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Calculation Result for TRACY Benchmark II using AGNES code

Expert Group on Criticality Excursion Analysis September 22, 2005. 2005-09-22. Calculation Result for TRACY Benchmark II using AGNES code. Yuichi YAMANE, Yoshinori MIYOSHI Japan Atomic Energy Research Institute. TRACY Core. Core specifications Fuel : 10wt% enriched uranyl nitrate

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Calculation Result for TRACY Benchmark II using AGNES code

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  1. Expert Group on Criticality Excursion AnalysisSeptember 22, 2005 2005-09-22 Calculation Result for TRACY Benchmark II using AGNES code Yuichi YAMANE, Yoshinori MIYOSHI Japan Atomic Energy Research Institute

  2. TRACY Core • Core specifications • Fuel : 10wt% enriched uranyl nitrate • aqueous solution • Shape : Annular (50cm/7.6cm) Transient rod at the center hole • Limitations • Maximum Power ：5000MW • Total energy : 32 MJ/experiment ( = 1018 fissions) • Maximum excess reactivity: 3.0 $ • Reactivity insertion method • Rod withdrawal • Pulse withdrawal (Step insertion) • Ramp withdrawal • Fuel feed • Ramp feed Expert Group on Criticality Excursion Analysis

  3. TRACY Benchmark II • Ramp reactivity insertion by feeding fuel solution. • Excess reactivity; 0.5$ - 2.66$. • Initial reactivity; subcritical • U conc.; 379 – 422 gU/Lit. • Effective delayed neutron fraction; 7.5x10-3. • Neutron generation time; 4.6x10-5. - No external neutron source was used. Expert Group on Criticality Excursion Analysis

  4. Solution Level Difference Method • The inserted reactivity is evaluated as follows; C: 7.671x108 (cent/mm2), l: 102 (mm) Hc1: critical height without Tr-rod Hf: height at the end of reactivity insertion The estimated error of r is about 5%. Expert Group on Criticality Excursion Analysis

  5. AGNES code • One-point kinetics code • One-dimensional thermal conductivity model (solution-container-coolant) • The heat effects of the structural material and the air convection outside the core tank • Radiolytic dissociation gas void model Expert Group on Criticality Excursion Analysis

  6. Kinetic Parameters: R61 • SRAC + TWODANT with JENDL-3.2 • Neutron generation time : 4.51x10-5 • beff : 7.63x10-3 • Reactivity Temperature Coefficient : -3.9 cent/K, -1.8 cent/K2 • Reactivity Void Coefficient : -5.0x101 cent/%, -2.2x10-1 cent/%2 Expert Group on Criticality Excursion Analysis

  7. Example of Calculation: R61(2.64$, 0.05$/s) • The 1st peak and 2nd peak are well reproduced. • The 3rd peak is delayed and lower. Expert Group on Criticality Excursion Analysis

  8. Void Reactivity Feedback Model of AGNES • Void ratio is proportional to power density and excess gas concentration. • Gas concentration is proportional to power density. • C0, G, n, CD are main parameters and n and CD have been tuned. • Fi,j: Void ratio (%), • Ci,j: Concentration of radiolytic dissociation gas (mol/m3), • P : Power density (W/m3), • : energy – void transfer coefficient,(m6/J mol) C0 : Saturation concentration of gas (mol/m3), G : Radiolytic dissociation rate (mol/J), • : Decay constant of radiolytic gas (s), gi,j : Power distribution ratio H(x) : =1 for x>0, =0 for x<0. • vi,j: upward velocity of void (m/s2), • ri,j: Void radius in mesh i,j (m), • g : gravity acceleration (m/s2), • : energy – void transfer coefficient, CD : Resistance coefficient, CD = b0 + b2 F2i,j . Expert Group on Criticality Excursion Analysis

  9. Void Parameters: R61 • Energy-void transfer coefficient and resistance coefficient have been tuned so that the 2nd power peak has been reproduce well for R61. • AGNES’s void model ignores that Fi,j and Ci,j are lowered by pumped solution and convection due to pumping. * CD = b0 + b2 F2i,j Expert Group on Criticality Excursion Analysis

  10. Sensitivity to Void Parameter; n n : Energy-void transfer coefficient = 1x10-7 to 1x10-11 The shape of bottoms is changed. Expert Group on Criticality Excursion Analysis

  11. Sensitivity to Void Parameter; CD CD: Resistance coefficient = 2x10-8 to 8x10-8 The interval between peaks is changed. Expert Group on Criticality Excursion Analysis

  12. Kinetic Parameters: R76 • SRAC + TWODANT with JENDL-3.2 • Neutron generation time : 4.74x10-5 • beff : 7.59x10-3 • Reactivity Temperature Coefficient : -4.0 cent/K, -1.5 cent/K2 • Reactivity Void Coefficient : -4.7x101 cent/%, -1.9x10-1 cent/%2 Expert Group on Criticality Excursion Analysis

  13. Example of Calculation: R76(2.66$, 0.18$/s) • The 1st peak is well reproduced. • The 2nd peak and 3rd peak are delayed and lower. Expert Group on Criticality Excursion Analysis

  14. Kinetic Parameters: R159 • SRAC + TWODANT with JENDL-3.2 • Neutron generation time : 4.86x10-5 • beff : 7.55x10-3 • Reactivity Temperature Coefficient : -4.0 cent/K, -1.7 cent/K2 • Reactivity Void Coefficient : -4.3x101 cent/%, -1.5x10-1 cent/%2 Expert Group on Criticality Excursion Analysis

  15. Example of Calculation: R159(0.50$, 0.15$/s) • The 1st peak is well reproduced. • The power is lower after the 1st peak. Expert Group on Criticality Excursion Analysis

  16. Sensitivity to Excess Reactivity; 0.50$ Excess reactivity($) = 0.44 to 0.50 The profile with 0.46$ gives the best fit Expert Group on Criticality Excursion Analysis

  17. Preliminary Result and Summary • The 1st peak power and total released energy were reproduced within 2 to 15%. • Some values of the inserted reactivity and inverse period should be re-evaluated. Expert Group on Criticality Excursion Analysis

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