Previously conflated two different kinds of constraint:
- operational deadbands (|T_c - T_c0| <= 5 F) used by the DRC for mode
transitions. Symmetric bands around setpoint. Violating these is an
operator/operational issue, not a safety issue.
- safety limits (T_f <= 1200 C, T_c <= 320 C, n <= 1.15, etc.) are
hard one-sided halfspaces corresponding to physical damage mechanisms
or reactor-trip setpoints. THESE are what a safety barrier/reach must
discharge.
predicates.json now has three groups:
- operational_deadbands (t_avg_above_min, t_avg_in_range, p_above_crit)
- safety_limits (fuel_centerline, t_avg_high_trip, t_avg_low_trip,
n_high_trip, n_low_operation, cold_leg_subcooled)
- mode_invariants (inv1_holds, inv2_holds as conjunctions of safety_limits)
reach_operation.m and barrier_lyapunov.m both now report halfspace-by-
halfspace margins against inv2_holds. Attributable failure analysis:
we can see WHICH limit is tightest.
Reach tube (under +/-15% Q_sg load): passes all 6 safety halfspaces.
Tightest margin is n_high_trip at +0.138 (12% from trip). Temperature
directions have 10-870 K margin.
Lyapunov barrier (same): fails all 6. Worst is n_high_trip with -2365
margin — the ellipsoid says n could deviate by +/-2364, which is
physically meaningless. Anisotropy cost made visible per-direction.
Motivates SOS / polytopic barriers for the thesis chapter.
load_predicates.m now returns .operational_deadbands, .safety_limits,
and .mode_invariants. Existing callers that only used .constants or
.t_avg_in_range still work because those live under the old keys.
Hacker-Split: user caught that the barrier was checking the wrong
invariant; safety limits != operating deadband. Restructured so the
proof target matches the physical claim.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
predicates.json is the single source of truth for concretizing the
FRET-spec predicates (t_avg_above_min, t_avg_in_range, p_above_crit,
inv1_holds, inv2_holds) as polytopes {x : A x <= b}. Until now these
were abstract booleans in the synthesis spec; reach analysis
re-invented ad-hoc thresholds that weren't tied to the spec. Closes
the Thrust-1-meets-Thrust-3 seam.
T_standby now defined as T_c0 - 60 F = 275 C (from user review).
Replaces the earlier simplification where shutdown IC held all temps
at T_cold0. 275 C is inside the model's +/-50 C trust region around
operating point and above coolant saturation at reduced pressure.
load_predicates.m in MATLAB reads the JSON and resolves rhs_expr
strings (which reference plant-derived constants like T_c0, T_cold0,
T_standby) into numeric bounds. Returns per-predicate (A_poly, b_poly)
plus a constants struct.
main_mode_sweep.m now pulls T_standby from predicates and uses it
for shutdown + heatup ICs. Heatup horizon extended to 90 min to
cover the wider 60 F -> operating range at 28 C/hr tech-spec limit.
reach_operation.m reads delta_safe_Tc from the t_avg_in_range
halfspace instead of hardcoding +/-5 K. Current concretization is
+/-2.78 C (~5 F); LQR reach still shows 28x margin.
inv1_holds and inv2_holds are marked PLACEHOLDER in the JSON —
engineering best guesses, not derived from a specific plant's tech
specs or a DNBR correlation. Revisit before thesis defense.
Hacker-Split: single-source concretization for FRET predicates,
end seam with reach.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
