PSI - Issue 60

ScienceDirect Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2023) 000 – 000 Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2023) 000 – 000

Available online at www.sciencedirect.com

www.elsevier.com/locate/procedia

Procedia Structural Integrity 60 (2024) 541–552

www.elsevier.com/locate/procedia

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.074 2452-3216© 2024 T he Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) P eer-review under responsibility of the ICONS 2023 Organizers Abstract For postulated accident scenario of loss of coolant accident coupled with the failure of emergency core cooling system, the pressure tube will deform due to presence of decay heat. The pressure tube deforms due to creep and this shall ultimately result in a contact with the calandria tube. In this work, the time for this contact to happen is calculated considering the uncertainties in mechanical and thermal material properties of the material. Finite element analysis of temperature distribution in the pressure tube has been carried out considering heat dissipation by conduction, convection and radiation. The source is heat generation due to decay heat of fuel bundles inside pressure tube. The ballooning of the pressure tube material is modelled using the Norton’s creep law. The finite element model is validated using experimental results from literature. As the finite element model is very complex and time intensive, it is difficult to employ the traditional uncertainty propagation methods like Monte Carlo simulations. The uncertainty analysis in this work is performed using Wilk’s method. The time duration when the contact of pressure tube and Calandria tube would happen and the temperature of the pressure tube at that instant is estimated. The results are presented in terms of the 95 percentile values with a confidence of 95 percent. The analysis gives an upper bound to the contact time between pressure tube and Calandria tube during loss of coolant accident condition subject to unavailability of emergency core cooling system. Key Words : pressure tube ballooning, uncertainty analysis, Wilk’s method, severe accident analysis Nomenclature Coeff of thermal expansion (moderator) 4 Prandtl number between CT and moderator Emissivity of PT Q c activation energy of creep mechanism Viscosity of moderator Heat transfer due to radiation Stefan Boltzmann Constant R universal gas constant 1 Surface Area of PT enclosed by CT 2 Resistance due to conduction in air Specific heat capacity of moderator 2 Inner radius of CT k material constant 1 Outer radius of PT Conductivity of air 4 Rayleigh number Enclosed length of PT ℎ Temperature of PT n Stress exponent Temperature of CT 2452-3216© 2024 T he Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) P eer-review under responsibility of the ICONS 2023 Organizers Abstract For postulated accident scenario of loss of coolant accident coupled with the failure of emergency core cooling system, the pressure tube will deform due to presence of decay heat. The pressure tube deforms due to creep and this shall ultimately result in a contact with the calandria tube. In this work, the time for this contact to happen is calculated considering the uncertainties in mechanical and thermal material properties of the material. Finite element analysis of temperature distribution in the pressure tube has been carried out considering heat dissipation by conduction, convection and radiation. The source is heat generation due to decay heat of fuel bundles inside pressure tube. The ballooning of the pressure tube material is modelled using the Norton’s creep law. The finite element model is validated using experimental results from literature. As the finite element model is very complex and time intensive, it is difficult to employ the traditional uncertainty propagation methods like Monte Carlo simulations. The uncertainty analysis in this work is performed using Wilk’s method. The time duration when the contact of pressure tube and Calandria tube would happen and the temperature of the pressure tube at that instant is estimated. The results are presented in terms of the 95 percentile values with a confidence of 95 percent. The analysis gives an upper bound to the contact time between pressure tube and Calandria tube during loss of coolant accident condition subject to unavailability of emergency core cooling system. Key Words : pressure tube ballooning, uncertainty analysis, Wilk’s method, severe accident analysis Nomenclature Coeff of thermal expansion (moderator) 4 Prandtl number between CT and moderator Emissivity of PT Q c activation energy of creep mechanism Viscosity of moderator Heat transfer due to radiation Stefan Boltzmann Constant R universal gas constant 1 Surface Area of PT enclosed by CT 2 Resistance due to conduction in air Specific heat capacity of moderator 2 Inner radius of CT k material constant 1 Outer radius of PT Conductivity of air 4 Rayleigh number Enclosed length of PT ℎ Temperature of PT n Stress exponent Temperature of CT © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers Third International Conference on Structural Integrity 2023 (ICONS 2023) Probabilistic Assessment of Ballooning of Pressure Tube under Severe Accident Conditions A. Kumar a,c , M.K. Samal b,c,* , R. Rastogi b , V.K. Singh a , J. Chattopadhyay b,c a 1Integrated Nuclear Recycle Plant Construction, NRB, BARC, Tarapur 401502, India b Reactor Safety Division, BARC, Mumbai - 400085, India c Division of Engineering Sciences, Homi Bhabha National Institute, Mumbai - 400094, India Email: mksamal@barc.gov.in Third International Conference on Structural Integrity 2023 (ICONS 2023) Probabilistic Assessment of Ballooning of Pressure Tube under Severe Accident Conditions A. Kumar a,c , M.K. Samal b,c,* , R. Rastogi b , V.K. Singh a , J. Chattopadhyay b,c a 1Integrated Nuclear Recycle Plant Construction, NRB, BARC, Tarapur 401502, India b Reactor Safety Division, BARC, Mumbai - 400085, India c Division of Engineering Sciences, Homi Bhabha National Institute, Mumbai - 400094, India Email: mksamal@barc.gov.in