Editorial pass: tactical, operational, and strategic improvements

Tactical (sentence-level):
- Strengthened weak verbs and passive constructions
- Improved issue-point positioning (old info first, new info in stress position)
- Removed unnecessary hedging phrases
- Fixed active/passive voice for clarity

Operational (paragraph/section):
- Added transition sentences between major subsections
- Strengthened flow between State of the Art and Research Approach
- Added connecting tissue between continuous controller types
- Improved coherence within outcomes section

Strategic (document-level):
- Made 'what's new' explicit with highlighted innovation statement
- Added summary paragraph to State of the Art defining the verification gap
- Strengthened connections between sections for Heilmeier alignment
- Clarified how the three-layer approach unifies existing tools
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% GOAL PARAGRAPH % GOAL PARAGRAPH
The goal of this research is to develop a methodology for creating autonomous This research develops a methodology for creating autonomous control systems
control systems with event-driven control laws that have guarantees of safe and with event-driven control laws that guarantee safe and correct behavior.
correct behavior.
% INTRODUCTORY PARAGRAPH Hook % INTRODUCTORY PARAGRAPH Hook
Nuclear power relies on extensively trained operators who follow detailed Nuclear power relies on extensively trained operators who follow detailed
written procedures to manage reactor control. Based on these procedures and written procedures to manage reactor control. Operators interpret plant
operators' interpretation of plant conditions, operators make critical decisions conditions and make critical decisions about when to switch between control
about when to switch between control objectives. objectives.
% Gap % Gap
But, reliance on human operators has created an economic challenge for This reliance on human operators creates an economic challenge for
next-generation nuclear power plants. Small modular reactors face significantly next-generation nuclear power plants. Small modular reactors face per-megawatt
higher per-megawatt staffing costs than conventional plants. Autonomous control staffing costs that significantly exceed those of conventional plants. These
systems are needed that can safely manage complex operational sequences with the economic constraints demand autonomous control systems that safely manage
same assurance as human-operated systems, but without constant supervision. complex operational sequences with the same assurance as human-operated systems,
but without constant supervision.
% APPROACH PARAGRAPH Solution % APPROACH PARAGRAPH Solution
To address this need, we will combine formal methods from computer science with We will combine formal methods from computer science with control theory to
control theory to build hybrid control systems that are correct by construction. build hybrid control systems that are correct by construction.
% Rationale % Rationale
Hybrid systems use discrete logic to switch between continuous control modes, Hybrid systems use discrete logic to switch between continuous control modes,
similar to how operators change control strategies. Existing formal methods mirroring how operators change control strategies. Existing formal methods
generate provably correct switching logic but cannot handle continuous dynamics generate provably correct switching logic but cannot handle continuous dynamics
during transitions, while traditional control theory verifies continuous during transitions. Traditional control theory verifies continuous behavior but
behavior but lacks tools for proving discrete switching correctness. lacks tools for proving discrete switching correctness.
% Hypothesis and Technical Approach % Hypothesis and Technical Approach
We will bridge this gap through a three-stage methodology. First, we will A three-stage methodology will bridge this gap. First, we translate written
translate written operating procedures into temporal logic specifications using operating procedures into temporal logic specifications using NASA's Formal
NASA's Formal Requirements Elicitation Tool (FRET), which structures Requirements Elicitation Tool (FRET). FRET structures requirements into scope,
requirements into scope, condition, component, timing, and response elements. condition, component, timing, and response elements, enabling realizability
This structured approach enables realizability checking to identify conflicts checking that identifies conflicts and ambiguities before implementation.
and ambiguities in procedures before implementation. Second, we will synthesize Second, we synthesize discrete mode switching logic using reactive synthesis to
discrete mode switching logic using reactive synthesis generate deterministic automata that are provably correct by construction.
to generate deterministic automata that are provably Third, we develop continuous controllers for each discrete mode using standard
correct by construction. Third, we will develop continuous control theory and reachability analysis. We classify continuous modes based on
controllers for each discrete mode using standard control theory and their transition objectives, then employ assume-guarantee contracts and barrier
reachability analysis. We will classify continuous modes based on their certificates to prove that mode transitions occur safely and as the
transition objectives, and then employ assume-guarantee contracts and barrier deterministic automata specify. Local verification of continuous modes becomes
certificates to prove that mode transitions occur safely and as defined by the possible without global trajectory analysis across the entire hybrid system. An
deterministic automata. This compositional approach enables local verification Emerson Ovation control system will demonstrate this methodology.
of continuous modes without requiring global trajectory analysis across the
entire hybrid system. We will demonstrate this on an Emerson Ovation control system.
% Pay-off % Pay-off
This approach will demonstrate autonomous control can be used for complex This approach demonstrates that autonomous control can manage complex nuclear
nuclear power operations while maintaining safety guarantees. power operations while maintaining safety guarantees.
% OUTCOMES PARAGRAPHS % OUTCOMES PARAGRAPHS
If this research is successful, we will be able to do the following: If this research is successful, we will be able to do the following:
@ -52,31 +50,32 @@ If this research is successful, we will be able to do the following:
\item \textit{Synthesize written procedures into verified control logic.} \item \textit{Synthesize written procedures into verified control logic.}
% Strategy % Strategy
We will develop a methodology for converting written operating procedures We will develop a methodology for converting written operating procedures
into formal specifications. These specifications will be synthesized into into formal specifications. Reactive synthesis tools will then generate
discrete control logic using reactive synthesis tools. discrete control logic from these specifications.
% Outcome % Outcome
Control engineers will be able to generate mode-switching controllers from Control engineers will generate mode-switching controllers from regulatory
regulatory procedures with little formal methods expertise, reducing procedures with minimal formal methods expertise, reducing barriers to
barriers to high-assurance control systems. high-assurance control systems.
% OUTCOME 2 Title % OUTCOME 2 Title
\item \textit{Verify continuous control behavior across mode transitions. } \item \textit{Verify continuous control behavior across mode transitions.}
% Strategy % Strategy
We will develop methods using reachability analysis to ensure continuous control modes Reachability analysis will ensure continuous control modes satisfy discrete
satisfy discrete transition requirements. transition requirements.
% Outcome % Outcome
Engineers will be able to design continuous controllers using standard Engineers will design continuous controllers using standard practices while
practices while ensuring system correctness and proving mode transitions ensuring system correctness, proving that mode transitions occur safely at
occur safely at the right times. the right times.
% OUTCOME 3 Title % OUTCOME 3 Title
\item \textit{Demonstrate autonomous reactor startup control with safety \item \textit{Demonstrate autonomous reactor startup control with safety
guarantees. } guarantees.}
% Strategy % Strategy
We will implement this methodology on a small modular reactor simulation A small modular reactor simulation using industry-standard control hardware
using industry-standard control hardware. % Outcome will implement this methodology.
Control engineers will be able to implement high-assurance autonomous % Outcome
controls on industrial platforms they already use, enabling users to Control engineers will implement high-assurance autonomous controls on
achieve autonomy without retraining costs or developing new equipment. industrial platforms they already use, enabling autonomy without retraining
costs or developing new equipment.
\end{enumerate} \end{enumerate}

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@ -1,9 +1,8 @@
\section{Goals and Outcomes} \section{Goals and Outcomes}
% GOAL PARAGRAPH % GOAL PARAGRAPH
The goal of this research is to develop a methodology for creating autonomous This research develops a methodology for creating autonomous hybrid control
hybrid control systems with mathematical guarantees of safe and correct systems with mathematical guarantees of safe and correct behavior.
behavior.
% INTRODUCTORY PARAGRAPH Hook % INTRODUCTORY PARAGRAPH Hook
Nuclear power plants require the highest levels of control system reliability, Nuclear power plants require the highest levels of control system reliability,
@ -22,26 +21,27 @@ Small modular reactors, in particular, face per-megawatt staffing costs far
exceeding those of conventional plants and threaten their economic viability. exceeding those of conventional plants and threaten their economic viability.
% Critical Need % Critical Need
What is needed is a method to create autonomous control systems that safely The nuclear industry needs autonomous control systems that safely manage complex
manage complex operational sequences with the same assurance as human-operated operational sequences with the same assurance as human-operated systems, but
systems, but without constant human supervision. without constant human supervision.
% APPROACH PARAGRAPH Solution % APPROACH PARAGRAPH Solution
To address this need, we will combine formal methods with control theory to We will combine formal methods with control theory to build hybrid control
build hybrid control systems that are correct by construction. systems that are correct by construction.
% Rationale % Rationale
Hybrid systems use discrete logic to switch between continuous control modes, Hybrid systems use discrete logic to switch between continuous control modes,
mirroring how operators change control strategies. Existing formal methods can mirroring how operators change control strategies. Existing formal methods
generate provably correct switching logic from written requirements, but they generate provably correct switching logic from written requirements but cannot
cannot handle the continuous dynamics that occur during transitions between handle the continuous dynamics that occur during transitions between modes.
modes. Meanwhile, traditional control theory can verify continuous behavior but Traditional control theory verifies continuous behavior but lacks tools for
lacks tools for proving correctness of discrete switching decisions. proving correctness of discrete switching decisions. This gap between discrete
and continuous verification prevents end-to-end correctness guarantees.
% Hypothesis % Hypothesis
By synthesizing discrete mode transitions directly from written operating Our approach closes this gap by synthesizing discrete mode transitions directly
procedures and verifying continuous behavior between transitions, we can create from written operating procedures and verifying continuous behavior between
hybrid control systems with end-to-end correctness guarantees. If existing transitions. If existing procedures can be formalized into logical
procedures can be formalized into logical specifications and continuous dynamics specifications and continuous dynamics verified against transition requirements,
verified against transition requirements, then autonomous controllers can be then autonomous controllers can be built that are provably free from design
built that are provably free from design defects. defects.
% Pay-off % Pay-off
This approach will enable autonomous control in nuclear power plants while This approach will enable autonomous control in nuclear power plants while
maintaining the high safety standards required by the industry. maintaining the high safety standards required by the industry.
@ -74,10 +74,10 @@ If this research is successful, we will be able to do the following:
\item \textbf{Verify continuous control behavior across mode transitions.} \item \textbf{Verify continuous control behavior across mode transitions.}
% Strategy % Strategy
We will establish methods for analyzing continuous control modes to ensure We will establish methods for analyzing continuous control modes to ensure
they satisfy discrete transition requirements. Using classical control they satisfy discrete transition requirements. Classical control theory for
theory for linear systems and reachability analysis for nonlinear dynamics, linear systems and reachability analysis for nonlinear dynamics will verify
we will verify that each continuous mode safely reaches its intended that each continuous mode safely reaches its intended transitions.
transitions. % Outcome
Engineers will design continuous controllers using standard practices while Engineers will design continuous controllers using standard practices while
iterating to ensure broader system correctness, proving that mode iterating to ensure broader system correctness, proving that mode
transitions occur safely and at the correct times. transitions occur safely and at the correct times.
@ -99,8 +99,18 @@ If this research is successful, we will be able to do the following:
\end{enumerate} \end{enumerate}
% IMPACT PARAGRAPH Innovation % IMPACT PARAGRAPH Innovation
The innovation in this work is unifying discrete synthesis with continuous These three outcomes—procedure translation, continuous verification, and
hardware demonstration—together establish a complete methodology from regulatory
documents to deployed systems.
\textbf{The key innovation} unifies discrete synthesis with continuous
verification to enable end-to-end correctness guarantees for hybrid systems. verification to enable end-to-end correctness guarantees for hybrid systems.
While formal methods can verify discrete logic and control theory can verify
continuous dynamics, no existing methodology bridges both with compositional
guarantees. This work establishes that bridge by treating discrete specifications
as contracts that continuous controllers must satisfy, enabling verification of
each layer independently while guaranteeing correct composition.
% Outcome Impact % Outcome Impact
If successful, control engineers will create autonomous controllers from If successful, control engineers will create autonomous controllers from
existing procedures with mathematical proof of correct behavior. High-assurance existing procedures with mathematical proof of correct behavior. High-assurance

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@ -1,11 +1,11 @@
\section{State of the Art and Limits of Current Practice} \section{State of the Art and Limits of Current Practice}
The principal aim of this research is to create autonomous reactor control This research aims to create autonomous reactor control systems that are
systems that are tractably safe. To understand what is being automated, we must tractably safe. Understanding what we automate requires first understanding how
first understand how nuclear reactors are operated today. This section examines nuclear reactors operate today. This section examines reactor operators and the
reactor operators and the operating procedures we aim to leverage, then operating procedures we leverage, investigates limitations of human-based
investigates limitations of human-based operation, and concludes with current operation, and concludes with current formal methods approaches to reactor
formal methods approaches to reactor control systems. control systems.
\subsection{Current Reactor Procedures and Operation} \subsection{Current Reactor Procedures and Operation}
@ -14,8 +14,8 @@ routine operations, abnormal operating procedures for off-normal conditions,
Emergency Operating Procedures (EOPs) for design-basis accidents, Severe Emergency Operating Procedures (EOPs) for design-basis accidents, Severe
Accident Management Guidelines (SAMGs) for beyond-design-basis events, and Accident Management Guidelines (SAMGs) for beyond-design-basis events, and
Extensive Damage Mitigation Guidelines (EDMGs) for catastrophic damage Extensive Damage Mitigation Guidelines (EDMGs) for catastrophic damage
scenarios. These procedures must comply with 10 CFR 50.34(b)(6)(ii) and are scenarios. These procedures must comply with 10 CFR 50.34(b)(6)(ii). NUREG-0899
developed using guidance from NUREG-0899~\cite{NUREG-0899, 10CFR50.34}, but their provides guidance for their development~\cite{NUREG-0899, 10CFR50.34}, but this
development relies fundamentally on expert judgment and simulator validation development relies fundamentally on expert judgment and simulator validation
rather than formal verification. Procedures undergo technical evaluation, rather than formal verification. Procedures undergo technical evaluation,
simulator validation testing, and biennial review as part of operator simulator validation testing, and biennial review as part of operator
@ -30,9 +30,9 @@ and completeness.} Current procedure development relies on expert judgment and
simulator validation. No mathematical proof exists that procedures cover all simulator validation. No mathematical proof exists that procedures cover all
possible plant states, that required actions can be completed within available possible plant states, that required actions can be completed within available
timeframes, or that transitions between procedure sets maintain safety timeframes, or that transitions between procedure sets maintain safety
invariants. Paper-based procedures cannot ensure correct application, and even invariants. Paper-based procedures cannot ensure correct application. Even
computer-based procedure systems lack the formal guarantees that automated computer-based procedure systems lack the formal guarantees automated reasoning
reasoning could provide. could provide.
Nuclear plants operate with multiple control modes: automatic control, where the Nuclear plants operate with multiple control modes: automatic control, where the
reactor control system maintains target parameters through continuous reactivity reactor control system maintains target parameters through continuous reactivity
@ -55,8 +55,11 @@ startup/shutdown sequences, mode transitions, and procedure implementation.
\subsection{Human Factors in Nuclear Accidents} \subsection{Human Factors in Nuclear Accidents}
Current-generation nuclear power plants employ over 3,600 active NRC-licensed Having established how nuclear plants currently operate through written
reactor operators in the United States~\cite{operator_statistics}. These procedures and human operators, we now examine why this human-centered approach
poses fundamental limitations. Current-generation nuclear power plants employ
over 3,600 active NRC-licensed reactor operators in the United
States~\cite{operator_statistics}. These
operators divide into Reactor Operators (ROs), who manipulate reactor controls, operators divide into Reactor Operators (ROs), who manipulate reactor controls,
and Senior Reactor Operators (SROs), who direct plant operations and serve as and Senior Reactor Operators (SROs), who direct plant operations and serve as
shift supervisors~\cite{10CFR55}. Staffing typically requires at least two ROs shift supervisors~\cite{10CFR55}. Staffing typically requires at least two ROs
@ -96,6 +99,12 @@ error contribution despite four decades of improvements demonstrates that these
limitations are fundamental rather than a remediable part of human-driven control. limitations are fundamental rather than a remediable part of human-driven control.
\subsection{Formal Methods} \subsection{Formal Methods}
The persistent human error problem motivates exploration of formal methods to
provide mathematical guarantees of correctness that human-centered approaches
cannot achieve. This subsection examines recent formal methods work in nuclear
control and identifies their limitations for autonomous hybrid systems.
\subsubsection{HARDENS} \subsubsection{HARDENS}
The High Assurance Rigorous Digital Engineering for Nuclear Safety (HARDENS) The High Assurance Rigorous Digital Engineering for Nuclear Safety (HARDENS)
@ -180,11 +189,11 @@ liveness property.
%source: https://symbolaris.com/logic/dL.html %source: https://symbolaris.com/logic/dL.html
While dL allows for the specification of these liveness and safety properties, While dL allows for the specification of these liveness and safety properties,
actually proving them for a given hybrid system is quite difficult. Automated actually proving them for a given hybrid system is difficult. Automated proof
proof assistants such as KeYmaera X exist to help develop proofs of systems assistants such as KeYmaera X exist to help develop proofs of systems using dL,
using dL, but so far have been insufficient for reasonably complex hybrid but have been insufficient for reasonably complex hybrid systems. The main issue
systems. The main issue behind creating system proofs using dL is state space behind creating system proofs using dL is state space explosion and
explosion and non-terminating solutions. non-terminating solutions.
%Source: that one satellite tracking paper that has the problem with the %Source: that one satellite tracking paper that has the problem with the
%gyroscopes overloding and needing to dump speed all the time %gyroscopes overloding and needing to dump speed all the time
Approaches have been made to alleviate Approaches have been made to alleviate
@ -194,7 +203,21 @@ methods, but are far from a complete methodology to design systems with.
Instead, these approaches have been used on systems that have been designed a Instead, these approaches have been used on systems that have been designed a
priori, and require expert knowledge to create the system proofs. priori, and require expert knowledge to create the system proofs.
%Maybe a limitation here? Something about dL doesn't scale or help in design \textbf{LIMITATION:} \textit{Logic-based hybrid system verification has not
%very much, so the limitation is that logic based hybrid system approaches have scaled to system design.} While dL and related approaches can verify hybrid
%not been used in the DESIGN of autonomous controllers, only in the analysis of systems post-hoc, they require expert knowledge and have been applied only to
%systems that already exist. systems designed a priori. State space explosion prevents their use in the
design loop for complex systems like nuclear reactor startup procedures.
\subsection{Summary: The Verification Gap}
Current practice reveals a fundamental gap: human operators provide operational
flexibility but introduce persistent reliability limitations, while formal
methods provide correctness guarantees but have not scaled to complete hybrid
control design. HARDENS verified discrete logic without continuous dynamics.
Differential dynamic logic can express hybrid properties but requires
post-design expert analysis. No existing methodology synthesizes provably
correct hybrid controllers from operational procedures with verification
integrated into the design process. This gap—between discrete-only formal
methods and post-hoc hybrid verification—defines the challenge this research
addresses.

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@ -15,22 +15,21 @@
% ---------------------------------------------------------------------------- % ----------------------------------------------------------------------------
% 1. INTRODUCTION AND HYBRID SYSTEMS DEFINITION % 1. INTRODUCTION AND HYBRID SYSTEMS DEFINITION
% ---------------------------------------------------------------------------- % ----------------------------------------------------------------------------
Previous approaches to autonomous control have verified Previous approaches to autonomous control verified discrete switching logic or
discrete switching logic or continuous control behavior, but not both continuous control behavior, but not both simultaneously. Today's continuous
simultaneously. Validation of continuous controllers today consists of controller validation consists of extensive simulation trials. Human operators
extensive simulation trials. Discrete switching logic for routine operation drive discrete switching logic for routine operation; their evaluation includes
has been driven by human operators, whose evaluation includes simulated simulated control room testing and human factors research. Neither method
control room testing and human factors research. Neither method, despite provides rigorous guarantees of control system behavior, despite being
being extremely resource intensive, provides rigorous guarantees of control extremely resource intensive. HAHACS bridges this gap by composing formal
system behavior. HAHACS bridges this gap by composing formal methods from methods from computer science with control-theoretic verification, formalizing
computer science with control-theoretic verification, formalizing reactor reactor operations using the framework of hybrid automata.
operations using the framework of hybrid automata.
The challenge of hybrid system verification lies in the interaction between The challenge of hybrid system verification lies in the interaction between
discrete and continuous dynamics. Discrete transitions change the governing discrete and continuous dynamics. Discrete transitions change the governing
vector field, creating discontinuities in the system's behavior. Traditional vector field, creating discontinuities in the system's behavior. Traditional
verification techniques designed for purely discrete or purely continuous verification techniques designed for purely discrete or purely continuous
systems cannot handle this interaction directly.Our methodology addresses this systems cannot handle this interaction directly. Our methodology addresses this
challenge through decomposition. We verify discrete switching logic and challenge through decomposition. We verify discrete switching logic and
continuous mode behavior separately, then compose these guarantees to reason continuous mode behavior separately, then compose these guarantees to reason
about the complete hybrid system. This two-layer approach mirrors the structure about the complete hybrid system. This two-layer approach mirrors the structure
@ -38,10 +37,10 @@ of reactor operations themselves: discrete supervisory logic determines which
control mode is active, while continuous controllers govern plant behavior control mode is active, while continuous controllers govern plant behavior
within each mode. within each mode.
To build a high-assurance hybrid autonomous control system (HAHACS), we must Building a high-assurance hybrid autonomous control system (HAHACS) requires
first establish a mathematical description of the system. This work draws on first establishing a mathematical description of the system. This work draws on
automata theory, temporal logic, and control theory. A hybrid system is a automata theory, temporal logic, and control theory. A hybrid system is a
dynamical system that has both continuous and discrete states. The specific type dynamical system with both continuous and discrete states. The specific type
of system discussed in this proposal is a continuous autonomous hybrid system. of system discussed in this proposal is a continuous autonomous hybrid system.
This means that the system does not have external input and that continuous This means that the system does not have external input and that continuous
states do not change instantaneously when discrete states change. For our states do not change instantaneously when discrete states change. For our
@ -73,9 +72,13 @@ where:
The creation of a HAHACS amounts to the construction of such a tuple together The creation of a HAHACS amounts to the construction of such a tuple together
with proof artifacts demonstrating that the intended behavior of the control with proof artifacts demonstrating that the intended behavior of the control
system is satisfied by its actual implementation. This approach is tractable now system is satisfied by its actual implementation.
because the infrastructure for each component has matured. The novelty is not in
the individual pieces, but in the architecture that connects them. By defining \textbf{What is new:} This approach is tractable now because the infrastructure
for each component has matured, but no existing work composes them for
end-to-end hybrid system verification. The novelty lies in the architecture that
connects discrete synthesis with continuous verification through well-defined
interfaces. By defining
entry, exit, and safety conditions at the discrete level first, we transform the entry, exit, and safety conditions at the discrete level first, we transform the
intractable problem of global hybrid verification into a collection of local intractable problem of global hybrid verification into a collection of local
verification problems with clear interfaces. Verification is performed per mode verification problems with clear interfaces. Verification is performed per mode
@ -145,8 +148,14 @@ complex reactor operations.
% ---------------------------------------------------------------------------- % ----------------------------------------------------------------------------
\subsection{System Requirements, Specifications, and Discrete Controllers} \subsection{System Requirements, Specifications, and Discrete Controllers}
Human control of nuclear power can be divided into three different scopes:
strategic, operational, and tactical. Strategic control is high-level and Having defined the hybrid system mathematical framework, we now establish how to
construct such systems from existing operational knowledge. The key insight is
that nuclear operations already have a natural hybrid structure that maps
directly to the automaton formalism.
Human control of nuclear power divides into three scopes: strategic,
operational, and tactical. Strategic control is high-level and
long-term decision making for the plant. This level has objectives that are long-term decision making for the plant. This level has objectives that are
complex and economic in scale, such as managing labor needs and supply chains to complex and economic in scale, such as managing labor needs and supply chains to
optimize scheduled maintenance and downtime. The time scale at this level is optimize scheduled maintenance and downtime. The time scale at this level is
@ -355,8 +364,9 @@ according to operating procedures.
\subsection{Continuous Control Modes} \subsection{Continuous Control Modes}
The synthesis of the discrete operational controller is only half of an With the discrete controller synthesized and provably correct, we turn to the
autonomous controller. These control systems are hybrid, with both discrete and continuous dynamics that execute within each discrete mode. The synthesis of the
discrete operational controller is only half of an autonomous controller. These control systems are hybrid, with both discrete and
continuous components. This section describes the continuous control modes that continuous components. This section describes the continuous control modes that
execute within each discrete state, and how we verify that they satisfy the execute within each discrete state, and how we verify that they satisfy the
requirements imposed by the discrete layer. It is important to clarify the scope requirements imposed by the discrete layer. It is important to clarify the scope
@ -478,8 +488,10 @@ appropriate to the fidelity of the reactor models available.
\subsubsection{Stabilizing Modes} \subsubsection{Stabilizing Modes}
Stabilizing modes are continuous controllers with an objective of maintaining a While transitory modes drive the system toward exit conditions, stabilizing
particular discrete state indefinitely. Rather than driving the system toward an modes maintain the system within a desired operating region. Stabilizing modes
are continuous controllers with an objective of maintaining a particular
discrete state indefinitely. Rather than driving the system toward an
exit condition, they keep the system within a safe operating region. Examples exit condition, they keep the system within a safe operating region. Examples
include steady-state power operation, hot standby, and load-following at include steady-state power operation, hot standby, and load-following at
constant power level. Reachability analysis for stabilizing modes may not be a constant power level. Reachability analysis for stabilizing modes may not be a
@ -535,8 +547,9 @@ controller.
\subsubsection{Expulsory Modes} \subsubsection{Expulsory Modes}
Expulsory modes are continuous controllers responsible for Transitory and stabilizing modes handle nominal operations. When the plant
ensuring safety when failures occur. They are designed for robustness rather deviates from expected behavior, expulsory modes take over. Expulsory modes are
continuous controllers responsible for ensuring safety when failures occur. They are designed for robustness rather
than optimality. The control objective is to drive the plant to a safe shutdown than optimality. The control objective is to drive the plant to a safe shutdown
state from potentially anywhere in the state space, under degraded or uncertain state from potentially anywhere in the state space, under degraded or uncertain
dynamics. Examples include emergency core cooling, reactor SCRAM sequences, and dynamics. Examples include emergency core cooling, reactor SCRAM sequences, and

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@ -22,9 +22,9 @@ approximately 23--30\% of the total levelized cost of electricity, translating
to \$21--28 billion annually for projected datacenter demand. to \$21--28 billion annually for projected datacenter demand.
This research directly addresses the multi-billion-dollar O\&M cost challenge This research directly addresses the multi-billion-dollar O\&M cost challenge
through high-assurance autonomous control. Current nuclear operations require through the high-assurance autonomous control methodology developed in this
full control room staffing for each reactor, whether large conventional units or work. Current nuclear operations require full control room staffing for each
small modular designs. These staffing requirements drive the high O\&M costs reactor, whether large conventional units or small modular designs. These staffing requirements drive the high O\&M costs
that make nuclear power economically challenging, particularly for smaller that make nuclear power economically challenging, particularly for smaller
reactor designs where the same staffing overhead must be spread across lower reactor designs where the same staffing overhead must be spread across lower
power output. Synthesizing provably correct hybrid controllers from formal power output. Synthesizing provably correct hybrid controllers from formal