NSUF - Nuclear Science User Facilities

- High Fluence Embrittlement Database and ATR Irradiation Facility for LWR Vessel Life Extension

Full Details
Principal Investigator
Name:
G. Robert Odette
Email:
[email protected]
Phone:
(208) 526-6918
Project Contact
Name:
Mikhail Sokolov
Email:
[email protected]
Team Members:
Name: Institution: Expertise: Status:
Brian D. Wirth University of California - Berkeley
Randy K. Nanstad Oak Ridge National Laboratory
Takuya Yamamoto University of California - Santa Barbara
Experiment Details:
Experiment Title:
High Fluence Embrittlement Database and ATR Irradiation Facility for LWR Vessel Life Extension)
Project Summary
Embrittlement of RPV steels over operating periods up to 80 effective full power years, corresponding to a maximum neutron fluence up to 10^20 n/cm2 (E > 1 MeV), is a critical issue that may limit LWR plant life extension. An important unresolved RPV embrittlement issue is predicting transition temperature shifts (TTS) at high fluences (> ˜ 6x10^19 n/cm2), which are well beyond the range of the existing surveillance database. Indeed, there are virtually no low flux irradiation data at these fluence levels. Notably,however, current embrittlement models systematically and significantly under-predict embrittlement (TTS) in the existing high flux test reactor database at high fluence [1]. However, neutron flux has strong and very complex effects on embrittlement; indeed, increasing flux can increase, decrease or leave unaffected the TTS, depending on all the other irradiation and material conditions.Currently no US irradiation facility exists to carry out intermediate flux neutron irradiations pertinent to pressure boundary and other structural materials to resolve these issues. Thus UCSB, in collaboration with ORNL and UCB, propose to develop a new ATR irradiation facility for intermediate flux neutron irradiations in a Small I position [2]. The proposed facility will fill a major hole in the existing RPV embrittlement database at high fluence, as well as providing data for resolving a number of other important embrittlement issues. The proposed Small I facility involves an irradiation capsule that is shielded from thermal neutrons, and instrumented and actively heated to maintain good (<±5°C) temperature control. The capsules will contain more than 2000 specimens in at lease three temperature zones, nominally at 270, 290 and 310 °C. Peak flux levels of ˜ 4.5x10^12 n/cm2-s (10-20 times lower than for most other high fluence data) will produce a fluence of 10^20 n/cm2 in a one-year irradiation. Disc multipurpose coupons, disc compact tension fracture, sub-sized tensile and special purpose specimens will provide mechanical property data, as well as detailed characterization of the irradiation induced microstructures, using state-of-the-art techniques. Critical and scientifically important issues, such as the formation of late blooming phases that result in severe embrittlement in low copper steels, will be explored. The greatly enhanced embrittlment database will be used to develop robust, physically based models to predict TTS to and beyond end of extended life conditions. UCSB and ORNL, with many decades of experience in designing and successfully carrying out major irradiation studies, will collaborate with INL to design and implement the facility. UCSB, ORNL and UCB, who are internationally recognized leaders in various sophisticated characterization studies as well as materials modeling research, will carry out the post irradiation examinations along with their large network of worldwide collaborators. This program will not only provide critical early insight on embrittlement at high fluence, but will also lay a foundation for developing other ATR RPV steel irradiation facilities for longer-term irradiations at even lower and more vessel pertinent neutron fluxes.
Relevance
The justification of the proposed research is the large impact it will have on the DOE Light Water Reactor (LWR) Sustainability Program Plan (LWRSP). The LWRSP is directed at extending the life of existing nuclear power plants to at least 80 years. Launched in FY 2009, the program has defined the necessary R&D needed to meet this objective, including the key area of Nuclear Materials Aging and Degradation. As one of the primary permanent components, the RPV requires significant research. Portions of the following are edited language taken from the LWRSP Roadmap and the associated foundational white paper [1,2] (note RK Nanstad was a co-author on both documents).

Although existing physically-motivated and statistically-calibrated models of Charpy V-notch (CVN)-indexed transition temperature shifts are generally well correlated with existing embrittlement data, they are not fully quantitative, do not treat all potentially significant variables and variable combinations, and cannot be reliably extrapolated to the high fluences associated with 80 years of RPV operation. Only a few examples of the many significant technical issues that need to be addressed include the following



1. High fluence, long irradiation times, and flux effects: A lack of data at high fluences at low flux (long times) create large uncertainties for embrittlement predictions. Obtaining such data for life extension will require test reactor experiments at higher neutron fluxes. Substantial research is needed to apply such data to low flux RPV conditions. Moreover, there is now widespread evidence that so-called “late blooming phases (LBPs)” (rich in nickel and manganese) develop at relatively high fluence in low copper steels. LBPs are not currently accounted for in regulatory models, posing serious negative implications to RPV life extension.



2. Material variability and surrogate materials: Material variability has received increasing attention in recent years. Many surveillance programs contain CVN specimens of different steels than those in the RPV itself. Indeed, the variables needed to describe the actual vessel steels are in many, and perhaps most, cases unknown. New approaches are needed to enable reliable embrittlement predictions of vessel safety margins in the face of such uncertainties.



3. High-nickel steels: Higher nickel results in more severe embrittlement. Moreover, the subject of high-nickel content is related to concerns of high fluence embrittling features such as LBP and dislocation loops. The strong synergistic interactions between copper, nickel, manganese, and phosphorus are not understood at higher fluence.



More generally, the LWRSP on materials aging issues will require high quality infrastructure, including, and perhaps especially, pertinent irradiation facilities. Developing a series of such facilities in the ATR presents a tremendous opportunity for the LWRSP and the ATR NSUF. The proposed research represents a “first step” to develop a series of such facilities at ATR, while at the same time creating a new and critically important embrittlement database. This effort will benefit greatly from the expertise and many decades of reactor materials research of the investigators, and especially the vast experience in large-scale irradiation programs at ORNL and UCSB.
Book / Journal Publications

"Fracture Toughness Characterization of Reactor Pressure Alloys from the ATR-2 Experiment" M. Sokolov, X. Chen, R.K. Nanstad, G. Robert Odette, Takuya Yamamoto, Peter Wells, 2017 Link

"Fracture Toughness Characterization of Highly Irradiated Reactor Pressure Vessel Weld from the ATR-2 Experiment" Mikhail Sokolov, Xiang Chen, G. Robert Odette, OSTI.gov Technical Report 2018 Link

"Direct comparison of nanoindentation and tensile test results on reactor-irradiated materials" David Krumwiede, Takuya Yamamoto, Tarik Saleh, Stuart Maloy, G. Robert Odette, Peter Hosemann, Journal of Nuclear Materials 504 2018 135-143 Link

"Cluster dynamics modeling of Mn-Ni-Si precipitates in ferritic-martensitic steel under irradiation" Jia-Hong Ke, Huibin Ke, G. Robert Odette, Dane Morgan, Journal of Nuclear Materials 498 2018 83-88 Link

"Dose rate dependence of Cr precipitation in an ion-irradiated Fe18Cr alloy" Elaina Reese, Nathan Almirall, Takuya Yamamoto, Scott Tumey, G. Robert Odette, Emmanuelle Marquis, Scripta Materialia 146 2018 213-217 Link

"On the use of charged particles to characterize precipitation in irradiated reactor pressure vessel steels with a wide range of compositions" Nathan Almirall, Peter Wells, Takuya Yamamoto, G. Robert Odette, Journal of Nuclear Materials 536 2020 Link

"Flux effects in precipitation under irradiation – Simulation of Fe-Cr alloys" JH Ke, ER Reese, Emmanuelle Marquis, G. Robert Odette, DD Morgan, Acta Materialia 164 2019 586-601 Link

"CuMnNiSi precipitate evolution in irradiated reactor pressure vessel steels: Integrated Cluster Dynamics and experiments" Mahmood Mamivand, Peter Wells, Huibin Ke, G. Robert Odette, Dane Morgan, Acta Maerialia 180 2019 199-217

"A kinetic lattice Monte Carlo study of post-irradiation annealing of model reactor pressure vessel steels" G. Robert Odette, Shipeng Shu, Peter Wells, Dane Morgan, Journal of Nuclear Materials 2019 312-322 Link

"Microstructural examination of neutron, proton and self-ion irradiation damage in a model Fe9Cr alloy" Jack Haley, S. de Moraes Shubeita, P. Wady, A.J. London, G. Robert Odette, S. Lozano, Steve Roberts, Journal of Nuclear Materials 533 2020 Link

"An Atom Probe Tomography Study of the Through Wall Attenuation Effect on Cu-rich Precipitate Formation in a Reactor Pressure Vessel Steel" Philip Edmondson, Caleb Massey, Mikhail Sokolov, Thomas Rosseel, Journal of Nuclear Materials 543 2021 Link

"Precipitation in reactor pressure vessel steels under ion and neutron irradiation: On the role of segregated network dislocations" G. Robert Odette, Nathan Almirall, Takuya Yamamoto, Acta Materialia 212 2021 Link

"The effect of phosphorus on precipitation in irradiated reactor pressure vessel (RPV) steels" Mukesh Bachhav, Nathan Almirall, Takuya Yamamoto, Emmanuelle Marquis, G. Robert Odette, Journal of Nuclear Materials 585 2023 Link

"A Low Flux High Fluence Transition Temperature Shift Reduced Order Prediction Model" G. Robert Odette, Nuclear Engineering and Technology 53 2019 2610-2615 Link

"A more holistic characterisation of internal interfaces in a variety of materials via complementary use of transmission Kikuchi diffraction and Atom probe tomography" Paul Bagot, Ben Jenkins, James Douglas, G. Robert Odette, Applied Surface Science 528 2020 Link

"Using alpha hulls to automatically and reproducibly detect edge clusters in atom probe tomography datasets" Paul Bagot, Ben Jenkins, Materials Characterisation 160 2020 Link

"The effect of composition variations on the response of steels subjected to high fluence neutron irradiation" Paul Bagot, Ben Jenkins, Nathan Almirall, G. Robert Odette, Materialia 11 2020 Link

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The Nuclear Science User Facilities (NSUF) is the U.S. Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Through peer-reviewed proposal processes, the NSUF provides researchers access to neutron, ion, and gamma irradiations, post-irradiation examination and beamline capabilities at Idaho National Laboratory and a diverse mix of university, national laboratory and industry partner institutions.

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