For the first time, the influence of pore closure on elastic modulus in the UK's Magnox and Advanced Gas Cooled Reactors (AGRs) graphite was determined by subjecting the graphite samples to high hydrostatic pressure and dynamic loading. Two grades of nuclear graphite were tested; anisotropic Pile Grade A (PGA) which was used in the Magnox reactors, and semi-isotropic Gilsocarbon as used in the AGRs [1]. The volumetric strain was measured in two directions during compression and separately the velocity of sound through the samples was also determined as a function of confinement pressure. Under hydrostatic loading, the stiffness of PGA graphite was reduced after a few percent of volume strain before increasing again after about ∼20% volumetric strain. Gilsocarbon showed similar behaviour to PGA at lower volumetric strain (∼10 to 13%) however due to Gilsocarbon having a higher density and lower porosity compared to PGA, the response was generally stiffer than PGA. During unloading, significant hysteresis was observed in both graphite grades, with the sample volume almost fully recovering when the pressure was completely removed. Micromechanical models are used to explain the poro-elastic response of graphite during hydrostatic compaction, and to make comparisons and extend data on the influence of pore change due to oxidation on modulus.

首次通过对石墨样品施加高静水压力和动态载荷来确定孔隙闭合对英国 Magnox 和先进气冷反应堆 (AGR) 石墨弹性模量的影响。测试了两个等级的核石墨；Magnox 反应器中使用的各向异性 A 级桩 (PGA) 和 AGR 中使用的半各向同性硅灰 [1]。体积应变在压缩过程中在两个方向上测量，并且通过样品的声速也分别确定为限制压力的函数。在静水载荷下，PGA 石墨的刚度在体积应变的几个百分点后降低，然后在约 20% 的体积应变后再次增加。在较低的体积应变（~10% 至 13%）下，Gilsocarbon 表现出与 PGA 相似的行为，但是由于与 PGA 相比，Gilsocarbon 具有更高的密度和更低的孔隙率，因此响应通常比 PGA 更硬。在卸载过程中，在两种石墨等级中都观察到了明显的滞后现象，当完全去除压力时，样品体积几乎完全恢复。微观力学模型用于解释静水压实过程中石墨的孔隙弹性响应，并对氧化引起的孔隙变化对模量的影响进行比较和扩展数据。当压力完全消除时，样品体积几乎完全恢复。微观力学模型用于解释静水压实过程中石墨的孔隙弹性响应，并对氧化引起的孔隙变化对模量的影响进行比较和扩展数据。当压力完全消除时，样品体积几乎完全恢复。微观力学模型用于解释静水压实过程中石墨的孔隙弹性响应，并对氧化引起的孔隙变化对模量的影响进行比较和扩展数据。