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@ -156,40 +156,9 @@ considerations: integration with legacy systems, human-system interaction in
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realistic operational contexts, and regulatory acceptance of formal methods as
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realistic operational contexts, and regulatory acceptance of formal methods as
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primary assurance evidence remain as significant challenges.
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primary assurance evidence remain as significant challenges.
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\subsubsection{Temporal Logic and Formal Specification}
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\subsubsection{Sequent Calculus and Differential Dynamic Logic}
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A separate line of work
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Formal verification of any system requires a precise language for stating
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extends temporal logics to verify hybrid systems
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what the system must do. Temporal logic provides this language by extending
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classical propositional logic with operators that express properties over
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time. Where propositional logic can state that a condition is true or false,
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temporal logic can state that a condition must always hold, must eventually
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hold, or must hold until some other condition is met. This expressiveness
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makes temporal logic the foundation for specifying reactive systems---systems
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that continuously interact with their environment and must satisfy ongoing
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behavioral requirements.
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For nuclear control applications, temporal logic captures exactly the kinds
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of properties that matter: safety properties (``the reactor never enters an
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unsafe configuration''), liveness properties (``the system eventually reaches
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operating temperature''), and response properties (``if coolant pressure
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drops, shutdown initiates within bounded time''). These properties can be
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derived directly from operating procedures and regulatory requirements,
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creating a formal link between existing documentation and verifiable system
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behavior.
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NASA's Formal Requirements Elicitation Tool (FRET) bridges the gap between
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natural language requirements and temporal logic specifications. FRET
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provides a structured intermediate language that allows engineers to define
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temporal behavior without writing raw logic formulas. The HARDENS project
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used FRET for requirement capture, and it has been validated on aerospace
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systems including a Lift+Cruise aircraft with 53 formalized
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requirements~\cite{Pressburger2023}. FRET's ability to start with imprecise
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natural language and iteratively refine it into well-posed specifications
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makes it particularly suited to formalizing nuclear operating procedures.
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\subsubsection{Differential Dynamic Logic}
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A separate line of work extends temporal logics to verify hybrid systems
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directly. The result has been the field of differential dynamic logic (dL). dL
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directly. The result has been the field of differential dynamic logic (dL). dL
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introduces two additional operators into temporal logic: the box operator and
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introduces two additional operators into temporal logic: the box operator and
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the diamond operator. The box operator \([\alpha]\phi\) states that for some
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the diamond operator. The box operator \([\alpha]\phi\) states that for some
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@ -30,12 +30,7 @@ exist.}
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This research directly addresses the multi-billion-dollar O\&M cost challenge
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This research directly addresses the multi-billion-dollar O\&M cost challenge
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through high-assurance autonomous control. Current nuclear operations require
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through high-assurance autonomous control. Current nuclear operations require
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full control room staffing for each reactor, whether large conventional units
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full control room staffing for each reactor, whether large conventional units
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or small modular designs. Over 3,600 active NRC-licensed reactor operators
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or small modular designs. These staffing requirements drive the high O\&M
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work in the United States~\cite{operator_statistics}, divided into Reactor
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Operators (ROs) and Senior Reactor Operators
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(SROs)~\cite{10CFR55}. Staffing requires at least two ROs and one SRO per
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unit~\cite{10CFR50.54}, with each operator requiring several years of
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training and NRC licensing. These staffing requirements drive the high O\&M
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costs that make nuclear power economically challenging, particularly for
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costs that make nuclear power economically challenging, particularly for
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smaller reactor designs where the same staffing overhead must be spread
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smaller reactor designs where the same staffing overhead must be spread
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across lower power output. Synthesizing provably correct hybrid controllers
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across lower power output. Synthesizing provably correct hybrid controllers
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