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{{#Wiki_filter:NRC Technical Assessment of Additive Manufacturing Laser-Directed Energy Deposition
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: 1. Introduction and Purpose This document provides a U.S. Nuclear Regulatory Commission (NRC) technical assessment of the impact on component performance of the identified differences between additive manufacturinglaser-directed energy deposition (L-DED) and traditional manufacturing methods and the aspects of L-DED not addressed by codes and standards or regulations. This assessment is primarily based upon the technical information and gap analysis developed by Oak Ridge National Laboratory (ORNL) in a technical letter report (TLR) entitled, Review of Advanced Manufacturing Techniques and Qualification Processes for Light Water Reactors Laser-Directed Energy Deposition Additive Manufacturing (Agencywide Documents Access &
Management System (ADAMS) Accession No. ML21292A187) (hereafter referred to as the ORNL TLR). This assessment, combined with the ORNL TLR, highlights key technical information related to L-DED-fabricated components in nuclear power plants and fulfills the deliverable for L-DED under Subtask 1A of the Action Plan for Advanced Manufacturing Technologies (AMTs), Revision 1, dated June 23, 2020 (ADAMS Accession No. ML19333B973).
: 2. NRC Identification and Assessment of Differences This section describes the differences between an L-DED-fabricated component and a traditionally manufactured component, assesses the impact that the identified difference has on component performance, and identifies specific technical considerations related to L-DED-fabricated components. The overall impact to plant safety (e.g., safety significance) is a function of component performance and the specific component application, such as its intended safety function. This report does not include the impact on plant safety, as such an assessment would not be possible without considering a specific component application.
The staff identified the differences between L-DED fabrication and traditional manufacturing processes by reviewing the information and gap analysis rankings from the ORNL TLR and other relevant technical information (e.g., NRC regulatory and research experience, technical meetings and conferences, codes and standards activities, Electric Power Research Institute and U.S. Department of Energy products and activities). The identified differences originated either as important aspects or gaps of the L-DED process or component performance as defined here:
* important aspect: part of the AMT fabrication process or component performance that needs to be considered and carefully controlled during manufacturing (e.g., powder quality for the laser powder directed energy deposition [LP-DED] process)
* gap: part of the AMT fabrication process or component performance that is not well known or understood due to limited information and data Two tables show the results of this technical assessment. Table 1 includes the material-generic differences for the L-DED process and component performance compared to traditional manufacturing. Table 2 includes additional material-specific differences for 316L stainless steel, which is the alloy relevant to L-DED-fabricated nuclear applications with the greatest quantity of information currently available in the open literature. While Table 2 is based on the available information in the open literature for 316L stainless steel, the differences identified in Table 2
 
involving material-specific properties and performance would likely need to be considered for any new material to be fabricated using L-DED. In general, any nuclear L-DED-fabricated component needs to have material-specific data for the proposed processing and post-processing parameters to ensure adequate component performance in its environment, including various properties (e.g., fracture toughness, tensile strength) and aging mechanisms (e.g., thermal aging, irradiation effects, and stress-corrosion cracking (SCC)). It is important to note that the feedstock (i.e., powder vs. wire) may impact the differences listed in the tables.
Tables 1 and 2 note the impact that the feedstock has on a specific difference, as appropriate.
The following columns in Tables 1 and 2 identify and provide technical information on the L-DED process and component performance:
* Difference:
o Corresponding ORNL Gaps: Identification of corresponding gaps from Section 3.4 of the ORNL TLR.
* Definition: Brief description of the difference with the L-DED process.
* NRC Ranking:
o Importance: Impact on final component performance considering the likelihood of occurrence or magnitude of degradation in conjunction with the ease of detection or ability to mitigate.
A high ranking would signify that the difference has a significant impact on component performance.
A medium ranking would signify that the difference has a moderate impact on component performance.
A low ranking would signify that the difference has a minimal impact on component performance.
o Knowledge/Manageability: Description of how well understood and manageable the difference is.
* Key Technical Information: Technical information for the consideration of L-DED-fabricated components for use in nuclear power plants.
: 3.      Codes and Standards Section 3.5 of the ORNL TLR provides a comprehensive overview of the existing standards relevant to L-DED as well as a detailed analysis of standards identified as highly relevant to nuclear applications. Significantly fewer standards are available for L-DED than for laser powder bed fusion (LPBF). One standard, American Welding Society (AWS) D20.1M, Specification for Fabrication of Metal Components using Additive Manufacturing, is generic to both LPBF and L-DED and may serve as a reasonable starting point for the consideration and development of codes and standards for L-DED for nuclear applications.
In addition, Table 15 from the ORNL TLR identifies several LPBF-specific standards that have no L-DED equivalents to date. These LPBF standards cover a range of important topics that should also be addressed for L-DED, including the following:
* design (LPBF specific: International Standards Organization (ISO)/American Society for Testing and Materials (ASTM) 52911-1:2019, Additive manufacturingDesignPart 1:
Laser-based powder bed fusion of metals)
* 316L stainless steel composition and tensile specifications (LPBF specific:
ASTM F3184-16, Standard Specification for Additive Manufacturing Stainless Steel Allow (UNS S31603) with Powder Bed Fusion)
* process control (LPBF specific: MSFC-SPEC-3717, Specification for Control and Qualification of Laser Powder Bed Fusion Metallurgical Processes; ASTM/ISO 52904:2019, Additive manufacturingProcess characteristics and performancePractice for metal powder bed fusion process to meet critical applications)
* material property evaluation specifications (LPBF specific: MSFC-STD-3716, Standard for Additively Manufactured Spaceflight Hardware by Laser Powder Bed Fusion in Metals)
* thermal post-processing (LPBF specific: ASTM F3301-18a, Standard for Additive ManufacturingPost Processing MethodsStandard Specification for Thermal Post-Processing Metal Parts Made Via Powder Bed Fusion)
In general, the ORNL TLR recommendations emphasize that properties and microstructure cannot be extricated from the geometry and scan strategy. Therefore, the codes and standards approach for L-DED should focus on establishing a consistent process for component qualification that recognizes that geometry affects material properties and performance and allows the process to vary the geometry while still maintaining qualification. The use of in-process data combined with destructive sampling and modeling and simulation tools may be one approach that could enable the qualification process to be robust and aligned with the unique aspects of L-DED and other AM technologies.
: 4.      Summary and Conclusion In Tables 1 and 2 of this report, the staff has identified and assessed the material-generic differences for the L-DED process and component performance as well as the material-specific differences for 316L stainless steel compared to conventional manufacturing. The staff also discussed gaps in existing codes and standards that should be addressed to support L-DED use in nuclear applications.
 
Table 1 Technical InformationL-DED Generic Difference                                        NRC Ranking (Corresponding        Definition                                Knowledge/                      Key Technical Information Importance ORNL Gaps)1                                                  Manageability Machine process      Medium Machine Machine process
* Control of L-DED files is needed to ensure process control includes the process control    control is very          control. Improper file control can significantly impact software controlling could impact final manageable with QA        final component properties and performance and affect L-DED Machine the scan strategy of    component          including appropriate    fabrication replication. Cybersecurity, database Process Control the L-DED machine    performance, but calibration.                traceability, management of software updates, and and the machine      it is expected to                            similar items are highly important to ensuring end-use (Software and File calibration to      be managed                                  component quality.
Control, L-DED reliably fabricate    through
* Machine calibration is vital for fabrication replication, Machine      components.          appropriate quality                          particularly ensuring correct feedstock deposition Calibration)                        assurance                                    parameters, laser power, laser spot size, travel speed, (QA)provisions.                              and atmospheric quality control in addition to geometric tolerances. For LP-DED, this includes contamination minimization if recycling powder.
Powder quality      High Powder        Powder quality can
* Detailed powder characterization and control, covers the          quality can have a  be challenging to      preventing powder contamination, and maintenance of important            significant impact  manage, and the        an inert gas environment are important factors in characteristics of  on the final        effects on final        ensuring powder quality and reducing powder variability.
the powder, such    component          component
* Powder contamination is a critical issue that may as composition and  performance and    performance are        adversely affect material properties and process by size distribution,  knowledge/          material specific.      introducing oxides and changing chemical composition.
Powder and how it is        manageability      Powder quality is an
* Thorough cleanliness activities, dedication of LP-DED Feedstock Quality managed in the      challenges.        area of active          machines to specific alloys, and periodic replacement of production process                      research to            feedstock conveying tubes and components can (Contamination before the build                        understand the          address powder contamination.
Management for process                                  critical powder
* LP-DED can achieve high powder utilization exceeding LP-DED, (e.g., sieving,                          characteristics for a  90 percent in some cases, which makes powder reuse Feedstock reuse, storage,                          given alloy and their  less essential than in LPBF.
Characterization, contamination).                          impacts on
* Powder reuse can provide substantial cost benefits but Powder Reuse component              can introduce significant variability in powder Management) performance. Powder    composition. Powder characterization and the also has more          establishment of associated acceptance criteria may be variables to control,  warranted to reuse powder, especially for and industry has less  safety-significant components.
experience with it as compared to wire feedstock.
 
Difference                                        NRC Ranking (Corresponding          Definition                              Knowledge/                        Key Technical Information Importance ORNL Gaps)1                                                    Manageability Wire quality covers Medium Wire        The ability to ensure
* Laser wire directed energy deposition (LW-DED) the important      quality can have a the conformance of        applications almost always use welding wire feedstock characteristics,    significant impact welding consumables      certified by the manufacturer to conform to AWS or ISO such as wire        on the              to applicable            standards for the specific alloy and wire product in Wire Feedstock    composition and    performance of      standards is well        question.
Quality      diameter and how it the final          established for
* There is a long-established history of ensuring welding is managed in the  component, but      industrial welding      consumables conform to applicable standards for (Feedstock      production process wire generally      applications, with a    industrial welding applications.
Characterization)  before the build    involves fewer      lengthy history of
* Wire chemistry and processing path must be tightly process            variables and      established quality      controlled.
(e.g., storage). uncertainties than control.
* Contamination concerns are well understood and are powder.                                      less of a concern than for powder feedstock.
Build process      Medium Build        This issue is
* Build interruptions (planned and unplanned) can have a management and      interruptions and  manageable with QA        very significant impact on component quality and L-DED Build      control includes    loss of process    and the use of in situ    should be avoided.
Process      monitoring          control can        monitoring and
* In situ monitoring without feedback control can be used Management and parameters during      adversely impact    environmental sensor      to identify issues in the build process in real time and Control      fabrication using  component          data.                    may be used in conjunction with other approaches to environmental      performance by                                demonstrate process control.
(L-DED        sensors, in situ    creating defects,  Knowledge is
* In situ monitoring with feedback control is still a Environmental    monitoring, and    altering local      relatively limited and    developing area of research and should be carefully Sensor Data, In evaluating the        material            still maturing on the    managed and its effectiveness definitively Situ Monitoring  effects of build    microstructure      use of in situ            demonstrated if proposed for use during production.
and Feedback,    interruptions.      and properties,    monitoring with
* Management, storage, retrieval, and analysis of the Planned and                          and creating        feedback control          data generated during the L-DED process are critical Unplanned Build                        warping and        designed to correct      for accelerating process optimization, although Interruptions, Data                    distortion due to  defects automatically    guidance for the proper identification, handling, and Management)                          changing the        during the build          evaluation of this information is still under development.
thermal            process.
distribution by cooling.
Witness specimens Medium Witness        Witness specimens
* The most highly representative test specimens are Witness or witness coupons specimens offer      may be useful for          obtained from end-use component geometries.
Specimens are test specimens one approach to      identifying build          o Geometry impacts, particularly thickness, on witness that are fabricated demonstrating      issues such as                specimen microstructure and properties should be concurrently with e process control by  delamination or other        considered and addressed.
 
Difference                                          NRC Ranking (Corresponding      Definition                                  Knowledge/                      Key Technical Information Importance ORNL Gaps)1                                                    Manageability nd-use                measuring            events that may
* Optimal witness specimen parameters (geometry, size, components and        properties from      result in component      location, spatial orientation, and frequency) depend used to confirm        parts built          rejection. However,      highly on the end-use component geometry and the build quality and      coincidentally with the use of witness        goal of the witness testing approach (e.g., monitoring component              the service          specimens for            build issues as part of process control or generating performance.          component.          optimizing and            representative material properties data as part of generating                process qualification).
quantitative data for
* When sectioning end-use geometries is not feasible, qualification is less    functional evaluations of the relationship between the well established and      acceptability of the end-use geometries (e.g., burst could involve            tests, inspections) and the use of simplified witness demonstration that        specimen geometries would need to be demonstrated.
the specimen is representative of the final component.
Thermal post-          High Thermal        Post-processing heat
* Post-processing heat treatments without HIP generally processing            post-processing      treatments are          are designed to provide two benefits, stress relief or includes methods      should make          commonly done for        annealing (or both), but they likely have little impact on used after the initial material            L-DED and                porosity or flaws.
component build        properties and      conventional            o Stress-relief heat treatments will primarily reduce that involve          performance more materials and are              residual stresses from the as-built part without elevated              homogeneous          fairly well                otherwise affecting the microstructure or properties.
temperatures, such and similar to          understood. HIP is      o Annealing heat treatments should greatly reduce or as hot isostatic      those of            also a                    eliminate residual stress as well as coarsen the pressing (HIP) and conventional            well-established          microstructure (to improve toughness) and reduce Thermal Post- heat treatments, to forged materials        method, but it is less    heterogeneity in microstructure and properties.
processing  improve material      and may              commonly used for
* HIP may be beneficial for reducing residual stress, properties and        significantly        conventional            porosity, heterogeneity, and internal cracks, while also performance by        impact              materials where          coarsening the microstructure (to improve toughness).
increasing density considerations          porosity is not a
* For all thermal post-processing approaches, and reducing          related to the      significant issue.      material-specific demonstration is important to identify porosity.              other L-DED-                                  adequate heat treatment or HIP parameters to achieve specific topics                              desired improvements in microstructure, properties, identified in lower                          heterogeneity, porosity, and fabrication flaws.
rows. Conversely,
* Thermal post-processing may significantly impact component                                    considerations related to the other L-DED-specific performance may
 
Difference                                          NRC Ranking (Corresponding        Definition                                Knowledge/                          Key Technical Information Importance ORNL Gaps)1                                                  Manageability be degraded if                                topics identified in lower rows (e.g., porosity, residual thermal post-                                  stress, initial fracture toughness).
processing is not used.
The geometry of      High Local          Local geometry
* The role of geometry on local microstructure and the component and    geometry impacts    impacts are highly      properties is one of the key differences between the heat transfer    can have a          dependent on the        L-DED-produced components and conventionally characteristics from  significant impact  material and            produced ones.
the component        on component        geometry of the final
* Local geometry significantly impacts thermal profiles build directly affect performance if not  component. They can    during fabrication, which affects the local microstructure Local Geometry  local microstructure  managed or          be managed through      and properties.
Impacts on    (e.g., grain size    addressed.          post-processing and      o For example, a thin section with relatively rapid Component    and orientation),                          sampling/witness            cooling rates will likely have a much finer Properties and  which can affect                          specimens to                microstructure than a thicker section with a slower Performance    material properties                        measure the impacts.        cooling rate because more surrounding material is and performance,                                                      melted.
(L-DED Design    including SCC                                                      o As a result, the variation in microstructure as a Considerations,  susceptibility.                                                        function of geometry will affect local material Geometry-Scan properties such as strength, ductility, and toughness.
Strategy
* Post-processing and scan strategy refinement have the Interactions, potential to minimize the local geometry impacts; Inspection of however, the effects on properties and performance can Fabricated vary significantly based on the geometry and materials Components) used.
* If used, witness specimens representing the thinnest section are needed to bound the material properties of the component.
* The advantages of L-DED to fabricate components with as-built internal features can make the inspection of the component features more difficult.
Heterogeneity and Heterogeneity and      High                This effect is
* Heterogeneity generally manifests with different Anisotropy in  anisotropy            Heterogeneity and generally well            properties in the build direction relative to the other two Properties  generally manifest    anisotropy in L-    understood but          directions due to the nature of the layer-by-layer build as different          DED-fabricated      requires specific      process. This impacts the microstructure and fabrication (Material Property properties in the    components differ measures to                defect structure and generally creates poorer properties Sampling    build direction      significantly from  manage, whether        between build layers.
 
Difference                                          NRC Ranking (Corresponding        Definition                                Knowledge/                        Key Technical Information Importance ORNL Gaps)1                                                    Manageability Methodology,  relative to the other those in            through an
* Thermal post-processing with appropriate parameters Heterogeneity)  two directions due conventional            appropriate sampling    would be expected to make material properties and to the nature of the materials, which      methodology            performance more homogeneous and similar to those of layer-by-layer build are largely          (e.g., witness          conventionally forged materials.
process. This        isotropic, and can specimens) or
* For example, in as-fabricated and stress-relieved 316L impacts the          have a significant thermal post-            stainless steel, the variation in microstructure due to microstructure and impact on              processing, to help    geometry causes preferential crack growth directions for fabrication defect    component            minimize this effect. fatigue cracks.
structure and        performance if not generally creates    addressed in the poorer properties    design, between build        fabrication, or layers.              post-fabrication process.
Residual stresses    Medium Residual There is significant
* L-DED components typically experience significant as-form during the      stress and          knowledge related to    fabricated residual stress.
Residual Stress L-DED build          associated          managing the
* High residual stress may result in warping, cracking, and process and can      defects can          potential negative      delamination; however, these events typically can be (Residual Stress lead to warping,      negatively impact impacts of residual        detected visually.
Warping,    cracking, and        component            stress, including
* In addition, residual stress can make the component Cracking, and  delamination if not performance.          through optimizing      susceptible to future degradation such as SCC or fatigue Delamination)  properly managed.                          the build process,      from the presence of high tensile residual stress on the post-processing, or      surface.
inspection.
* Thermal post-processing with appropriate parameters would be expected to relieve residual stress.
Porosity includes    High                Techniques to
* Porosity is known to adversely affect fatigue life, SCC, the size,            Unacceptable        manage porosity in      and irradiation-assisted stress-corrosion cracking distribution, and    levels of porosity  the build process are    (IASCC), though the precise quantitative impact total volume of      can have a          known, but porosity      depends on the material and porosity characteristics Porosity    voids and pores in    significant impact  can be challenging to    (pore frequency, pore size, pore morphology, and total the L-DED            on component        mitigate through        void fraction).
(Porosity    component.            performance. By      thermal post-
* Machine parameters and scan strategy refinement have Measurement)                          the nature of        processing.              the potential to address porosity concerns; however, L-DED, the                                    they may vary significantly based on the geometry and porosity may have                            materials used.
smaller size and higher density
 
Difference                                        NRC Ranking (Corresponding        Definition                              Knowledge/                        Key Technical Information Importance ORNL Gaps)1                                                  Manageability than in forged
* Porosity is more prevalent in LP-DED than LW-DED due materials.                                  to the internal porosity and trapped gas in powder feedstock that does not exist in wire feedstock.
* For post-processing, HIP with appropriate parameters has been demonstrated to reduce porosity and produce properties more similar to those of conventionally forged materials.
Surface finish (or  High Surface        L-DED components
* Surface roughness is generally greater in as-built L-DED surface roughness)  finish can have a    can be finished using  parts than in similar forged materials.
refers to the      significant impact  traditional post-      o The layer-by-layer nature of LP-DED, combined with measure of the      on component        processing                the tendency to weld unmelted powder particles to the texture of the part performance,        techniques.                component surfaces, produces a rough outer surface surface.            particularly                                    in LP-DED.
Processing          through increased                            o LW-DED typically results in a bead-like surface due to Surface Finish  techniques that are susceptibility to                              the layer-by-layer deposition but does not give the conducted to        fatigue and SCC                                added roughness of attached particles.
(Surface      improve surface    initiation.
* Higher surface roughness can lead to reduced fatigue Roughness)      finish include                                                  life and lower SCC and corrosion resistance.
machining, shot
* Surface finish can be improved by post-processing such peening, and                                                    as subtractive machining or other surface treatments.
chemical treatment.
* For components with complicated geometries, hybrid manufacturing approaches (iterating between additive and subtractive steps) may be necessary to reach all surfaces for post-processing.
Note 1: Section 3.4 of the ORNL TLR discusses the corresponding ORNL gaps.
 
Table 2 Technical Information316L L-DED Stainless Steel Material Specific Difference                                    NRC Ranking of Significance (Corresponding          Definition                                    Knowledge/                      Key Technical Information Importance ORNL Gaps)1                                                          Manageability Tensile properties. Low Failure due to        316L L-DED stainless
* High porosity would likely degrade tensile tensile overload is not a steel materials have        performance but would have a greater impact common failure mode      generally sufficient data    on other material properties.
Tensile Properties in nuclear components, showing similar or and it is no more likely superior tensile (Tensile in L-DED materials due properties compared to Properties) to their similar or      those of similar forged superior tensile          materials.
properties.
Initial fracture    High Low initial          Limited data are
* Limited data on 316L L-DED stainless steel toughness refers to fracture toughness can available on fracture          materials have shown significantly lower initial the materials      lead to brittle          toughness for 316L L-      fracture toughness, depending on post-starting fracture  component failure if not DED stainless steel          processing, than for similar forged materials.
toughness upon      adequately managed.      materials. Post-            This may be due to porosity or other defects that entering service                              processing should          may be reduced with optimized processing Initial Fracture  after fabrication.                            improve fracture            parameters and thermal post-processing.
Toughness                                                    toughness and minimize      o However, 316L L-DED stainless steel is still any difference.                expected to have adequate initial toughness.
(Fracture
* Data in representative environments are Toughness) important to demonstrate that fracture toughness will be adequate to meet component design assumptions.
* Thermal post-processing with appropriate parameters would be expected to improve fracture toughness.
Thermal aging      High Thermal aging        The NRC is not aware of
* Data in representative environments are refers to the      can lead to brittle      any significant data on    important to demonstrate that fracture reduction in        component failure if not thermal aging behavior      toughness does not degrade excessively due to fracture toughness adequately managed.        of 316L L-DED stainless    thermal aging and will be adequate to meet Thermal Aging    after significant                            steel materials.            component design assumptions.
time at elevated
* Thermal post-processing with appropriate temperature, which                                                        parameters would be expected to make material is a known aging                                                          properties and performance more similar to mechanism for                                                            those of conventional forged materials.
stainless steels containing
 
Difference                                    NRC Ranking of Significance (Corresponding      Definition                                      Knowledge/                        Key Technical Information Importance ORNL Gaps)1                                                        Manageability significant levels of ferrite.
SCC refers to        High SCC can lead to    Very limited data exist
* Data in representative environments are stress-corrosion      component failure if not on SCC behavior of            important to demonstrate that material crack initiation and  adequately managed.      316L L-DED stainless          performance due to SCC will not be degraded to growth of            Local material          steel materials, although    a greater degree in L-DED materials than in susceptible          characteristics          SCC is a known                forged materials.
SCC and materials under      (i.e., grain boundary    degradation mode in
* Post-processing with appropriate parameters Corrosion roughly constant      chemistry and            light-water reactors.        would be expected to make material properties Resistance stress operating      microstructure) may                                    and performance more similar to those of conditions due to    amplify differences with                              conventional forged materials.
(SCC and IASCC, the corrosive        conventional materials
* In 316L stainless steel, the silicon content in the Corrosion environment.          not apparent in other                                  powder can create oxides that have adverse Resistance)
Corrosion refers to  tests (e.g., tensile).                                effects on SCC growth rates. Acceptance other corrosion                                                              criteria for powder (virgin and recycled) should processes that may                                                          consider oxide content.
be active in the environment.
Fatigue refers to    Medium While fatigue    Limited data are
* Without adequate post-processing, surface the initiation and    can be a concern and    available in the literature  roughness is known to be a greater issue with L-propagation of        lead to component        on the fatigue life of L-    DED materials and can reduce fatigue life.
cracks due to cyclic  failure, other post-    DED materials
* Fatigue properties also depend on post-loading with or      processing steps such    compared to                  processing heat treatment and component without              as surface finishing,    conventionally                porosity.
environmental        residual stress          manufactured materials.
* Limited data suggest high-cycle fatigue life may effects playing a    reduction, and HIP heat                                be reduced compared to that of conventional Fatigue    significant role in  treatments can be used                                316L stainless steel, while low-cycle fatigue life the process.          to improve fatigue                                    is comparable to that of conventional 316L (Fatigue)                        susceptibility in many                                stainless steel.
applications.
* Stress-relieved (without annealing heat treatment) 316L L-DED stainless steel shows anisotropic fatigue strength and preferential crack growth directions due to the columnar microstructure.
* Data in representative environments are important to support fatigue calculations,
 
Difference                                      NRC Ranking of Significance (Corresponding          Definition                                    Knowledge/                      Key Technical Information Importance ORNL Gaps)1                                                          Manageability including for environmentally assisted fatigue, in L-DED materials.
Irradiation effects  High Irradiation effects Very limited data exist
* Data in representative environments are refer to the impact are highly relevant to    on irradiation effects,      important to demonstrate that irradiation effects of neutron          address for irradiated  particularly neutron        will not be significantly greater in L-DED irradiation on      reactor internals        irradiation, on the          materials than in forged materials.
various aspects of components in              behavior of 316L L-DED
* Post-processing with appropriate parameters material properties light-water reactors,    stainless steel materials. would be expected to make material properties Irradiation Effects and performance,    which can lead to                                    and performance more similar to those of including, but not  premature component                                  conventional forged materials.
(SCC and IASCC, limited to, loss of  failures. Local material
* Current studies point to reduced Irradiation-fracture toughness, characteristics                                        irradiation-induced  defects in L-DED Assisted IASCC, and void      (i.e., grain boundary                                components    compared    to those produced with Degradation) swelling.            chemistry and                                        conventional manufacturing. However, the microstructure) may                                  understanding is very limited, and research is amplify differences with                              ongoing. Additional research is likely needed to conventional materials                                understand performance differences.
not apparent in other tests (e.g., tensile).
High-temperature    High                    Very limited data exist
* For high-temperature operating environments aging effects refer High-temperature,        on high-temperature,        (as discussed in ASME Boiler and Pressure to any              time-dependent aging    time-dependent aging        Vessel Code, Section III, Division 5), data in time-dependent      effects are of high      effects for 316L            representative environments are important to aging mechanisms importance to                stainless steel L-DED        demonstrate that high-temperature, time-relevant to elevated component integrity for materials.                    dependent aging effects in L-DED materials will High-temperatures (as    the elevated operating                                be equivalent to or acceptable when compared Temperature, discussed in        temperatures expected                                to those in forged materials.
Time-Dependent American Society    for many advanced
* Post-processing with appropriate parameters Aging Effects of Mechanical        reactor designs.                                      would  be expected to make material properties (e.g., Creep and Engineers (ASME)                                                          and  performance    more similar to those of Creep-Fatigue)
Boiler and                                                                conventional forged materials.
Pressure Vessel Code, Section III, Division 5),
including creep and creep-fatigue.
 
Difference                                  NRC Ranking of Significance (Corresponding        Definition                                    Knowledge/                      Key Technical Information Importance ORNL Gaps)1                                                        Manageability Weld integrity      High Welds can be a      The NRC is not aware of
* Data in representative environments are refers to the      location of degradation any significant data on        important to demonstrate that welds with L-DED properties and      and may behave            weld integrity for 316L L-  base materials will perform similarly to those Weld Integrity  performance of the  significantly differently DED stainless steel          with conventionally manufactured base weld and            with L-DED materials. materials.                  materials.
surrounding heat-affected zone.
Weldability refers  Medium Weldability is    The NRC is not aware of
* Very limited information has been published on to the ability to  a concern but should      any significant data on      the results of using traditional joining methods successfully weld a not greatly impact        the weldability of 316L      on L-DED components.
material to another component                L-DED stainless steel
* Higher oxygen content, residual stress, and component without  performance as long as    materials. Existing          microstructural segregation may affect the Weldability/
unacceptable        satisfactory welds        welding standards to        optimal parameters for welding on 316L L-DED Joining defects.            passing ASME Boiler      demonstrate weldability      stainless steel compared to on conventional and Pressure Vessel      and accept final            316L stainless steel.
(Weldability)
Code requirements can    manufactured welds are
* Weldability should be demonstrated for L-DED be made.                  expected to remain          materials, but the existing welding standards applicable for L-DED        and demonstration processes should be components.                  sufficient.
Note 1: Section 3.4 of the ORNL TLR discusses the corresponding ORNL gaps.}}

Revision as of 19:36, 16 January 2022

Technical Assessment of Additive Manufacturing-Laser Directed Energy Deposition
ML21292A188
Person / Time
Issue date: 11/17/2021
From:
Office of Nuclear Regulatory Research
To:
M. Yoo
Shared Package
ML21292A186 List:
References
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