ML21274A008
| ML21274A008 | |
| Person / Time | |
|---|---|
| Issue date: | 10/13/2021 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| M. Yoo | |
| References | |
| Download: ML21274A008 (7) | |
Text
Preliminary Results from Assessment of Advanced Manufacturing Technologies (AMT) for Reactor Materials and Components Mark Yoo, Matthew Hiser, Amy Hull US Nuclear Regulatory Commission, Rockville, MD, USA 46th MPA-Seminar October 12-13, 2021
46th MPA-Seminar - October 12-13, 2021 Abstract The Nuclear Regulatory Commission (NRC) is aware of industry interest in using advanced manufacturing technologies (AMTs) to fabricate components both for new plant construction and repair and replacement in operating plants. AMTs include novel manufacturing techniques as well as more established techniques and material processing methods that have not traditionally been used in the U.S. nuclear industry and have yet to be formally standardized.
Initial AMTs that the NRC is focused upon based on high industry interest include laser powder bed fusion (LPBF) and laser-directed energy deposition (L-DED) additive manufacturing (AM) methods, powder metallurgy-hot isostatic pressing (PM-HIP), electron beam welding (EBW),
and cold spray. These technologies have several potential benefits, including flexible production of limited quantities of components for replacements, new repair options, reduced time and cost for fabrication, and improved performance due to less welding and machining during part fabrication and installation. Research is being conducted to establish a knowledge base for AMTs and provide support for NRCs independent evaluation of licensee applications of AMTs for safety-significant components. The near-term goal of this research is to assess differences between conventional and AMT-fabricated components to identify potential gaps in performance. This paper will present perspectives on the completed research in this program and the areas where future work might be beneficial to support future regulatory decision making.
Keywords: advanced manufacturing technologies (AMTs), laser powder bed fusion and directed energy deposition additive manufacturing methods, powder metallurgy-hot isostatic pressing, electron beam welding, cold spray, additive manufacturing (AM) 1 Introduction The Nuclear Regulatory Comissions (NRCs) approach to preparing to regulate and review industry proposals for using advanced manufacturing technologies (AMTs) in commercial nuclear applications focuses on identifying differences with AMT relative to conventional manufacturing [1]. Initial AMTs based on industry interest include laser powder bed fusion (LPBF) and laser-directed energy deposition (L-DED) additive manufacturing (AM) methods, powder metallurgy-hot isostatic pressing (PM-HIP), electron beam welding (EBW), and cold spray (CS) [2]. The general steps to demonstrating and qualifying new materials for new applications, such as process qualification, process control, performance demonstration, and quality assurance, are identical for both conventional and AMT fabrication methods.
However, AMT fabrication methods, such as LPBF and L-DED, are less mature, and codes and standards are still evolving, which present unique challenges in demonstrating that these components will perform adequately [1-4]. The AM process can produce significantly different microstructures, properties, and initial defect characteristics, all of which should be well characterized and understood. The NRCs approach to AMTs is to identify the safety-significant differences between AMTs and conventional manufacturing to focus limited resources on the areas of greatest importance. Revision 1 of NRCs AMT Action Plan [3]
outlines the technical, regulatory, and communications and knowledge management activities that the NRC is conducting and stresses the need to ensure that NRC staff is prepared to review AMT applications from the nuclear industry.
2 NRCs Technology-Neutral Assessment Approach Working with the U.S. Department of Energy (DOE) National Laboratories, the NRC is developing a series of technical reports reviewing the five selected AMTs. Following each technical report, NRC staff is preparing technical assessments that highlight key technical information related to AMT-fabricated components in nuclear power plants. Following this, the NRC staff is preparing draft guidelines documents (DGDs) which build on the NRC
46th MPA-Seminar - October 12-13, 2021 technical assessments and provide guidelines, when finalized, to the NRC staff by identifying important considerations when reviewing a submittal requesting the use of a specific AMT. In addition to these technology-specific guidelines, there is a technology-generic guidelines document that has been drafted titled Draft AMT Review Guidelines [5]. Figure 1 depicts the documents that will be issued for each AMT and their connections into the overall guidelines and anticipated guidance for AMTs.
Fig. 1 Technical Basis and Regulatory Guidelines Documents for Developing Guidance for Initial AMTs [6]
As of October 2021, the NRC has issued technical letter reports for LPBF [7] and CS [8] and the technical assessment [9] and DGD [10] for LPBF. By mid-2022, the technical products are anticipated to be completed for all five initial AMTs.
3 Technical Assessment of LPBF NRC staff has completed its technical assessment of LPBF and developed a draft guidelines document for LPBF [7, 10]. The technical assessment discusses the safety significance of the identified differences between LPBF and traditional manufacturing methods and the aspects of LPBF not addressed by codes and standards or regulations. Staff identified the differences between LPBF fabrication and traditional manufacturing processes by reviewing the information and gap analysis rankings from technical report for LPBF, as well as other relevant technical information (e.g., NRC regulatory and research experience, technical meetings and conferences, codes and standards activities, Electric Power Research Institute and DOE products and activities). The results of this technical assessment are organized into two categories. One category includes the material-generic differences for LPBF process and product performance compared to traditional manufacturing. The second category includes additional material-specific differences for 316L stainless steel, which is the alloy relevant to
46th MPA-Seminar - October 12-13, 2021 LPBF-fabricated nuclear applications with the greatest quantity of information currently available in the open literature. While this category is based on the available information in the open literature for 316L, the identified differences involving material-specific properties and performance would likely need to be considered for any new material to be fabricated using LPBF. In general, an important need for any nuclear LPBF-fabricated component is material-specific data for the proposed processing and post-processing parameters to ensure adequate component performance in environment, including various properties (e.g., fracture toughness, tensile strength) and aging mechanisms (e.g., thermal aging, irradiation effects, and stress corrosion cracking [SCC]).
LPBF uses a laser to melt or fuse powder together in a bed of powder.
Generally, LPBF is most advantageous for more complex geometries. Potential applications include smaller American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 components, fuel hardware, and small reactor vessel internal components. In early 2020, Westinghouse installed a thimble plugging device in the Byron Unit 2 reactor. More recently, in spring 2021, stainless steel 316L fuel assembly hardware was installed at Browns Ferry by Framatome. Oak Ridge National Laboratory printed Framatomes winged channel fastener body, as shown in Figure 2. Installation was done without prior NRC approval under 10 Code of Fig. 2 Second US nuclear power plant Federal Regulation 50.59. Application of LPBF 4 NRC Technical Assessment of DED The NRCs technical review of DED is currently ongoing and focused on DED with a laser heat source (i.e., L-DED). L-DED is an AM process based on wire or powder fed through the nozzle into a laser heat source as shown in Figure 3. It is fundamentally micro-welding using robotics and computer controls. This AMT can be used to fabricate complex geometries, and in some applications, assemblies with tens to hundreds of parts can be reduced to a single, as-fabricated component. In addition to geometric design freedom, L-DED allows for an advanced degree of composition design freedom, as the feedstock material can be mixed dynamically to locally tune portions of a particular component. However, these high degrees of design freedom create a corresponding burden to characterize and control material properties.
46th MPA-Seminar - October 12-13, 2021 Potential applications of L-DED are similar to LPBF, although slightly larger components may be practical due to faster production. DED has the comparative advantages of higher deposition speed, larger possible build volumes, and the option for direct integration with subtractive machining tools, while the minimum feature size resolution and microstructures are coarser than LPBF. LPBF can accomodate builds of up to about 34 kg
[75 lbs] whereas DED can accomodate the fabrication of nuclear components of up to roughly 227 kg [500 lbs]. Thus, Fig. 3 Schematic of L-DED process [11]
compared to LPBF, somewhat larger ASME Code Class 1, 2, and 3 components, fuel hardware, and reactor vessel internal components can be produced by L-DED.
5 NRC Technical Assessment of PM-HIP and Electron Beam Welding NRCs technical review of PM-HIP and EBW is currently ongoing. Work presented at the 2020 NRC Workshop on Advanced Manufacturing Technologies for Nuclear Applications [12]
highlighted these AMTs potential use for nuclear components, particularly thick-section low-alloy steels in reactor pressure vessels. This included the benefits of PM-HIP and Rolls-Royces perspective on a pathway to introduce PM-HIP components into nuclear plants. Rolls-Royce also discussed an analysis of key gaps and potential risks in the process, including powder quality, can failure, cracking during quenching, and scaling limitations.
Potential applications are much more diverse than for LPBF and DED, ranging from fairly small components up to reactor pressure vessels. All sizes of ASME Code Class 1, 2, and 3 components and reactor internals can be accommodated. Particularly focused on use with EBW, PM-HIP is being investigated to potentially fabricate the NuScale reactor vessel.
PM-HIP can handle sizes of up to 1.2 m [4 ft] in diameter and a weight of 45-4,500 kg [100-10,000 lbs].
Together, PM-HIP and EBW may be complementary techniques, that offer potential benefits such as reducing in-service inspection requirements and shorter fabrication time. Use Fig. 4 Reactor vessel head manufactured using of PM-HIP with EBW for larger PM-HIP [12]
nuclear components looks promising but requires larger HIP and EBW fabrication capabilities that are in development.
46th MPA-Seminar - October 12-13, 2021 6 NRC Technical Assessment of Cold Spray The NRCs technical review of CS is currently ongoing. The NRC staff is identifying and assessing the process considerations and knowledge gaps associated with using CS for nuclear applications as well as the importance of knowledge gaps based on specific CS application needs. The staff is also identifying gaps in existing codes and standards that should be addressed to support CS use in nuclear applications. CS is being used increasingly for defense applications, particularly for high-wear applications [12]. The assessment is largely based on the technical information and gap analysis report developed by the Pacific Northwest National Lab [8].
Powder is sprayed at supersonic velocities onto a metal surface and forms a diffusion bond with the part.
This can be used to repair existing parts or as a mitigation process.
Potential applications include chloride-induced stress corrosion cracking mitigation or repair in spent fuel canisters as well as Fig. 5 Cold Spray process schematic [8]
mitigation or repair of SCC in light-water reactor applications.
7 Summary To support near- and medium-term use of AMTs in nuclear applications, the industry and researchers should focus on developing data to support the qualification of AMT materials.
These data can be used to support codes and standards development and provide a technical basis to support implementation. The NRC is implementing its AMT Action Plan through technical and regulatory activities in preparation for reviewing industry proposals for the safe use of AM and AMTs. Through the AMT Action Plan, the NRC is actively working to develop guidance as appropriate to inform industry research efforts in support of AMT qualification.
References
[1] Hiser, M., Schneider, A., Audrain, M., and Hull, A., Regulatory Research Perspective on Additive Manufacturing for Nuclear Component Applications JNM 546 (January 2021) 152726
[2] Nuclear Energy Institute, Roadmap for Regulatory Acceptance of Advanced Manufacturing Methods in the Nuclear Energy Industry, May 2019 (ADAMS Accession No. ML19134A087).
[3] U.S. Nuclear Regulatory Commission, Action Plan for Advanced Manufacturing Technologies (AMTs), Revision 1 (2020) (ADAMS Accession No. ML19333B980).
[4] ASME PTB-13-2021, Criteria for Pressure Retaining Metallic Components Using Additive Manufacturing, 2021.
[5] U.S. Nuclear Regulatory Commission, Draft Advanced Manufacturing Technologies Review Guidelines, July 2021 (ADAMS Accession No. ML21074A037).
[6] U.S. Nuclear Regulatory Commission, NRC Draft Guidelines Document - Laser Powder Bed Fusion, Presentation for NRC Public Meeting, September 16, 2021 (ADAMS Accession No. ML21257A218).
46th MPA-Seminar - October 12-13, 2021
[7] Simpson, J.; Dehoff, R. Review of Advanced Manufacturing Techniques and Qualification Processes for LWRs - Laser Powder Bed Fusion Additive Manufacturing, September 2020 (ADAMS Accession No. ML20351A292).
[8] U.S. Nuclear Regulatory Commission, TLR-RES/DE/REB-2021-12, Assessment of Cold Spray Technology for Nuclear Power Applications, September 2021 (ADAMS Accession No. ML21263A107)
[9] U.S. Nuclear Regulatory Commission, NRC Technical Assessment of Additive Manufacturing - Laser Powder Bed Fusion, January 2021 (ADAMS Accession No. ML20351A292)
[10] U.S. Nuclear Regulatory Commission, Draft Guidelines Document for Additive ManufacturingLaser Powder Bed Fusion, July 2021 (ADAMS Accession No. ML21074A040).
[11] https://www.osti.gov/pages/servlets/purl/1437906.
[12] U.S. Nuclear Regulatory Commission, RIL 2021-03, NRC Workshop on Advanced Manufacturing Technologies for Nuclear Applications, Part 1- Workshop Summary (ADAMS Accession No. ML21113A081).
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