Best estimate approach for the evaluation of critical heat flux phenomenon in the boiling water reactors
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T. Kaliatka
,
A. Kaliatka
Abstract
Because of the uncertainties associated with the definition of Critical Heat Flux (CHF), the best estimate approach should be used. In this paper the application of best-estimate approach for the analysis of CHF phenomenon in the boiling water reactors is presented. At first, the nodalization of RBMK-1500, BWR-5 and ABWR fuel assemblies were developed using RELAP5 code. Using developed models the CHF and Critical Heat Flux Ratio (CHFR) for different types of reactors were evaluated. The calculation results of CHF were compared with the well-known experimental data for light water reactors. The uncertainty and sensitivity analysis of ABWR 8 × 8 fuel assembly CHFR calculation result was performed using the GRS (Germany) methodology with the SUSA tool. Finally, the values of Minimum Critical Power Ratio (MCPR) were calculated for RBMK-1500, BWR-5 and ABWR fuel assemblies. The paper demonstrate how, using the results of sensitivity analysis, to receive the MCPR values, which covers all uncertainties and remains best estimated.
Abstract
Wegen der mit der Definition der kritischen Wärmestromdichten (CHF) verbundenen Unsicherheiten sollte der Best-Estimate-Ansatz verwendet werden. In diesem Beitrag wird die Anwendung des Best Estimate Ansatzes zur Analyse der CHF-Phänomene in Siedewasserreaktoren vorgestellt. Zuerst wurde die Nodalisation von RBMK-1500, BWR-5 und ABWR-Brennelementanordnungen mit Hilfe des RELAP5-Codes entwickelt. Damit wurden die CHF und das kritische Wärmestromverhältnis (CHFR) für verschiedene Reaktortypen bestimmt. Die Rechenergebnisse der CHF wurden verglichen mit den gut bekannten experimentellen Daten für Leichtwasserreaktoren. Die Unsicherheits- und Sensitivitätsanalyse der ABWR-8 × 8-Brennelementanordnung wurden mit Hilfe des von der GRS entwickelten Programmsystems SUSA durchgeführt. Zum Schluss wurden die Werte des minimalen kritischen Leistungsverhältnisses (MCPR) für RBMK-1500, BWR-5 und ABWR-Brennelementanordnungen berechnet. Der Beitrag zeigt, wie man mit Ergebnissen der Sensitivitätsanalyse MCPR-Werte erhält, die alle Unsicherheiten abdecken und beste Schätzwerte bleiben.
Acknowledgements
A part of the present study has been carried out during the fellowship training supported by Wakasawan Research Energy Center in Research Institute of Nuclear Engineering (RINE), University of Fukui. The authors wish to express gratitude to the above organizations. Authors would like to acknowledge Prof. M. Uno in RINE for his considerable advice about physical properties of nuclear fuel.
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Books · Bücher
Communication on the Safety Case for a Deep Geological Repository. NEA Report No. 7336, Published by OECD/NEA, 2017, 87 pp., in English, available online at:
http://www.oecd-nea.org/rwm/pubs/2017/
Communication has a specific role to play in the development of deep geological repositories. Building trust with the stakeholders involved in this process, particularly within the local community, is key for effective communication between the authorities and the public. There are also clear benefits to having technical experts hone their communication skills and having communication experts integrated into the development process. This report has compiled lessons from both failures and successes in communicating technical information to non-technical audiences. It addresses two key questions in particular: what is the experience base concerning the effectiveness or non-effectiveness of different tools for communicating safety case results to a non-technical audience and how can communication based on this experience be improved and included into a safety case development effort from the beginning?
When discussing technical issues with public stakeholders, an explanation of the national regulatory framework for ensuring safety should first be provided, giving an overview of defence-in-depth and emergency preparedness, in particular, to demonstrate the completeness of the regulatory process and build public confidence in the regulator’s competency. Generally, it is recommended to start the presentation by explaining how the facility has been designed to be safe, rather than presenting calculations of the risks from failed waste containers. In presenting technical issues to the public, materials presented should be tailored to engage the audience and should take into account their education levels, interests, risk perceptions and preferred methods of reviewing information. Tools such as photos, diagrams, animations are effective in illustrating the complex, long-term process of repository evolution. In dealing with critical observations, it is important to understand the emotion behind the issue and recognise that stakeholders may have a different concept or definition of risk than technical experts or regulators. When communicating about risk, being honest about the inherent uncertainties and presenting information in an uncomplicated and open manner can help build the public’s trust, as well as increase receptivity to understanding and discussing issues constructively.
To illustrate how to communicate measures used to support repository safety in a safety case, Chapter 4 provides a more detailed and in-depth discussion of the major points to be discussed in order to convey a safety case, and in that context discusses the use of indicators as well as the regulations and plans for retrievability and monitoring in communicating a safety case. Monitoring may consist of qualitative and quantitative parameters and can be an effective means to address public concerns if set up appropriately. Clear rules governing the planning and performance of monitoring as well as the sharing of the results will avoid a potential distrust in the information.
The use of indicators is one possible line of reasoning to provide additional assurance of repository performance. Engaging the public in developing the use of indicators and/or assisting non-technical audiences to understand the applications/interpretations of different indicators and monitoring of results could enable local communities to better appreciate the functions of the engineered barriers and the repository system.
A supplementary discussion of the potential uses of natural analogues is provided in Chapter 4. There has long been a debate regarding the potential value of using analogues for public communication and confidence building. The visual appeal of some analogues (e. g. the longevity of Roman establishments) has led some countries to bring analogue information into their engagement with non-technical audiences. Despite this, it is still not proven that analogues are effective in explaining disposal concepts and long-term safety. One potential problem of using analogues in public communication, as in the case of indicators, is the concern of “over interpretation”. Therefore, it is important to mention the conditions and limitations of an analogue. Provided that analogues are used appropriately, qualitative analogues can be used for general confidence building in parallel with using quantitative analogues as technical inputs in safety assessments (see NEA/RWM(2013)10). To improve effective communication with non-technical stakeholders, the use of analogues in a real two-way dialogue is recommended.
© 2017 Carl Hanser Verlag GmbH & Co. KG
Artikel in diesem Heft
- Frontmatter
- Best estimate approach for the evaluation of critical heat flux phenomenon in the boiling water reactors
- Coupled neutronic core and subchannel analysis of nanofluids in VVER-1000 type reactor
- PCTRAN enhancement for large break loss of coolant accident concurrent with loss of offsite power in VVER-1000 simulation
- Experimental study of natural circulation flow instability in rectangular channels
- Exerimental method and preliminary studies of the passive containment water film evaporation mass transfer
- Automated generation of burnup chain for reactor analysis applications
- Fission source sampling in coupled Monte Carlo simulations
- Hysteresis phenomenon in nuclear reactor dynamics
- Investigation of neutronic and safety parameters variation in 5 MW research reactor due to U3O8Al fuel conversion to ThO2 + U3O8Al
- Implementation of meso-scale radioactive dispersion model for GPU
- Solution of the multilayer multigroup neutron diffusion equation in cartesian geometry by fictitious borders power method
- Half-space albedo problem with modified FN method for linear and quadratic anisotropic scattering
Artikel in diesem Heft
- Frontmatter
- Best estimate approach for the evaluation of critical heat flux phenomenon in the boiling water reactors
- Coupled neutronic core and subchannel analysis of nanofluids in VVER-1000 type reactor
- PCTRAN enhancement for large break loss of coolant accident concurrent with loss of offsite power in VVER-1000 simulation
- Experimental study of natural circulation flow instability in rectangular channels
- Exerimental method and preliminary studies of the passive containment water film evaporation mass transfer
- Automated generation of burnup chain for reactor analysis applications
- Fission source sampling in coupled Monte Carlo simulations
- Hysteresis phenomenon in nuclear reactor dynamics
- Investigation of neutronic and safety parameters variation in 5 MW research reactor due to U3O8Al fuel conversion to ThO2 + U3O8Al
- Implementation of meso-scale radioactive dispersion model for GPU
- Solution of the multilayer multigroup neutron diffusion equation in cartesian geometry by fictitious borders power method
- Half-space albedo problem with modified FN method for linear and quadratic anisotropic scattering
