function p = pke_params()
% PKE_PARAMS  Returns the parameter struct for the coupled PKE + T/H model.
%
%  All plant parameters, kinetic data, and steady-state conditions live here.
%  Modify this file to change the reactor you're modeling.

    p = struct();

    % --- Neutronics ---
    % Prompt neutron generation time for a typical PWR with enriched UO2 fuel
    % and a water-moderated thermal spectrum. Literature range: 1e-5 to 5e-4 s;
    % 1e-4 is a standard mid-range value (Duderstadt & Hamilton, Ch. 6).
    p.Lambda = 1e-4;  % prompt neutron generation time [s]

    % 6-group delayed neutron data for U-235 thermal fission (Keepin et al.,
    % Phys. Rev. 107, 1957). These are the canonical values used in virtually
    % all PKE models. Total beta_eff ~ 650 pcm.
    p.beta_i   = [0.000215; 0.001424; 0.001274; 0.002568; 0.000748; 0.000273];
    p.lambda_i = [0.0124;   0.0305;   0.111;    0.301;    1.14;     3.01];
    p.beta = sum(p.beta_i);

    % --- Thermal-hydraulic ---
    % 1000 MWth is a round number representative of a 2-loop PWR (e.g.,
    % Westinghouse 2-loop class). Actual plants range ~1800-3400 MWth for
    % 2-loop to 4-loop designs.
    p.P0   = 1000e6;   % nominal thermal power [W]

    % Fuel mass: representative of total UO2 inventory in the core.
    % A typical 4-loop PWR has ~100,000 kg UO2; scaled down for 1000 MWth.
    p.M_f  = 50000;    % fuel mass [kg]

    % UO2 specific heat at operating temperatures (~400-800 C). Published
    % values range 250-350 J/kg-K (MATPRO / Fink correlation); 300 is a
    % standard lumped value for transient analysis.
    p.c_f  = 300;      % fuel specific heat [J/kg-K]

    % Coolant mass in the core region. Based on core volume fraction of
    % water in a PWR (~40% moderator-to-fuel ratio) and active core volume.
    p.M_c  = 20000;    % coolant mass in core [kg]

    % Pressurized water specific heat at ~15.5 MPa, ~300 C. NIST/IAPWS
    % gives cp ~ 5.4-5.5 kJ/kg-K in this range.
    p.c_c  = 5450;     % coolant specific heat [J/kg-K]

    % Lumped fuel-to-coolant heat transfer coefficient x area. Chosen so that
    % the steady-state fuel-to-coolant dT = P0/hA = 20 C, which is in the
    % right ballpark for the average pellet-to-bulk-coolant temperature drop
    % in a lumped single-node fuel model.
    p.hA   = 5e7;      % fuel-to-coolant heat transfer coeff * area [W/K]

    % Primary coolant mass flow rate. Typical PWR: ~4000-6000 kg/s per loop.
    % 5000 kg/s gives core dT = P0/(W*c_c) ~ 36.7 C, consistent with a
    % ~35-38 C core rise in operating PWRs.
    p.W    = 5000;      % coolant mass flow rate [kg/s]

    % Coolant mass in SG + hot/cold leg piping. Represents the ex-core primary
    % inventory that participates in the loop transport delay. Larger than M_c
    % because the SG tubes and piping hold significant volume.
    p.M_sg = 30000;    % coolant mass in SG + hot/cold leg piping [kg]

    % --- Reactivity feedback coefficients ---
    % Doppler coefficient: fuel temperature feedback, predominantly from
    % U-238 resonance broadening. Typical BOL range: -2 to -3 pcm/K
    % (Todreas & Kazimi). -2.5 pcm/K is a standard mid-cycle value.
    p.alpha_f = -2.5e-5;  % fuel (Doppler) [dk/k per K]

    % Moderator temperature coefficient: captures water density change with
    % temperature and its effect on neutron moderation/absorption. Typical
    % range: -5 to -50 pcm/K depending on boron concentration and burnup.
    % -10 pcm/K is moderate (mid-cycle, moderate boron).
    p.alpha_c = -1.0e-4;  % coolant (moderator) [dk/k per K]

    % --- Steady-state (derived from energy balance at P0, n=1) ---
    %  Q_sg = P0, all dT/dt = 0
    %  T_hot - T_cold = P0 / (W*c_c)
    %  T_c = (T_hot + T_cold) / 2
    %  T_f = T_c + P0 / hA
    % Cold leg temperature of 290 C (554 F) is typical for a PWR at full
    % power (Westinghouse plants: ~288-293 C depending on design).
    p.T_cold0 = 290;                                % inlet coolant [C]
    p.dT_core = p.P0 / (p.W * p.c_c);              % core delta-T [C]
    p.T_hot0  = p.T_cold0 + p.dT_core;
    p.T_c0    = (p.T_hot0 + p.T_cold0) / 2;        % avg coolant [C]
    p.T_f0    = p.T_c0 + p.P0 / p.hA;              % fuel [C]

end