ML23122A306

NRC Scientific Computer Code Investment Plan Public

ML23122A306
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Issue date:	05/03/2023
From:	Kenneth Armstrong, Matthew Bernard, Antony Calvo Office of Nuclear Regulatory Research
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NRC Scientific Computer Code Investment Plan Office of Nuclear Regulatory Research Working Group Kenneth Armstrong Matthew Bernard Antony Calvo Version 2 (May 2023)

TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................. i LIST OF FIGURES ....................................................................................................................... ii LIST OF TABLES.......................................................................................................................... ii

1. INTRODUCTION ............................................................................................. 1 1.1 Purpose ........................................................................................................... 1 1.2 Background ..................................................................................................... 1

2. CODE MAINTENANCE AND DEVELOPMENT .............................................. 3 2.1 Overview.......................................................................................................... 3 2.2 Code Maintenance and Distribution ................................................................ 4 2.2.1 Minimal Maintenance ................................................................................. 4 2.2.2 Active Maintenance ................................................................................... 5 2.3 Code Development .......................................................................................... 5 2.3.1 New Feature Development ........................................................................ 5 2.3.2 State-ofthe-Practice Development............................................................ 5 2.3.3 Code Modernization................................................................................... 6 2.3.4 Code Consolidation ................................................................................... 7 2.4 Additional Considerations ................................................................................ 7 2.4.1 Code Verification and Validation................................................................ 7 2.4.2 Code Interoperability.................................................................................. 8 2.4.3 Code Integration with External Codes ....................................................... 9

3. CODE MANAGEMENT LIFECYCLE AND INVESTMENT PROCESS............ 9 3.1 Overview.......................................................................................................... 9 3.2 Identification, Documentation, and Resource Planning of Code Needs ........ 11 3.3 Code Needs Meeting ..................................................................................... 12 3.4 Investment Plan Planning Considerations ..................................................... 12 3.5 Code Annual Review ..................................................................................... 13 3.6 Recommendations......................................................................................... 13 APPENDIX 1. CODE INVESTMENT PLAN

SUMMARY

........................................................... 14 APPENDIX 2. CODE MODERNIZATION AND CONSOLIDATION ACTIVITIES ...................... 20 APPENDIX 3. CODE INVESTMENT CHART TEMPLATE ........................................................ 21 i

LIST OF FIGURES Figure 1 Overview of NRC Scientific Computer Codes .............................................................................. 3 Figure 2 Scientific Computer Code Investment Activities ............................................................ 4 Figure 3 FAST model of an ATF assembly .................................................................................. 6 Figure 4 Depiction of how code modernization can streamline code infrastructure. .................... 6 Figure 5 Depiction of how interoperable codes can be utilized for advanced applications. ......... 9 Figure 6 NRC Scientific Computer Code Lifecycle and Investments ......................................... 10 Figure 7 Code Investment Chart Template ................................................................................. 21 LIST OF TABLES Table 1 NRC-Developed Scientific Computer Codes ................................................................. 2 Table 2 Examples of Experimental Programs in Support of Regulatory Decisionmaking............ 8 Table 3 NRC Scientific Computer Code Development Annual Investment Cycle...................... 11 Table 5 Code Resource Considerations .................................................................................... 12 Table 6 Code Investment Plan Summary (as of May 2023) ...................................................... 14 Table 7 Code Modernization and Consolidation Activities (as of May 2023) ............................. 20 ii

Scientific Computer Code Investment Plan Office of Nuclear Regulatory Research

1. INTRODUCTION 1.1 Purpose The purpose of this code investment plan (CIP) is to proactively manage the agencys maintenance and development of its scientific computer codes (hereinafter referred to as scientific codes) through development and documentation of the investment strategies needed to meet current and future regulatory decisionmaking needs for the agency. By accounting for the scientific codes needs and the resource requirements, the U.S. Nuclear Regulatory Commission (NRC) will continue to meet its safety and security mission, while also making the needed investments to be ready to regulate new and advanced technologies.

The scope of this plan focuses on the NRCs scientific codes. Additionally, the NRC uses commercial-off-the-shelf (COTS) software packages such as MathWorks and ANSYS to inform regulatory decisionmaking, which are not accounted for in this plan. The software vendors perform the maintenance and update of their COTS software packages, and the agency purchases licenses to utilize those tools.

This CIP:

• Provides the NRC with an integrated management tool for its scientific codes.

• Informs future budget formulations.

• Assists in appropriately resourcing scientific code requirements.

• Identifies human capital and staff expertise requirements.

This plan is a living document with formal updates at least annually.

1.2 Background

Scientific codes are used daily by the NRC, industry, academic, and international community to support safety, security, and regulatory decisionmaking. The NRC maintains, develops, and acquires from other entities (such as the Department of Energy (DOE), the Environmental Protection Agency (EPA), commercial software vendors, etc.), scientific codes required to ensure the safety and security of the nuclear power plant operating fleet; spent fuel storage and transportation packages and facilities; fuel cycle facilities; nuclear materials; decommissioning activities; research and test reactors; and expected new commercial nuclear power facilities activities. These scientific codes support the independent technical basis development and are often depended on for confirmatory analysis in support of regulatory decisionmaking.

In FY2020, RES surveyed the NRC offices and initially identified 43 scientific codes (40 codes as of May 2023) in which the NRC was directly supporting code development; and which the agency is expected to need in future activities. These codes range from complex, integrated codes, with over 500,000 lines of programming text for reactor thermal-hydraulic analysis where the entire 1

reactor system and surrounding environment is modeled, to simpler codes that perform dose assessment analyses, which may have less than 1,000 lines of programming text. Table 1 provides a listing of the scientific codes grouped by area of analysis which they support.

Table 1 NRC-Developed Scientific Computer Codes Scientific Computer Scientific Computer Area of Analysis Area of Analysis Code Code Accident Progression and MELCOR Geographic OLYMPUS DISS Source Term RTT PiMAL Graphical User Interface ARCON SNAP Atmospheric Dispersion PAVAN IDHEAS-ECA Human Reliability TEPHRA SACADA Chemical Dispersion HABIT BREATH Consequence MACCS MULTIFLO Hydrology DandD TPA GENII xFlo Decommissioning MILDOS 3D STRESS RESRAD FAVPRO Materials VSP FES GALE LEAPOR NRCDose3 SCALE Neutronics RADTRAD PARCS Dose Assessment NRC RADTRAN Probabilistic Risk xLPR RASCAL Assessment SAPHIRE VARSKIN+ Record Database Radiological Toolbox External Hazards PVHM-YM RELAP5 Thermal-Hydraulics Fuels FAST TRACE Some NRC code investment resourcing requirements are supported by international program involvement. For example, cooperative programs such as the Code Application and Maintenance Program (CAMP), Cooperative Severe Accident Research Program (CSARP), and Radiation Protection Computer Code Analysis and Maintenance Program (RAMP) help foster and formalize cost sharing arrangements. Cooperative membership contributions support periodic user meetings, training, and related code support; participation in experimental programs to validate the codes; and support requests from domestic and international users for changes to the codes beyond those supported by NRC.

Figure 1 depicts the scientific codes by (a) agency lead organization for code development, (b) agency regulatory financial business line sponsor, and (c) indicates how many of the scientific codes receive external funding through code sharing programs. RES maintains most of the scientific codes developed by the NRC.

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Figure 1 Overview of NRC Scientific Computer Codes RES annually reviews the scientific codes (currently 40 in total) to determine investment requirements based on code usage needs within the next 7 years. As part of this effort, NRC scientific code development leads, and their contractors are surveyed to evaluate development needs and use cases for computer code modernization and consolidation. The result of this assessment serves as the basis for the code investment plan moving forward and indicates the following:

• Twenty-five (25) of the codes require ongoing investments to support expected regulatory decisionmaking.

o These codes require ongoing maintenance and development that represent the current pace of advancements made by industry.

o Three (3) codes are currently undergoing code modernization, with two (2) more planned.

o Eight (8) codes are being consolidated into three (3) codes.

• Fifteen (15) codes were placed in an archival state not expected to support decisionmaking activities within the next 7 years.

Appendix 1 provides the detailed list of the 40 scientific codes and investment status. Appendix 2 list the current major code modernization and consolidation strategies.

2. CODE MAINTENANCE AND DEVELOPMENT 2.1 Overview The NRCs active scientific codes require routine maintenance and development to meet current and future regulatory needs. Specifically, the following investment activities are considered: 1) code maintenance and distribution (required foundational activity), 2) code and new feature developments (regular updates to maintain code to state-ofthe-practice), and 3) larger efforts to modernize and/or consolidate the codes that may periodically be needed to ensure functionality and improve maintainability. Figure 2 provides a representation of these key activities with greater detail in Section 2.2 and 2.3 below.

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Figure 2 Scientific Computer Code Investment Activities 2.2 Code Maintenance and Distribution Code maintenance and distribution is required to provide users with functioning scientific codes.

Required resource efforts range from minimal maintenance for codes not currently in use but may be needed in the future to more significant updates to maintain the actively used scientific codes.

Without annual maintenance 1) the codes slowly fall into noncompliance with current information technology and development practices, 2) issues and bugs found by the analyst wont be addressed, and 3) functionality may be lost over time. Domestic and international scientific code distribution is also considered as part of code maintenance.

2.2.1 Minimal Maintenance Scientific codes which are not actively used and are not projected to be needed for regulatory decisionmaking activities within the next 7 years but may be needed in the future are placed in a long-term, minimal maintenance status to retain useability with nominal resource allocations.

Additionally, some codes are minimally maintained while undergoing code consolidation. Codes placed in this status are either, 1) minimally maintained at the NRC or 2) sent to the Radiation Safety Information Computational Center (RSICC) at Oak Ridge National Laboratory (ORNL).

RSICC provides the minimal maintenance support and distributes the codes. Once transferred to RSICC, the code is removed from the list of NRC codes. The NRC can retrieve scientific codes from RSSIC, should they be needed in the future. The codes that are being minimally maintained at RSICC are numerous, whereas there are currently only 15 codes being minimally maintained by the NRC.

Due to the overlap in functionality, NRC decided in the 2010 timeframe to have TRACE be the agencys state-ofthe-practice thermal-hydraulics and systems analysis computer code; and forgo active maintenance of the RELAP5 code of similar capabilities. The NRC is currently minimally maintaining RELAP5 to keep it running to potentially 1) evaluate a licensing action that may come in using RELAP5 models or 2) support CAMP members that would like to use RELAP5.

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Additionally, there are 8 codes being minimally maintained by the NRC to support the evaluation of a future deep geologic disposal for spent nuclear fuel. We are likely years away from needing to rely on these codes, which will require future deliberations by Congress to determine the ultimate spent fuel repository strategy.

2.2.2 Active Maintenance Scientific codes which are currently used to support regulatory decisionmaking activities undergo active maintenance to resolve issues, ensure stability/operability with current operating systems, ensure information technology (IT) security compliance, and improve IT architecture portability (e.g., desktop/cloud usability). This maintenance is performed on a continual basis and resources are captured in the budget annually to ensure usability of the code.

2.3 Code Development Code development efforts are planned events to provide updated capabilities. Code development efforts range from smaller updates to decrease uncertainty in model output to larger code modifications and rewrites of the fundamental code structure.

2.3.1 New Feature Development New feature development efforts are minor code changes that enhance the code usability or improve the inherent confidence in the model output. Examples include code improvements that reduce uncertainty in safety margins, improve uncertainty analysis/qualification, expand the range of code applicability, or use information from experimental results to improve code predictions.

These developments are lower level of efforts and are generally not formally captured via research Work Requests1 but are shared with the regulatory offices via this CIP.

2.3.2 State-ofthe-Practice Development State-ofthe-Practice development is defined technological code development that are at a similar pace with the advancements made by industry. In contrast, State-ofthe-Art is defined as code development activities that are cutting-edge often on the leading edge of the industry.

The NRC performs state-ofthe-practice scientific code development inline with advancements made by industry, and inline with current code development practices to prepare for new application submittals. State-ofthe-practice scientific code development activities are generally executed via internal research Work Requests with the requesting office. For example, the MELCOR severe accident scientific code is undergoing state-ofthe-practice development to be ready to support advanced non-light-water reactor designs. In another example, Figure 3 depicts the FAST fuel performance code which was updated to include a new capability for modeling Iron-Chromium-Aluminum (FeCrAl) fuel cladding in anticipation of accident tolerant fuel (ATF) application reviews. State-ofthe-practice development is only appropriate for scientific codes under active maintenance.

1 Work Requests and RES-initiated research are discussed and agreed upon (as appropriate) with the requesting regulatory office and to develop corresponding project plans prior to the commencement of work.

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Figure 3 FAST model of an ATF assembly 2.3.3 Code Modernization Code modernization is important for active scientific codes to ensure long-term usability. Code modernization efforts involve modifying or rewriting the fundamental code structure to incorporate new capabilities, address obsolescence issues, reduce analysis runtime, ensure interoperability with other codes, and adhere to modern software development and IT best-practices. Code modernization can be performed on a continual or periodic basis. Code modernization can span in scope from integrating code improvements such as parallelization to a complete overhaul of the fundamental programing to utilize updates to an existing programing language or transition to a completely different programing language. While showing IT networking infrastructure, Figure 4 portrays how years of code development can result in a code that is poorly patchworked, inefficient to run, challenging to maintain, and needing further development as demonstrated by the networking cables on the left. However, code modernization will help organize, package, and streamline the code as represented by the cables on the right side.

Figure 4 Depiction of how code modernization can streamline code infrastructure.

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2.3.4 Code Consolidation Code consolidation efforts improve NRC efficiency by reducing the number of individual codes maintained to a fewer number of codes that provides expanded capabilities. Consolidation of similar codes can provide the following benefits:

• Reduce functional redundancy between codes.

• Reduce overall code lifecycle development, maintenance, and distribution costs to maintain and distribute multiple similar codes.

• Reduce the lack of standardized code programming amongst different programmers.

• Reduce lack of standardized quality assurance.

• Reduce agency resources associated with streamlining analyses.

2.4 Additional Considerations 2.4.1 Code Verification and Validation Verification and validation testing (V&V) are continual and required whenever changes are made to the scientific computer codes. V&V ensures that the code is functioning properly before use in regulatory decisionmaking.

• Verification ensures that code features are implemented correctly and do not degrade existing code predictive capability.

• Validation provides confirmation that code features are predicting parameters accurately and meet the intended requirements.

For many NRC codes, validation tests are performed by comparing code predictions to experimental data to quantify code prediction accuracy. The wide range of physical phenomena experienced in a nuclear power plant during normal operations and transients can reveal limitations in the available experimental data and modeling. Therefore, NRC developers must determine their codes applicability to a given physical phenomena. To do this, many NRC code developers follow a well-documented and rigorous methodology for scientific computer code validation called the Code Scaling, Applicability, and Uncertainty (CSAU) described in NUREG/CR5249 (ML030380473). In situations where the CSAU methodology determines that a codes validation basis needs improvements, experimental data is acquired by the NRC. Over the past few decades, as the NRC validation basis has expanded, the NRC now primarily leverages multi-national agreements and multi-lateral experimental programs to obtain experimental data for code development and validation. NRC participation in these international programs is integral to obtain data needs that are difficult to replicate with current NRC resources.

NRC participation enables input to the experimental condition selections to address NRC data needs. Table 2 provides some examples of experimental data used to support regulatory decisionmaking.

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Table 2 Examples of Experimental Programs in Support of Regulatory Decisionmaking Experimental Regulatory Issue Data Use Facility Primary Generic Safety Issue 191, Experimental data from a test campaign was used to Coolant Loop Assessment of Debris demonstrate the TRACE code applicability to relevant (PKL) Test Accumulation on conditions. TRACE was used to provide analyses Facility Pressurized Water which bounded the consequences of core blockages Reactors Sump to support resolution of the issue Performance Karlstein Plant transient and stability More than 15,000 tests were conducted on numerous Thermal measurements to support boiling- water reactors (BWR) and pressurized- water Hydraulic Test license amendment reactors (PWR) bundle designs to demonstrate the Facility requests for the Maximum TRACE code applicability plant stability transients (KATHY) Extended Load Line Limit Analysis Plus (MELLLA+)

Halden 10 CFR 50.46(c) The experimental data was used to develop fuel Reactor Regulation Development material properties and increase understanding of and Fuel Performance cladding burst phenomena Behavior Modeling Studsvik (a) Fuel fragmentation, (a) The experimental data is being used to develop Cladding relocation, and dispersal on and assess fuel material properties and behavior Integrity high burnup fuel. models. Data will increase understanding of fuel Project-Phase (b) Spent fuel cladding fragmentation, relocation, and dispersal during a loss-IV (SCIP IV) performance behavior data ofcoolant accident. This data will also support licensing activities related to high burnup fuel behavior and the ongoing increased enrichment rulemaking activity.

(b) The experimental data is being used to develop and assess spent fuel material properties and degradation models. Data will provide additional confidence in understanding hydride reorientation and provide additional thermal creep and fission gas release data Second Applicability of Regulatory Reactivity-initiated accident tests performed in the Framework for Guide 1.236, TREAT reactor will demonstrate whether existing Irradiation Pressurized-Water guidance and models for uranium dioxide (UO2) fuel in Experiments Reactor Control Rod zirconium alloy cladding are applicable for UO2 fuel at (FIDES-II) Ejection and Boiling-Water high burnup, UO2 fuel with dopants, and fuel with Reactor Control Rod Drop chromium-coated zirconium alloy cladding Accidents, to new fuel designs and to burnup above 68 GWd/MTU Rod Bundle Regulatory safety reviews The experimental data is being used to develop Heat Transfer involving core reflood improved correlations for reflood modeling design (RBHT) Test phenomena during basis accidents Facility transient and accident analysis 2.4.2 Code Interoperability As industry continues to be interested in advanced designs (e.g., ATF and non-light-water reactors) and recovering the analytical uncertainty margin to gain operational efficiencies (e.g.,

power uprates, Maximum Extended Load Line Limit Analysis Plus, long-term operations),

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interoperability between related codes will become increasing important. The outcome of this approach will be more accurate and efficient computer code analyses.

2.4.3 Code Integration with External Codes NRC and DOE, through a longstanding cooperative nuclear safety relationship and Memorandum of Understandings (MOUs), are leveraging the technical and scientific capabilities of the DOE National Laboratories (or DOE Labs) in the areas of advanced fuels and advanced reactors. For example, as depicted in Figure 5, efforts are underway in RES to couple several of the DOEs (and DOE Labs) high performance computer codes with NRCs computer codes in preparation for expected advanced fuel designs and advanced reactor submittals. EPA scientific codes are also being considered for some of the NRCs radiation protection applications.

Figure 5 Depiction of how interoperable codes can be utilized for advanced applications.

3. CODE MANAGEMENT LIFECYCLE AND INVESTMENT PROCESS 3.1 Overview The NRCs scientific code management lifecycle is a continuous, comprehensive, and collaborative process to ensure that the codes are available to support current, future, and emerging regulatory decisionmaking. The lifecycle starts with the maintenance of the current codes as depicted in Figure 2 (above). The scientific computer code lifecycle includes annual processes to identify, document, prioritize, and resource code investment requirements. All these activities are vital to a computer codes lifecycle and should be planned over time and within the agencys budget cycles. The annual process is illustrated in Figure 6.

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Figure 6 NRC Scientific Computer Code Lifecycle and Investments The specific steps, leads, and deliverables associated with the Annual Investment Cycle are defined in Table 3. The process starts with the identification and documentation of code investment needs from the code development leads. These needs are consolidated into a spreadsheet and Division level alignment is sought of the larger investment needs across the agency. Next, this input enters the Office(s) budget formulation process, which is prioritized to align resources at the office level and prioritize input with other needs of the agency. Finally, after budget formulation is achieved, the result will be entered into the annual CIP update documentation.

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Table 3 NRC Scientific Computer Code Development Annual Investment Cycle Internal NRC Step Process Task Lead Timeframe Deliverable Identification and documentation of code needs and gaps over a 7-year time Code window, including task descriptions and Code Investment Charts Development resource requirements. (Input is for planning Lead, with purposes and depends 1 1st level June Resource planning considerations: code on future funding supervisor maintenance, distribution, new feature request reviews and (Branch and state-ofpractice development, availability)

Chief) review modernization, consolidation, V&V, experimental data needs.

CIP Code Collect Code Investment Chart input and 2 Investment CIP database July consolidates into a summary Table.

Plan lead Code Review CIP database and supporting Development Code Investment Charts, with a focus on Lead, 1st, code needs and resources Updated CIP database and 2nd level 3 requirements. and Code Investment August supervisor Charts (Division Presentation of code requirements to Director)

Business Line Lead reviews Code Development Integrate code needs and resources Lead, with Updated budget request 4 requirements into the RES budget September 1st level information Office Prioritization List formulation prioritization list.

supervisor review RES supervisors, Alignment on RES budget formulation regulatory Updated budget request October-5 prioritization list. offices, and information December financial reviews RES Budget Updated budget input to Formal budget formulation request entry January-6 Formulation the Office of the Chief and alignment. March Lead Financial Officer Code 7 CIP Update and release annual CIP update. Investment CIP Update April Plan lead 3.2 Identification, Documentation, and Resource Planning of Code Needs The Code Development Investment Plan monitors a seven-year resource allocation process to include the execution year, enactment year, and a five-year planning and budgeting period. This wider planning period provides greater opportunity to prioritize and plan for code investment needs within fiscal constraints. To capture code investment requirements, the Code Development Lead performs an initial assessment of the code needs leveraging information from developers, 11

users, and program offices. The initial needs are documented using the Code Investment Charts (Appendix 3). This initial assessment considers:

• Maintenance requirements, minimal vs. active (sections 2.2.1 and 2.2.2), training, and distribution of that code to stakeholders.

• Code development to address gaps in an analysis function that are not currently available but are needed now, or for an anticipated future regulatory decisionmaking activity.

o New Feature Development (Section 2.3.1) for minor code changes that enhance the code usability or improve the inherent confidence in the model output.

o State-ofthe-Practice Development (Section 2.3.2) for larger code changes inline with advancements made by industry and current code development practices to prepare for new application submittals (generally via Work Requests).

• Code consolidation and modernization activities.

• V&V and experimental data requirements.

• Subject matter and code development expertise.

3.3 Code Needs Meeting The Code Needs Meeting objective is to finalize code investment intake request to enable resource planning. The Code Development Lead and licensing sponsor leads participate in this meeting. The Code Development Lead presents the code investment intake request discussing the status and proposed activities to address maintenance, development, and any other requirements. Participants provide input including any additional needs or considerations for that code. The Code Development Lead then performs updates to and adds resource planning requirements to the Code Investment Charts. This meeting may be part of a larger User Need Meeting, where all the activities sponsored by a licensing Division are presented. Any updates to the Code Investment Charts from this meeting are sent to the Code Investment Plan Lead.

3.4 Investment Plan Planning Considerations As previously mentioned, code management involves a variety of planning considerations from recurring maintenance through modernization. Table 5 provides a summary of the different planning considerations that code development leads should consider when developing their resource plan.

Table 4 Code Resource Considerations Resource Planning Description Activity COTS Codes The NRC, where possible, should leverage COTS codes before developing new or duplicative capabilities.

Code from Other Entities The NRC, where possible, should leverage other available scientific codes such as those from other agencies (e.g., DOE and EPA), and others domestically or internationally available.

Code Investment The NRC, where possible, should leverage cooperative programs to Leveraging benefit the collective domestic and international needs for confirmatory tools.

Cloud Computing The NRC, where possible, should focus code development efforts to leverage cloud computing strategies to fully actualize the potential of 12

cloud-based technologies while ensuring thoughtful execution that incorporates practical realities to improve return on investment, service, quality, and security.

Minimal Maintenance If a code is planned for minimal maintenance, then the annual resource requirements should be included at a nominal level in the agencys budget or accounted for in the RISCC contract. Codes in this status will have no other maintenance or development resource requirements.

Active Maintenance All active codes will have a recurring maintenance cost to resolve issues, ensure stability/operability with current operating systems, ensure IT security compliance, and improve architecture portability.

New Feature Minor code changes that enhance the code usability or improve the Development inherent confidence in the model output.

State-ofthe-Practice Code developments should be considered when updates are needed to Development incorporate advancements made by industry and prepare for new application submittals.

Code Modernization and These are typically more resource significant efforts that may span multiple Consolidation fiscal years (FYs) and may need to be staggered over time to ensure financial stability. The resources required should be planned for the full scope of the project to ensure the expected final code deliverable will be achieved from the investment. Code modernization and consolidation plans should delineate the maintenance costs before and after modernization.

Experimental Data Experimental data needs to validate computer code updates should be Needs included during resource planning for the code update. Code updates should align with when data will be available and the integration of that data into the analysis code.

V&V V&V must be performed when changes are made to the NRC scientific computer codes to ensure usability for regulatory decisionmaking.

Resources for V&V should be planned and committed when resources are planned for the code development activity.

Distribution Domestic and international scientific code distribution should also be included as part of code maintenance. Additionally, RISCC provides distribution support for many of the NRC scientific computer codes in a long-term maintenance status. Resource requirements for this service should be included as part of this plan.

3.5 Code Annual Review The scientific computer codes are reviewed annually, and the code maintenance strategy and investment needs are documented using a Code Investment Chart (Appendix 3). The code review is outlined in Table 3 and initiated by the CIP lead.

3.6 Recommendations Based on experiences from implementation and feedback from code development leads, RES supervisors, and regulatory offices we have identified several operational improvements moving forward. First, to improve the organization of essential budget formulation information, a centralized internal database could be utilized to collect and display information more effectively for reviews. Second, to improve communication we should utilize common terminology (e.g., code maintenance, development, modernization, and consolidation) in describing all code investments.

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APPENDIX 1. CODE INVESTMENT PLAN

SUMMARY

Table 5 Code Investment Plan Summary (as of May 2023)

Code Development Needs Code Planned Code Optimization Maintenance Strategy Strategy Scientific Primary Code Code NRC Computer Purpose Business Leveraged Active Minimal Modernization Consolidation Usage Code Line Sponsor Need Need Tool to interactively analyze the tendency for faults and fractures Spent Fuel 3D STRESS to slip or dilate based on a user- Storage and Low No X specified three- dimensional (3D) Transportation stress state.

A code system to calculate In Process atmospheric relative Yes ARCON New Reactors Medium X (FY21FY26) concentrations in building wakes (RAMP)

SIERRA (implements RG 1.194).

A hydrology code to estimate Spent Fuel BREATH infiltration over long time periods Storage and Low No X based on atmospheric inputs. Transportation A soil containment code to Decommissio calculate radionuclide Yes DandD ning and Low- Low X concentrations in soil for plants. (RAMP)

Level Waste A probabilistic fracture mechanics code for piping applications. Developed to Extremely quantify the probability of rupture Low of primary piping systems subject Operating Yes Probability of High X to active degradation Reactors (EPRI)

Rupture mechanisms to assess (xLPR) compliance with the requirements of 10 CFR Part 50, Appendix A, General Design Criterion 4.

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A code used for steady- state and transient analysis, respectively, of the behavior of a Operating Yes (Fuels Completed in FAST High X single fuel rod under normal, Reactors Program) FY20 transient, and accident conditions.

Deterministic and probabilistic Soon fracture mechanics analysis for Operating (FAVPRO In Process FAVPRO Medium X reactor pressure vessel (RPV) Reactors User (FY20FY24) integrity evaluations. Group)

A code for predictive crack growth due to primary water Flaw stress corrosion cracking Evaluation Operating (PWSCC) and performs High No X Software Reactors deterministic leak-before break (FES) analyses for primary water system piping.

A code for calculating the release of radioactive material in gaseous In Process Yes GALE and liquid effluents from BWRs New Reactors Medium X (FY21FY26)

(RAMP) and PWRs. SIERRA A code that estimates radionuclide concentrations in the environment and dose to humans Operating Yes GENII from acute or chronic exposures Low X Reactors (RAMP) from radiological releases to the environment or initial contamination conditions.

Used to estimate control room habitability when a major release Planned Yes HABIT of toxic chemicals in the vicinity New Reactors Medium X (FY25FY28)

(RAMP) of environments (implements RG RABIT 1.78).

The Integrated Human Event Analysis System for Event Condition Analysis (IDHEAS-IDHEAS- Operating ECA) is a human reliability High No X ECA Reactors analysis (HRA) tool to calculate human error probabilities for NRC's risk-informed applications.

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A code used to calculate leak Operating LEAPOR Low No X rates from cracks in piping. Reactors A severe accident consequence computer code developed to analyze the offsite consequences Operating Yes Planned MACCS High X of a hypothetical release of Reactors (CSARP) (FY25FY27) radioactive material to the environment.

A severe accident and Operating Yes In Process MELCOR High X containment analysis code. Reactors (CSARP) (FY18FY24)

Used to estimate the radiological Decommissio impact from airborne emission Yes MILDOS ning and Low- Medium X from uranium milling and mining (RAMP)

Level Waste facility (based on RG 3.59).

Subsurface thermo-hydrological Spent Fuel MULTIFLO code with transport & reactive Storage and Low No X chemistry. Transportation Code for evaluating routine radioactive effluents from NPPs In Process using a graphical user interface Yes NRCDose3 New Reactors Medium X (FY21FY26) that contains NRC code (RAMP)

SIERRA XOQ/DOQ, LADTAP II and GASPAR II.

A web-based geographical data Spent Fuel OLYMPUS and information sharing system Storage and Low No X DISS designed to search and retrieve Transportation geographic data at its source.

A code used to perform 3D dynamic core neurotics analysis Operating Yes PARCS to predict steady-state and High X Consider Reactors (CAMP) transient reactor behavior in operating events and accidents.

An atmospheric dispersion code system for evaluating design- In Process Yes PAVAN basis accidental radioactivity New Reactors Low X (FY21FY26)

(RAMP) releases from nuclear power SIERRA stations (implements RG 1.145).

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A graphical user interface with Operating pre-processor and post-Reactors processor capabilities which Yes PiMAL & Medium X assists users in developing (RAMP)

Nuclear MCNP input decks and running Material Users the codes.

Used to calculate the likelihood of Spent Fuel PVHM-YM new volcanic events forming at Storage and Low No X specific locations. Transportation Provides ready access to data of Planned Radiological interest in radiation safety and Operating Yes Low X (FY26FY29)

Toolbox protection of workers and Reactors (RAMP)

VARSKIN+

members of the public.

A code to determine the time-Planned dependent dose at user-specified Operating Yes RADTRAD High X (FY25FY28) locations for design basis Reactors (RAMP)

RABIT accident scenarios.

A code used to calculate the New Reactors expected radiological NRC & Spent Fuel Yes consequences and risks Medium X RADTRAN Storage and (RAMP) associated with the transportation Transportation of radioactive material.

An emergency response code used to calculate dose Operating Yes Planned RASCAL projections for radiological High X Reactors (RAMP) (FY23FY27) releases for a range from 10 to 100 miles.

Best-estimate systems analysis of transients, including loss-ofcoolant accidents, in light- Operating Yes RELAP5 Medium X water reactors and related Reactors (CAMP) neutronic-thermal-hydraulic systems.

A suite of tools for environmental radiological dose assessment. Decommissio RESRAD Considers risks of exposure to ning and Low- High RAMP X residual radioactivity through nine Level Waste environmental pathways.

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The Reactor Technical Tool is an application for assessment of Operating RTT reactor core damage and spent Low No X Reactors fuel pool status during and emergency.

A Data Collection Tool for Operating SACADA Simulator Training used to Medium No X Reactors improve HRA techniques.

The Systems Analysis Programs for Hands-on Integrated Reliability is used for performing Operating In Process SAPHIRE High No X probabilistic risk assessments for Reactors (FY20-26)

Level 1 and Level 2 PRA analysis.

The SCALE codes is used for Operating nuclear data analysis and library Reactors &

generation, radioactive source SCALE Spent Fuel High Yes (DOE) X term characterization, criticality, Storage and reactor physics, and sensitivity Transportation and uncertainty applications.

A graphical user interface to prepare input for other codes (e.g., TRACE, RELAP5, Operating Yes SNAP High X MELCOR, SCALE), as well as Reactors (CAMP) providing visualization and runtime features.

Simulates airborne transport and Spent Fuel surface deposition of high-level TEPHRA Storage and Low No X waste and ash from a volcanic Transportation eruption plume.

A code used to analyze the disposal of high-level nuclear Spent Fuel waste and the ability of the TPA Storage and Low No X natural and engineered barriers Transportation to isolate high-level water from the biosphere.

A best-estimate, thermal-hydraulic reactor systems code Operating Yes TRACE High X Consider under development for light-water Reactors (CAMP) reactor systems.

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The code calculates dose from skin contamination, wound Operating dosimetry; neutron dosimetry; Planned Reactors & Yes VARSKIN+ and eye dosimetry. The skin and Medium X (FY26FY29)

Nuclear (RAMP) wound dosimetry implement an VARSKIN+

Material Users alpha dosimetry model for shallow skin assessments.

A code that couples site, building, Visual and sample location visualization Decommissio Yes Sample Plan capabilities with optimal sampling ning and Low- Low X (RAMP)

(VSP) design and statistical analysis Level Waste strategies.

A subsurface thermo-hydrological Spent Fuel code used to evaluate the xFlo Storage and Medium No X disposal of high-level nuclear Transportation waste.

Note: Timeline for code modernization and consolidation are for planning purposes and depend on future funding request reviews and availability.

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APPENDIX 2. CODE MODERNIZATION AND CONSOLIDATION ACTIVITIES Table 6 Code Modernization and Consolidation Activities (as of May 2023)

Activity Brief Description of the Activity Start Completion Code Consolidation:

Phase 1-SIERRA Consolidation of ARCON, GALE, NRCDose3, and PAVAN into a single code. FY21 FY26 (Atmospheric Codes)

Code Consolidation:

Phase 2-RABIT Consolidation of SNAP/RADTRAD and HABIT into a single code. FY25 FY28 (Habitability Codes)

Code Consolidation:

Phase 3-VARSKIN+ Consolidation of VARSKIN+ and Radiological Toolbox into a single code. FY26 FY28 (Dose Codes)

Modernization of FAVOR to transition to state-ofpractice software development practices; Code Modernization:

conversion to object-oriented, parallel, Fortran 2018 source code; consolidation of 3 FY20 FY24 FAVOR subprograms into 1; major upgrades to QA and V&V program and pedigree.

Modernization of MELCOR to transition to state-ofpractice software development Code Modernization:

practices to incorporate a more flexible code maintenance approach and enhance FY18 FY25 MELCOR modeling of advanced technologies.

Modernization of SAPHIRE to transition to state-ofpractice software development practices in a cloud-based operating environment to support long-term maintenance and Code Modernization:

more complex models. Beyond FY26 SAPHIRE modernization will continue as part of the FY20 FY26 SAPHIRE routine revision in response to user needs, advances in state-ofpractice, and identification of new analytical or computational capabilities.

Modernization of RASCAL to transition to state-ofpractice software development Code Modernization:

practices to incorporate a more flexible code maintenance approach and enhance FY25 FY28 RASCAL modeling of advanced technologies.

Modernization of MACCS to transition to state-ofpractice software development practices Code Modernization:

to incorporate a more flexible code maintenance approach and enhance modeling of FY25 FY27 MACCS advanced technologies.

Code Modernization:

Being evaluated. TBD TBD PARCS Code Modernization:

Being evaluated. TBD TBD TRACE Note: Timeline for code modernization and consolidation are for planning purposes and depend on future funding request reviews and availability.

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APPENDIX 3. CODE INVESTMENT CHART TEMPLATE Figure 7 Code Investment Chart Template 21