Results of the LIVE-L4 Experiment on Melt Behavior in the RPV Lower Head

2010 ◽  
Author(s):  
Alexei Miassoedov ◽  
Thomas Cron ◽  
Jerzy Foit ◽  
Xiaoyang Gaus-Liu ◽  
Alexander Palagin ◽  
...  
Keyword(s):  
Heat Generation ◽  
Molten Pool ◽  
Transient Behavior ◽  
Assessment Process ◽  
Severe Accident ◽  
Mushy Region ◽  
Thermal Hydraulics ◽  
Lower Head ◽  
Post Test ◽  
Crust Thickness

The development of a corium pool in the lower head and its behavior is still a critical issue and is of great importance to assess the severe accident progression consequences to ensure the nuclear plant safety. Therefore, experimental efforts are a vital element of the assessment process, providing hard data and insights of the complicated multi-component, highly turbulent corium pool dynamics. It is essential to consider the whole evolution of the accident, including e.g. formation and growth of the in-core melt pool, characteristics of corium arrival in the lower head, and molten pool behavior after the debris re-melting. These phenomena have a strong impact on a potential termination of a severe accident. The general objective of the LIVE program at the Karlsruhe Institute of Technology (KIT) is to study these phenomena experimentally in large-scale 3D geometry and in supporting separate-effects tests, with emphasis on the transient behavior. The LIVE-L4 experiment was performed using a non-eutectic melt (KNO3-NaNO3) as a simulant fluid. Besides the transient behavior, for which the LIVE-L4 test provides qualified data on temperature evolution in the molten pool and crust growth rates, the experiment addresses other important phenomena, such as the local distribution of heat flux, and the influence of solidification on the thermal-hydraulics of the pool, i.e. the possible existence of a mushy region and its impact on the heat transfer. In the post-test analysis crust thickness profile along the vessel wall, the crust composition and the morphology were determined. The results of this experiment also allow a comparison with findings obtained earlier in other experimental programs. The LIVE-L4 experimental results are being used for the assessment of correlations and development and validation of mechanistic models for the description of molten pool behavior. These calculations are complemented by analyses with the CFD code CONV (thermal hydraulics of heterogeneous, viscous and heat-generating melts) which was developed at IBRAE. The CONV code was applied to simulate the LIVE-L4 test: a) assuming homogeneous heat generation in the liquid and b) accounting for wire heaters used to simulate the heat generation in the melt. Though the results of calculations demonstrate satisfactory agreement with the experimental measurements, deficiencies in the code prediction have been identified regarding e.g. the prediction of the crust thickness. The paper summarizes the objectives of the LIVE program, the main results obtained in the LIVE-L4 experiment and the results of the post-test calculations performed with the CONV code.

scholarly journals Development of failure evaluation method for BWR Lower head in severe accident; - Creep damage evaluation based on thermal-hydraulics and structural analyses -

2016 ◽  
Vol 3 (3) ◽  
pp. 15-00682-15-00682 ◽  
Author(s):  
Jinya KATSUYAMA ◽  
Yoshihito YAMAGUCHI ◽  
Yoshiyuki NEMOTO ◽  
Yoshiyuki KAJI ◽  
Hiroyuki YOSHIDA
Keyword(s):  
Evaluation Method ◽  
Creep Damage ◽  
Severe Accident ◽  
Damage Evaluation ◽  
Thermal Hydraulics ◽  
Lower Head ◽  
Failure Evaluation

In-Vessel Retention Modeling Capabilities of SCDAP/RELAP5-3D©

2002 ◽  
Author(s):  
D. L. Knudson ◽  
J. L. Rempe
Keyword(s):  
Heat Transfer ◽  
Molten Pool ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Complex Processes ◽  
Lower Head ◽  
Environmental Laboratory ◽  
Molten Materials ◽  
Core Materials

Molten core materials may relocate to the lower head of a reactor vessel in the latter stages of a severe accident. Under such circumstances, in-vessel retention (IVR) of the molten materials is a vital step in mitigating potential severe accident consequences. Whether IVR occurs depends on the interactions of a number of complex processes including heat transfer inside the accumulated molten pool, heat transfer from the molten pool to the reactor vessel (and to overlying fluids), and heat transfer from exterior vessel surfaces. SCDAP/RELAP5-3D© has been developed at the Idaho National Engineering and Environmental Laboratory to facilitate simulation of the processes affecting the potential for IVR, as well as processes involved in a wide variety of other reactor transients. In this paper, current capabilities of SCDAP/RELAP5-3D© relative to IVR modeling are described and results from typical applications are provided. In addition, anticipated developments to enhance IVR simulation with SCDAP/RELAP5-3D© are outlined.

LIVE Experiments on Melt Behavior in the RPV Lower Head

2008 ◽  
Author(s):  
Alexei Miassoedov ◽  
Thomas Cron ◽  
Jerzy Foit ◽  
Xiaoyang Gaus-Liu ◽  
Silke Schmidt-Stiefel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Molten Pool ◽  
Vessel Wall ◽  
Flux Distribution ◽  
Severe Accident ◽  
Experimental Program ◽  
Strong Impact ◽  
Residual Water ◽  
Heat Flux Distribution ◽  
Lower Head

Behavior of the corium pool in the lower head is still a critical issue in understanding of PWR core meltdown accidents. One of the key parameter for assessing the vessel mechanical strength is the resulting heat flux at the pool-vessel interface. A number of studies [1]–[3] have already been performed to pursue the understanding of a severe accident with core melting, its course, major critical phases and timing and the influence of these processes on the accident progression. Uncertainties in modeling these phenomena and in the application to reactor scale will undoubtedly persist. These include e.g. formation and growth of the in-core melt pool, relocation of molten material after the failure of the surrounding crust, characteristics of corium arrival in residual water in the lower head, corium stratifications in the lower head after the debris re-melting [4]. These phenomena have a strong impact on a potential termination of a severe accident. The main objective of the LIVE program [5] at FZK is to study the core melt phenomena both experimentally in large-scale 3D geometry and in supporting separate-effects tests, and analytically using CFD codes in order to provide a reasonable estimate of the remaining uncertainty band under the aspect of safety assessment. Within the LIVE experimental program several tests have been performed with water and with non-eutectic melts (mixture of KNO3 and NaNO3) as simulant fluids. The results of these experiments, performed in nearly adiabatic and in isothermal conditions, allow a direct comparison with findings obtained earlier in other experimental programs (SIMECO, ACOPO, BALI, etc.) and will be used for the assessment of the correlations derived for the molten pool behavior. The information obtained from the LIVE experiments includes heat flux distribution through the reactor pressure vessel wall in transient and steady state conditions, crust growth velocity and dependence of the crust formation on the heat flux distribution through the vessel wall. Supporting post-test analysis contributes to characterization of solidification processes of binary non-eutectic melts. Complimentary to other international programs with real corium melts, the results of the LIVE activities provide data for a better understanding of in-core corium pool behavior. The experimental results are being used for development of mechanistic models to describe the in-core molten pool behavior and their implementation in the severe accident codes like ASTEC. The paper summarizes the objectives of the LIVE program and presents the main results obtained in the LIVE experiments up to now.

Post test calculations of a severe accident experiment for VVER-440 reactors by the ATHLET code

Kerntechnik ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. 362-370
Author(s):  
H. György ◽  
I. Trosztel
Keyword(s):  
Severe Accident ◽  
Post Test

Coupling of a Reactor Analysis Code and a Lower Head Thermal Analysis Solver

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Hiroshi Madokoro ◽  
Alexei Miassoedov ◽  
Thomas Schulenberg
Keyword(s):  
Structural Analysis ◽  
Message Passing ◽  
Message Passing Interface ◽  
Severe Accident ◽  
Coupled Analysis ◽  
Accident Analysis ◽  
Analysis Tool ◽  
Lower Head ◽  
Calculation Results ◽  
Reactor Pressure

Due to the recent high interest on in-vessel melt retention (IVR), development of detailed thermal and structural analysis tool, which can be used in a core-melt severe accident, is inevitable. Although RELAP/SCDAPSIM is a reactor analysis code, originally developed for U.S. NRC, which is still widely used for severe accident analysis, the modeling of the lower head is rather simple, considering only a homogeneous pool. PECM/S, a thermal structural analysis solver for the reactor pressure vessel (RPV) lower head, has a capability of predicting molten pool heat transfer as well as detailed mechanical behavior including creep, plasticity, and material damage. The boundary condition, however, needs to be given manually and thus the application of the stand-alone PECM/S to reactor analyses is limited. By coupling these codes, the strength of both codes can be fully utilized. Coupled analysis is realized through a message passing interface, OpenMPI. The validation simulations have been performed using LIVE test series and the calculation results are compared not only with the measured values but also with the results of stand-alone RELAP/SCDAPSIM simulations.

Instituting an Outcomes Assessment Effort: Lessons from the Field

2000 ◽  
Vol 81 (1) ◽  
pp. 85-89 ◽  
Author(s):  
William F. Mecca ◽  
Ann Rivera ◽  
Andrew J. Esposito
Keyword(s):  
Outcomes Assessment ◽  
Family Counseling ◽  
Assessment Process ◽  
Assessment Instruments ◽  
New Haven ◽  
Non Profit ◽  
Multiple Modalities ◽  
Outcomes Evaluation ◽  
Post Test ◽  
Treatment Plans

Family Counseling of Greater New Haven, Inc., is a private, non-profit, mental health outpatient clinic serving children, adults, couples, and families using multiple modalities. In September 1997, in response to pressures for outcomes evaluation from funders and others, the agency launched an outcomes assessment effort using the Problem Solving Inventory (PSI). The instrument is administered at intake and at 90 days or upon termination. A comparison of pre-test with post-test scores indicates some degree of improvement in 96% of agency clients who completed both pre- and post-tests. Obstacles to instituting the outcomes assessment effort are discussed. Initially, the authors identify a lack of human resources for the project, a lack of understanding of the assessment process, and resistance to the assessment process as obstacles. These may be attributed to fear about personal accountability and a misuse of the data collected, and were overcome by education of agency staff. The authors share lessons they have learned about how to successfully institute an outcomes assessment effort. These include: designating staff to oversee the outcomes assessment work; involving clinicians very early in the process, and inviting their input on both process and product; carefully choosing assessment instruments to be closely aligned with program goals; and using the outcomes data for multiple purposes which are meaningful to various constituents within the agency, i.e., treatment plans, quality assurance, marketing, etc.

scholarly journals Developing Competency-Based Assessment for Library Professionals

2015 ◽  
Vol 3 (1) ◽  
pp. 14-28 ◽  
Author(s):  
Marilyn Harhai ◽  
Janice Krueger
Keyword(s):  
Student Learning ◽  
High Performance ◽  
Information Science ◽  
Program Improvement ◽  
Assessment Process ◽  
Workplace Performance ◽  
Professional Programs ◽  
Traditional Assessment ◽  
Post Test ◽  
Competency Based

The assessment process for student learning is often influenced and guided by well-defined standards and competencies dictated by various accrediting bodies that oversee graduate professional programs culminating in the master’s degree. When applied in an accredited library and information science (LIS) program, traditional assessment techniques, such as portfolios, grades, and authentic assessments consistently affirmed student high performance, leaving little room to demonstrate student learning and program improvement. Consequently, the program redefined its assessment plan through the development of a pre-/post-test survey instrument that aligned with learning outcomes, the curriculum, and professional competencies. Pre-test responses were analyzed through SPSS to ascertain initial findings and effectiveness of the instrument to gauge student learning and workplace performance. Implications for student advisement, curriculum adjustments, program improvement, and strengthening the assessment plan for accreditation emerged. Areas for further development, particularly in the work environment, and research were also identified.

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