Nuclear Reactor Moderator Materials

Kelly, Brian

doi:10.1002/9783527603978.mst0109

Cited by 3 publications

(1 citation statement)

References 49 publications

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“…The type of high-purity graphite known as nuclear graphite is used in nuclear reactors as a neutron moderator and structural component in the reactor core for providing a pathway for coolant and control rods. ,, Fast neutrons impinge on the graphite, displacing carbon atoms from their equilibrium positions in the crystal lattice to metastable interstitial positions between carbon layer planes. This leads to dimensional changes in the graphite structure and ultimately changes in its physical properties. − Isotropic graphite is preferred over anisotropic graphite for use as a moderator in reactors because it shows greater resistance to this neutron irradiation damage, relative to anisotropic graphite. ,, As a result, isotropic graphite has a longer lifetime in service than anisotropic graphite. However, the properties and, hence, structural integrity of graphite are dependent upon its precursor material and the processing conditions used to make it.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study on Structural Parameters of Graphitized Coal–Petroleum Co-cokes and Pennsylvania Anthracites, with Implications for Their Use

2014

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Nuclear-grade graphite samples, anisotropic commercial graphite, graphitized co-cokes, and anthracites were characterized using X-ray diffraction, Raman spectroscopy, and temperature-programmed oxidation. Through evaluation of relationships between structural parameters, it was observed there is better likelihood to obtain isotropic or near-isotropic graphite from co-cokes than anthracites. The addition of coal to petroleum feed, i.e., vacuum resid or decant oil, reduces the concentration of large isochromatic units in a co-coke structure, thus leading to a graphitic structure that lacks anisotropic character upon graphitization of the co-coke. The structural characteristics of graphitized anthracites showed more similarities to anisotropic commercial graphite, in comparison to graphitized co-cokes. It was also found that coking a vacuum resid/coal blend offers better potential for producing an isotropic or near-isotropic graphite than the coking of a decant oil/coal blend. Increasing the co-coking temperature from 465 to 500°C appeared to favor obtaining isotropic or near-isotropic graphite upon graphitization.

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