NSUF 18-1393: In situ Study of the Irradiation Anisotropy in Fine Grain Nuclear-grade Graphite
Nuclear-grade graphite has been used worldwide in numerous reactors including Magnox, AGRs, RBMKs and HTRs such as HTTR and HTR-10, and it is also a critical material in many Gen IV reactor designs operating at much higher temperature. One of the main life-limiting factors for graphite components is the dimensional change with irradiation. Ideally, isotropic dimensional change is desired, however, from the many different grades of Gen IV nuclear graphite (mainly isotropic fine-grained grades), an anisotropy in volume change was observed after neutron irradiation at temperatures up to 950°C. For instance, ORNL observed 20-30% difference in dimensional anisotropy in IG 110 graphite (presented by A. A. Campbell at INGSM-2017, Baltimore), NRG reported a wide range of fine grain graphite manufactured in Japan, US and Europe all demonstrated dimensional anisotropy in directions along the grain and perpendicular to it (presented by M.C.R. Heijna at INGSM-2017, Baltimore). This type of anisotropic behaviour implies that the end of HTR core life is reached at different dpa levels in different directions which comprise the safety and management of the reactor core. Although it is a problem pertinent to GenIV reactors worldwide, the mechanism behind this is not fully understood. This proposed project aims to shed light on this question by conducting in situ TEM with Kr ion implantation to observe the development of irradiation damage in such fine grain graphite with the emphasis on the defects formation, behaviour of the nano-scale pores formed parallel to the basal planes, dimensional change of individual crystallite and crystallite clusters. Only by such in situ testing, the underlying mechanism for dimensional anisotropy can be deconvoluted from complex systems and to be understood.
Additional Info
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| Abstract | Nuclear-grade graphite has been used worldwide in numerous reactors including Magnox, AGRs, RBMKs and HTRs such as HTTR and HTR-10, and it is also a critical material in many Gen IV reactor designs operating at much higher temperature. One of the main life-limiting factors for graphite components is the dimensional change with irradiation. Ideally, isotropic dimensional change is desired, however, from the many different grades of Gen IV nuclear graphite (mainly isotropic fine-grained grades), an anisotropy in volume change was observed after neutron irradiation at temperatures up to 950°C. For instance, ORNL observed 20-30% difference in dimensional anisotropy in IG 110 graphite (presented by A. A. Campbell at INGSM-2017, Baltimore), NRG reported a wide range of fine grain graphite manufactured in Japan, US and Europe all demonstrated dimensional anisotropy in directions along the grain and perpendicular to it (presented by M.C.R. Heijna at INGSM-2017, Baltimore). This type of anisotropic behaviour implies that the end of HTR core life is reached at different dpa levels in different directions which comprise the safety and management of the reactor core. Although it is a problem pertinent to GenIV reactors worldwide, the mechanism behind this is not fully understood. This proposed project aims to shed light on this question by conducting in situ TEM with Kr ion implantation to observe the development of irradiation damage in such fine grain graphite with the emphasis on the defects formation, behaviour of the nano-scale pores formed parallel to the basal planes, dimensional change of individual crystallite and crystallite clusters. Only by such in situ testing, the underlying mechanism for dimensional anisotropy can be deconvoluted from complex systems and to be understood. |
| Award Announced Date | 2018-05-17T10:57:44.91 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Dong Liu |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1393 |