KUREAS (pronounced as 'curious') is a suite of open-source browser-based modules for complex system or facility reliability analysis and probabilistic risk assessment (PRA). Each module is a standalone HTML file — no server, no build step, no installation. Open in any modern browser and start working.

Designed for reliability, risk, safety, and system engineers performing what-if performance analysis, KUREAS provides professional-grade functionality for small and large technical projects.

The suite includes full SAPHIRE file format interoperability and adherence to the SAPHIRE NUREG guidelines (NUREG/CR-7039), as well as OpenPSA Model Exchange Format export support.

• Quick Start
• Module Overview
• KUREAS-HA — Hazard Analysis
• KUREAS-FTL — Fault Tree Logic Editor
• KUREAS-ETL — Event Tree Logic
• KUREAS-SYS — System Evaluation
• KUREAS-SEQ — Process Operational Logic
• KUREAS-BAYES — Bayesian Evaluation Module
• KUREAS-REPORT — Report Generator
• KUREAS-KNOW — Knowledge Base Editor (coming soon)
• Data Flow
• File Formats
• Technical Stack
• Regulatory References
• License

1. Clone or download the repository.
2. Open any .html file in a modern browser (Chrome, Edge, Firefox, Safari).
3. There is no step 3.

Each module is entirely self-contained. All dependencies are loaded from CDNs at runtime. No Node.js, no npm install, no build process.

System-level knowledge management: define structures, systems, and components (SSCs); analyze failure modes including stochastic failures, seismic failures, fire failures, and common-cause failures; model system success logic, derive fault trees, uncertainty, importance measures; advanced JavaScript fast binary decision-diagram (BDD) based cut set solver; 3D script-based visualization and fluid flow representation.

• 5-pane workspace — Component List (Pane A), System Info bar (Pane B), SSCs in System (Pane C), "How the System Works" editor (Pane D), and Edit SSC details (Pane E); all panes are resizable
• SSC management — define SSCs with name, description, SSC type, and component type; reuse templates, add multiple failure modes per SSC with individual probability data; duplicate, edit, and delete SSCs and failure modes
• Probability types:
  • Direct Probability — mean value with distribution parameters (CNI, Lognormal, Normal, Gamma, Beta, Uniform, etc.)
  • Demand (Binomial) — demand probability and number of demands
  • Fails While Operating (Poisson) — failure rate and mission time
  • **Fails While Operating (Poisson) with a per-feet failure rate ** — failure rate, mission time, and lenth of component (e.g., piping)
  • Fails in Standby — failure rate and inspection interval
  • Fails While Operating with Repair — failure rate, mission time, and repair time
  • Logic T/F Flag — house events (TRUE/FALSE)
  • Qualitative — Low / Medium / High mapped to configurable probability values in Settings
  • Linked System — probability computed from another .KNOW_SYS file (resolved automatically in failure analysis)
  • Screened — excluded from analysis (probability = 0)
  • SPAR-H — human error probability
• System Modeling Script — "How the System Works" text editor with clickable keyword/SSC insertion, line numbers, and syntax highlighting; keywords include SYSTEM WORKS =, AND, OR, NOT, RELIES ON, WORKS, FAILS, UNLESS, WHEN, IF/THEN, IS TRUE/IS FALSE, ARE IN/ARE NOT IN, comparison operators, variables, and modules
• Check Script — validates logic for syntax errors, unmatched parentheses, and unknown identifiers; auto-creates missing SSCs
• "How the System Fails" modal — full-screen failure analysis with:
  • Fault tree text view and interactive graphic (canvas with zoom/pan)
  • Minimal cut sets with MCUB and BDD probability
  • Importance measures table: RIR, RRR, Probability of Contribution (PC), and SWIM
  • Uncertainty analysis
  • Configurable scatter plot of any two importance measures with labeled data points
• Special Failure Modes and Data — Seismic failure modeling with build-in SSC fragilities from NUREG/CR-3558, NUREG/CR-4659, and NUREG/CR-2680; fire failure modeling with build in fire-frequencies from NUREG-2169, and CCF including beta and alpha factors from INL/EXT-21-65527
• FMEA editor — full-screen modal with SSC list and auto-generated Mermaid.js FMEA block diagrams; add effects, severity, detection, and mitigation fields per failure mode
• P&ID editor — full-screen Piping and Instrumentation Diagram editor with SSC icons based upon the ISA5.1 P&ID symbol standard
• Reliability Designer™ — A way to quickly modify component failure probabilities (higher or lower) and see the impact on the overall system. Then, for an adjusted component probability, there is an estimate (using Bayesian inference) of how many tests would be required to meet that reliability target with 95% probability.
• Common-Cause Failures — automatically apply a beta-factor or alpha-factor based CCF events to cut sets
• Comparison — Compare two system designs to support risk-informed decision making
• Built-in reliability database — multiple generic data sources are built into the GUI
• Reliability database — load .relDB or .fmeaDB files into the Component List (Pane A); drag components to add them to the system; export SSC data back to .relDB or .fmeaDB
• Import — boundary conditions from SEQ files; basic events from .KNOW_FTL files (creates SSCs with probability data)
• Export — Reliability Database (.relDB), FMEA Database (.fmeaDB), KUREAS-FTL Fault Tree (.KNOW_FTL with pre-computed cut sets)
• Report generation — Word (.doc) and Markdown (.md) with 11 configurable sections: System Name, Extended Description, SSC Information, FMEA Information, System Works Expression, Supercomponent Information, Fault Tree Logic, Fault Tree Graphics, Fault Tree Cut Sets, Importance Measure Graphic, Importance Measure Table; in-browser preview with print
• Settings — font size, font family, background (light / dark / gray), probability display digits, SSC sort order, qualitative probability mapping (Low/Medium/High values), and layout reset

Comprehensive hazard identification, screening, and frequency quantification for complex facility initiating event analysis.

• Hierarchical hazard list — 4-level tree structure (Category → Group → Type → Event) with start-from-scratch, load from JSON/CSV, or merge with existing lists
• Multi-state analysis — analyze hazards across multiple plant operating states (e.g., full power, low power, shutdown) with configurable time fractions and reorderable state columns
• Multiple occurrence models:
  • Frequency — direct frequency with lognormal, normal, gamma, beta, uniform, log-uniform, histogram, or constrained noninformative (CNI) distributions
  • Probability per Opportunity — opportunity rate × conditional probability with the same distribution suite
  • Hazard Curve — tabular magnitude vs. frequency data with paste-from-Excel support
  • NUREG-2169 Fire Ignition — built-in Table 4-4 data with multi-source bin selection, component count scaling, and propagation factor: Final Freq = (Table Freq / # Components) × Propagation Factor
  • Screening — screen out hazards by low frequency, low consequence, or not applicable, with screening rationale preserved in reports
• Hazard categorization — configurable frequency-based categories (e.g., Anticipated, Design Basis, Beyond Design Basis) with customizable names, frequency range boundaries, and display in reports and exports
• Hazard frequency visualization — interactive logarithmic frequency plot across all operating states with color-coded state overlays
• Rich text documentation — per-hazard supporting information using a built-in rich text editor with font control, headings, and lists
• In-browser report preview — full report rendered in an iframe with download (.doc) and print options
• Report sections — facility info, operating schedule, hazard summary table, individual hazard details, fire hazards (NUREG-2169), screened hazards, and unanalyzed hazards
• Export — Word (.doc) report, Markdown (.md), SAPHIRE files (.BEI, .BED, .FTL), and Excel-compatible CSV hazard summary
• Settings — font size, font family, background theme, operating state colors, default states, hazard categorization scheme

Full fault tree authoring, visualization, and analysis environment with SAPHIRE and OpenPSA interoperability.

• Create or import — start a blank project from scratch or import SAPHIRE MAR-D files (.FTL, .BED, .BEI, .GTD, .FTC) via multi-file selection; also loads native .KNOW_FTL project files
• Full editing — add, delete, rename, and edit gates and basic events; modify descriptions, probabilities, and notes; copy/paste sub-tree structures; drag-and-drop basic events and fault trees onto the canvas
• Graphical and Textual Tree View — view and edit fault tree logic using a graphics- or text-based editor.
• Full solving and quantification — Advanced and fast cut set generation, Monte Carlo uncertainty analysis, importance measure generation
• Scope-aware editing — when editing shared nodes (appearing in multiple locations), choose to apply changes to one instance or all instances across the project; name conflict detection prevents collisions between gates and basic events
• Gate types — AND, OR, NOT, NAND, N-of-M Voting, and Transfer gates; Transfer gates auto-resolve to display referenced sub-trees
• Interactive canvas — zoom, pan, expand/collapse, click-to-edit, right-click-to-pin, and search by name
• Cut set analysis — load cut sets from .FTC files; floating, draggable results window sorted by probability contribution with fault tree top event probability
• Basic Event List — floating, draggable/resizable window listing all basic events with inline editing and drag-to-canvas functionality
• Change tracking — append-only change log with timestamps (View Changes button); undo support (Ctrl+Z, up to 50 levels); unsaved changes warning on close
• Export — SAPHIRE MAR-D (.FTL, .BEI), KUREAS native (.KNOW_FTL), and OpenPSA Model Exchange Format (.xml) with per-tree selection
• Import — SAPHIRE MAR-D, KUREAS native (.KNOW_FTL), and OpenPSA Model Exchange Format (.xml)
• Settings — font size, node size, color mode (full color / grayscale / single custom color), font family, connection lines (arrows / no arrows / dotted), line style (curved down / curved up / straight), line thickness, background (light / dark / blue grid / engineering green), probability display, default zoom level
• Report generation — Word (.doc) and Markdown (.md) with 11 configurable sections: System Name, Extended Description, SSC Information, FMEA Information, System Works Expression, Supercomponent Information, Fault Tree Logic, Fault Tree Graphics, Fault Tree Cut Sets, Importance Measure Graphic, Importance Measure Table; in-browser preview with print
• Persistence — projects stored in IndexedDB for browser-session persistence; save to .KNOW_FTL files for local storage

Event tree visualization tool implementing a backwards-recursive algorithm that correctly mirrors SAPHIRE's ETL format branching logic.

• SAPHIRE file import — reads .ETL (event tree logic) files including headers, top event types, logic sections, sequence metadata, and top event descriptions
• Additional file support — .BED (basic event descriptions), .BEI (basic event information), and .SQC (sequence cut sets) for enriched analysis
• Backwards algorithm — proprietary rendering approach that works from end states back to the initiating event, producing correct branch placement matching SAPHIRE's own layout logic
• Interactive canvas — pan and zoom with click-to-hide/show individual sequences
• Branch labeling modes — show success/failure labels, show S/F abbreviations, or hide branch labels
• Color modes — full color, black and white, or grayscale rendering for print-ready output
• Sequence analysis — view sequence paths with end states, transfer flags, and frequency data
• Cut set integration — associate sequence-level cut sets from .SQC files with visual sequences
• Multi-tree support — load files containing multiple event trees and navigate between them

Define accident sequences using facility operational scripting and associated diagrams — flowcharts that capture the logical progression from initiating events through system responses to end states.

• Script creation — create scripts describing how a facility responds to initiating events
• Diagram creation — create flowcharts with node types: Initiating Event, Function, Transition, and End State; rendered using Mermaid.js
• Shared operational scripts — reusable scripts that describe how a facility operates
• Hazard data integration — import HA_*.KNOW files to populate initiating events with frequencies and operating state assignments
• Boundary conditions — Boolean, State, and User-Defined types; integrated with NUREG-2169 fire ignition data
• Operating state modeling — nodes can reference and transition between defined plant operating states
• Event tree generation — automatically generate event tree structures from POL diagram logic with Mermaid code clipboard copy and PNG export
• Rich text notes — attach formatted documentation to any node
• Report generation — Word (.doc) export with sequence documentation

Management of component knowledge for operational behavior and experience to support Bayesian analysis of how components fail.

• Create or import — start a blank project from scratch or import generic failure information files (.relDB, .xlsx)
• Full editing — add, delete, rename, and edit tracked items for Bayesian analysis
• Change tracking — ability to verify and lock tracked items with an internal change tracking database
• Export — SAPHIRE MAR-D (.BEI), KUREAS native (.relDB), and OpenPSA Model Exchange Format (.xml)
• Report generation — Word (.doc) and Markdown with selectable report elements and in-browser preview
• Settings — GUI font size, font family, project settings
• Failure mode models:
  • Demand (Binomial) — demand failure probability
  • Fails While Operating (Poisson) — failure rate
  • Fails in Standby — failure rate

Central integration hub that assembles data from all other KUREAS modules into cohesive safety analysis reports.

• Multi-source loading — load project or .KNOW_RPT files from any KUREAS module (HA, SYS, SEQ); auto-detects file type and extracts available elements
• Drag-and-drop assembly — drag elements from loaded files into the report; reorder by dragging within the report structure
• Custom elements — add free-form text sections with rich text editing, tables, and formatted content
• Insertable elements — create reusable report sections (boilerplate text, standard tables); save to .ELEMENTS files and load into any future report
• Reference manager — grid-based reference editor with save/load to .KNOW files
• Acronym generator — feature to auto-generate all acronyms found in the report text
• Captions and Numbering — use of Word page numbering, figure/table numbering, and table of contents
• Word export — generate Word (.docx) reports with proper font sizing, styles, page numbering, margin control, captions, and embedded content
• Project persistence — save editable report as *.KNOW_REPORT for continued editing
• Auto Updating — loading an updated .KNOW_RPT file will update the associated report section

General-purpose viewer and editor for the .KNOW file format used across all KUREAS modules.

• File browser — open any .KNOW file to browse its contents in a structured tree view
• Auto-detection — recognizes file type (HA, SYS, SEQ, REPORT) and displays with appropriate formatting
• Direct editing — edit values, add or remove fields, and save modified files
• Folder operations — work with a directory of .KNOW files simultaneously (requires File System Access API: Chrome, Edge, or Opera)
• Debugging tool — inspect data structures, troubleshoot integration issues between modules

                             ┌────────────────┐
                             │  KUREAS-BAYES  │
                             │  (components)  │
                             └──────┬─────────┘
                                    │ .KNOW_BAYES
                                    ▼
  ┌──────────────┐           ┌──────────────┐
  │  KUREAS-HA   │           │  KUREAS-SYS  │
  │  (Hazards)   │           │  (Systems)   │
  └──────┬───────┘           └──────┬───────┘
         │ HA_*.KNOW                │ .KNOW_SYS / .KNOW_FTL
         ▼                          ▼
  ┌──────────────┐           ┌──────────────┐
  │  KUREAS-SEQ  │           │  KUREAS-FTL  │
  │  (Sequences) │           │ (Fault Trees)│
  └──────┬───────┘           └─┬────┬───────┘
         │ SEQ_*.KNOW          │    │ .KNOW_FTL / .FTL
         ▼                     │    ▼
  ┌──────────────┐           ┌──────────────┐
  │  KUREAS-ETL  │◄──────────│  SAPHIRE     │
  │ (Event Trees)│  .ETL     │  (external)  │
  └──────┬───────┘           └──────────────┘
         │
         ▼  All .KNOW_RPT files
  ┌──────────────┐
  │ KUREAS-REPORT│
  │  (Reports)   │
  └──────────────┘

Modules are not strictly sequential — you can start with any module, work in parallel, and iterate. The .KNOW file system enables seamless data exchange.

KUREAS-FTL exports to the OpenPSA Model Exchange Format (MEF) — an XML-based standard for fault tree data exchange between PSA tools.

All modules are single-file HTML applications with dependencies loaded from CDNs:

Any modern browser with ES6+ support. Tested on Chrome, Edge, Firefox, and Safari. No server-side components required. Chrome or Edge recommended for File System Access API features (KUREAS-KNOW folder operations).

KUREAS incorporates data and methodology from the following NRC publications:

• NUREG-2169 — Nuclear Power Plant Fire Ignition Frequency and Non-Suppression Probability Estimation Using the Updated Fire Events Database (Table 4-4 fire ignition frequencies are built into KUREAS-HA)
• NUREG/CR-7039 — Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) Version 8 (SAPHIRE file format specifications used throughout the suite)
• NUREG-CR-6883 — The SPAR-H Human Reliability Analysis Method (Gertman, Blackman, Byers, Marble, Smith, 2005) — reference document for human reliability analysis
• INL/EXT-10-18533 — SPAR-H Step-by-Step Guidance (Whaley, Kelly, Boring, Galyean, 2011) — procedural guidance for the SPAR-H method

MIT License — Copyright (c) 2025–2026 Curtis Lee Smith See individual module files for full license text.

Developed by Curtis Lee Smith and Claude.ai (Anthropic)