 nm, 532 nm, and 778 nm, respectively. Through scanning electron microscopy, the cross-section energy spectrum and time-of-flight secondary ion mass spectrometry, resistance levels of the matrix graphite to molten salt infiltration were analyzed. The results demonstrate that adding a certain proportion of MCMB powders can improve the anti-infiltration ability of A3-3. Meanwhile, the closer the particle size of MCMB is to the pore diameter of A3-3, the smaller the average pore diameter of MDG and the greater the densification. As a matrix graphite of fuel elements in MSR was involved, the thermal and mechanical properties of matrix graphite MDG were also studied. When densified by the MCMB matrix graphite, MDGs can meet the molten salt anti-infiltration requirements for MSR operation.

• Carbon letters
• /
• v.11 no.4
• /
• pp.304-310
• /
• 2010

To manufacture a carbon/carbon composite the coal tar pitch was used as the matrix precursor and the PAN (polyacrylonitrile)-based carbon fiber was used as the reinforcing material to weave 3-directional preform. For pressure carbonization HIP equipment was used to produce a maximum temperature of $1000^{\circ}C$ and a maximum pressure of 100 MPa. The carbonization was induced by altering the dwell temperature between $250^{\circ}C$ and $420^{\circ}C$, which is an ideal temperature for the moderate growth of the mesophase nucleus that forms within the molten pitch during the pressure carbonization process. The application of high pressure during the carbonization process inhibits the mesophase growth and leads to the formation of spherical carbon particles that are approximately 30 nm in size. Most particles were spherical, but some particles were irregularly shaped. The spread of the carbon particles was larger on the surface of the carbon fiber than in the interior of the matrix pocket.