NSUF 17-1025: Atom Probe Tomography Investigations of nm-Scale Precipitates in Advanced Reactor Pressure Vessel Super Clean Steels in the UCSB Advanced Test Reactor (ATR-2) Neutron Irradiation Experiment

This proposal covers characterization of a set of advanced RPV alloys by atom probe tomography. These steels were irradiated to a fluence of ˜ 1.4x10^20 n/cm^2 at Tirr ˜ 250°C in the UCSB ATR-2 experiment. Several past RTEs from UCSB characterized these identical alloys with APT at Tirr ˜ 290°C. While the majority of LWRs operate at ˜ 290°C, the Tirr for others ranges down ˜ 250°C or lower. Understanding the effect of Tirr on precipitate formation is important not only for direct application to these lower Tirr conditions but also for developing advanced thermo-kinetic models of precipitation. APT studies will help to quantify the LBP precipitates that formed under irradiation at lower temperatures. These results will then be compared with APT & Small-Angle Neutron Scattering (SANS) data from steels irradiated at 290°C at the same flux and fluence to isolate the role of Tirr. Resolving these temperature effects, where little test reactor data is now available, is critical to reliably predicting precipitate formation. Overall, this project should be seen as programmatic sponsored work aimed at supporting the LWRSP RPV task and is an important contribution to the PI’s PhD thesis. The primary experimental objectives of this proposal include: 1) Measure volume fraction, size, number densities and precipitate compositions of MNSPs formed under irradiation at high fluence ˜ 1.4x10^20 n/cm^2 at Tirr ˜ 250°C in the UCSB ATR-2 experiment. 2) Examine and quantify segregation of Ni/Mn/Si/P to microstructural features such as grain boundaries, dislocations and dislocation loops. These experimental objectives will be achieved within 6 months of the date of the award. The expected period to finish all FIB sample preparation is within one week. APT at CAES will be scheduled directly following this time period as APT needle samples become available. Data analysis will be performed over the next several months by PI.

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필드	값
Abstract	This proposal covers characterization of a set of advanced RPV alloys by atom probe tomography. These steels were irradiated to a fluence of ˜ 1.4x10^20 n/cm^2 at Tirr ˜ 250°C in the UCSB ATR-2 experiment. Several past RTEs from UCSB characterized these identical alloys with APT at Tirr ˜ 290°C. While the majority of LWRs operate at ˜ 290°C, the Tirr for others ranges down ˜ 250°C or lower. Understanding the effect of Tirr on precipitate formation is important not only for direct application to these lower Tirr conditions but also for developing advanced thermo-kinetic models of precipitation. APT studies will help to quantify the LBP precipitates that formed under irradiation at lower temperatures. These results will then be compared with APT & Small-Angle Neutron Scattering (SANS) data from steels irradiated at 290°C at the same flux and fluence to isolate the role of Tirr. Resolving these temperature effects, where little test reactor data is now available, is critical to reliably predicting precipitate formation. Overall, this project should be seen as programmatic sponsored work aimed at supporting the LWRSP RPV task and is an important contribution to the PI’s PhD thesis. The primary experimental objectives of this proposal include: 1) Measure volume fraction, size, number densities and precipitate compositions of MNSPs formed under irradiation at high fluence ˜ 1.4x10^20 n/cm^2 at Tirr ˜ 250°C in the UCSB ATR-2 experiment. 2) Examine and quantify segregation of Ni/Mn/Si/P to microstructural features such as grain boundaries, dislocations and dislocation loops. These experimental objectives will be achieved within 6 months of the date of the award. The expected period to finish all FIB sample preparation is within one week. APT at CAES will be scheduled directly following this time period as APT needle samples become available. Data analysis will be performed over the next several months by PI.
Award Announced Date	2017-09-20T12:34:59.443
Awarded Institution	Center for Advanced Energy Studies
Facility	Microscopy and Characterization Suite
Facility Tech Lead	Alina Zackrone, Yaqiao Wu
Irradiation Facility	None
PI	Nathan Almirall
PI Email	[email protected]
Project Type	RTE
RTE Number	1025