176. The effects of fast neutron irradiation on the pore structure of reactor moderator graphite

Ashton, B.W.; Brocklehurst, J.E.; Kelly, Brian

doi:10.1016/0008-6223(73)90512-5

Cited by 1 publication

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“…In addition, mercury porosimetry appears to indicate that it is changes to the small pores, less than ∼1μm, that influence volumetric change in irradiated graphite. 83 The cumulative closure of this accommodation plus other structure effects will enhance the influence of the crystal c -axis dimensional changes. Thus equation (21) has been modified by the inclusion of an influence function ‘ F ’ (a function of both fluence and temperature) to give: …”

Section: Analysis Of Irradiation-induced Dimensional Changementioning

confidence: 99%

Dimensional change, irradiation creep and thermal/mechanical property changes in nuclear graphite

Marsden

Haverty

Bodel

et al. 2016

International Materials Reviews

106

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Since the start of the 'nuclear age' graphite has been employed as a moderator in around 100 nuclear reactors, and today there are still some 30 graphite-moderated reactors operating and there are plans for new Generation IV high-temperature reactors. Many of the graphite moderator reactors now producing power are operating beyond their original design life. Therefore in some cases, to aid the reactor operators and designers, the existing graphite irradiation databases need to be extended either to a higher temperature or higher neutron fluence. Furthermore, data are needed for the different grades of graphite that are available at present. This can either be achieved by expensive, time consuming irradiation programmes or by improving the understanding of the mechanisms and processes which lead to irradiationinduced dimensional and property changes in the graphite core components. This review looks at three of the most important graphite properties which change with exposure to irradiation, namely dimensional change, irradiation creep and thermal expansion. The behaviour of UK AGR, Magnox and an experimental grade of German reactor graphite are explored in some detail. First graphite reactor core design is briefly discussed, giving examples of typical graphite components and core arrangements. Issues related to aging graphite component and core behaviour are illustrated through examples of component internal and thermal stress generation, and issues related to whole core behaviour are also outlined. Second the manufacture and microstructure of different nuclear graphite grades are discussed, highlighting how the choice of raw materials and manufacturing technique influences the graphite properties. Third the coefficient of thermal expansion, dimensional change and irradiation creep are analysed using microstructural and averaging methods which are used to relate crystal to bulk properties by accounting for graphite crystal orientation and porosity. These techniques, which were first applied to nuclear graphite in the 1960s, are extended and discussed with the aim of trying to lend some understanding to the role the microstructural crystallite and porosity distributions play in defining the dimensional stability and properties of virgin graphite, irradiated graphite and stressed graphite.

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Section: Analysis Of Irradiation-induced Dimensional Changementioning

confidence: 99%