Experimental Investigation of Melt Coolability and Ablation Behavior of Oxidic Sacrificial Material at Prototypic Conditions in Scaled Down Core Catcher

2019 ◽  
Vol 5 (4) ◽  
Author(s):  
Samyak S. Munot ◽  
Ganesh V ◽  
Parimal P. Kulkarni ◽  
Arun K. Nayak
Keyword(s):  
Average Rate ◽  
Ablation Rate ◽  
Heat Temperature ◽  
Melt Pool ◽  
Simulated Experiment ◽  
Maximum Value ◽  
Sacrificial Material ◽  
Core Catcher ◽  
Core Meltdown ◽  
Time Required

To minimize the potential risk of design extension conditions (DEC) with core meltdown, some advanced reactors employ ex-vessel core catchers which stabilize and cool the corium for prolonged period by strategically flooding it. This paper describes the coolability of the melt pool and ablation process in a scaled down ex-vessel core catcher employing sacrificial material which reduces the specific volumetric heat, temperature, and density of the melt pool. To understand these phenomena, a simulated experiment was carried out. The experiment was performed by melting about 500 kg of corium simulant using thermite reaction at about 2500 °C. The bricks of oxidic sacrificial material were arranged in the core catcher vessel which was surrounded by a tank filled with water up to a certain level. After the time required for melt inversion, water was introduced to flood the test section from the top. The melt pool temperatures were monitored at various locations using “K” and “C” type thermocouples to obtain ablation depth at different elevations with time. The results show that the coolability of the molten pool in the presence of water for the present geometry is achievable with outside vessel temperatures not exceeding 100 °C. A ceramic stable crust was observed at the top surface of the melt pool, which prevented water ingression into the molten corium. The ablation rate was found to be maximum at the lower corners of the brick arrangement with the maximum value being 0.75 mm/s. An average rate of about 0.18 mm/s was obtained in the brick matrix.

Prothrombin Evaluation as Obtained by Kinetics Studies of Antigen-Antibody Reaction in a Laser Nephelometer

1984 ◽  
Vol 52 (01) ◽  
pp. 015-018 ◽  
Author(s):  
A Girolami ◽  
A Sticchi ◽  
R Melizzi ◽  
L Saggin ◽  
G Ruzza
Keyword(s):  
Liver Cirrhosis ◽  
Cirrhotic Patient ◽  
Maximum Rate ◽  
Serum Proteins ◽  
Clotting Factors ◽  
Kinetics Studies ◽  
Maximum Value ◽  
Time Required ◽  
Antigen Antibody ◽  
Kinetics Of

SummaryLaser nephelometry is a technique which allows the evaluation of the concentration of several serum proteins and clotting factors. By means of this technique it is also possible to study the kinetics of the reaction between antigen and antibody. We studied the kinetics of the reaction between prothrombin and an antiprothrombin antiserum using several prothrombins namely: Prothrombin Padua, prothrombin Molise, which are two congenital dysprothrombinemias, cirrhotic, coumarin or normal prothrombins. Different behaviors in the kinetics of the reactions were shown even when the concentration of prothrombins was about the same in all plasma tested. These differences were analyzed by means of a computer (Apple II 48 RAM) programmed to solve four unknown equations (Rodbard’s equation). From the data so obtained one can see that when voltages at the beginning and at the end of the reaction are in all cases about the same, a clear difference in the time required to reach half the maximum value of the voltage can still be demonstrated. This parameter, which is expressed in minutes, is longer in coumarin and prothrombin Molise than in controls. On the contrary it is shorter in prothrombin Padua and has about the same value of controls in the cirrhotic patient. Moreover the time at which the maximum rate is obtained is longer in coumarin and prothrombin Molise than in controls and shorter in liver cirrhosis and prothrombin Padua. In conclusion data obtained show that coumarin prothrombin behaves in a different way from cirrhotic prothrombin and also that there is a different behaviour between the two congenital dysprothrombinemias.

Study on Melt Coolability and Water Ingression Through Melt Pool in Scaled Down Core Catcher—The Influence of Vessel Angle

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Ganesh V. ◽  
Parimal P. Kulkarni ◽  
Arun K. Nayak
Keyword(s):  
Temperature History ◽  
Bottom Plate ◽  
Transient Temperature ◽  
Test Evaluation ◽  
The Core ◽  
Melt Pool ◽  
Core Catcher ◽  
Post Test ◽  
History Of ◽  
Series Of Experiments

Abstract An ex-vessel core catcher is generally used in advanced reactors to mitigate core melt scenarios by stabilizing and cooling the corium for prolonged period by strategically flooding it. The side indirect cooling along with delayed top flooding of water ensures that the water interacts with the oxidic components only after melt inversion. However, water ingression either through the top of melt pool or through the crust–vessel gap may lead to unoxidized metal–water interaction in the melt leading to hydrogen production. To avoid this deleterious scenario, water ingression into the bulk of the melt is to be avoided. In this study, a series of experiments using a scaled down core catcher has been conducted to study the phenomena of melt coolability and water ingression by varying the bottom vessel angle of the core catcher. Three different angles of the bottom plate were considered: 10, 20, and 30 deg. The melt used was a corium simulant in the form of CaO–B2O3.The transient temperature history of melt pool, inside and outside vessel surface temperatures along with the post-test evaluation of the test section reveals that the bottom angle has an effect on water ingression and the resultant melt eruption at different locations. The tests conducted showed that the scaled down core catcher with 10-deg inclination of the bottom plate does not exhibit water ingression, whereas the 20- and 30-deg angle-scaled down core catchers showed water ingression and subsequent melt eruption.

New sacrificial material for ex-vessel core catcher

2015 ◽  
Vol 467 ◽  
pp. 778-784 ◽  
Author(s):  
Andrei A. Komlev ◽  
Vyacheslav I. Almjashev ◽  
Sevostian V. Bechta ◽  
Vladimir B. Khabensky ◽  
Vladimir S. Granovsky ◽  
...  
Keyword(s):  
Sacrificial Material ◽  
Core Catcher

scholarly journals Fast and Reliable Locating of Points with the Maximum Value of Total Electromagnetic Field Using a Modern Experimental Method for Radio Coverage in Urban Environment

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
Petar S. Medjedovic ◽  
Darko S. Suka
Keyword(s):  
Electromagnetic Field ◽  
Experimental Method ◽  
Monitoring Network ◽  
Optimal Choice ◽  
City Centre ◽  
Maximum Value ◽  
Em Field ◽  
The Republic ◽  
Time Required ◽  
Banja Luka

This research has been performed within the project “prediction, measurement, and analysis of composite electromagnetic field of artificial radiation sources,” funded by the Ministry of Science and Technology of the Republic of Srpska, Bosnia and Herzegovina. The ultimate goal of the project is the installation of a monitoring network for continuous measurement and recording of nonionizing electromagnetic (EM) radiation levels in the wider area of Banja Luka city centre covering about 10 km2. For this reason it was necessary to make an optimal choice from a dozen of measurement points with the maximum value levels of total EM field. It was a difficult task, because in this case, with the resolution of 5m × 5m, approximately 400,000 points should be examined. Therefore, the pedestrian zones, areas, and routes with significantly smaller surfaces but with the largest flow of people have been examined, so the time required for their mapping with values of total EM field has been reduced to a more realistic framework. In this paper, in the volume allowed by the defined criteria, a fast and reliable experimental method has been described, which has been examined at one of the studied areas in the named project, with surface of 0.008 km2.

scholarly journals ESFR SMART PROJECT CONCEPTUAL DESIGN OF IN-VESSEL CORE CATCHER

2021 ◽  
Vol 247 ◽  
pp. 01002
Author(s):  
Joel Guidez ◽  
Antoine Gerschenfeld ◽  
Janos Bodi ◽  
Konstantin Mikityuk ◽  
Francisco Alvarez-Velarde ◽  
...  
Keyword(s):  
Natural Convection ◽  
Fast Reactor ◽  
Passive Control ◽  
Mitigation Strategies ◽  
Severe Accident ◽  
Fukushima Accident ◽  
The Core ◽  
Core Catcher ◽  
Thermal Calculations ◽  
Core Meltdown

Even before Fukushima accident occurred, the safety authorities have required that new power plant designs must take into account beyond design-basis accidents including possible core meltdown. Among the mitigation strategies, the corium retention must be ensured, so a core catcher is implemented in the design of the Generation IV Sodium-cooled Fast Reactor. An internal core catcher within the vessel (in-vessel retention) is the option chosen for the European Sodium-cooled Fast Reactor investigated in the H2020 ESFR-SMART project. The new core investigated in ESFR SMART with lower void effect has a better behavior in case of severe accident. The use of passive control rods is also an improvement for prevention of severe accident. Moreover, we have in the ESFR SMART core dedicated tubes for corium discharge that should allow discharging quickly the melted materials and should help to prevent large criticality. Calculations show that after several seconds, these discharge tubes begin to open, and the corium arrives by this preferential way on the core catcher, quicker and in limited quantities at the beginning of the accident. However, the core catcher is designed to be able to retain the whole core meltdown. Its design allows good possibilities of cooling by natural convection of sodium. Some thermal calculations were provided with a multi-layer concept but the global mechanical conception seems difficult. So a one layer core catcher in molybdenum, material compatible with sodium and used on the core catcher of the last SFR, started in 2016: BN 800, is investigated. Explanations are given on the choice of this material proposed for the catcher and used for thermal calculations. With the proposed design, the corium is spread on the core catcher and the residual power of the corium can be dispelled by natural convection by the sodium circulating around and above the core catcher without boiling of sodium if the melted core is less than about 25% of whole core. In case of bigger quantities of melted core, boiling of sodium could appear under the core catcher. Further less conservative calculations would be necessary to better know the limit.

scholarly journals Dielectric loss due to polar molecules in solid paraffin wax

1939 ◽  
Vol 172 (951) ◽  
pp. 502-517 ◽  
Keyword(s):  
Relaxation Time ◽  
Dielectric Loss ◽  
Maximum Rate ◽  
Angular Frequency ◽  
Rate Of Change ◽  
Polar Molecules ◽  
Dielectric Polarization ◽  
Specific Energy Loss ◽  
Maximum Value ◽  
Time Required

According to most theories of dielectric loss the maximum rate of change of dielectric constant and the maximum value of the specific energy loss per unit volume occur at an angular frequency ω (= 2 πv ) which is the inverse of a quantity r known as the relaxation time of the dielectric. The relaxation time is the time required for the polarization of the dielectric to revert to 1/ ϵ of its value after the removal of the applied electric field: and this is a quantity which can be determined experimentally. According to Debye’s theory of polar molecules, part of the dielectric polarization is due to the orientation of the dipoles in line with the applied field and the relaxation time is related closely to the time taken for the molecules to revert to their random positions after removal of the field.

NOISE-ENHANCED TRANSMISSION OF TIME-MODULATED NEUROTRANSMITTER RANDOM POINT TRAINS IN A NOISY NEURON

2016 ◽  
Vol 24 (02n03) ◽  
pp. 367-383 ◽  
Author(s):  
TIANQUAN FENG ◽  
MING YI
Keyword(s):  
Neuron Model ◽  
Additive Noise ◽  
Average Rate ◽  
Random Point ◽  
Noise Power ◽  
Enhanced Transmission ◽  
Maximum Value ◽  
Optimal Value ◽  
Snr Gain ◽  
Noise Power Density

We numerically investigate the transmission of time-modulated random point trains in a conductance-based neuron model by including shot noise described as additive noise trains. The results show that additive noise trains can induce neuron responses exhibiting correlation with the temporally modulated random point trains. In addition, the additive noise power density can be increased up to an optimal value where the output signal-noise ratio (SNR) reaches a maximum value. This property of noise-enhanced transmission of random point trains can be related to the stochastic resonance (SR) phenomenon. More interestingly, we find that the SNR gain can exceed unity and can also be optimized by tuning the average rate of the input random point trains. The present study illustrates the potential to utilize the additive noise and temporally modulated random point trains for optimizing the response of the neuron to inputs, as well as a guidance in the design of information processing devices to random neuron spiking.

A Study of the Behaviour of Double Oxide Films in Al Alloy Melts

2013 ◽  
Vol 765 ◽  
pp. 260-265 ◽  
Author(s):  
Mahmoud El-Sayed ◽  
Hanadi G. Salem ◽  
Abdel-Razik Kandeil ◽  
William D. Griffiths
Keyword(s):  
Mechanical Properties ◽  
Oxide Film ◽  
Average Rate ◽  
Oxide Films ◽  
Reaction Rates ◽  
Fatigue Properties ◽  
Al Alloy ◽  
Double Oxide ◽  
Alloy Castings ◽  
Time Required

The mechanical properties of Al castings are reduced by inclusions, particularly double oxide films, or bifilms, which are formed due to surface turbulence of the liquid metal during handling and/or pouring. These defects have been reported not only to decrease the tensile and fatigue properties of Al alloy castings, but also to increase their scatter. Recent research has suggested that the nature of oxide film defects may change with time, as the air inside the bifilm would react with the surrounding melt leading to its consumption, which may enhance the mechanical properties of Al alloy castings. In order to follow changes in the composition of the internal atmosphere of a double oxide film defect within an Al melt, a series of analogue experiments were carried out to determine the changes in gas composition of an air bubble trapped in a melt of commercial purity Al, subjected to stirring. The bubble contents were analysed using a mass spectrometer to determine their change in composition with time. Also, the solid species inside the bubbles solidified in the melt were analysed. The results suggested that first oxygen and then nitrogen inside the bubble were consumed, with consumption rates of 2.5x10-6 and 1.3x10-6 mol m-2s-1, respectively. Also, hydrogen diffused into the bubble from the melt at an average rate of 3.4x10-7 mol m-2s-1, although the rate of H diffusion increased significantly after the consumption of most of the oxygen inside the bubble. Based upon these reaction rates the time required for a typical alumina bifilm to lose all its oxygen and nitrogen was determined to be just under 10 minutes.

Mitigation of a Core Meltdown Scenario by Means of a Core Catcher Located Inside the Reactor Pressure Vessel

2004 ◽  
Author(s):  
D. Aquaro ◽  
N. Zaccari
Keyword(s):  
Pressure Vessel ◽  
Effective Conductivity ◽  
Severe Accident ◽  
Mechanical Resistance ◽  
Internal Cooling ◽  
Pebble Bed ◽  
Original Solution ◽  
The Core ◽  
Core Catcher ◽  
Core Meltdown

This paper describes an original solution of core catcher to managing the in vessel retention of the Corium in the accidental event of the core meltdown. The solution envisaged intends to verify the possibility of managing the accidental event within the pressure vessel, ensuring that the CORIUM is confined and cooled. The core catcher, elaborated at the DIMNP, is made of a ceramic pebbel bed (Alumina Al2O3) contained in a metallic or Ceramic Matrix Composite (CMC) structure. The paper illustrates a theoretical model to simulate the thermal-mechanical behaviour of the pebble beds under extremely high loads, developed by the authors. This model has been used to design the core catcher and to determine the effective conductivity and the effective stiffness of the pebble bed. These values have been used in order to implement a numerical model of the core catcher. The results of the thermal and mechanical coupled simulation have permitted to determine the maximum time that the core catcher could resist and the mechanical resistance of the core catcher in the case of RPV external or internal cooling. The preliminary analyses performed have emphasised the good performance of pebble bed core catcher in order to mitigate the envisaged severe accident.

Sign in / Sign up

Export Citation Format

Share Document