NSUF 16-645: B and Li grain boundary segregation in irradiated LWR steels
Boron is a trace element present either as an intentional addition or as an unintentional impurity in most Ni alloys and stainless steels, including those currently used in nuclear reactors. 20% of natural boron is B10, which has a very large thermal neutron cross section (3840 barns). Therefore the transmutation of B10(n, a)Li7 under mixed spectrum (i.e. containing thermal neutrons) irradiation is described to occur “early”. In the context of LWR structural materials, the segregation of B (specifically B10) to grain boundaries and its subsequent transmutation to He (the a particle) and Li7 have been a topic of some concern, but whose contribution to materials degradation has been difficult to assess because of the challenges in measuring directly the local distribution of B10, Li, and He. Measurements of the local distribution of B10 and Li (which is linked one-to-one to He) are now accessible by atom probe tomography, although measurement of the local distribution of He is not. The proposal aims to examine the local distribution of B10 and Li, in materials that supports research associated with LWR material degradation issues, specifically intergranular cracking during welding of irradiated materials. This will be performed using atom probe tomography comparing grain boundary chemistry in non-irradiated and neutron irradiated stainless steels manufactured controlled amounts of B. This project will advance the understanding to heat-to-heat variations of materials performance, which is key to assessing reliability in long-term operation and to motivating improvement of existing predictions models and which therefore constitutes an essential step in support of the DOE objectives of developing safe, secure and sustainable expansion of nuclear energy. It should be noted that this project leverages existing efforts at EPRI that will allow linkage of welding behaviors (investigated elsewhere) to the microstructures developed under neutron irradiation characterized through this proposal. This project will be starting in mid 2016 and extend to early 2017.
Additional Info
| Field | Value |
|---|---|
| Abstract | Boron is a trace element present either as an intentional addition or as an unintentional impurity in most Ni alloys and stainless steels, including those currently used in nuclear reactors. 20% of natural boron is B10, which has a very large thermal neutron cross section (3840 barns). Therefore the transmutation of B10(n, a)Li7 under mixed spectrum (i.e. containing thermal neutrons) irradiation is described to occur “early”. In the context of LWR structural materials, the segregation of B (specifically B10) to grain boundaries and its subsequent transmutation to He (the a particle) and Li7 have been a topic of some concern, but whose contribution to materials degradation has been difficult to assess because of the challenges in measuring directly the local distribution of B10, Li, and He. Measurements of the local distribution of B10 and Li (which is linked one-to-one to He) are now accessible by atom probe tomography, although measurement of the local distribution of He is not. The proposal aims to examine the local distribution of B10 and Li, in materials that supports research associated with LWR material degradation issues, specifically intergranular cracking during welding of irradiated materials. This will be performed using atom probe tomography comparing grain boundary chemistry in non-irradiated and neutron irradiated stainless steels manufactured controlled amounts of B. This project will advance the understanding to heat-to-heat variations of materials performance, which is key to assessing reliability in long-term operation and to motivating improvement of existing predictions models and which therefore constitutes an essential step in support of the DOE objectives of developing safe, secure and sustainable expansion of nuclear energy. It should be noted that this project leverages existing efforts at EPRI that will allow linkage of welding behaviors (investigated elsewhere) to the microstructures developed under neutron irradiation characterized through this proposal. This project will be starting in mid 2016 and extend to early 2017. |
| Award Announced Date | 2016-04-11T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kory Linton |
| Irradiation Facility | None |
| PI | Emmanuelle Marquis |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 645 |