scholarly journals Modeling Axial Relocation of Fragmented Fuel During Loss of Coolant Conditions by Using ABAQUS

2020 ◽  
Author(s):  
Zehua Ma ◽  
Koroush Shirvan ◽  
Wei Li ◽  
Yingwei Wu
Keyword(s):  
Thermal Stresses ◽  
Element Model ◽  
Irradiation Creep ◽  
Irradiation Hardening ◽  
Fuel Pellets ◽  
Loss Of Coolant Accident ◽  
Fission Gas ◽  
Loss Of Coolant ◽  
Single Balloon ◽  
Nuclear Fuel Pellets

Abstract In a light-water reactor, during normal operating condition, the UO2 nuclear fuel pellets undergo fragmentation primarily due to presence of thermal stresses, fission gas development and pellet-clad mechanical interaction. Under Loss of Coolant Accident (LOCA) conditions, a portion of fuel fragments can freely move downwards to the ballooning region due to the significant cladding deformation. The fuel relocation can localize the heat load and in turn accelerate the cladding balloon and burst process. Cladding burst is of great concern because of the potential for fuel dispersal into coolant and clad structural stability. In our work, we built up a finite element model considering cladding balloon, fuel relocation and its resultant thermal feedback during LOCA condition with ABAQUS. The clad balloon model includes phase transformation, swelling, thermal and irradiation creep, irradiation hardening and annealing and other important thermal-mechanical properties. The mass of relocation model was verified against the analytical cases of single balloon and twin balloons. The cladding balloon model combined with fuel thermal conductivity degradation was verified against fuel performance code, FRAPTRAN. Finally, with the evolution of pellet-cladding gap, the fuel mass relocation was calculated and compared against the IFA-650.4 transient test from the Halden reactor.

Requirements for the Modeling of Medium-Term Behavior of Nuclear Containment Concrete for a “Loss of Coolant Accident” Analysis

2016 ◽  
Vol 711 ◽  
pp. 916-923
Author(s):  
Alain Sellier ◽  
Thierry Vidal ◽  
Hugo Cagnon ◽  
Laurie Buffo-Lacarriere ◽  
Stéphane Multon
Keyword(s):  
Temperature Scale ◽  
Scale Effects ◽  
Element Model ◽  
Early Age ◽  
Rate Dependency ◽  
Nuclear Containment ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Concrete Damage ◽  
Transient Thermal

The objective of this research is to understand the behavior of concrete subjected to temperatures up to 180°C and to gas absolute pressures up to 5 bars applied during the two weeks envisioned in the “loss of coolant accident” (LOCA) scenario. Previous studies about delayed mechanical behavior of concrete have pointed out an increase of delayed strains with the temperature rise: the basic creep can be multiplied by a factor 10 at 80°C, and coupling between creep and heating can lead to damage and to transient thermal creep. These phenomena could be predominant if the LOCA induced conditions are maintained several days and more probably several weeks. So, a model able to predict the cracking and the gas leakages has to be developed. It has to consider these phenomena and their coupling with other possible causes of concrete damage previous to the LOCA. In fact, if the LOCA occurs on structure already damaged by early age cracking or endogenous chemical reactions, such as AAR or ettringite, the leakage risk could be increased. The paper will focus on some important aspects of these phenomena (creep rate dependency on temperature, scale effects at early age, damage induced by swelling reactions), and on their coupling in a finite element model.

scholarly journals The VINON-LOCA test facility: exploring the LOCA phenomenology through an out-of-pile thermal sequence on irradiated pressurized fuel rod

2021 ◽  
Vol 253 ◽  
pp. 06002
Author(s):  
B. Biard ◽  
C. Colin ◽  
S. Bernard ◽  
V. Marty ◽  
G. Volle ◽  
...  
Keyword(s):  
Gamma Camera ◽  
Test Facility ◽  
Flow Meters ◽  
Loss Of Coolant Accident ◽  
Fission Gas ◽  
Loss Of Coolant ◽  
Post Test ◽  
Set Up ◽  
Fuel Fragmentation ◽  
Fission Gas Release

Since the out-of-pile semi-integral tests performed at Studsvik in 2011 for the NRC [1] and the Halden Loss-Of-Coolant Accident (LOCA) test series IFA-650 [2], a major safety interest has raised for Fuel Fragmentation, Relocation and Dispersal (FFRD) during a LOCA sequence. In addition to the characteristics of the fuel ejected from the rod after the clad failure, the fuel behaviour before the clad failure is still to be investigated, especially its fragmentation and its possible relocation within the rod during the clad ballooning phase. Furthermore, the chronology and the sequencing of these phenomena is of particular interest. For this purpose, the VINON-LOCA program, lying in the framework of a trilateral agreement between EDF, Framatome and CEA, is aimed at performing Out-Of-Pile heating tests on irradiated repressurized fuel rods, reproducing a typical Loss Of Coolant Accident thermal sequence. The VINON-LOCA experimental set-up is located in the so-called VERDON lab of the LECA-STAR hot cell complex. This lab was dedicated to the VERDON-ISTP program [3]. The VINON-LOCA set-up is thus largely instrumented for addressing not only these FFRD topics, but also Fission Gas Release (FGR), combining both online measurement (gamma stations, gamma camera, acoustic sensor, pressure, temperatures, flow meters, microGC…), and preand post-test characterization (gamma scanning, tomography, metrology, fuel fragments weighing and sieving, gas analyses…). An extensive and substantial qualification campaign has been performed to validate the furnace design regarding the desired test conditions, and to qualify the instrumentation. Following some preliminary modelling and calculations, it has included tests on an out-of-cell twin mockup and tests on dummy inactive rods in the hot cell. This allowed achieving successfully the first experimental qualification test of the program end of 2019 on an irradiated UO2 fuel rodlet. A second irradiated experiment is planned with increased instrumentation capabilities, notably a 2D gamma camera for online fuel motion detection.

Thin film samples: a new methodology for investigating the mechanisms of fission gas releases from nuclear fuel during a LOCA

MRS Advances ◽  
2016 ◽  
Vol 1 (35) ◽  
pp. 2439-2445
Author(s):  
Guillaume Brindelle ◽  
Gianguido Baldinozzi ◽  
Hélène Capdevila ◽  
Lionel Desgranges ◽  
Yves Pontillon
Keyword(s):  
Thin Film ◽  
Nuclear Fuel ◽  
Basic Mechanism ◽  
Loss Of Coolant Accident ◽  
Fission Gas ◽  
Loss Of Coolant ◽  
Significant Step

ABSTRACTAccurately predicting fission gas releases (FGR) from high burn-up fuels during off-normal conditions, such as a loss-of-coolant accident (LOCA), is an important, major challenge. A significant step forward would be to identify and assess the basic mechanisms causing this FGR. A helpful way of better understanding these basic mechanisms is to separate these effects and to perform irradiations on materials simulating the nuclear fuel. Mesoporous or dense CeO2 and UO2 samples (with thin film geometry) were selected for these studies as materials representative of irradiated fuels. A basic mechanism to obtain a better understanding of FGR is described and a new methodology using thin film samples is developed to test the validity of this mechanism.

scholarly journals A Study of Prediction Model Improvement for Air-Oxidation Breakaway in a Postulated Spent Nuclear Fuel Pool Complete Loss of Coolant Accident

2021 ◽  
Vol 13 (3) ◽  
pp. 1442
Author(s):  
Sanggil Park ◽  
Jaeyoung Lee ◽  
Min Bum Park
Keyword(s):  
Kinetic Model ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Complete Loss ◽  
Air Oxidation ◽  
Loss Of Coolant Accident ◽  
Spent Nuclear Fuel Pool ◽  
Loss Of Coolant ◽  
Model Derivation ◽  
Model Improvement

The temperature of zirconium alloy cladding on the postulated spent nuclear fuel pool complete loss of coolant accident is abruptly increased at a certain time and the cladding is almost fully oxidized to weak ZrO2 in the air. This abrupt temperature escalation phenomenon induced by the air-oxidation breakaway is called a zirconium fire. Although an air-oxidation breakaway kinetic model correlated between time and temperature has been implemented in the MELCOR code, it is likely to bring about unexpected large errors because of many limitations of model derivation. This study suggests an improved time–temperature correlated kinetic model using the Johnson–Mehl equation. It is based on that the air-oxidation breakaway is initiated by the phase transformation from the tetragonal to monoclinic ZrO2 at the oxide–metal interface in the cladding. This new model equation is also evaluated with the Zry-4 air-oxidation literature data. This equation resulted in the almost similar air-oxidation breakaway timing to the actual experimental data at 800 °C. However, at 1000 °C, it showed an error of about 8 min. This could be inferred from the influence of the ZrN phase change due to the nitrogen existing in air.

Analysis of loss of coolant accident without ECCS and DHRS in an integral pressurized water reactor using RELAP/SCDAPSIM

2021 ◽  
Vol 134 ◽  
pp. 103648
Author(s):  
Katarzyna Skolik ◽  
Chris Allison ◽  
Judith Hohorst ◽  
Mateusz Malicki ◽  
Marina Perez-Ferragut ◽  
...  
Keyword(s):  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant
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