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Dynamic Response to Pulsed Beam Operation in Accelerator Driven Subcritical Reactors Ali Ahmad Supervisor: Dr Geoff Parks University Nuclear Technology Forum April, 2011

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Overview UNTF 2011 Ali Ahmad Introduction Characterisation of the dynamic response in ADSR The PTS-ADS code The thermo-mechanical stress analysis in the fuel cladding

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Introduction UNTF 2011 Ali Ahmad “Fukushima disaster causes fallout for nuclear industry worldwide” The Guardian 29 March 2011 “The world energy demand is expected to grow by approx 50% from 2007 to 2035” International Energy Outlook 2010, US EIA Safety Sustainability AgendaAgenda

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Characterisation of the dynamic response in ADSR UNTF 2011 Ali Ahmad FFAG accelerator seems to be the most suitable option for ADSR because: - High beam intensity - High efficiency of power consumption - High stability in operation - Cheaper than Linac FFAG works in a pulsed mode Frequent core temperature variations Thermal cyclic fatigue in the cladding? Agenda

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The PTS-ADS code UNTF 2011 Ali Ahmad Agenda

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The PTS-ADS code: Fuel Pin Heat Transfer Model UNTF 2011 Ali Ahmad Assumptions: 1-The axial power distribution has a sinusoidal form 2-The heat generation rate is uniform across the radial direction inside the fuel 3- Heat transfer only occurs in the radial direction The fuel pin heat equation can be written as:

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The PTS-ADS code: Fuel Pin Heat Transfer Model UNTF 2011 Ali Ahmad Steady state case In matrix form: Are functions of temperature Solve using Newton’s iteration method

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The PTS-ADS code: Fuel Pin Heat Transfer Model UNTF 2011 Ali Ahmad Transient state case The matrix form of the transient heat equation is: Rearrange:

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The PTS-ADS code: Neutronic Model UNTF 2011 Ali Ahmad Six-group Point Kinetics model: Total reactivity can be written as:

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The PTS-ADS code: Validation Case Study UNTF 2011 Ali Ahmad Benchmark study on beam interruptions in XADS The PTS-ADS coupled model was compared to three other codes selected from a benchmark study on beam interruption for the Experimental ADS* (80 MWt, MOX, Lead-Bismuth coolant). -TRAC-MOD -SIMADS -SAS4ADS *) A. D’Angelo et al. Benchmark on beam interruptions in an accelerator driven system final report on phase I calculations, Tech. Rep. NEA/NSC/DOC(2003)17, NEA (2003).

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The PTS-ADS code: Validation Case Study UNTF 2011 Ali Ahmad

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The PTS-ADS code: Validation Case Study

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UNTF 2011 Ali Ahmad The PTS-ADS code: Validation Case Study

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UNTF 2011 Ali Ahmad The PTS-ADS code: Validation Case Study

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The thermo-mechanical stress analysis in the fuel cladding UNTF 2011 Ali Ahmad Fuel pin geometry and the physical properties of the fuel, cladding and coolant materials are taken from the XADS data sheet. Beam characteristics: - Frequency 1 Hz - Beam off time 10, 50 and 100 ms Local linear power: W/m (XADS ref case) W/m (Industrial ADSR) Agenda

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The thermo-mechanical stress analysis in the fuel cladding UNTF 2011 Ali Ahmad Life prediction of the fuel pin cladding In a nuclear reactor, the integrity of the structural materials in general and of the fuel cladding in particular is of high importance. Cladding failure Fission products leakage to the primary coolant circuit The thermal stress on the cladding can be calculated using: Define the stress amplitude : The stress amplitude is related to the failure limit N f by Basquin’s Law: where is the fatigue strength coefficient and b is the fatigue strength exponent

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The thermo-mechanical stress analysis in the fuel cladding UNTF 2011 Ali Ahmad Both and b can be estimated experimentally for certain materials at certain temperatures. The cladding material in this study is T91 stainless steel. Temperature (°C) (MPa) b −0.052Indefinite −0.093Indefinite

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Conclusions UNTF 2011 Ali Ahmad The integrity of the fuel cladding of an ADSR can be assumed to be unaffected by the repetitive temperature fluctuations due to pulsed operation mode.

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Future Work UNTF 2011 Ali Ahmad Use the PTS-ADS code to measure the temperature variations in the fuel cladding when subjected to beam interruptions (t> 1 second) and predict the stress-life behaviour for that case Study the influence of other factors such as radiation damage and creep on the cladding fatigue life Further development of the PTS-ADS code to include the ability study all ADSR transients and for different core configurations

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