{
  "id": "PWR-EOL-REFERENCE-PROPOSAL-r1",
  "created_at": "2026-10-15T16:44:22.165514+00:00",
  "status": "Analyst proposal for checkpoint A; not accepted or used in a study run",
  "intended_use": "Material/history-specific residual preload estimate at a declared reference exposure endpoint. Not a prediction for an operating PWR assembly or its actual service life.",
  "user_requirement": "basis/eol-intended-use-decision-r1.json",
  "user_reference_choice": "basis/eol-reference-history-choice-r1.json",
  "source": {
    "url": "https://proceedings.cns-snc.ca/index.php/pcns/article/download/4116/4115/4151",
    "title": "Griffiths et al. (2008), Spectral Effects on Stress Relaxation of Inconel X-750 Springs in CANDU Reactors",
    "review": "research/nru-x750-applicability-r1.json",
    "pdf_sha256": "f85118df450194dc60c8eaa0bf5cc9c298ace7dcff29259e335730b935ddfa8c",
    "pages": [
      6,
      8
    ]
  },
  "sourced_reference_conditions": {
    "alloy": "Inconel X-750",
    "form": "Hot-rolled plate, rolling-direction specimens",
    "aging_temperature_K": 977,
    "aging_duration_h": 24,
    "irradiation_environment": "NRU flowing water",
    "fast_neutron_energy_threshold_MeV": 1,
    "fast_flux_range_n_m2_s": [
      1.5e+17,
      1.8e+17
    ],
    "temperature_K_figure_label": 573,
    "temperature_K_body_nominal": 570,
    "restraint": "Constrained bent beam, periodic unloaded-curvature observations",
    "fit": "R(F) = 0.915 * exp(-1e-25 * F), F in n/m2; unrelaxed stress ratio",
    "fit_uncertainty": "No confidence interval or coefficient covariance established by this review"
  },
  "proposed_study_reference_endpoint": {
    "fast_fluence_n_m2": 6e+24,
    "classification": "Analyst-selected endpoint within the visually observed 573 K data span; not a separately reported test record",
    "temperature_policy": "Use the curve labelled 573 K, retain the source nominal 570 K wording; do not interpolate a temperature dependence from two curves.",
    "flux_policy": "Retain the source flux range. No detailed time-resolved irradiation schedule or shutdown history is claimed.",
    "applicability": "NRU-reference exposure only. No PWR spectrum conversion or burnup-to-fluence equivalence is supplied.",
    "meaning_of_eol": "End of the explicitly selected reference exposure, not an asserted reactor fuel lifetime"
  },
  "mechanical_transfer_proposals": {
    "cladding": "Zircaloy-4, unchanged",
    "support_material_scope": "Propose X-750 for the compliant spring/dimple surrogate; the actual shape/manufacturing equivalence to the tested plate is not established.",
    "initial_forces_N": {
      "spring": 5,
      "dimple_1": 2.5,
      "dimple_2": 2.5
    },
    "force_mapping": "For residual installed preload only, propose F_EOL = R(F_endpoint) * F_initial under fixed restraint and unchanged stress-to-force geometry. This transfer is an assumption, not a published grid-force result.",
    "stiffness_mapping": "Keep the supplied 50/20 N/mm effective tangents independent. Do not multiply the retained preload by 20/50 again. Derive endpoint unloaded interference from endpoint preload and its assigned tangent.",
    "bow_history": "Reference relaxation occurs at the installed restraint. Solve bow/contact subsequently as an endpoint load case. This does not predict simultaneous bow growth and irradiation relaxation.",
    "contact_output": "Report retained installed preload, bow-induced force change, and final unilateral contact force separately. A released contact carries zero force; later recontact is not negative retained preload."
  },
  "fit_handling": {
    "intercept": "The reported fit has R(0)=0.915. Do not implement this as a physical instantaneous preload loss or as a continuous life-history integrator.",
    "endpoint_use": "Use the published finite-exposure fit for the proposed endpoint estimate. Preserve initial installed preload as a separate supplied/proposed state.",
    "sensitivity": "Compare an explicitly alternative unity-anchored exponential and an analyst-selected slope variation of ±25%. Neither is a confidence interval or a replacement calibration.",
    "range_policy": "No extrapolation beyond the inspected 573 K point range; no interpolation in alloy, treatment or temperature; no silent fluence/dpa conversion."
  },
  "checkpoint_A_decisions": [
    "Accept or revise the X-750 treatment and NRU reference exposure endpoint.",
    "Accept or revise stress-retention-to-preload transfer and endpoint-only bow loading.",
    "Accept or revise the handling of the non-unity fitted intercept and stated sensitivities.",
    "Record that no statistical force interval, PWR service-life prediction, or actual grid manufacturing equivalence is established."
  ],
  "remaining_before_physical_acceptance": [
    "Engineering review of the assumptions above",
    "Deterministic workflow producer and exact result/validation bindings",
    "Support/contact geometry applicability and equilibrium checks at B",
    "Uncertainty reporting that retains the unavailable source fit uncertainty"
  ]
}