Compare commits

..

5 Commits
draft ... main

3 changed files with 13 additions and 113 deletions

10
.gitignore vendored
View File

@ -38,3 +38,13 @@ Thumbs.db
.idea/ .idea/
*.sty *.sty
.DS_Store .DS_Store
*.aux
*.bbl
*.blg
*.fdb_latexmk
*.fls
*.log
*.pdf
*.toc
*.out
*.synctex.gz

View File

@ -586,115 +586,6 @@ mode approach is sound for nuclear failures. Shows safety can be proven even
when controller deviates from nominal (pp.85-107, UCA 1 when controller deviates from nominal (pp.85-107, UCA 1
analysis).} analysis).}
\subsection{Preliminary Results}
In order to demonstrate the feasibility of this research proposal, we applied
this approach to HAHACS creation to a simple nuclear reactor model, with limited
procedural guidance. We created a simple point kinetics reactor model with
a two-node thermal hydraulics model. The reactor assumes plant parameters and
material properties consistent with a Uranium-235 pressurized water reactor. For
the reactor core, six precursor groups are included, and fuel temperature and
moderator temperature feedback are implemented. For the thermal hydraulics,
basic convection assumptions are made about the heat generated from the fuel's
reactivity, while the coolant is assumed to be single phase water. The
differential equations representing each part of the system are described as
follows.
The point kinetics equations with delayed neutron precursors govern the
neutron population $n(t)$ and precursor concentrations $C_i(t)$:
%
\begin{equation}
\frac{dn}{dt} = \frac{\rho(t) - \beta}{\Lambda} n(t)
+ \sum_{i=1}^{6} \lambda_i C_i(t)
\label{eq:pke}
\end{equation}
%
\begin{equation}
\frac{dC_i}{dt} = \frac{\beta_i}{\Lambda} n(t) - \lambda_i C_i(t),
\quad i = 1, \ldots, 6
\label{eq:precursors}
\end{equation}
%
where $\rho$ is the total reactivity, $\beta = \sum \beta_i$ is the total
delayed neutron fraction, $\Lambda$ is the prompt neutron generation time,
$\lambda_i$ are the precursor decay constants, and $\beta_i$ are the
individual group delayed neutron fractions.
The two-node thermal hydraulics model couples fuel temperature $T_f$ and
coolant temperature $T_c$:
%
\begin{equation}
m_f c_{p,f} \frac{dT_f}{dt} = P(t) - h_{gap} A_s (T_f - T_c)
\label{eq:fuel_temp}
\end{equation}
%
\begin{equation}
m_c c_{p,c} \frac{dT_c}{dt} = h_{gap} A_s (T_f - T_c)
- \dot{m} c_{p,c} (T_c - T_{inlet})
\label{eq:coolant_temp}
\end{equation}
%
where $P(t)$ is the fission power proportional to $n(t)$, $h_{gap}$ is the
gap heat transfer coefficient, $A_s$ is the heat transfer surface area,
$\dot{m}$ is the coolant mass flow rate, and $T_{inlet}$ is the coolant
inlet temperature.
Reactivity is a sum of several different sources. First, reactivity is
a factor of the fuel itself. Second, temperature feedback effects from both
fuel and moderator will change the total reactivity. Finally, control rods
directly add or subtract reactivity in the system by their movement:
%
\begin{equation}
\rho(t) = \rho_{ext}(t) + \alpha_f (T_f - T_{f,0})
+ \alpha_m (T_c - T_{c,0})
\label{eq:reactivity}
\end{equation}
%
where $\rho_{ext}$ is the externally applied reactivity from control rod
position, $\alpha_f$ and $\alpha_m$ are the fuel and moderator temperature
coefficients of reactivity, and $T_{f,0}$ and $T_{c,0}$ are reference
temperatures. These equations were implemented in a MATLAB code to simulate
the simple reactor model.
First, a discrete controller was created by writing FRETish specifications
according to the diagram shown in Figure~\ref{fig:hybrid_automaton}. A full
list of the specifications created is included in
Appendix~\ref{APPENDIX}.\dasnote{need to actually create the appendix}. This
was then synthesized into an automaton using reactive synthesis
tools.\dasnote{This will depend once reactive synthesis is done---JKind?
Kind2? Strix?} Once this automaton was created, continuous controllers were
developed in MATLAB for each discrete control mode. The end result was a
hybrid system with discrete modes and continuous controllers created based
on logical specifications, but were not yet verified.
Once the continuous controllers were created, reachability analysis was
performed on the transitory modes. For this example, there is only one
transitory mode: the heatup mode. For this mode, the entry temperature
$T_{MIN}$ was included as an entry condition, while other states were given
physically reasonable bounds. Reachability analysis confirmed that the
continuous controller satisfied the transitory mode requirement from
Section~3.2.1:\dasnote{Need to reference the specific reachability
condition equation once earlier sections are finalized}
%
\[
\text{Reach}(\mathcal{X}_{entry}, f_{heatup}, [0,T]) \subseteq
\mathcal{X}_{safe} \land \text{Reach}(\mathcal{X}_{entry}, f_{heatup},
[0,T]) \cap \mathcal{X}_{exit} \neq \emptyset
\]
Once the transitory mode was complete, the stabilizing mode of power operation
was analyzed using a barrier certificate search.\dasnote{More needed here:
what are the bounds of the invariant set? What tool was used for the SOS
search? What degree polynomial for the barrier function?}
Finally, the expulsory SCRAM mode was considered. For this example, the failure
modes were kept relatively simple. We assumed possible failure modes of coolant
fouling, where the coolant thermal properties have changed drastically, and a
secondary system coolant leak, where power demand increases dramatically. For
both of these cases, reachability analysis was performed to evaluate that the
dynamics of the system could safely reach a low power, low temperature state for
the possible operating range of the reactor.
\subsection{Industrial Implementation} \subsection{Industrial Implementation}
The methodology described above must be validated on realistic systems using The methodology described above must be validated on realistic systems using
@ -721,4 +612,3 @@ system experts at Emerson ensures that implementation details of the Ovation
platform are handled correctly. Direct industry collaboration also provides an platform are handled correctly. Direct industry collaboration also provides an
immediate pathway for technology transfer and alignment with practical immediate pathway for technology transfer and alignment with practical
deployment requirements. deployment requirements.

View File

@ -11,7 +11,7 @@
% === SPLIT'S EDITING COMMENTS === % === SPLIT'S EDITING COMMENTS ===
% Set to 1 for edit mode (wider margins, visible comments) % Set to 1 for edit mode (wider margins, visible comments)
% Set to 0 for final mode (normal margins, comments hidden) % Set to 0 for final mode (normal margins, comments hidden)
\newcommand{\editmode}{1} \newcommand{\editmode}{0}
\ifnum\editmode=1 \ifnum\editmode=1
% Edit mode: load todonotes, adjust margins % Edit mode: load todonotes, adjust margins
@ -59,9 +59,9 @@
\begin{document} \begin{document}
\pagenumbering{roman} % \pagenumbering{roman}
\maketitle \maketitle
\input{1-goals-and-outcomes/research-statement.tex} % \input{1-goals-and-outcomes/research-statement.tex}
\newpage \newpage
\tableofcontents \tableofcontents
\newpage \newpage