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A Roadmap for NEAMS Capability Transfer

The vision of the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program is to bring truly predictive modeling and simulation (M&S) capabilities to the nuclear engineering community in order to enable a new approach to the design and analysis of nuclear energy systems. From its inception, the NEAMS program has always envisioned a broad user base for its software and scientific products, including researchers within the DOE complex, nuclear industry technology developers and vendors, and operators. However activities to date have focused almost exclusively on interactions with NEAMS sponsors, who are also near-term users of NEAMS technologies. The task of the NEAMS Capability Transfer (CT) program element for FY2011 is to develop a comprehensive plan to support the program's needs for user outreach and technology transfer. In order to obtain community input to this plan, a 'NEAMS Capability Transfer Roadmapping Workshop' was held 4-5 April 2011 in Chattanooga, TN, and is summarized in this report. The 30 workshop participants represented the NEAMS program, the DOE and industrial user communities, and several outside programs. The workshop included a series of presentations providing an overview of the NEAMS program and presentations on the user outreach and technology transfer experiences of (1) The Advanced Simulation and Computing (ASC) program, (2) The Standardized Computer Analysis for Licensing Evaluation (SCALE) project, and (3) The Consortium for Advanced Simulation of Light Water Reactors (CASL), followed by discussion sessions. Based on the workshop and other discussions throughout the year, we make a number of recommendations of key areas for the NEAMS program to develop the user outreach and technology transfer activities: (1) Engage not only DOE, but also industrial users sooner and more often; (2) Engage with the Nuclear Regulatory Commission to facilitate their understanding and acceptance of NEAMS approach to predictive M&S; (3) Place requirements gathering from prospective users on a more formal footing, updating requirements on a regular basis and incorporate them into planning and execution of the project in a traceable fashion; (4) Seek out the best available data for validation purposes, and work with experimental programs to design and carry out new experiments that satisfy the need for data suitable for validation of high-fidelity M&S codes; (5) Develop and implement program-wide plans and policies for export control, licensing, and distribution of NEAMS software products; (6) Establish a program of sponsored alpha testing by experienced users in order to obtain feedback on NEAMS codes; (7) Provide technical support for NEAMS software products; (8) Develop and deliver documentation, tutorial materials, and live training classes; and (9) Be prepared to support outside users who wish to contribute to the codes.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Target Trailing With Safe Navigation for Maritime Autonomous Surface Vehicles

This software implements a motion-planning module for a maritime autonomous surface vehicle (ASV). The module trails a given target while also avoiding static and dynamic surface hazards. When surface hazards are other moving boats, the motion planner must apply International Regulations for Avoiding Collisions at Sea (COLREGS). A key subset of these rules has been implemented in the software. In case contact with the target is lost, the software can receive and follow a "reacquisition route," provided by a complementary system, until the target is reacquired. The programmatic intention is that the trailed target is a submarine, although any mobile naval platform could serve as the target. The algorithmic approach to combining motion with a (possibly moving) goal location, while avoiding local hazards, may be applicable to robotic rovers, automated landing systems, and autonomous airships. The software operates in JPL s CARACaS (Control Architecture for Robotic Agent Command and Sensing) software architecture and relies on other modules for environmental perception data and information on the predicted detectability of the target, as well as the low-level interface to the boat controls.

Wolf, Michael↗

Hanford Site Sustainability Program, Richland, Washington - 12464

In support of implementation of Executive Order (EO) 13514, Federal Leadership in Environmental, Energy and Economic Performance, the Hanford Site Sustainability Plan [1] was developed to implement strategies and activities required to achieve the prescribed goals in the EO as well as demonstrate measurable progress in environmental stewardship at the Hanford Site. The Hanford Site has made significant progress in the area of environmental stewardship through multiple initiatives to reduce energy consumption and GHG emissions, despite increased demands in those areas due to accelerated cleanup work driven by ARRA funding. Future plans, contingent on available funding, include additional enhancements in the areas of fleet management, including installation of additional charging stations and continued acquisition of alternate fueled vehicles, implementation of one or more of the recommendations from the Feasibility Study on reducing GHG emissions from employee commuting, and potential diversion of solid waste from on-site landfills. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Site Sustainability Plan (FY2020)

United States Department of Energy (DOE) O 436.1, Departmental Sustainability, requires each DOE site to develop and commit to implementing an annual Site Sustainability Plan (SSP) that identifies that site's contributions toward meeting DOE sustainability goals. These sustainability goals are reinforced by Executive Order (EO) 13834, Efficient Federal Operations. Sandia personnel conduct mission activities at four primary locations: Sandia National Laboratories/New Mexico (SNL/NM); SNL/California (SNL/CA), SNL/ Tonopah Test Range (SNL/TTR) in Nevada; and SNL/Kauai Test Facility (SNL/KTF) in Hawaii. Sandia personnel also conduct mission activities at other locations, Carlsbad, New Mexico; and Amarillo, Texas. Each location has unique energy, water, and transportation fuel resource management challenges. SNL/NM and SNL/CA account for most of Sandia's total energy, water, and transportation fuel use and building square footage. Therefore, although the goals and targets of this plan include all locations, sustainability activities focus predominantly on the SNL/NM and SNL/CA locations.

54 ENVIRONMENTAL SCIENCES↗

Office of Nuclear Energy Knowledge Management Program Situational Analysis Report

Knowledge management (KM) has been a high priority for the Department of Energy (DOE) Office of Nuclear Energy (NE) for the past several years. NE Programs are moving toward well-established knowledge management practices and a formal knowledge management program has been established. Knowledge management is being practiced to some level within each of the NE programs. Although it continues to evolve as NE programs evolve, a formal strategic plan that guides the implementation of KM has been developed. Despite the acceptance of KM within DOE NE, more work is necessary before the NE KM program can be considered fully successful. Per Dr. David J. Skyrme[1], an organization typically moves through the following evolutionary phases: (1) Ad-hoc - KM is being practiced to some level in some parts of the organization; (2) Formal - KM is established as a formal project or program; (3) Expanding - the use of KM as a discipline grows in practice across different parts of the organization; (4) Cohesive - there is a degree of coordination of KM; (5) Integrated - there are formal standards and approaches that give every individual access to most organizational knowledge through common interfaces; and (6) Embedded - KM is part-and-parcel of everyday tasks; it blends seamlessly into the background. According to the evolutionary phases, the NE KM program is operating at the two lower levels, Ad-hoc and Formal. Although KM is being practiced to some level, it is not being practiced in a consistent manner across the NE programs. To be fully successful, more emphasis must be placed on establishing KM standards and processes for collecting, organizing, sharing and accessing NE knowledge. Existing knowledge needs to be prioritized and gathered on a routine basis, its existence formally recorded in a knowledge inventory. Governance to ensure the quality of the knowledge being used must also be considered. For easy retrieval, knowledge must be organized according to a taxonomy that mimics nuclear energy programs. Technologies need to be established to make accessing the knowledge easier for the user. Finally, knowledge needs to be used as part of a well defined work process.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Experiences with Extra-Vehicular Activities in Response to Critical ISS Contingencies

The maturation of the International Space Station (ISS) design from the proposed Space Station Freedom to today's current implementation resulted in external hardware redundancy vulnerabilities in the final design. Failure to compensate for or respond to these vulnerabilities could put the ISS in a posture to where it could no longer function as a habitable space station. In the first years of ISS assembly, these responses were to largely be addressed by the continued resupply and Extra-Vehicular Activity (EVA) capabilities of the Space Shuttle. Even prior to the decision to retire the Space Shuttle, it was realized that ISS needed to have its own capability to be able to rapidly repair or replace external hardware without needing to wait for the next cargo resupply mission. As documented in a previous publicatoin5, in 2006 development was started to baseline Extra- Vehicular Activity (EVA, or spacewalk) procedures to replace hardware components whose failure would expose some of the ISS vulnerabilities should a second failure occur. This development work laid the groundwork for the onboard crews and the ground operations and engineering teams to be ready to replace any of this failed hardware. In 2010, this development work was put to the test when one of these pieces of hardware failed. This paper will provide a brief summary of the planning and processes established in the original Contingency EVA development phase. It will then review how those plans and processes were implemented in 2010, highlighting what went well as well as where there were deficiencies between theory and reality. This paper will show that the original approach and analyses, though sound, were not as thorough as they should have been in the realm of planning for next worse failures, for documenting Programmatic approval of key assumptions, and not pursuing sufficient engineering analysis prior to the failure of the hardware. The paper will further highlight the changes made to the Contingency EVA preparation team structure, approach, goals, and the resources allocated to its work after the 2010 events. Finally, the authors will overview the implementation of these updates in addressing failures onboard the ISS in 2012, 2013, and 2014. The successful use of the updated approaches, and the application of the approaches to other spacewalks, will demonstrate the effectiveness of this additional work and make a case for putting significant time and resources into pre-failure planning and analysis for critical hardware items on human-tended spacecraft.

Van Cise, E. A.↗

Experiences with Extra-Vehicular Activities in Response to Critical ISS Contingencies

The maturation of the International Space Station (ISS) design from the proposed Space Station Freedom to today's current implementation resulted in external hardware redundancy vulnerabilities in the final design. Failure to compensate for or respond to these vulnerabilities could put the ISS in a posture where it could no longer function as a habitable space station. In the first years of ISS assembly, these responses were to largely be addressed by the continued resupply and Extra-Vehicular Activity (EVA) capabilities of the Space Shuttle. Even prior to the decision to retire the Space Shuttle, it was realized that ISS needed to have its own capability to be able to rapidly repair or replace external hardware without needing to wait for the next cargo resupply mission. As documented in a previous publication, in 2006 development was started to baseline Extra-Vehicular Activity (EVA, or spacewalk) procedures to replace hardware components whose failure would expose some of the ISS vulnerabilities should a second failure occur. This development work laid the groundwork for the onboard crews and the ground operations and engineering teams to be ready to replace any of this failed hardware. In 2010, this development work was put to the test when one of these pieces of hardware failed. This paper will provide a brief summary of the planning and processes established in the original Contingency EVA development phase. It will then review how those plans and processes were implemented in 2010, highlighting what went well as well as where there were deficiencies between theory and reality. This paper will show that the original approach and analyses, though sound, were not as thorough as they should have been in the realm of planning for next worse failures, for documenting Programmatic approval of key assumptions, and not pursuing sufficient engineering analysis prior to the failure of the hardware. The paper will further highlight the changes made to the Contingency EVA preparation team structure, approach, goals, and the resources allocated to its work after the 2010 events. Finally, the authors will overview the implementation of these updates in addressing failures onboard the ISS in 2012, 2013, and 2014. The successful use of the updated approaches, and the application of the approaches to other spacewalks, will demonstrate the effectiveness of this additional work and make a case for putting significant time and resources into pre-failure planning and analysis for critical hardware items on human-tended spacecraft.

Van Cise, E. A.↗

The Relationship of Hydrology in the Green River to Colorado Pikeminnow Populations

The Federally listed Colorado Pikeminnow (CP) (Ptychocheilus Lucius) has been declining in the Green River Basin over the last 20 years. Muth et al. (2000) recommended flows and temperatures to benefit endangered fish species downstream of Flaming Gorge Dam on the Green River. The recommendations identified a range of flows during the base flow period (flows that occur after the annual snowmelt runoff period, usually from early summer to the following spring) that were intended to benefit CP. The recommendations indicated that the mean flow for the summer–winter period should be established each year on the basis of anticipated hydrologic conditions, but adjustments could be made if hydrologic conditions change. Flow should gradually decline from peak flow to base flow, with the base flow reached by early to middle summer (depending on hydrologic conditions) and maintained through February. The rate of decline should depend on rates of decline in Yampa River flows and the recommended rates of decline for dam releases. No specific recommendations were made for base flow variation in Reach 1, but variation around the annual mean base flow should be restricted to achieve recommended levels of variation in Reach 2 (middle Green River) (Table 5.5 in Muth et al. 2000). Implementation of the flow and temperature recommendations served as the proposed action for an EIS on Flaming Gorge Dam operations. A Biological Assessment of the impacts on endangered species of implementing the recommendations was prepared and a Biological Opinion that called for development of a study plan to examine the effects of implementation. Projects to address this evaluation were identified in the Green River Study Plan and have been conducted since then. The purpose of the Study Plan was to identify and recommend to the Recovery Program those monitoring or research projects necessary for implementation and evaluation of the flow and temperature recommendations. Those projects included studies to evaluate the anticipated effects of implementing the recommendations (including potential adverse effects identified in the 2006 Biological Opinion) and studies to examine recognized uncertainties of the recommendations. A new recovery program summer base flow study plan was approved in September of 2020 to evaluate stable and elevated summer base flows below Flaming Gorge Dam intended to benefit CP spawning and rearing success. Anecdotal observations suggest CP production may have been higher in years prior to flow restrictions for endangered fish. Based on long-term CP monitoring data in the Green River, Bestgen and Hill (2016) concluded that CP would benefit from higher summer baseflows (1,700-3,000 ft 3 /sec) with flows above or below associated with lower abundance of age-0 CP. Therefore, flexibility in the ROD is currently being utilized to establish higher stable summer base flows in an attempt create more advantageous conditions for spawning and rearing CP. These fish recovery flows are restrictive to WAPA in the summer months, therefore it is necessary to conduct an analysis of historic river data relationships to CP abundance to better understand if the recommended fish flows (elevated and stable base flows) are necessary for fish recovery.

54 ENVIRONMENTAL SCIENCES↗

Regional Transmission Planning: A review of practices following FERC Order Nos. 890 and 1000

Federal Energy Regulatory Commission (FERC) Order Nos. 890 and 10001 established requirements that transmission planning regions must follow in regional transmission planning and allocating the costs of new transmission facilities. Order No. 890, issued in 2007, outlined general requirements for local as well as regional transmission planning practices and procedures. Order No. 1000, issued in 2011, laid out specific requirements for: (1) regional transmission planning; (2) consideration of transmission needs driven by public policy requirements; (3) non-incumbent transmission development; (4) interregional transmission coordination; and (5) cost allocation for transmission facilities that have been selected in a regional transmission plan for purposes of cost allocation. This report reviews how these FERC orders are being implemented by the 12 transmission planning regions recognized by FERC.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Implementation of Glycolic Acid Flowsheet in the Defense Waste Processing Facility (DWPF) - 17348

The disposition of high level waste (HLW) into canistered waste forms began at Savannah River Site (SRS) in 1996. For its entire processing history, DWPF has added formic acid as a pretreatment step in producing acceptable melter feed from incoming waste sludges sent from the HLW Tank Farms. While this process has been used to successfully produce more than 4,000 radioactive canisters, the addition of formic acid and its tendency to catalytically decompose in the presence of trace quantities of noble metals adds substantial process complexity in order to safely accommodate hydrogen generation and pH shifting during batch operations. Research efforts have been in progress for several years to identify a chemical surrogate for formic acid which performs the essential process functions without the associated negative consequences. The final analytical work to demonstrate the effectiveness of glycolic acid in the DWPF is nearly complete and a project team has been created to safely integrate the new acid into the chemical process. The project team is currently executing an implementation schedule which addresses safety basis development, revision to operations procedures and training, facility modifications, chemical procurement, and updated process monitoring. Introduction of glycolic acid into DWPF is currently scheduled to take place in early 2017, beginning with a blended flowsheet of glycolic and formic acid and ultimately transitioning to glycolic-only processing. This paper provides an overview of planned glycolic acid flowsheet implementation in the DWPF. This paper discusses several issues related to implementing such a significant change to the chemical process including: 1) Process chemistry differences between the two flowsheets with quantitative comparison for several properties of interest; 2) Technical approach to hazards analysis and safety basis development strategy; 3) Status of project execution for major deliverables; and 4) Path forward for facility modifications related to legacy formic acid support equipment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

SU-E-T-465: Dose Calculation Method for Dynamic Tumor Tracking Using a Gimbal-Mounted Linac

Purpose: Dynamic tumor tracking using the gimbal-mounted linac (Vero4DRT, Mitsubishi Heavy Industries, Ltd., Japan) has been available when respiratory motion is significant. The irradiation accuracy of the dynamic tumor tracking has been reported to be excellent. In addition to the irradiation accuracy, a fast and accurate dose calculation algorithm is needed to validate the dose distribution in the presence of respiratory motion because the multiple phases of it have to be considered. A modification of dose calculation algorithm is necessary for the gimbal-mounted linac due to the degrees of freedom of gimbal swing. The dose calculation algorithm for the gimbal motion was implemented using the linear transformation between coordinate systems. Methods: The linear transformation matrices between the coordinate systems with and without gimbal swings were constructed using the combination of translation and rotation matrices. The coordinate system where the radiation source is at the origin and the beam axis along the z axis was adopted. The transformation can be divided into the translation from the radiation source to the gimbal rotation center, the two rotations around the center relating to the gimbal swings, and the translation from the gimbal center to the radiation source. After operating the transformation matrix to the phantom or patient image, the dose calculation can be performed as the no gimbal swing. The algorithm was implemented in the treatment planning system, PlanUNC (University of North Carolina, NC). The convolution/superposition algorithm was used. The dose calculations with and without gimbal swings were performed for the 3 × 3 cm{sup 2} field with the grid size of 5 mm. Results: The calculation time was about 3 minutes per beam. No significant additional time due to the gimbal swing was observed. Conclusions: The dose calculation algorithm for the finite gimbal swing was implemented. The calculation time was moderate.

07 ISOTOPE AND RADIATION SOURCES↗

Stakeholder participation in health impact assessment: A multicultural approach

The literature on impact assessment (HIA) registers the importance of stakeholder participation in the assessment process, but still lacks a model for engaging stakeholders of diverse ethnic, professional and sectorial backgrounds. This paper suggests that the multicultural approach can contribute to HIA through a revision of the generic 5-step HIA model, and its implementation in a metropolitan plan in Southern Israel. The health issue scoped by the stakeholders in the HIA is related to land uses in the vicinity of the national hazardous industry and hazardous waste site. The stakeholders were representatives of the diverse populations at stake, including rural Bedouins and Jewish city dwellers, as well as representatives from the public sector, private sector, non-governmental organizations and academia. The case study revealed that a multicultural stakeholder participation process helps to uncover health issues known to the community which were not addressed in the original plan, and provides local knowledge regarding health conditions that is especially valuable when scientific data is uncertain or absent. It enables diverse stakeholders to prioritize the health issues that will be assessed. The case study also reveals ways in which the model needs revisions and improvements such as in recruitment of diverse participants. This paper presents a multicultural model of HIA and discusses some of the challenges that are faced when HIA is implemented in the context of current decision-making culture. -- Highlights: • We revised the generic HIA model in light of the multicultural approach. • We tested the model in a case study of zoning a hazardous industry site. • Multicultural stakeholder participation uncovers health issues known to communities. • It enables community prioritization of health issues. • We present a model for multicultural stakeholder participation in HIA.

54 ENVIRONMENTAL SCIENCES↗

Ground-tended payload operations of Space Station Freedom

The concepts and capabilities that supported ground-tended Space Station Freedom (SSF) utilization and operations are described. On-board computer control support capabilities are required, and potential approaches for computer sequencing are discussed. An integrated process which links the planning processes with the implementation and execution of the operations is required to perform continuous, long-term utilization of SSF. Payload designs that make accommodations for ground-tended operation can be supported by the operations infrastructure. The payload operations integration center and Space Station Control Center are to support continuous operations of payloads that are designed to be operated from the ground. An overall process of ground-tended payload operations which links the weekly planning and continuous ground-tended execution functions is defined.

Noneman, Steven R.↗

Application of the ORIGEN Fallout Analysis Tool and the DELFIC Fallout Planning Tool to National Technical Nuclear Forensics

The objective of this project was to provide a robust fallout analysis and planning tool for the National Technical Nuclear Forensics interagency ground sample collection team. Their application called for a fast-running, portable mission-planning tool for use in response to emerging improvised nuclear device (IND) post-detonation situations. The project met those goals by research and development of models to predict the physical, chemical, and radiological properties of fallout debris. ORNL has developed new graphical user interfaces for two existing codes, the Oak Ridge Isotope Generation (ORIGEN) code and the Defense Land Fallout Interpretive Code (DELFIC). ORIGEN is a validated, radionuclide production and decay code that has been implemented into the Fallout Analysis Tool to predict the fallout source term nuclide inventory after the detonation of an IND. DELFIC is a validated, physics-based, research reference fallout prediction software package. It has been implemented into the Fallout Planning Tool and is used to predict the fractionated isotope concentrations in fallout, particle sizes, fractionation ratios, dose rate, and integrated dose over the planned collection routes - information vital to ensure quality samples for nuclear forensic analysis while predicting dose to the sample collectors. DELFIC contains a particle activity module, which models the radiochemical fractionation of the elements in a cooling fireball as they condense into and onto particles to predict the fractionated activity size distribution for a given scenario. This provides the most detailed physics-based characterization of the fallout source term phenomenology available in an operational fallout model.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Streamlined Approach for Environmental Restoration (SAFER) Plan for Corrective Action Unit 572: Test Cell C Ancillary Building and Structures - Nevada National Security Site, Nevada with ROTC 1

This Streamlined Approach for Environmental Restoration (SAFER) Plan addresses the actions needed to achieve closure for Corrective Action Unit (CAU) 572, Test Cell C Ancillary Building and Structures, identified in the Federal Facility Agreement and Consent Order (FFACO). CAU 572 comprises the following corrective action sites (CASs) located in Area 25 of the Nevada National Security Site: CAS 25-33-01, Building 3220, Equipment Building; CAS 25-33-02, Building 3230, Motor Drive Building; CAS 25-33-03, Building 3231, Pump House; CAS 25-33-04, Building 3232, Cryogenic Evaluation Lab; CAS 25-99-22, Ancillary Facilities. This plan provides the methodology for field activities needed to gather the necessary information for closing CAU 572. There is sufficient information and process knowledge from historical documentation and investigations of similar sites regarding the expected nature and extent of potential contaminants to recommend closure of CAU 572 using the SAFER process. Additional information will be obtained by conducting a field investigation before selecting the appropriate corrective action. It is anticipated that the results of the field investigation and implementation of corrective actions will support a defensible recommendation that no further corrective action is necessary. The purpose of the corrective action investigation (CAI) will be to document and verify the adequacy of existing information; to affirm the decision for either clean closure, closure in place, or no further action; and to provide sufficient data to implement the corrective action. The actual corrective action selected will be based on characterization activities implemented under this SAFER Plan. If it is determined that complete clean closure cannot be accomplished during the CAI, then a hold point will have been reached and the Nevada Division of Environmental Protection (NDEP) will be consulted to determine whether the remaining contamination will be closed under the alternative corrective action of closure in place. This will be presented in a closure report that will be prepared and submitted to NDEP for review and approval.

54 ENVIRONMENTAL SCIENCES↗

MO-D-213-01: Workflow Monitoring for a High Volume Radiation Oncology Center

Purpose: Implement a center wide communication system that increases interdepartmental transparency and accountability while decreasing redundant work and treatment delays by actively monitoring treatment planning workflow. Methods: Intake Management System (IMS), a program developed by ProCure Treatment Centers Inc., is a multi-function database that stores treatment planning process information. It was devised to work with the oncology information system (Mosaiq) to streamline interdepartmental workflow.Each step in the treatment planning process is visually represented and timelines for completion of individual tasks are established within the software. The currently active step of each patient’s planning process is highlighted either red or green according to whether the initially allocated amount of time has passed for the given process. This information is displayed as a Treatment Planning Process Monitor (TPPM), which is shown on screens in the relevant departments throughout the center. This display also includes the individuals who are responsible for each task.IMS is driven by Mosaiq’s quality checklist (QCL) functionality. Each step in the workflow is initiated by a Mosaiq user sending the responsible party a QCL assignment. IMS is connected to Mosaiq and the sending or completing of a QCL updates the associated field in the TPPM to the appropriate status. Results: Approximately one patient a week is identified during the workflow process as needing to have his/her treatment start date modified or resources re-allocated to address the most urgent cases. Being able to identify a realistic timeline for planning each patient and having multiple departments communicate their limitations and time constraints allows for quality plans to be developed and implemented without overburdening any one department. Conclusion: Monitoring the progression of the treatment planning process has increased transparency between departments, which enables efficient communication. Having built-in timelines allows easy prioritization of tasks and resources and facilitates effective time management.

60 APPLIED LIFE SCIENCES↗

Improving IMRT-plan quality with MLC leaf position refinement post plan optimization

Purpose: In intensity-modulated radiation therapy (IMRT) planning, reducing the pencil-beam size may lead to a significant improvement in dose conformity, but also increase the time needed for the dose calculation and plan optimization. The authors develop and evaluate a postoptimization refinement (POpR) method, which makes fine adjustments to the multileaf collimator (MLC) leaf positions after plan optimization, enhancing the spatial precision and improving the plan quality without a significant impact on the computational burden. Methods: The authors' POpR method is implemented using a commercial treatment planning system based on direct aperture optimization. After an IMRT plan is optimized using pencil beams with regular pencil-beam step size, a greedy search is conducted by looping through all of the involved MLC leaves to see if moving the MLC leaf in or out by half of a pencil-beam step size will improve the objective function value. The half-sized pencil beams, which are used for updating dose distribution in the greedy search, are derived from the existing full-sized pencil beams without need for further pencil-beam dose calculations. A benchmark phantom case and a head-and-neck (HN) case are studied for testing the authors' POpR method. Results: Using a benchmark phantom and a HN case, the authors have verified that their POpR method can be an efficient technique in the IMRT planning process. Effectiveness of POpR is confirmed by noting significant improvements in objective function values. Dosimetric benefits of POpR are comparable to those of using a finer pencil-beam size from the optimization start, but with far less computation and time. Conclusions: The POpR is a feasible and practical method to significantly improve IMRT-plan quality without compromising the planning efficiency.

60 APPLIED LIFE SCIENCES↗

Fundamental Path Optimization Strategies for Extrusion-based Additive Manufacturing

Extrusion-based additive manufacturing processes begin with a software program, called a slicer, that generates layer geometry and fits toolpaths to each layer to define where material is to be extruded or deposited. Before the toolpaths are output as g-code for the additive manufacturing system to execute, the toolpaths should be optimized. Many complex optimization approaches using graph theory, Chinese postman problem, and other complex mathematical models exist, but these approaches are rarely used in daily printing operations and are not available through common slicing programs such as Cura and PrusaSlicer. Instead, path planning and optimization typically revolves around simpler, fully automated approaches such as inside out and next closest. This paper will explore the fundamental optimization strategies for toolpath planning and document a new implementation, available via open-source slicing software, that allows for greater control of the path planning process.

Roschli, Alex [ORNL] (ORCID:0000000213084632)↗