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\newpage
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\section{Broader Impacts}
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Nuclear power presents both a compelling application domain and an urgent
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economic challenge. Recent interest in powering artificial intelligence
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infrastructure has renewed focus on small modular reactors (SMRs), particularly
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for hyperscale datacenters requiring hundreds of megawatts of continuous power.
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Deploying SMRs at datacenter sites would minimize transmission losses and
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eliminate emissions from hydrocarbon-based alternatives. However, the economics
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of nuclear power deployment at this scale demand careful attention to operating
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costs.
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According to the U.S. Energy Information Administration's Annual Energy Outlook
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2022, advanced nuclear power entering service in 2027 is projected to cost
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\$88.24 per megawatt-hour~\cite{eia_lcoe_2022}. Datacenter electricity demand is
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projected to reach 1,050 terawatt-hours annually by
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2030~\cite{eesi_datacenter_2024}. If this demand were supplied by nuclear power,
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the total annual cost of power generation would exceed \$92 billion. Within this
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figure, operations and maintenance represents a substantial component. The EIA
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estimates that fixed O\&M costs alone account for \$16.15 per megawatt-hour,
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with additional variable O\&M costs embedded in fuel and operating
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expenses~\cite{eia_lcoe_2022}. Combined, O\&M-related costs represent
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approximately 23-30\% of the total levelized cost of electricity, translating to
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\$21-28 billion annually for projected datacenter demand.
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This research directly addresses the multi-billion dollar O\&M cost challenge
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through implementations of high-assurance autonomous control. Current nuclear
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operations require full control room staffing for each reactor, whether large
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conventional units or small modular designs. These staffing requirements drive
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the high O\&M costs that make nuclear power economically challenging,
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particularly for smaller reactor designs where the same staffing overhead must
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be spread across lower power output. By synthesizing provably correct hybrid
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controllers from formal specifications, we can automate routine operational
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sequences that currently require constant human oversight. This enables a
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fundamental shift from direct operator control to supervisory monitoring, where
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operators can oversee multiple autonomous reactors rather than manually
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controlling individual units.
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The correct-by-construction methodology is critical for this transition.
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Traditional automation approaches cannot provide sufficient safety guarantees
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for nuclear applications, where regulatory requirements and public safety
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concerns demand the highest levels of assurance. By formally verifying both the
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discrete mode-switching logic and the continuous control behavior, this research
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will produce controllers with mathematical proofs of correctness. These
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guarantees enable automation to safely handle routine operations—such as startup
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sequences, power level changes, and normal operational transitions—that
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currently require human operators to follow written procedures. Operators will
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remain in supervisory roles to handle off-normal conditions and provide
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authorization for major operational changes, but the routine cognitive burden of
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procedure execution shifts to provably correct automated systems that are much
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cheaper to operate.
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SMRs represent an ideal deployment target for this technology. Nuclear Regulatory
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Commission certification requires extensive documentation of control procedures,
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operational requirements, and safety analyses written in structured natural
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language. As described in our approach, these regulatory documents can be
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translated into temporal logic specifications using tools like FRET, then
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synthesized into discrete switching logic using reactive synthesis tools, and
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finally verified using reachability analysis and barrier certificates for the
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continuous control modes. The infrastructure of requirements and specifications
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is already complete as part of the licensing process, creating a direct pathway
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from existing regulatory documentation to formally verified autonomous
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controllers.
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Beyond reducing operating costs for new reactors, this research will establish a
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generalizable framework for autonomous control of safety-critical systems. The
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methodology of translating operational procedures into formal specifications,
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synthesizing discrete switching logic, and verifying continuous mode behavior
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applies to any hybrid system with documented operational requirements. Potential
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applications include chemical process control, aerospace systems, and autonomous
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transportation, where similar economic and safety considerations favor increased
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autonomy with provable correctness guarantees. By demonstrating this approach in
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nuclear power—one of the most regulated and safety-critical domains—this
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research will establish both the technical feasibility and regulatory pathway
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for broader adoption across critical infrastructure.
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@ -0,0 +1,118 @@
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\section{Goals and Outcomes}
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% GOAL PARAGRAPH
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The goal of this research is to develop a methodology for creating autonomous
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hybrid control systems with mathematical guarantees of safe and correct
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behavior.
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% INTRODUCTORY PARAGRAPH Hook
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Nuclear power plants require the highest levels of control system reliability,
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where failures can result in significant economic losses, service interruptions,
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or radiological release.
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% Known information
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Currently, nuclear plant operations rely on extensively trained human operators
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who follow detailed written procedures and strict regulatory requirements to
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manage reactor control. These operators make critical decisions about when to
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switch between different control modes based on their interpretation of plant
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conditions and procedural guidance.
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% Gap
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However, this reliance on human operators prevents the introduction of
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autonomous control capabilities and creates a fundamental economic challenge for
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next-generation reactor designs. Emerging technologies like small modular
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reactors face significantly higher per-megawatt staffing costs than conventional
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plants, threatening their economic viability.
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% Critical Need
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What is needed is a way to create autonomous control systems that can safely
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manage complex operational sequences with the same level of assurance as
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human-operated systems, but without requiring constant human supervision.
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% APPROACH PARAGRAPH Solution
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To address this need, we will combine formal methods from computer science with
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control theory to build hybrid control systems that are correct by construction.
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% Rationale
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Hybrid systems use discrete logic to switch between continuous control modes,
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similar to how operators change control strategies. Existing formal methods can
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generate provably correct switching logic from written requirements, but they
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cannot handle the continuous dynamics that occur during transitions between
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modes. Meanwhile, traditional control theory can verify continuous behavior but
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lacks tools for proving correctness of discrete switching decisions.
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% Hypothesis
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By synthesizing discrete mode transitions directly from written operating
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procedures and verifying continuous behavior between transitions, we can create
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hybrid control systems with end-to-end correctness guarantees. If we can
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formalize existing procedures into logical specifications and verify that
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continuous dynamics satisfy transition requirements, then we can build
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autonomous controllers that are provably free from design defects.
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% Pay-off
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This approach will enable autonomous control in nuclear power plants while
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maintaining the high safety standards required by the industry.
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% Qualifications
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This work is conducted within the University of Pittsburgh Cyber Energy Center,
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which provides access to industry collaboration and Emerson control hardware,
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ensuring that solutions developed are aligned with practical implementation
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requirements.
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% OUTCOMES PARAGRAPHS
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If this research is successful, we will be able to do the following:
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\begin{enumerate}
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% OUTCOME 1 Title
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\item \textbf{Translate written procedures into verified control logic.}
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% Strategy
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We will develop a methodology for converting existing written operating
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procedures into formal specifications that can be automatically synthesized
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into discrete control logic. This process will use structured intermediate
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representations to bridge natural language procedures and mathematical
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logic.
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% Outcome
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Control system engineers will be able to generate verified mode-switching
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controllers directly from regulatory procedures without requiring expertise
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in formal methods, reducing the barrier to creating high-assurance control
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systems.
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% OUTCOME 2 Title
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\item \textbf{Verify continuous control behavior across mode transitions.}
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% Strategy
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We will establish methods for analyzing continuous control modes to ensure
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they satisfy the discrete transition requirements. Using a combination of
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classical control theory for linear systems and reachability analysis for
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nonlinear dynamics, we will verify that each continuous mode can safely
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reach its intended transitions.
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% Outcome
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Engineers will be able to design continuous controllers using standard
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practices while iterating to ensure broader system correctness, proving that
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mode transitions occur safely and at the right times.
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% OUTCOME 3 Title
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\item \textbf{Demonstrate autonomous reactor startup control with safety
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guarantees.}
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% Strategy
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We will apply this methodology to develop an autonomous controller for
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nuclear reactor startup procedures, implementing it on a small modular
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reactor simulation using industry-standard control hardware. This
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demonstration will prove correctness across multiple coordinated control
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modes from cold shutdown through criticality to power operation.
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% Outcome
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We will provide evidence that autonomous hybrid control can be realized in
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the nuclear industry with current control equipment, establishing a path
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toward reducing operator staffing requirements while maintaining safety.
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\end{enumerate}
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% IMPACT PARAGRAPH Innovation
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The innovation in this work is the unification of discrete synthesis and
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continuous verification to enable end-to-end correctness guarantees for hybrid
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systems.
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% Outcome Impact
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If successful, control engineers will be able to create autonomous controllers
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from existing procedures with mathematical proof of correct behavior.
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High-assurance autonomous control will become practical for safety-critical
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applications.
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% Impact/Pay-off
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This capability is essential for the economic viability of next-generation
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nuclear power. Small modular reactors represent a promising solution to growing
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energy demands, but their success depends on reducing per-megawatt operating
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costs through increased autonomy. This research will provide the tools to
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achieve that autonomy while maintaining the exceptional safety record required
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by the nuclear industry.
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@ -2,23 +2,26 @@
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106
Writing/ERLM/metrics-of-success/v2.tex
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|
||||
\newpage
|
||||
\section{Metrics for Success}
|
||||
|
||||
This research will be measured by advancement through Technology Readiness
|
||||
Levels, progressing from fundamental concepts to validated prototype
|
||||
demonstration. The work begins at TRL 2-3 and aims to reach TRL 5, where system
|
||||
components operate successfully in a relevant laboratory environment. This
|
||||
section explains why TRL advancement provides the most appropriate success
|
||||
metric and defines the specific criteria required to achieve TRL 5.
|
||||
|
||||
Technology Readiness Levels provide the ideal success metric because they
|
||||
explicitly measure the gap between academic proof-of-concept and practical
|
||||
deployment. This gap is precisely what this work aims to bridge. Academic
|
||||
metrics like papers published or theorems proved cannot capture practical
|
||||
feasibility. Empirical metrics like simulation accuracy or computational speed
|
||||
cannot demonstrate theoretical rigor. TRLs measure both dimensions
|
||||
simultaneously. Advancing from TRL 3 to TRL 5 requires maintaining theoretical
|
||||
rigor while progressively demonstrating practical feasibility. Formal
|
||||
verification must remain valid as the system moves from individual components to
|
||||
integrated hardware testing.
|
||||
|
||||
The nuclear industry requires extremely high assurance before deploying new
|
||||
control technologies. Demonstrating theoretical correctness alone is
|
||||
insufficient for adoption. Conversely, showing empirical performance without
|
||||
formal guarantees fails to meet regulatory requirements. TRLs capture this dual
|
||||
requirement naturally. Each level represents both increased practical maturity
|
||||
and sustained theoretical validity. Furthermore, TRL assessment forces explicit
|
||||
identification of remaining barriers to deployment. The nuclear industry already
|
||||
uses TRLs for technology assessment, making this metric directly relevant to
|
||||
potential adopters. Reaching TRL 5 provides a clear answer to industry questions
|
||||
about feasibility and maturity in a way that academic publications alone cannot.
|
||||
|
||||
The work currently exists at TRL 2-3. Formal synthesis and hybrid control
|
||||
verification principles have been established through prior research, placing
|
||||
the fundamental approach at TRL 2. The SmAHTR simulation model and initial
|
||||
procedure analysis place specific components at early TRL 3, where proof of
|
||||
concept has been partially demonstrated for individual elements but not
|
||||
integrated. The target state is TRL 5. Moving from current state to target
|
||||
requires achieving three intermediate levels, each representing a distinct
|
||||
validation milestone:
|
||||
|
||||
\paragraph{TRL 3 \textit{Critical Function and Proof of Concept}}
|
||||
For this research, TRL 3 means demonstrating that each component of the
|
||||
methodology works in isolation. SmAHTR startup procedures must be translated
|
||||
into temporal logic specifications that pass realizability analysis. A discrete
|
||||
automaton must be synthesized with interpretable structure. At least one
|
||||
continuous controller must be designed with reachability analysis proving that
|
||||
transition requirements are satisfied. Independent review must confirm that
|
||||
specifications match intended procedural behavior. This proves the fundamental
|
||||
approach on a simplified startup sequence.
|
||||
|
||||
\paragraph{TRL 4 \textit{Laboratory Testing of Integrated Components}}
|
||||
For this research, TRL 4 means demonstrating a complete integrated hybrid
|
||||
controller in simulation. All SmAHTR startup procedures must be formalized with
|
||||
a synthesized automaton covering all operational modes. Continuous controllers
|
||||
must exist for all discrete modes. Verification must be complete for all mode
|
||||
transitions using reachability analysis, barrier certificates, and
|
||||
assume-guarantee contracts. The integrated controller must execute complete
|
||||
startup sequences in software simulation with zero safety violations across
|
||||
multiple consecutive runs. This proves that formal correctness guarantees can be
|
||||
maintained throughout system integration.
|
||||
|
||||
\paragraph{TRL 5 \textit{Laboratory Testing in Relevant Environment}}
|
||||
For this research, TRL 5 means demonstrating the verified controller on
|
||||
industrial control hardware through hardware-in-the-loop testing. The discrete
|
||||
automaton must be implemented on the Emerson Ovation control system and verified
|
||||
to match synthesized specifications exactly. Continuous controllers must execute
|
||||
at required rates. The ARCADE interface must establish stable real-time
|
||||
communication between Ovation hardware and SmAHTR simulation. Complete
|
||||
autonomous startup sequences must execute via hardware-in-the-loop across the
|
||||
full operational envelope. The controller must handle off-nominal scenarios to
|
||||
validate that expulsory modes function correctly. For example, simulated sensor
|
||||
failures must trigger appropriate fault detection and mode transitions, and loss
|
||||
of cooling scenarios must activate SCRAM procedures as specified. Graded
|
||||
responses to minor disturbances are outside the scope of this work. Formal
|
||||
verification results must remain valid with discrete behavior matching
|
||||
specifications and continuous trajectories remaining within verified bounds.
|
||||
This proves that the methodology produces verified controllers implementable on
|
||||
industrial hardware.
|
||||
|
||||
These levels define progressively more demanding demonstrations. TRL 3 proves
|
||||
individual components work. TRL 4 proves they work together in simulation. TRL 5
|
||||
proves they work on actual hardware in realistic conditions. Each level builds
|
||||
on the previous while adding new validation requirements.
|
||||
|
||||
Progress will be assessed quarterly through collection of specific data
|
||||
comparing actual results against TRL advancement criteria. Specification
|
||||
development status indicates progress toward TRL 3. Synthesis results and
|
||||
verification coverage indicate progress toward TRL 4. Simulation performance
|
||||
metrics and hardware integration milestones indicate progress toward TRL 5. The
|
||||
research plan will be revised only when new data invalidates fundamental
|
||||
assumptions. Unrealizable specifications indicate procedure conflicts requiring
|
||||
refinement or alternative reactor selection. Unverifiable dynamics suggest model
|
||||
simplification or alternative verification methods are needed. Unachievable
|
||||
real-time performance requires controller simplification or hardware upgrades.
|
||||
Any revision will document the invalidating data, the failed assumption, and the
|
||||
modified pathway with adjusted scope.
|
||||
|
||||
This research succeeds if it achieves TRL 5 by demonstrating a complete
|
||||
autonomous hybrid controller with formal correctness guarantees operating on
|
||||
industrial control hardware through hardware-in-the-loop testing in a relevant
|
||||
laboratory environment. This establishes both theoretical validity and practical
|
||||
feasibility, proving that the methodology produces verified controllers and that
|
||||
implementation is achievable with current technology. It provides a clear
|
||||
pathway for nuclear industry adoption and broader application to safety-critical
|
||||
autonomous systems.
|
||||
296
Writing/ERLM/research-approach/v4.tex
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296
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Normal file
@ -0,0 +1,296 @@
|
||||
\newpage
|
||||
\section{Research Approach}
|
||||
|
||||
This research will overcome the limitations of current practice to build
|
||||
high-assurance hybrid control systems for critical infrastructure. Hybrid
|
||||
systems combine continuous dynamics (flows) with discrete transitions (jumps),
|
||||
which can be formally expressed as:
|
||||
|
||||
\begin{equation}
|
||||
\dot{x}(t) = f(x(t),q(t),u(t))
|
||||
\end{equation}
|
||||
|
||||
\begin{equation}
|
||||
q(k+1) = \nu(x(k),q(k),u(k))
|
||||
\end{equation}
|
||||
|
||||
Here, $f(\cdot)$ defines the continuous dynamics while $\nu(\cdot)$ governs
|
||||
discrete transitions. The continuous states $x$, discrete state $q$, and
|
||||
control input $u$ interact to produce hybrid behavior. The discrete state $q$
|
||||
defines which continuous dynamics mode is currently active. Our focus centers
|
||||
on continuous autonomous hybrid systems, where continuous states remain
|
||||
unchanged during jumps—a property naturally exhibited by physical systems. For
|
||||
example, a nuclear reactor switching from warm-up to load-following control
|
||||
cannot instantaneously change its temperature or control rod position, but can
|
||||
instantaneously change control laws.
|
||||
|
||||
To build these systems with formal correctness guarantees, we must accomplish
|
||||
three main thrusts:
|
||||
|
||||
\begin{enumerate}
|
||||
\item Translate operating procedures and requirements into temporal logic
|
||||
formulae
|
||||
|
||||
\item Create the discrete half of a hybrid controller using reactive synthesis
|
||||
|
||||
\item Develop continuous controllers to operate between modes, and verify
|
||||
their correctness using reachability analysis
|
||||
|
||||
\end{enumerate}
|
||||
|
||||
The following sections discuss how these thrusts will be accomplished.
|
||||
|
||||
\subsection{$(Procedures \wedge FRET) \rightarrow Temporal Specifications$}
|
||||
|
||||
The motivation behind this work stems from the fact that commercial nuclear
|
||||
power operations remain manually controlled by human operators, despite
|
||||
significant advances in control systems sophistication. The key insight is that
|
||||
procedures performed by human operators are highly prescriptive and
|
||||
well-documented. This suggests that human operators in nuclear power plants may
|
||||
not be entirely necessary given today's available technology.
|
||||
|
||||
Written procedures and requirements in nuclear power are sufficiently detailed
|
||||
that we may be able to translate them into logical formulae with minimal effort.
|
||||
If successful, this approach would enable automation of existing procedures
|
||||
without requiring system reengineering. To formalize these procedures, we will
|
||||
use temporal logic, which captures system behaviors through temporal relations.
|
||||
Linear Temporal Logic (LTL) provides four fundamental operators: next ($X$),
|
||||
eventually ($F$), globally ($G$), and until ($U$). These operators enable
|
||||
precise specification of time-dependent requirements.
|
||||
|
||||
Consider a nuclear reactor SCRAM requirement expressed in natural language:
|
||||
\textit{``If a high temperature alarm triggers, control rods must immediately
|
||||
insert and remain inserted until operator reset.''} This plain language
|
||||
requirement can be translated into a rigorous logical specification:
|
||||
|
||||
\begin{equation}
|
||||
G(HighTemp \rightarrow X(RodsInserted \wedge (\neg RodsWithdrawn\ U\
|
||||
OperatorReset)))
|
||||
\end{equation}
|
||||
|
||||
This specification precisely captures the temporal relationship between the
|
||||
alarm condition, the required response, and the persistence requirement. The
|
||||
global operator $G$ ensures this property holds throughout system operation,
|
||||
while the next operator $X$ enforces immediate response. The until operator
|
||||
$U$ maintains the state constraint until the reset condition occurs.
|
||||
|
||||
The most efficient path to accomplish this translation is through NASA's
|
||||
Formal Requirements Elicitation Tool (FRET). FRET employs a specialized
|
||||
requirements language called FRETish that restricts requirements to easily
|
||||
understood components while eliminating ambiguity. FRETish bridges natural
|
||||
language and mathematical specifications through a structured English-like
|
||||
syntax that is automatically translatable to temporal logic.
|
||||
|
||||
FRET enforces this structure by requiring all requirements to contain six
|
||||
components: %CITE FRET MANUAL
|
||||
|
||||
\begin{enumerate}
|
||||
\item Scope: \textit{What modes does this requirement apply to?}
|
||||
\item Condition: \textit{Scope plus additional specificity}
|
||||
\item Component: \textit{What system element does this requirement affect?}
|
||||
\item Shall
|
||||
\item Timing: \textit{When does the response occur?}
|
||||
\item Response: \textit{What action should be taken?}
|
||||
\end{enumerate}
|
||||
|
||||
FRET provides functionality to check the \textit{realizability} of a system.
|
||||
Realizability analysis determines whether written requirements are complete by
|
||||
examining the six structural components. Complete requirements are those that
|
||||
neither conflict with one another nor leave any behavior undefined. Systems
|
||||
that are not realizable from their procedure definitions and design
|
||||
requirements present problems beyond autonomous control implementation. Such
|
||||
systems contain behavioral inconsistencies that represent the physical
|
||||
equivalent of software bugs. Using FRET during autonomous controller
|
||||
development allows us to identify and resolve these errors systematically.
|
||||
|
||||
The second category of realizability issues involves undefined behaviors that
|
||||
are typically left to human judgment during control operations. This
|
||||
ambiguity is undesirable for high-assurance systems, since even well-trained
|
||||
humans remain prone to errors. By addressing these specification gaps in FRET
|
||||
during autonomous controller development, we can deliver controllers free from
|
||||
these vulnerabilities.
|
||||
|
||||
FRET provides the capability to export requirements in temporal logic format
|
||||
compatible with reactive synthesis tools. This export functionality enables
|
||||
progression to the next step of our approach: synthesizing discrete mode
|
||||
switching behavior from the formalized requirements.
|
||||
|
||||
\subsection{$(TemporalLogic \wedge ReactiveSynthesis) \rightarrow
|
||||
DiscreteAutomata$}
|
||||
|
||||
Reactive synthesis is an active research field in computer science focused on
|
||||
generating discrete controllers from temporal logic specifications. The term
|
||||
``reactive'' indicates that the system responds to environmental inputs to
|
||||
produce control outputs. These synthesized systems are finite in size, where
|
||||
each node represents a unique discrete state. The connections between nodes,
|
||||
called \textit{state transitions}, specify the conditions under which the
|
||||
discrete controller moves from state to state. This complete mapping of possible
|
||||
states and transitions constitutes a \textit{discrete automaton}. Discrete
|
||||
automata can be represented graphically as a series of nodes that are discrete
|
||||
states, with traces indicating transitions between states. From the automaton
|
||||
graph, it becomes possible to fully describe the dynamics of the discrete system
|
||||
and develop intuitive understanding of system behavior. Hybrid systems
|
||||
naturally exhibit discrete behavior amenable to formal analysis through these
|
||||
finite state representations.
|
||||
|
||||
We will employ state-of-the-art reactive synthesis tools, particularly Strix,
|
||||
which has demonstrated superior performance in the Reactive Synthesis
|
||||
Competition (SYNTCOMP) through efficient parity game solving algorithms. Strix
|
||||
translates linear temporal logic specifications into deterministic automata
|
||||
automatically while maximizing generated automata quality. Once constructed, the
|
||||
automaton can be straightforwardly implemented using standard programming
|
||||
control flow constructs. The graphical representation provided by the automaton
|
||||
enables inspection and facilitates communication with controls programmers who
|
||||
may not have formal methods expertise.
|
||||
|
||||
We will use discrete automata to represent the switching behavior of our hybrid
|
||||
system. This approach yields an important theoretical guarantee: because the
|
||||
discrete automaton is synthesized entirely through automated tools from design
|
||||
requirements and operating procedures, we can prove that the automaton—and
|
||||
therefore our hybrid switching behavior—is \textit{correct by construction}.
|
||||
Correctness of the switching controller is paramount to this work. Mode
|
||||
switching represents the primary responsibility of human operators in control
|
||||
rooms today. Human operators possess the advantage of real-time judgment—when
|
||||
mistakes occur, they can correct them dynamically with capabilities that extend
|
||||
beyond written procedures. Autonomous control lacks this adaptive advantage.
|
||||
Instead, we must ensure that autonomous controllers replacing human operators
|
||||
will not make switching errors between continuous modes. By synthesizing
|
||||
controllers from logical specifications with guaranteed correctness, we
|
||||
eliminate the possibility of switching errors.
|
||||
|
||||
\subsection{$(DiscreteAutomata \wedge ControlTheory \wedge Reachability)
|
||||
\rightarrow ContinuousModes$}
|
||||
|
||||
While discrete system components will be synthesized with correctness
|
||||
guarantees, they represent only half of the complete system. Autonomous
|
||||
controllers like those we are developing exhibit continuous dynamics within
|
||||
discrete states, as described by $f(\cdot)$ in Equation 1. This section
|
||||
describes how we will develop continuous control modes, verify their
|
||||
correctness, and address the unique verification challenges of hybrid systems.
|
||||
|
||||
The approach described for producing discrete automata yields physics-agnostic
|
||||
specifications that represent only half of a complete hybrid autonomous
|
||||
controller. These automata alone cannot define the full behavior of the
|
||||
control systems we aim to construct. The continuous modes will be developed
|
||||
after discrete automaton construction, leveraging the automaton structure and
|
||||
transitions to design multiple smaller, specialized continuous controllers.
|
||||
|
||||
The discrete automaton transitions are key to the supervisory behavior of the
|
||||
autonomous controller. These transitions mark decision points for switching
|
||||
between continuous control modes and define their strategic objectives. We
|
||||
will classify three types of high-level continuous controller objectives based
|
||||
on discrete mode transitions:
|
||||
|
||||
\begin{enumerate}
|
||||
\item \textbf{Stabilizing:} A stabilizing control mode has one primary
|
||||
objective: maintaining the hybrid system within its current discrete mode.
|
||||
This corresponds to steady-state normal operating modes, such as a
|
||||
full-power load-following controller in a nuclear power plant. Stabilizing
|
||||
modes can be identified from discrete automata as nodes with only incoming
|
||||
transitions.
|
||||
|
||||
\item \textbf{Transitory:} A transitory control mode has the primary goal of
|
||||
transitioning the hybrid system from one discrete state to another. In
|
||||
nuclear applications, this might represent a controlled warm-up procedure.
|
||||
Transitory modes ultimately drive the system toward a stabilizing
|
||||
steady-state mode. These modes may have secondary objectives within a
|
||||
discrete state, such as maintaining specific temperature ramp rates before
|
||||
reaching full-power operation.
|
||||
|
||||
\item \textbf{Expulsory:} An expulsory mode is a specialized transitory mode
|
||||
with additional safety constraints. Expulsory modes ensure the system is
|
||||
directed to a safe stabilizing mode during failure conditions. For example,
|
||||
if a transitory mode fails to achieve its intended transition, the
|
||||
expulsory mode activates to immediately and irreversibly guide the system
|
||||
toward a globally safe state. A reactor SCRAM exemplifies an expulsory
|
||||
continuous mode: when initiated, it must reliably terminate the nuclear
|
||||
reaction and direct the reactor toward stabilizing decay heat removal.
|
||||
|
||||
\end{enumerate}
|
||||
|
||||
Building continuous modes after constructing discrete automata enables local
|
||||
controller design focused on satisfying discrete transitions. The primary
|
||||
challenge in hybrid system verification is ensuring global stability across
|
||||
transitions. Current techniques struggle with this problem because dynamic
|
||||
discontinuities complicate verification. This work alleviates these problems by
|
||||
designing continuous controllers specifically with transitions in mind. By
|
||||
decomposing continuous modes according to their required behavior at transition
|
||||
points, we avoid solving trajectories through the entire hybrid system. Instead,
|
||||
we can use local behavior information at transition boundaries. To ensure
|
||||
continuous modes satisfy their requirements, we will employ three main
|
||||
techniques: reachability analysis, assume-guarantee contracts, and barrier
|
||||
certificates.
|
||||
|
||||
\textbf{Reachability Analysis:} Reachability analysis computes the reachable set
|
||||
of states for a given input set. While trivial for linear continuous systems,
|
||||
recent advances have extended reachability to complex nonlinear systems. We will
|
||||
use reachability to define continuous state ranges at discrete transition
|
||||
boundaries and verify that requirements are satisfied within continuous modes.
|
||||
Recent advances using neural network approximations of Hamilton-Jacobi equations
|
||||
have demonstrated significant speedups while maintaining safety guarantees for
|
||||
high-dimensional systems, expanding the practical applicability of these
|
||||
methods.
|
||||
|
||||
\textbf{Assume-Guarantee Contracts:} Assume-guarantee contracts will be
|
||||
employed when continuous state boundaries are not explicitly defined. For any
|
||||
given mode, the input range for reachability analysis is defined by the output
|
||||
ranges of discrete modes that transition to it. This compositional approach
|
||||
ensures each continuous controller is prepared for its possible input range,
|
||||
enabling subsequent reachability analysis without requiring global system
|
||||
analysis.
|
||||
|
||||
\textbf{Barrier Certificates:} Finally, we will use barrier certificates to
|
||||
prove that mode transitions are satisfied. Barrier certificates ensure that
|
||||
continuous modes on either side of a transition behave appropriately. Control
|
||||
barrier functions provide a method to certify safety by establishing
|
||||
differential inequality conditions that guarantee forward invariance of safe
|
||||
sets. For example, a barrier certificate can guarantee that a transitory mode
|
||||
transferring control to a stabilizing mode will always move away from the
|
||||
transition boundary, rather than destabilizing the target stabilizing mode.
|
||||
|
||||
Combining these three techniques will enable us to prove that continuous
|
||||
components of our hybrid controller satisfy discrete requirements, and thus,
|
||||
complete system behavior. To demonstrate this methodology, we will develop an
|
||||
autonomous startup controller for a Small Modular Advanced High Temperature
|
||||
Reactor (SmAHTR). SmAHTR represents an ideal test case as a liquid-salt cooled
|
||||
reactor design with well-documented startup procedures that must transition
|
||||
through multiple distinct operational modes: initial cold conditions, controlled
|
||||
heating to operating temperature, approach to criticality, low-power physics
|
||||
testing, and power ascension to full operating capacity. We have already
|
||||
developed a high-fidelity SmAHTR model in Simulink that captures the
|
||||
thermal-hydraulic and neutron kinetics behavior essential for verifying
|
||||
continuous controller performance under realistic plant dynamics. The
|
||||
synthesized hybrid controller will be implemented on an Emerson Ovation control
|
||||
system platform, which is representative of industry-standard control hardware
|
||||
deployed in modern nuclear facilities. The Advanced Reactor Cyber Analysis and
|
||||
Development Environment (ARCADE) suite will serve as the integration layer,
|
||||
managing real-time communication between the Simulink simulation and the Ovation
|
||||
controller. This hardware-in-the-loop configuration enables validation of the
|
||||
controller implementation on actual industrial control equipment interfacing
|
||||
with a realistic reactor simulation, providing assessment of computational
|
||||
performance, real-time execution constraints, and communication latency effects.
|
||||
By demonstrating autonomous startup control on this representative platform, we
|
||||
will establish both the theoretical validity and practical feasibility of the
|
||||
synthesis methodology for deployment in actual small modular reactor systems.
|
||||
|
||||
This unified approach addresses a fundamental gap in hybrid system design by
|
||||
bridging formal methods and control theory through a systematic, tool-supported
|
||||
methodology. By translating existing nuclear procedures into temporal logic,
|
||||
synthesizing provably correct discrete switching logic, and developing verified
|
||||
continuous controllers, we create a complete framework for autonomous hybrid
|
||||
control with mathematical guarantees. The result is an autonomous controller
|
||||
that not only replicates human operator decision-making but does so with formal
|
||||
assurance that switching logic is correct by construction and continuous
|
||||
behavior satisfies safety requirements. This methodology transforms nuclear
|
||||
reactor control from a manually intensive operation requiring constant human
|
||||
oversight into a fully autonomous system with higher reliability than
|
||||
human-operated alternatives. More broadly, this approach establishes a
|
||||
replicable framework for developing high-assurance autonomous controllers in any
|
||||
domain where operating procedures are well-documented and safety is paramount.
|
||||
|
||||
% COMMENTS FOR FUTURE REVISION:
|
||||
% 1. Add concrete examples throughout (specific nuclear procedures, requirements)
|
||||
% 2. Include a figure showing the overall workflow/methodology
|
||||
% 3. Consider adding a subsection on validation approach
|
||||
% 4. Strengthen the connections between subsections
|
||||
% 5. Add discussion of limitations and assumptions
|
||||
232
Writing/ERLM/risks-and-contingencies/v2.tex
Normal file
232
Writing/ERLM/risks-and-contingencies/v2.tex
Normal file
@ -0,0 +1,232 @@
|
||||
\newpage
|
||||
\section{Risks and Contingencies}
|
||||
|
||||
This research relies on several critical assumptions that, if invalidated,
|
||||
would require scope adjustment or methodological revision. The primary risks to
|
||||
successful completion fall into four categories: computational tractability of
|
||||
synthesis and verification, complexity of the discrete-continuous interface,
|
||||
completeness of procedure formalization, and hardware-in-the-loop integration
|
||||
challenges. Each risk has associated indicators for early detection and
|
||||
contingency plans that preserve research value even if core assumptions prove
|
||||
false. The staged project structure ensures that partial success yields
|
||||
publishable results and clear identification of remaining barriers to
|
||||
deployment.
|
||||
|
||||
\subsection{Computational Tractability of Synthesis}
|
||||
|
||||
The first major assumption is that formalized startup procedures will yield
|
||||
automata small enough for efficient synthesis and verification. Reactive
|
||||
synthesis scales exponentially with specification complexity, which creates risk
|
||||
that temporal logic specifications derived from complete startup procedures may
|
||||
produce automata with thousands of states. Such large automata would require
|
||||
synthesis times exceeding days or weeks, preventing demonstration of the
|
||||
complete methodology within project timelines. Reachability analysis for
|
||||
continuous modes with high-dimensional state spaces may similarly prove
|
||||
computationally intractable. Either barrier would constitute a fundamental
|
||||
obstacle to achieving the research objectives.
|
||||
|
||||
Several indicators would provide early warning of computational tractability
|
||||
problems. Synthesis times exceeding 24 hours for simplified procedure subsets
|
||||
would suggest that complete procedures are intractable. Generated automata
|
||||
containing more than 1,000 discrete states would indicate that the discrete
|
||||
state space is too large for efficient verification. Specifications flagged as
|
||||
unrealizable by FRET or STRIX would reveal fundamental conflicts in the
|
||||
formalized procedures. Reachability analysis failing to converge within
|
||||
reasonable time bounds would show that continuous mode verification cannot be
|
||||
completed with available computational resources.
|
||||
|
||||
The contingency plan for computational intractability is to reduce scope to a
|
||||
minimal viable startup sequence. This reduced sequence would cover only cold
|
||||
shutdown to criticality to low power hold, omitting power ascension and other
|
||||
operational phases. The subset would still demonstrate the complete
|
||||
methodology while reducing computational burden. The research contribution
|
||||
would remain valid even with reduced scope, proving that formal hybrid control
|
||||
synthesis is achievable for safety-critical nuclear applications. The limitation
|
||||
to simplified operational sequences would be explicitly documented as a
|
||||
constraint rather than a failure.
|
||||
|
||||
Reachability analysis specifically can exploit time-scale separation inherent in
|
||||
reactor dynamics. Fast thermal transients can be treated quasi-steady relative
|
||||
to slower nuclear kinetics, which enables decomposition into smaller subsystems.
|
||||
Temperature dynamics operate on time scales of seconds to minutes, while neutron
|
||||
kinetics respond in milliseconds to seconds for prompt effects and hours for
|
||||
xenon poisoning. These distinct time scales permit separate analysis with
|
||||
conservative coupling assumptions between subsystems, dramatically reducing the
|
||||
dimensionality of reachability computations.
|
||||
|
||||
Mitigation strategies exist even before contingency plans become necessary.
|
||||
Access to the University of Pittsburgh Center for Research Computing provides
|
||||
high-performance computing resources if single-workstation computation proves
|
||||
insufficient. Parallel synthesis algorithms and distributed reachability
|
||||
analysis can leverage these resources to extend computational feasibility.
|
||||
Compositional verification approaches using assume-guarantee reasoning can
|
||||
decompose monolithic verification problems into tractable subproblems, each of
|
||||
which can be solved independently before composition.
|
||||
|
||||
\subsection{Discrete-Continuous Interface Formalization}
|
||||
|
||||
The second critical assumption concerns the mapping between boolean guard
|
||||
conditions in temporal logic and continuous state boundaries required for mode
|
||||
transitions. This interface represents the fundamental challenge of hybrid
|
||||
systems: relating discrete switching logic to continuous dynamics. Temporal
|
||||
logic operates on boolean predicates, while continuous control requires
|
||||
reasoning about differential equations and reachable sets. Guard conditions that
|
||||
require complex nonlinear predicates may resist boolean abstraction, making
|
||||
synthesis intractable. Continuous safety regions that cannot be expressed as
|
||||
conjunctions of verifiable constraints would similarly create insurmountable
|
||||
verification challenges. The risk extends beyond static interface definition to
|
||||
dynamic behavior across transitions: barrier certificates may fail to exist for
|
||||
proposed transitions, or continuous modes may be unable to guarantee convergence
|
||||
to discrete transition boundaries.
|
||||
|
||||
Early indicators of interface formalization problems would appear during both
|
||||
synthesis and verification phases. Guard conditions requiring complex nonlinear
|
||||
predicates that resist boolean abstraction would suggest fundamental misalignment
|
||||
between discrete specifications and continuous realities. Continuous safety
|
||||
regions that cannot be expressed as conjunctions of half-spaces or polynomial
|
||||
inequalities would indicate that the interface between discrete guards and
|
||||
continuous invariants is too complex. Failure to construct barrier certificates
|
||||
proving safety across mode transitions would reveal that the continuous dynamics
|
||||
cannot be formally related to discrete switching logic. Reachability analysis
|
||||
showing that continuous modes cannot reach intended transition boundaries from
|
||||
all possible initial conditions would demonstrate that the synthesized discrete
|
||||
controller is incompatible with achievable continuous behavior.
|
||||
|
||||
The primary contingency for interface complexity is to restrict continuous modes
|
||||
to operate within polytopic invariants. Polytopes are state regions defined as
|
||||
intersections of linear half-spaces, which map directly to boolean predicates
|
||||
through linear inequality checks. This restriction ensures tractable synthesis
|
||||
while maintaining theoretical rigor, though at the cost of limiting
|
||||
expressiveness compared to arbitrary nonlinear regions. The discrete-continuous
|
||||
interface remains well-defined and verifiable with polytopic restrictions,
|
||||
providing a clear fallback position that preserves the core methodology.
|
||||
Conservative over-approximations offer an alternative approach: a nonlinear safe
|
||||
region can be inner-approximated by a polytope, sacrificing operational
|
||||
flexibility to maintain formal guarantees. The three-mode classification already
|
||||
structures the problem to minimize complex transitions, with critical safety
|
||||
properties concentrated in expulsory modes that can receive additional design
|
||||
attention.
|
||||
|
||||
Mitigation strategies focus on designing continuous controllers with discrete
|
||||
transitions as primary objectives from the outset. Rather than designing
|
||||
continuous control laws independently and verifying transitions post-hoc, the
|
||||
approach uses transition requirements as design constraints. Control barrier
|
||||
functions provide a systematic method to synthesize controllers that guarantee
|
||||
forward invariance of safe sets and convergence to transition boundaries. This
|
||||
design-for-verification approach reduces the likelihood that interface
|
||||
complexity becomes insurmountable. Focusing verification effort on expulsory
|
||||
modes---where safety is most critical---allows more complex analysis to be
|
||||
applied selectively rather than uniformly across all modes, concentrating
|
||||
computational resources where they matter most for safety assurance.
|
||||
|
||||
\subsection{Procedure Formalization Completeness}
|
||||
|
||||
The third assumption is that existing SmAHTR startup procedures contain
|
||||
sufficient detail and clarity for translation into temporal logic specifications.
|
||||
Nuclear operating procedures, while extensively detailed, were written for human
|
||||
operators who bring contextual understanding and adaptive reasoning to their
|
||||
interpretation. Procedures may contain implicit knowledge, ambiguous directives,
|
||||
or references to operator judgment that resist formalization in current
|
||||
specification languages. Underspecified timing constraints, ambiguous condition
|
||||
definitions, or gaps in operational coverage would cause synthesis to fail or
|
||||
produce incorrect automata. The risk is not merely that formalization is
|
||||
difficult, but that current procedures fundamentally lack the precision required
|
||||
for autonomous control, revealing a gap between human-oriented documentation and
|
||||
machine-executable specifications.
|
||||
|
||||
Several indicators would reveal formalization completeness problems early in the
|
||||
project. FRET realizability checks failing due to underspecified behaviors or
|
||||
conflicting requirements would indicate that procedures do not form a complete
|
||||
specification. Multiple valid interpretations of procedural steps with no clear
|
||||
resolution would demonstrate that procedure language is insufficiently precise
|
||||
for automated synthesis. Procedures referencing ``operator judgment,'' ``as
|
||||
appropriate,'' or similar discretionary language for critical decisions would
|
||||
explicitly identify points where human reasoning cannot be directly formalized.
|
||||
Domain experts unable to provide crisp answers to specification questions about
|
||||
edge cases would suggest that the procedures themselves do not fully define
|
||||
system behavior, relying instead on operator training and experience to fill
|
||||
gaps.
|
||||
|
||||
The contingency plan treats inadequate specification as itself a research
|
||||
contribution rather than a project failure. Documenting specific ambiguities
|
||||
encountered would create a taxonomy of formalization barriers: timing
|
||||
underspecification, missing preconditions, discretionary actions, and undefined
|
||||
failure modes. Each category would be analyzed to understand why current
|
||||
procedure-writing practices produce these gaps and what specification languages
|
||||
would need to address them. Proposed extensions to FRETish or similar
|
||||
specification languages would demonstrate how to bridge the gap between current
|
||||
procedures and the precision needed for autonomous control. The research output
|
||||
would shift from ``here is a complete autonomous controller'' to ``here is what
|
||||
formal autonomous control requires that current procedures do not provide, and
|
||||
here are language extensions to bridge that gap.'' This contribution remains
|
||||
valuable to both the nuclear industry and formal methods community, establishing
|
||||
clear requirements for next-generation procedure development and autonomous
|
||||
control specification languages.
|
||||
|
||||
Early-stage procedure analysis with domain experts provides the primary
|
||||
mitigation strategy. Collaboration through the University of Pittsburgh Cyber
|
||||
Energy Center enables identification and resolution of ambiguities before
|
||||
synthesis attempts, rather than discovering them during failed synthesis runs.
|
||||
Iterative refinement with reactor operators and control engineers can clarify
|
||||
procedural intent before formalization begins, reducing the risk of discovering
|
||||
insurmountable specification gaps late in the project. Comparison with
|
||||
procedures from multiple reactor designs---pressurized water reactors, boiling
|
||||
water reactors, and advanced designs---may reveal common patterns and standard
|
||||
ambiguities amenable to systematic resolution. This cross-design analysis would
|
||||
strengthen the generalizability of any proposed specification language
|
||||
extensions, ensuring they address industry-wide practices rather than
|
||||
SmAHTR-specific quirks.
|
||||
|
||||
\subsection{Hardware-in-the-Loop Integration Complexity}
|
||||
|
||||
The fourth assumption is that the ARCADE interface can provide stable real-time
|
||||
communication between Simulink simulation and Ovation control hardware at
|
||||
control rates required for reactor dynamics. Hardware-in-the-loop testing
|
||||
introduces timing constraints, communication latency, and platform compatibility
|
||||
challenges that are absent in pure simulation. Control rates for reactor systems
|
||||
typically range from 10-100 Hz for continuous control to millisecond response
|
||||
times for protection system actions. Control loop jitter, communication
|
||||
dropouts, or computational limitations in the Ovation PLC could prevent
|
||||
successful HIL validation even if the synthesized controller is theoretically
|
||||
correct. Real-time operating system constraints, network latency, and hardware
|
||||
execution speed may prove incompatible with verified timing assumptions embedded
|
||||
in the controller design.
|
||||
|
||||
Early indicators would identify hardware integration problems before they derail
|
||||
the entire validation effort. Communication dropouts or buffer overruns between ARCADE
|
||||
and Ovation would indicate that the interface cannot maintain stable real-time
|
||||
data exchange. The Ovation PLC proving unable to execute the synthesized
|
||||
automaton at required speed would reveal fundamental computational limitations
|
||||
of the target hardware platform. Timing analysis showing that hardware cannot
|
||||
meet real-time deadlines assumed during verification would demonstrate
|
||||
incompatibility between formal guarantees and physical implementation
|
||||
constraints.
|
||||
|
||||
The contingency plan is to demonstrate the controller in software-in-the-loop
|
||||
configuration with detailed timing analysis showing industrial hardware
|
||||
feasibility. Software-in-the-loop testing executes the complete verified
|
||||
controller in a real-time software environment that emulates hardware timing
|
||||
constraints without requiring physical hardware. Combined with worst-case
|
||||
execution time analysis of the synthesized automaton and continuous control
|
||||
algorithms, software-in-the-loop validation can provide strong evidence of
|
||||
implementability even without physical hardware demonstration. This approach
|
||||
maintains TRL 4 rather than TRL 5, but still validates
|
||||
the synthesis methodology and establishes a clear pathway to hardware
|
||||
deployment. The research contribution remains intact: demonstrating that formal
|
||||
hybrid control synthesis produces implementable controllers, with remaining
|
||||
barriers clearly identified as hardware integration challenges rather than
|
||||
fundamental methodological limitations.
|
||||
|
||||
Mitigation strategies leverage existing infrastructure and adopt early testing
|
||||
practices. ARCADE has been successfully used for reactor simulation HIL testing
|
||||
at the University of Pittsburgh, establishing feasibility in principle and
|
||||
providing institutional knowledge about common integration challenges. Conducting
|
||||
early integration testing during the synthesis phase, rather than deferring HIL
|
||||
attempts until late in the project, identifies timing constraints and
|
||||
communication requirements that can inform controller design. Early testing
|
||||
ensures that synthesized controllers are compatible with hardware limitations
|
||||
from the outset, rather than discovering incompatibilities after synthesis is
|
||||
complete. The Ovation platform supports multiple implementation approaches
|
||||
including function blocks, structured text, and ladder logic, which provides
|
||||
flexibility in how synthesized automata are realized and may enable workarounds
|
||||
if one implementation approach proves problematic.
|
||||
@ -1,3 +1,4 @@
|
||||
\newpage
|
||||
\section{State of the Art and Limits of Current Practice}
|
||||
|
||||
The principal aim of this research is to create autonomous reactor control
|
||||
@ -10,29 +11,6 @@ methods based approaches to building reactor control systems.
|
||||
|
||||
\subsection{Current Reactor Procedures and Operation}
|
||||
|
||||
Current generation nuclear power plants employ 3,600+ active NRC-licensed
|
||||
reactor operators in the United States. These operators are divided into Reactor
|
||||
Operators (ROs) who manipulate reactor controls and Senior Reactor Operators
|
||||
(SROs) who direct plant operations and serve as shift
|
||||
supervisors~\cite{10CFR55}. Staffing typically requires 2+ ROs with at least one
|
||||
SRO for current generation units. To become a reactor operator, an individual
|
||||
might spend up to six years to pass required training~\cite{princeton}.
|
||||
|
||||
The role of human operators is paradoxically both critical and
|
||||
problematic. Operators hold legal authority under 10 CFR Part 55 to make
|
||||
critical decisions including departing from normal regulations during
|
||||
emergencies. The Three Mile Island (TMI) accident demonstrated how
|
||||
``combination of personnel error, design deficiencies, and component
|
||||
failures'' led to partial meltdown when operators ``misread confusing
|
||||
and contradictory readings and shut off the emergency water
|
||||
system''~\cite{Kemeny1979}. The President's Commission on TMI identified
|
||||
a fundamental ambiguity: placing ``responsibility and accountability for
|
||||
safe power plant operations...on the licensee in all circumstances''
|
||||
without formal verification that operators can fulfill this
|
||||
responsibility under all conditions~\cite{Kemeny1979}. This tension
|
||||
between operational flexibility and safety assurance remains unresolved
|
||||
in current practice.
|
||||
|
||||
Nuclear plant procedures exist in a hierarchy: normal operating procedures for
|
||||
routine operations, abnormal operating procedures for off-normal conditions,
|
||||
Emergency Operating Procedures (EOPs) for design-basis accidents, Severe
|
||||
@ -91,6 +69,37 @@ decades of improvements in training and procedures, provides perhaps the
|
||||
most compelling motivation for formal automated control with
|
||||
mathematical safety guarantees.
|
||||
|
||||
Current generation nuclear power plants employ 3,600+ active NRC-licensed
|
||||
reactor operators in the United States. These operators are divided into Reactor
|
||||
Operators (ROs) who manipulate reactor controls and Senior Reactor Operators
|
||||
(SROs) who direct plant operations and serve as shift
|
||||
supervisors~\cite{10CFR55}. Staffing typically requires 2+ ROs with at least one
|
||||
SRO for current generation units~\cite{NRC WEBSITE IN ZOTERO FOR PRES}. To
|
||||
become a reactor operator, an individual spends several years to pass completed
|
||||
training~\cite{ALSO IN PRES FOLDER}. Current generation nuclear power plants
|
||||
employ 3,600+ active NRC-licensed reactor operators in the United States. These
|
||||
operators are divided into Reactor Operators (ROs) who manipulate reactor
|
||||
controls and Senior Reactor Operators (SROs) who direct plant operations and
|
||||
serve as shift supervisors~\cite{10CFR55}. Staffing typically requires 2+ ROs
|
||||
with at least one SRO for current generation units~\cite{NRC WEBSITE IN ZOTERO
|
||||
FOR PRES}. To become a reactor operator, an individual spends several years to
|
||||
pass completed training~\cite{ALSO IN PRES FOLDER}.
|
||||
|
||||
The role of these human operators is paradoxically both critical and
|
||||
problematic. Operators hold legal authority under 10 CFR Part 55 to make
|
||||
critical decisions including departing from normal regulations during
|
||||
emergencies. The Three Mile Island (TMI) accident demonstrated how ``combination
|
||||
of personnel error, design deficiencies, and component failures'' led to partial
|
||||
meltdown when operators ``misread confusing and contradictory readings and shut
|
||||
off the emergency water system''~\cite{Kemeny1979}. The President's Commission
|
||||
on TMI identified a fundamental ambiguity: placing ``responsibility and
|
||||
accountability for safe power plant operations...on the licensee in all
|
||||
circumstances'' without formal verification that operators can fulfill this
|
||||
responsibility under all conditions~\cite{Kemeny1979}.% CHECK THIS SOURCE...
|
||||
This tension between operational flexibility and safety assurance remains
|
||||
unresolved in current practice as the person responsible for reactor safety
|
||||
simultaneously is usually the root cause of a failure.
|
||||
|
||||
Multiple independent analyses converge on a striking statistic: 70--80\%
|
||||
of all nuclear power plant events are attributed to human error versus
|
||||
approximately 20\% to equipment failures~\cite{DOE-HDBK-1028-2009,WNA2020}. More
|
||||
@ -104,26 +113,31 @@ events involved active errors while 92\% were associated with latent errors
|
||||
persistence of this 70--80\% human error contribution despite four decades of
|
||||
continuous improvements in operator training, control room design, procedures,
|
||||
and human factors engineering. This suggests fundamental cognitive limitations
|
||||
rather than remediable deficiencies.
|
||||
rather than remediable deficiencies. %check all of these sources
|
||||
|
||||
The Three Mile Island Unit 2 accident on March 28, 1979 remains the definitive
|
||||
case study in human factors failures in nuclear operations. The accident began
|
||||
at 4:00 AM with a routine feedwater pump trip, escalating when a
|
||||
pressure-operated relief valve (PORV) stuck open---draining reactor
|
||||
coolant---but control room instrumentation showed only whether the valve had
|
||||
been commanded to close, not whether it actually closed. When Emergency Core
|
||||
Cooling System pumps automatically activated as designed, operators made the
|
||||
fateful decision to shut them down based on their incorrect assessment of plant
|
||||
conditions. The result was a massive loss of coolant accident and the core
|
||||
quickly began to overheat. During the emergency, operators faced more than 100
|
||||
simultaneous alarms, overwhelming their cognitive capacity~\cite{Kemeny1979}.
|
||||
The core suffered partial meltdown with 44\% of the fuel melting before the
|
||||
situation was stabilized. Quantitative risk analysis revealed the magnitude of
|
||||
failure in existing safety assessment methods: the actual core damage
|
||||
probability was approximately 5\% per year while Probabilistic Risk Assessment
|
||||
had predicted 0.01\% per year---a 500-fold underestimation. This
|
||||
dramatic failure demonstrated that human reliability could not be adequately
|
||||
assessed through expert judgment and historical data alone.
|
||||
%%%%% This seems like a bad paragraph. Doesn't really connect with the idea of
|
||||
%%%%% autonomy. Seems more like a design issue for the control room. With more
|
||||
%%%%% time it could be explained how doing things this way with requirements to
|
||||
%%%%% logic would catch that no indicator of actual valve position is a problem.
|
||||
% The Three Mile Island Unit 2 accident on March 28, 1979 remains the definitive
|
||||
% case study in human factors failures in nuclear operations. The accident began
|
||||
% at 4:00 AM with a routine feedwater pump trip, escalating when a
|
||||
% pressure-operated relief valve (PORV) stuck open---draining reactor
|
||||
% coolant---but control room instrumentation showed only whether the valve had
|
||||
% been commanded to close, not whether it actually closed. When Emergency Core
|
||||
% Cooling System pumps automatically activated as designed, operators made the
|
||||
% fateful decision to shut them down based on their incorrect assessment of plant
|
||||
% conditions. The result was a massive loss of coolant accident and the core
|
||||
% quickly began to overheat. During the emergency, operators faced more than 100
|
||||
% simultaneous alarms, overwhelming their cognitive capacity~\cite{Kemeny1979}.
|
||||
% The core suffered partial meltdown with 44\% of the fuel melting before the
|
||||
% situation was stabilized. Quantitative risk analysis revealed the magnitude of
|
||||
% failure in existing safety assessment methods: the actual core damage
|
||||
% probability was approximately 5\% per year while Probabilistic Risk Assessment
|
||||
% had predicted 0.01\% per year---a 500-fold underestimation. This
|
||||
% dramatic failure demonstrated that human reliability could not be adequately
|
||||
% assessed through expert judgment and historical data alone.
|
||||
% % how does autonomy fix these issues exactly? This seems like
|
||||
|
||||
\textbf{LIMITATION:} \textit{Human factors impose fundamental reliability
|
||||
limits that cannot be overcome through training alone.} Response time
|
||||
@ -143,7 +157,7 @@ project represents the most advanced application of formal methods to nuclear
|
||||
reactor control systems to date. HARDENS aimed to address the nuclear industry's
|
||||
fundamental dilemma: existing U.S. nuclear control rooms rely on analog
|
||||
technologies from the 1950s--60s. This technology is woefully out of date
|
||||
compared to modern control technoligies, and incurs significant risk and cost to
|
||||
compared to modern control technologies, and incurs significant risk and cost to
|
||||
plant operation. The NRC contracted Galois to demonstrate that Model-Based
|
||||
Systems Engineering and formal methods could design, verify, and implement a
|
||||
complex protection system meeting regulatory criteria at a fraction of typical
|
||||
@ -151,12 +165,14 @@ cost. The project delivered a Reactor Trip System (RTS) implementation with full
|
||||
traceability from NRC Request for Proposals and IEEE standards through
|
||||
formal architecture specifications to formally verified binaries and
|
||||
hardware running on FPGA demonstrator boards.
|
||||
%%% did it actually do an FPGA demonstration? Dubious.
|
||||
|
||||
HARDENS employed an array of formal methods tools and techniques across the
|
||||
verification hierarchy. High-level specifications used Lando, SysMLv2, and FRET
|
||||
(NASA JPL's Formal Requirements Elicitation Tool) to capture stakeholder
|
||||
requirements, domain engineering, certification requirements, and safety
|
||||
requirements. Requirements were formally analyzed for consistency, completeness,
|
||||
requirements. % this sentence is long af
|
||||
Requirements were formally analyzed for consistency, completeness,
|
||||
and realizability using SAT and SMT solvers. Executable formal models employed
|
||||
Cryptol to create an executable behavioral model of the entire RTS including all
|
||||
subsystems, components, and limited digital twin models of sensors, actuators,
|
||||
@ -169,14 +185,13 @@ Despite its accomplishments, HARDENS has a fundamental limitation directly
|
||||
relevant to hybrid control synthesis: the project addressed only discrete
|
||||
digital control logic without modeling or verifying continuous reactor dynamics.
|
||||
The Reactor Trip System specification and formal verification covered discrete
|
||||
state transitions (trip/no-trip decisions), digital sensor input processing
|
||||
through discrete logic, and discrete actuation outputs (reactor trip commands).
|
||||
However, the project did not address continuous dynamics of nuclear reactor
|
||||
physics. Real reactor safety depends on the interaction between continuous
|
||||
processes (temperature, pressure, neutron flux evolving according to
|
||||
differential equations) and discrete control decisions (trip/no-trip, valve
|
||||
open/close, pump on/off). HARDENS verified the discrete controller in isolation
|
||||
but not the closed-loop hybrid system behavior.
|
||||
state transitions such as trip/no-trip decisions, digital sensor input
|
||||
processing through discrete logic, and discrete actuation outputs such as
|
||||
reactor trip commands. However, the project did not address continuous dynamics
|
||||
of nuclear reactor physics. Real reactor safety depends on the interaction
|
||||
between continuous processes such as temperature, pressure, neutron flux
|
||||
evolving due to discrete control decisions. HARDENS verified the discrete
|
||||
controller in isolation but not the closed-loop hybrid system behavior.
|
||||
|
||||
\textbf{LIMITATION:} \textit{HARDENS addressed discrete control logic without
|
||||
continuous dynamics or hybrid system verification.} Verifying discrete control
|
||||
|
||||
76
Zettelkasten/Fleeting Notes/Weekly/2025_49.md
Normal file
76
Zettelkasten/Fleeting Notes/Weekly/2025_49.md
Normal file
@ -0,0 +1,76 @@
|
||||
---
|
||||
id: 2025-49
|
||||
title: Weekly — 2025-12-03
|
||||
type: Weekly
|
||||
created: 2025-12-03T21:01:29-05:00
|
||||
modified: 2025-12-03T21:01:29-05:00
|
||||
tags: [weekly]
|
||||
---
|
||||
|
||||
# Weekly - 2025 CW 49 (Wed 2025-12-03)
|
||||
|
||||
## Accomplishments
|
||||
|
||||
### ERLM
|
||||
- ✓ Draft Presentations
|
||||
|
||||
### Chair-Search
|
||||
- ✓ Make list of tasks for contact about student groups
|
||||
|
||||
## Pushed or Rescheduled
|
||||
|
||||
The following tasks had their due dates modified during the past week:
|
||||
|
||||
- Review and edit Goals and Outcomes section
|
||||
- Review and edit State of the Art section
|
||||
- Review and edit Research Approach section
|
||||
- Review and edit Metrics of Success section
|
||||
- Review and edit Risks and Contingencies section
|
||||
- Review and edit Broader Impacts section
|
||||
- Review and edit Budget section
|
||||
- Review and edit Schedule section
|
||||
- Verify RFP compliance for all sections
|
||||
- Final proofread and polish entire proposal
|
||||
- Review and edit Literature Review section
|
||||
- Review and edit Methodology Details section
|
||||
- Review and edit Expected Contributions section
|
||||
- Review and edit Timeline and Milestones section
|
||||
- Review and edit Team Qualifications section
|
||||
- Review and edit References section
|
||||
- Review and edit Appendices
|
||||
|
||||
## Cancelled or Deleted
|
||||
|
||||
No tasks were cancelled or deleted during this period.
|
||||
|
||||
## To Do
|
||||
|
||||
### Due This Week (Dec 4-10)
|
||||
|
||||
**ERLM Project - Editing Tasks (Due Tomorrow: Dec 4)**
|
||||
|
||||
All of the following editing tasks are due tomorrow and are high priority:
|
||||
|
||||
- Review and edit Goals and Outcomes section (Urgency: 22.1) ⚡ ACTIVE
|
||||
- Review and edit State of the Art section (Urgency: 22.1) ⚡ ACTIVE
|
||||
- Review and edit Research Approach section (Urgency: 18.1)
|
||||
- Review and edit Metrics of Success section (Urgency: 18.1)
|
||||
- Review and edit Risks and Contingencies section (Urgency: 18.1)
|
||||
- Review and edit Broader Impacts section (Urgency: 18.1)
|
||||
- Review and edit Budget section (Urgency: 18.1)
|
||||
- Review and edit Schedule section (Urgency: 18.1)
|
||||
- Verify RFP compliance for all sections (Urgency: 18.1)
|
||||
- Final proofread and polish entire proposal (Urgency: 18.1)
|
||||
- Review and edit Literature Review section (Urgency: 18.1)
|
||||
- Review and edit Methodology Details section (Urgency: 18.1)
|
||||
- Review and edit Expected Contributions section (Urgency: 18.1)
|
||||
- Review and edit Timeline and Milestones section (Urgency: 18.1)
|
||||
- Review and edit Team Qualifications section (Urgency: 18.1)
|
||||
- Review and edit References section (Urgency: 18.1)
|
||||
- Review and edit Appendices (Urgency: 18.1)
|
||||
- Update abstract based on final content (Urgency: 18.1)
|
||||
- Compile final PDF submission (Urgency: 18.1)
|
||||
|
||||
### High Priority
|
||||
|
||||
All high-priority tasks are already listed above in the "Due This Week" section.
|
||||
Loading…
x
Reference in New Issue
Block a user