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NucE 431W Core Design Presentation

NucE 431W Core Design Presentation. Bayshore Unit 1 Reload Core Design Group 13 Michael Bertino Michael Stachnik Submitted to: Dr. K Ivanov Dr. M. Avramova Mentor: Chris Wagener. Table of Contents. Introduction Loading Pattern Development Safety Analysis Operational Data

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NucE 431W Core Design Presentation

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  1. NucE 431W Core Design Presentation Bayshore Unit 1 Reload Core Design Group 13 Michael Bertino Michael Stachnik Submitted to: Dr. K Ivanov Dr. M. Avramova Mentor: Chris Wagener

  2. Table of Contents • Introduction • Loading Pattern Development • Safety Analysis • Operational Data • Thermal Hydraulics Analysis • Conclusion

  3. INTRODUCTION Student Objectives: • To be able to use the codes and methods used by Westinghouse to generate a core loading pattern for a cycle 13 Bayshore Unit 1 reactor and perform reload design analysis. • Perform an analysis for operational conditions and safety requirements for our core loading pattern. • Perform a thermo-hydraulic analysis on our core loading pattern for both steady state and transient conditions.

  4. What is ANC? • ANC (Advanced Nodal Code) • Multidimensional nodal code. • Licensed by NRC for PWR analysis • Calculates: • Core reactivity • Assembly power • Rodwise Power • Reactivity coefficients • Core depletion • Control rod and fission product worths

  5. Reactor Core Design CE 2-PWR Loop Core • Thermal Power=2700 MWt • 4 Control Rods • 217 assemblies • 5 guide tubes

  6. Plant Description • Inlet core temperature is programmed to vary from 532 to 549 from 0 % to 100 % power. • Control rods move from 0 to 137 steps withdrawn. • Rod insertion limits are a function of power. • Full power upper limit of the axial shape index (ASI) is -8 %.

  7. Loading Pattern Development

  8. Loading Pattern Development There are four criteria that must be evaluated to development an initial loading pattern (LP) • Energy(cycle length) • Fpeaking factor, ARO • HZP, MTC (all power levels) • Fuel Inventory

  9. Loading Pattern Parameters

  10. Gadolinia Burnable Absorber • 68 feed assemblies • 36 assemblies at 4.013 w/o U235 • 20 assemblies at 4.420 w/o U235 • 12 assemblies at 4.365 w/o U235 • Mixed with UO2, displaces fuel from the core. • Complex depletion chain. • No placement restrictions. • Optimized to reduced peaking within the assembly

  11. Summary of ANC Runs to Final LP

  12. Final Core Loading Pattern

  13. Energy, Cycle Length Requirement • EFPD is defined as the total amount of energy produced from BOC to EOC. • Boron Concentration must be reduced to 10 ppm at HZP conditions • The final burnup step is used to calculate the EFPD of the LP: 

  14. Energy, Cycle Length Requirement • The final burnup step SL213_BE15 concentration target to around 10 ppm for an EFPD of 468.2 but the boron concentration of the input was 16 ppm with an EFPD of 469.51. This limit is confirmed at the final burnup step as it should be.

  15. Energy, Cycle Length Requirement

  16. FH Limit Confirmation • FΔH is the normalized enthalpy rise in a given subchannel as the water flows from the bottom of the core to the top of the core. • Represents a localized power with in the core (local power > average power) • The peaking factor (FΔH) is defined in ANC by:

  17. FH Limit Confirmation

  18. FH Limit Confirmation • Below is the C-FDH for the 150 BU, the hottest step.

  19. FH Limit Confirmation • The figure below is the 12th step showing a peak in FΔH due to the boron burning up.

  20. MTC Limit Confirmation • The moderator temperature coefficient is defined as the reactivity change per one degree change in the fuel temperature. In a PWR, the moderator is water in the liquid form and the basic units of MTC are pcm/degree temperature. • The MTC of water is negative at most conditions due to as temperature increaseswater density decreasesmoderation decreasesless reactivity • The more boron that is dissolved in the moderator, the more positive the MTC will be. Water has a naturally negative temperature coefficient while boron has a naturally positive one.

  21. MTC Limit Confirmation • The MTC is checked at HZP conditions for the core, RELPOW=0 / • The MTC should also have no xenon, DEPLETE= HDALL, NAXE /

  22. MTC Limit Confirmation • The calculation to solve for the MTC of the first case to see if the limit was below 0.50 pcmF

  23. Loading Pattern Limit Confirmation

  24. Safety Analysis

  25. Westinghouse RSAC Process • Reload Safety Analysis Checklist. • Transient analyst does calculations to determine damage to the core and environment in case of accident. • Core Designer must confirm that reload design does not violate assumed values. • Always go to the extreme, worst case scenario • Safety calculations done in conservative manner.(most limiting condition)

  26. Safety Analysis Westinghouse RSAC Process: • Rodded FH • Rod Ejection Accident • Shutdown Margin

  27. Rodded FH • Rodded FH must be met when the leading control rod bank is in to is insertion limit (RIL). • The RIL is the deepest possible insertion for any rod bank. This is done to make sure there is enough rod worth left to shut down the core in case of accident or emergency.

  28. Rodded FH Input file for rodded FH: • Xenon must be reconstructed • Xenon must be skewed to save time

  29. Rodded FH

  30. Rodded FH • Below is the Rodded FH output from E-SUM:

  31. Rod Ejection Accident • A mechanical failure where a control rod is ejected from the core • Causes large power increase, fuel and clad temperature increase and increase in DNB • The limits found are the ejected rod worth Δρ(E), and the ejected rod hot channel factor FQ(E)

  32. Rod Ejection Accident • There are two limits evaluated at two conditions. • BOC, HFP, ARO, equilibrium xenon • EOC, HFP, ARO, no xenon • BOC, HZP, ARO, equilibrium xenon • EOC, HZP, ARO, non xenon

  33. Rod Ejection Accident, HFP • The most limiting rod ejection is at the EOC • The most limiting FQ is at BOC • Sample input deck from BOC RELPOW=1.00

  34. Rod Ejection Accident, HFP The output E-SRW for HFP BOC

  35. Rod Ejection Accident, HFP The output E-SRW for HFP EOC

  36. Rod Ejection Accident, HFP

  37. Rod Ejection Accident, HZP The rod ejection for HZP is the same thing except RELPOW=0 /

  38. Rod Ejection Accident, HZP The output E-SRW for HZP BOC

  39. Rod Ejection Accident, HZP The output E-SRW for HZP EOC

  40. Rod Ejection Accident, HZP

  41. Rod Ejection Accident

  42. Shutdown Margin • The amount of reactivity in the core at subcritical following a trip. • Shows that the operators will be able to safely shut down the core. • There are components that affect the SM in ANC: • Doppler Defect-fuel pellet temperature increases with power and so does resonance absorption due to Doppler. Doppler decrease reactivity • Voids-Local boiling in the moderator can also cause small voids to form. Voids decrease reactivity but collapsing gives a small increase. • Axial Flux redistribution-enthalpy in the core rises causing a flux tilt towards the bottom of the core. When its goes from HFP to HZP(power defect) there is no rise in enthalpy causing the flux to shift to the top of the core which increases reactivity.

  43. Shutdown Margin 4. Power Defect- amount of total reactivity associated with a change in power. It is larger at EOC because the MTC is more negative due to less boron. So reactivity increases. 5. Rod insertion allowance- cannot assume a full worth of control rod banks. The core may have only partially inserted rods at trip. The reactivity depends on how much rod worth there is. 6. Variable Moderator Temperature- The moderator temperature is greater at HFP so when it trips to HZP causes the temperature to decrease causing a spike in reactivity.

  44. Shutdown Margin Use six cases for ANC input: • K1- Base Case at Burnup of Interest (BOC or EOC) • EOC, boron should be set to 0 ppm • BOC, boron should be constant • K2-Rods at Insertion Limits • Lead bank is inserted which means less rod worth out of the core • Less negative reactivity upon trip • K3-Over-power/Over Temperature, Skew Power to Top of Core • Increase core power from 100%to 105% • Higher power means that the initial temperature will be higher and it will increase power defect • Xenon is skewed so that the AO shifts to most positive side(xenon to the bottom of the core, shifts power to the top • Increases the worth of partially inserted rods and the power defect

  45. Shutdown Margin • K4-Trip to Zero Power • Holds the Xenon, boron and D bank and it goes from HFP to HZP • K5-Full Core-All Rods In • All rods inserted in full core • K6-Worst Stuck Rod Out • Removes the worst stuck rod

  46. Shutdown Margin To calculate the shutdown margin we took the worst stuck rod case at BOC and EOC This meets the limit for the shutdown margin by 1.866%.

  47. Shutdown Margin

  48. Shutdown Margin

  49. Operational Data

  50. Operational Data Calculations that must be performed to make sure the core is running at normal conditions • Rod Worth • Xenon Worth • Differential Boron Worth • Isothermal Temperature Coefficient • Critical Boron Concentration

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