Stand-Alone Containment Analysis of the Phébus FPT-3 Test With the ASTEC and the MELCOR Codes

2018 ◽  
Author(s):  
Bruno Gonfiotti ◽  
Sandro Paci
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Research Programme ◽  
Severe Accident ◽  
Sensitivity Analyses ◽  
Correct Prediction ◽  
Control Rod ◽  
Melt Pool ◽  
Fuel Bundle ◽  
Pool Model

The Phébus FP experimental campaign (1988–2010) is recognized as one of the most relevant in the field of Severe Accident researches. During this international research programme, 4 tests were performed to investigate the degradation phenomena for a real PWR fuel bundle in strongly or weakly oxidizing conditions, considering different control rod materials and burn-up levels, plus 1 test studying the phenomena related to a melt pool scenario. These integral tests gave a fundamental improvement in the knowledge of the key phenomena occurring during a Severe Accident and the obtained data were also employed to develop numerical models for the safety analysis of these scenarios. The ASTEC and the MELCOR integral codes were two of the main international codes that have benefited from these experimental data. After the termination of the Phébus FP campaign, these two codes were furthermore improved, implementing more recent research findings. So, a continuous verification and validation work is necessary to check that the new improvements, implemented in such codes, also allow a better prediction of these past Phébus FP tests. Therefore, the aim of the present work is to re-analyze the Phébus FPT-3 test employing the up-to-date versions of the ASTEC and MELCOR codes. This FPT-3 test was also the basis for an international benchmark exercise carried out in the frame of the EU SARNET project. The performed analysis focuses only on the stand-alone containment aspects of the test, and a comparison against the results obtained by the different participants to the SARNET benchmark is also performed. An original analysis on the main differences obtained employing three different spatial nodalizations and a sensitivity analysis on the effects of different input parameters influencing the aerosol behavior are also proposed. These sensitivity analyses also show the need of a sufficient number of volumes for a correct prediction of the coupling between the containment thermal-hydraulics transient and the aerosol behavior. The results obtained show only a partial agreement with the experimental data and with the best calculations performed during the SARNET benchmark, due to user’s effects and code’s limitations as the ones present in the Iodine pool model in MELCOR.

scholarly journals Stand-Alone Containment Analysis of the Phébus FPT Tests with the ASTEC and the MELCOR Codes: The FPT-0 Test

2017 ◽  
Vol 2017 ◽  
pp. 1-25 ◽  
Author(s):  
Bruno Gonfiotti ◽  
Sandro Paci
Keyword(s):  
Fission Products ◽  
Severe Accident ◽  
Sensitivity Analyses ◽  
Light Water Reactors ◽  
Control Rod ◽  
Light Water ◽  
Severe Accidents ◽  
Fuel Bundle ◽  
Water Reactors

The integral Phébus tests were probably one of the most important experimental campaigns performed to investigate the progression of severe accidents in light water reactors. In these tests, the degradation of a PWR fuel bundle was investigated employing different control rod materials and burn-up levels in strongly or weakly oxidizing conditions. From the results of such tests, numerical codes such as ASTEC and MELCOR have been developed to describe the evolution of a severe accident. After the termination of the experimental Phébus campaign, these two codes were furthermore expanded. Therefore, the aim of the present work is to reanalyze the first Phébus test (FPT-0) employing the updated ASTEC and MELCOR versions to ensure that the new improvements introduced in such codes allow also a better prediction of these Phébus tests. The analysis focuses on the stand-alone containment aspects of this test, and the paper summarizes the main thermal-hydraulic results and presents different sensitivity analyses carried out on the aerosols and fission products behavior. This paper is part of a series of publications covering the four executed Phébus tests employing a solid PWR fuel bundle: FPT-0, FPT-1, FPT-2, and FPT-3.

scholarly journals Numerical Approach for the Estimation of Throat Heat Flux in Liquid Rocket Engines

2020 ◽  
Author(s):  
P. Concio ◽  
M. T. Migliorino ◽  
F. Nasuti
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Numerical Models ◽  
Numerical Approach ◽  
Experimental Information ◽  
Correct Prediction ◽  
Rocket Engines ◽  
Liquid Rocket Engines ◽  
Liquid Rocket

Abstract The problem of prediction of heat flux at throat of liquid rocket engines still constitutes a challenge, because of the little experimental information. Such a problem is of obvious importance in general, and becomes even more important when considering reusable engines. Unfortunately, only few indirect experimental data are available for the validation of throat heat flux prediction. On the numerical side, a detailed solution would require a huge resolution and codes able to solve at the same time combustion, boundary layer with possible finite-rate reactions, expansion up to at least sonic speed, and in some cases radiative heat flux. Therefore, it is important to validate, with the few experimental data available in the literature, simplified CFD approaches whose aim is to predict heat flux in the nozzle in affordable times. Results obtained by different numerical models based on a RANS approach show the correctness and quality of the approximations made, indicating the main phenomena to be included in modeling for the correct prediction of throat heat flux.

scholarly journals Standalone Containment Analysis of Four Phébus Tests with the ASTEC and the MELCOR Codes

2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Bruno Gonfiotti ◽  
Sandro Paci
Keyword(s):  
Nuclear Power ◽  
Fission Products ◽  
Severe Accident ◽  
Primary Circuit ◽  
Solid Base ◽  
Pressurized Water ◽  
Control Rod ◽  
Experimental Campaign ◽  
Fuel Bundle ◽  
Software Codes

After the severe accident (SA) occurred at the Three-Miles Island Nuclear Power Plant (NPP), important efforts on the investigation of the different phenomena during this kind of accidents have been started. Several experimental campaigns investigating one phenomenon at time or the combination of two or more phenomena have been performed. Today, the Phébus experimental campaign is probably the most important activity on the evaluation of the coupling among different phenomena. Four out of five tests investigated the degradation of an intact Pressurized Water Reactor (PWR) fuel bundle and the subsequent transport of Fission Products (FP) and Structural Materials (SM) through the primary circuit and into the containment, while the fifth test was only the degradation of a bed of PWR fuel bundle debris. These tests were performed between 1990 and 2010 at the CEA Cadarache laboratories (France) in a 5000:1 scaled facility. The main four tests varied the employed control rod materials, the fuel burn-up, and the oxidizing conditions of the atmosphere (strongly or weakly). The outcomes of this experimental campaign created a solid base for the understanding of the involved phenomena and allowed the development of models and software codes capable of simulating the evolution of a SA in a real NPP. ASTEC and MELCOR were two of the main SA codes profiting from the results of this Phébus campaign. These two codes were further improved in the latest years to account for the findings obtained in more recent experimental campaigns. A continuous verification and validation work is then necessary to check how the newer code’s versions reproduce the tests performed in these older experimental campaigns such as Phébus one. The present work is intended to be the final step of a series of publications covering the activities carried out at University of Pisa with the ASTEC and the MELCOR SA codes on the four Phébus tests employing an intact PWR fuel bundle. Because of the complexity and the extent of these tests, only the containment aspects were considered in the precedent works, i.e., only the thermal-hydraulics transient and its coupling with the FP and SM behavior. Then, general conclusions based on the outcomes of these precedent works are summarized in this work.

Influence of Boron Carbide on Core Degradation During Severe Accidents in LWRs

2012 ◽  
Author(s):  
Martin Steinbrück
Keyword(s):  
Boron Carbide ◽  
Nuclear Power ◽  
Source Term ◽  
Current Knowledge ◽  
Steel Structures ◽  
Severe Accident ◽  
Control Rod ◽  
Severe Accidents ◽  
Fuel Bundle ◽  
Water Reactors

Boron carbide (B4C) is widely used as neutron absorbing control rod material in light water reactors (LWRs). It was also applied in all units of the Fukushima Dai-ichi nuclear power plant. Although the melting temperature of B4C is 2450 °C, it initiates local, but significant melt formation in the core at temperatures around 1250 °C due to eutectic interactions with the surrounding steel structures. The B4C containing melt relocates and hence transports material and energy to lower parts of the fuel bundle. It is chemically aggressive and may attack other structure materials. Furthermore, the absorber melt is oxidized by steam very rapidly and thus contributes to the hydrogen source term in the early phase of a severe accident. After failure of the control rod cladding B4C reacts with the oxidizing atmosphere. This reaction produces CO, CO2, boron oxide and boric acids, as well as significant amount of hydrogen. It is strongly exothermic, thus causing considerable release of energy. No or only insignificant formation of methane was observed in all experiments with boron carbide. The paper will summarize the current knowledge on boron carbide behavior during severe accidents, and will try, also in the light of the Fukushima accidents, to draw some common conclusions on the behavior of B4C during severe accidents with the main focus on the consequences for core degradation and hydrogen source term.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

scholarly journals Stormwater harvesting in ephemeral streams: how to bypass clogging and unsaturated layers

2021 ◽  
Author(s):  
José D. Henao Casas ◽  
Fritz Kalwa ◽  
Marc Walther ◽  
Randolf Rausch
Keyword(s):  
Vadose Zone ◽  
Numerical Models ◽  
Water Storage ◽  
Sensitivity Analyses ◽  
Ephemeral Streams ◽  
Infiltration Rates ◽  
Stormwater Harvesting ◽  
Harvesting Systems ◽  
Study Case ◽  
Recharge Rates

AbstractTo cope with water scarcity in drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration. These stormwater harvesting systems are often accompanied by high evaporation rates and hygiene problems. This is commonly a consequence of low infiltration rates, which are caused by clogging layers that form on top of the soil profile and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using analytical equations, numerical models, and sensitivity analyses. Dams built in the channel of ephemeral streams (wadis) are selected as a study case to construct the numerical simulations. The modelling demonstrated that vadose-zone wells and infiltration trenches contribute to effective bypassing of the clogging layer. By implementing these solutions, recharge begins 2250–8100% faster than via infiltration from the bed surface of the wadi reservoir. The sensitivity analysis showed that the recharge rates are especially responsive to well length and trench depth. In terms of recharge quantity, the well had the best performance; it can infiltrate up to 1642% more water than the reservoir, and between 336 and 825% more than the trench. Moreover, the well can yield the highest cumulative recharge per dollar and high recharge rates when there are limitations to the available area. The methods investigated here significantly increased recharge rates, providing practical solutions to enhance aquifer water storage in drylands.

scholarly journals Optimization of Laser Powder Bed Fusion Processing Using a Combination of Melt Pool Modeling and Design of Experiment Approaches: Density Control

2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Morgan Letenneur ◽  
Alena Kreitcberg ◽  
Vladimir Brailovski
Keyword(s):  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Density Prediction ◽  
Melt Pool ◽  
Density Control ◽  
Pool Model ◽  
Conventional Material ◽  
Prediction Approach

A simplified analytical model of the laser powder bed fusion (LPBF) process was used to develop a novel density prediction approach that can be adapted for any given powder feedstock and LPBF system. First, calibration coupons were built using IN625, Ti64 and Fe powders and a specific LPBF system. These coupons were manufactured using the predetermined ranges of laser power, scanning speed, hatching space, and layer thickness, and their densities were measured using conventional material characterization techniques. Next, a simplified melt pool model was used to calculate the melt pool dimensions for the selected sets of printing parameters. Both sets of data were then combined to predict the density of printed parts. This approach was additionally validated using the literature data on AlSi10Mg and 316L alloys, thus demonstrating that it can reliably be used to optimize the laser powder bed metal fusion process.

Investigation of Quench-16 Experiment With MELCOR Computer Code

2014 ◽  
Author(s):  
Petya Vryashkova ◽  
Pavlin Groudev ◽  
Antoaneta Stefanova
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Initial Temperature ◽  
Computer Code ◽  
Air Flow Rate ◽  
Fuel Rod ◽  
Fuel Bundle ◽  
Oxygen Starvation ◽  
Air Ingress ◽  
Good Agreement

This paper presents a comparison of MELCOR calculated results with experimental data for the QUENCH-16 experiment. The analysis for the air ingress experiment QUENCH-16 has been performed by INRNE. The calculations have been performed with MELCOR code. The QUENCH-16 experiment has been performed on 27-th of July 2011 in the frame of the EC-supported LACOMECO program. The experiments have focused on air ingress investigation into an overheated core following earlier partial oxidation in steam. QUENCH-16 has been performed with limited pre-oxidation and low air flow rate. One of the main objectives of QUENCH-16 was to examine the interaction between nitrogen and oxidized cladding during a prolonged period of oxygen starvation. The bundle is made from 20 heated fuel rod simulators arranged in two concentric rings and one unheated central fuel rod simulator, each about 2.5 m long. The tungsten heaters were surrounded by annular ZrO2 pellets to simulate the UO2 fuel. The geometry and most other bundle components are prototypical for Western-type PWRs. To improve the obtained results it has been made a series of calculations to select an appropriate initial temperature of the oxidation of the fuel bundle and modified correlation oxidation of Zircaloy with MELCOR computer code. The compared results have shown good agreement of calculated hydrogen and oxygen starvation in comparison with test data.

Stand-Alone Containment Analysis of the PHÉBUS FPT-1 Test With the ASTEC and the MELCOR Codes

2016 ◽  
Author(s):  
Bruno Gonfiotti ◽  
Sandro Paci
Keyword(s):  
State Of The Art ◽  
External Environment ◽  
Fission Products ◽  
Severe Accident ◽  
Sensitivity Analyses ◽  
Complex Task ◽  
Primary Coolant ◽  
Control Volumes ◽  
Coolant System

The estimation of Fission Products (FPs) release from the containment system of a nuclear plant to the external environment during a Severe Accident (SA) is a quite complex task. In the last 30–40 years several efforts were made to understand and to investigate the different phenomena occurring in such a kind of accidents in the primary coolant system and in the containment. These researches moved along two tracks: understanding of involved phenomenologies through the execution of different experiments, and creation of numerical codes capable to simulate such phenomena. These codes are continuously developed to reflect the actual SA state-of-the-art, but it is necessary to continuously check that modifications and improvements are able to increase the quality of the obtained results. For this purpose, a continuous verification and validation work should be carried out. Therefore, the aim of the present work is to re-analyze the Phébus FPT-1 test employing the ASTEC (F) and MELCOR (USA) codes. The analysis focuses on the stand-alone containment aspects of the test, and three different modellisations of the containment vessel have been developed showing that at least 15/20 Control Volumes (CVs) are necessary for the spatial schematization to correctly predict thermal-hydraulics and the aerosol behavior. Furthermore, the paper summarizes the main thermal-hydraulic results, and presents different sensitivity analyses carried out on the aerosols and FPs behavior.

Sign in / Sign up

Export Citation Format

Share Document