645f2d8d27
Singular-perturbation reduction of the PKE+T/H system: set dn/dt=0,
solve algebraically n = Λ·Σλ_i·C_i / (β-ρ). State drops 10 -> 9 (no
n), removes Λ⁻¹ stiffness. Validated against full state on the heatup
scenario:
t [s] |Δn|/n_full T_c err [K]
60 3.7e-5 4e-6
300 3.8e-4 1.9e-4
1200 1.0e-3 2.2e-3
3000 5.0e-4 7.2e-3
Maximum relative error 0.1% on n, peak 7 mK on temperatures over
50 minutes. PJ approximation is excellent for slow heatup transients
(sub-prompt-critical regime).
Files:
- code/src/pke_th_rhs_pj.jl: reduced 9-state RHS
- code/scripts/validate_pj.jl: side-by-side sim
- code/scripts/reach_heatup_pj.jl: TMJets reach with PJ model
(probing T = 60, 300, 1800, 5400 s)
App v2 (Pluto):
- §9b: live ingestion of reach_operation_result.mat with per-
halfspace margins computed from JSON-defined inv2_holds.
- §9c: 2D projection chooser (n, T_f, T_c, T_cold) with reach
tube envelope overlay.
- §9d: PJ heatup reach summary (placeholder until first run lands).
Journal:
- Added 2026-04-20-overnight-prompt-jump.tex with PJ derivation,
validation table, soundness ledger update. apass markers for
the in-progress reach results.
This commit captures state mid-run; next commit will add the
populated reach results once TMJets returns.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
code
Plant model, controllers, and reach-analysis toolchain for the HAHACS preliminary example. All Julia.
What this is
A 10-state coupled neutronics + thermal-hydraulics model (point kinetic equations + lumped thermal loop) with continuous-mode controllers for each of the DRC modes (shutdown, heatup, operation, scram), plus a hand-rolled linear reach-tube propagator, a Lyapunov-ellipsoid barrier attempt, and scaffolding for TMJets-based nonlinear reach.
Ported from MATLAB on 2026-04-20 once the reach experiments made it
clear that Julia's stack (OrdinaryDiffEq, MatrixEquations,
ReachabilityAnalysis, LazySets, @taylorize) was the right tool
for everything we need going forward. The MATLAB originals are in
the git history.
Running
First time:
cd code
julia --project=. -e 'using Pkg; Pkg.instantiate()'
Subsequent:
julia --project=. scripts/main_mode_sweep.jl # all 5 DRC modes, figures
julia --project=. scripts/reach_operation.jl # operation-mode linear reach
julia --project=. scripts/barrier_lyapunov.jl # Lyapunov barrier attempt
julia --project=. scripts/barrier_compare_OL_CL.jl # OL vs CL barrier
julia --project=. scripts/reach_heatup_nonlinear.jl # nonlinear heatup (10s cap)
Figures save to ../docs/figures/. Reach results save to
../reachability/*.mat (gitignored).
Structure
See CLAUDE.md for the architectural overview and ../journal/ for
the invention-log-style narrative of how this code got written.
Dependencies
From Project.toml:
OrdinaryDiffEq— ODE solver, Rodas5 for stiff systems.MatrixEquations—arecfor LQR Riccati,lyapcfor Lyapunov.ReachabilityAnalysis+LazySets— reach sets and set operations.Plots— figures (GR backend by default).JSON— read../reachability/predicates.json.MAT— save results.
Manifest.toml is gitignored; regenerate locally on first
Pkg.instantiate().