NSUF 13-391: Ion-irradiation of Nuclear Grade NBG-18 and Highly Ordered Pyrolytic (HOPG) Graphites
Graphite is currently proposed for neutron moderation and structural support for the next generation high temperature reactors. Radiation creep is arguably the most important of the radiation effects that occur in graphite. A reactor grade graphite shows shrinkage followed by a positive dimensional change beyond a critical neutron fluence (dpa) which generally decreases with increasing irradiation temperature. At room temperature (300K) significant swelling is observed along the c-axis with smaller swelling rate along the a-axis possibly due to plane destruction and/or vacancy line/loop collapse. At higher temperatures pores and cracks that are formed during the processing stage collapse thus accommodating the enhanced swelling along the c-axis resulting in an overall shrinkage of volume. Beyond a critical dpa, a ‘turnaround’ behavior is observed indicating a leveling behavior for the shrinkage of pores and cracks. Funded by NEUP, neutron irradiation and creep investigations are being performed on NGB-18, a nuclear grade graphite that has been down selected for the next generation, very high temperature, gas cooled reactors. Given the irradiation time that spans several months for neutron irradiation, a plausible alternative for faster testing is by conducting experiments with ion irradiation that can speed up the damage rate by orders of magnitude. In the past neutron and ion damage has been reasonably correlated for several metallic structural materials, however, not for graphite. As the microstructure and irradiation damage mechanisms are significantly different from those in metals, a correlation between neutron and ion damage needs to be first established for proper interpretation of ion irradiation results. If a strong correlation is established, damage results from future ion irradiation tests that can be completed in days in a university setting can be correlated to neutron damage with reasonable confidence.
Additional Info
| Field | Value |
|---|---|
| Abstract | Graphite is currently proposed for neutron moderation and structural support for the next generation high temperature reactors. Radiation creep is arguably the most important of the radiation effects that occur in graphite. A reactor grade graphite shows shrinkage followed by a positive dimensional change beyond a critical neutron fluence (dpa) which generally decreases with increasing irradiation temperature. At room temperature (300K) significant swelling is observed along the c-axis with smaller swelling rate along the a-axis possibly due to plane destruction and/or vacancy line/loop collapse. At higher temperatures pores and cracks that are formed during the processing stage collapse thus accommodating the enhanced swelling along the c-axis resulting in an overall shrinkage of volume. Beyond a critical dpa, a ‘turnaround’ behavior is observed indicating a leveling behavior for the shrinkage of pores and cracks. Funded by NEUP, neutron irradiation and creep investigations are being performed on NGB-18, a nuclear grade graphite that has been down selected for the next generation, very high temperature, gas cooled reactors. Given the irradiation time that spans several months for neutron irradiation, a plausible alternative for faster testing is by conducting experiments with ion irradiation that can speed up the damage rate by orders of magnitude. In the past neutron and ion damage has been reasonably correlated for several metallic structural materials, however, not for graphite. As the microstructure and irradiation damage mechanisms are significantly different from those in metals, a correlation between neutron and ion damage needs to be first established for proper interpretation of ion irradiation results. If a strong correlation is established, damage results from future ion irradiation tests that can be completed in days in a university setting can be correlated to neutron damage with reasonable confidence. |
| Award Announced Date | 2012-12-20T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kumar Sridharan |
| Irradiation Facility | None |
| PI | Korukonda Murty |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 391 |