atw - February 2017

Modeling of Diffusion in Clay Waste Disposals
Neutron Induced Radioactive Nuclide Inventories of Light Water Reactors
HPCI Operation Modes Simulated with ATHLET-CD Regarding Phenomena in Fukushima-Daiichi
China Sets Sights on New World Markets

Operation Set for 2018 as Regulator Considers Olkiluoto-3 Licence Application


Finland has announced progress with its delayed nuclear project and has confirmed it will not be affected by anomalies discovered in some components manufactured for EPRs in France. The Olkiluoto- 3 European Pressurised Reactor (EPR) nuclear plant under construction in Finland is on schedule to begin commercial operation in 2018 with the country’s regulator preparing a safety assessment that will pave the way for fuel loading. Jouni Silvennoinen, senior vice-president for Olkiluoto- 3 at Teollisuuden Voima Oyj (TVO), told NucNet that fuel loading at the EPR plant, which is nine years behind schedule, is expected in the spring of 2018. He said construction and licensing of the plant are progressing.

Development of a New Methodology for Quantifying Nuclear Safety Culture

Kiyoon Han and Moosung Jae

Accident review reports in many highly risky industries indicate that organizations’ safety culture plays important roles in accidents. The term safety culture was first used by the International Nuclear Safety Advisory Group (INSAG) in 1986 to analyze the cause of the accident and establish accident prevention measures. In the present study, to supplement these shortcomings of existing safety culture assessment methods, a safety culture impact assessment model which is a new safety culture assessment model was developed. This model consists of a safety culture impact index and a safety culture impact quantification methodology. The safety culture impact index defined in the present study is intended to show the soundness of NPPs’ safety culture and can be used to secure the consistency of safety culture assessment and to prevent events due to the degradation of safety culture by periodically monitoring the state of safety culture.

Treatment with Iodine Pills – Not only in Switzerland: Judgement for the Assumption on Costs

Ulrike Feldmann

During a severe accident in a nuclear power plant the release of radioactive iodine is possible. A precautionary measure to prevent man from the reception of radioacitve iodine is an early and right taking of non-radioactive iodine pills. After the accident in Fukushima iodine tablets have been stored by authorities as an precautionary measures. In the case of an accident, a quick distribution should be possible. One question which arises are the costs bearers of such a storage. Are nuclear power plant operators responsible for such measures, carried out by the authorities?

The Modeling Method of Diffusion of Radio Activated Materials in Clay Waste Disposals

Reza Saberi, Majid Alinejad, Ali Mozaffari and Kamran Sepanloo

New nuclear power plants are necessary to meet today’s and future challenges of energy supply. Nuclear power is the only large-scale energy source that takes full responsibility for all its wastes. Nuclear wastes are particularly hazardous and hard to manage relative to different toxic industrial wastes. Three methods are presented and analysed to model the diffusion of the waste from the waste disposal to the bottom surface. For this purpose three software programmes such as ABAQUS, Matlab coding, Geostudio and ArcGIS have been applied.

Numeric Determination and Validation of Neutron Induced Radioactive Nuclide Inventories for Decommissioning and Dismantling of Light Water Reactors

Peter-W. Phlippen, Luc Schlömer, Roger Vallentin, Bernard Lukas and Stefan Palm

The deconstruction of nuclear power plants requires project planning and budgeting both during the project and in advance, as well as the secured provision of financial and human resources. When a facility is free from irradiated fuel, the reactor pressure vessel with the nuclear components as well as the biological shield determine the activity inventory of the facility, which almost exclusively consists of activated radionuclides located in the respective structures. Knowledge of the activity distribution and nuclide vectors of the involved components is of vital importance for deconstruction planning. In this context, the development of a computation procedure is described coupling the Monte Carlo method for the determination of neutron flux densities with a procedure to perform activation calculations for the determination of nuclide vectors. For this purpose, detailed knowledge of the material composition, particularly the trace-element concentrations of nitrogen and cobalt in steel and additionally of europium and caesium in concrete structures, considerably impacts the accuracy of the calculated activities. Extensive validation using data collected from various reactor facilities, such as nuclide activities, neutron flux densities, and neutron and gamma dose rates, demonstrates the reliability of the computed nuclide distributions showing ratios of computed over measured values of typically between 0.9 and 3. The practicality of the developed method as well as the convenient use of the results have already been demonstrated analysing several German BWR and PWR facilities and developing packaging strategies based on the produced results.

Decommissioning – Success with Preparation

Jörg Klasen, Rolf Schulz and Oliver Wilhelm

The decommissioning of a nuclear power plant poses a significant challenge for the operating company. The business model is turned upside down and a working culture developed for power operation has to be adapted while necessary knowhow for the upcoming tasks has to be built up. The trauma for the employees induced by the final plant shut-down has to be considered and respected. The change of working culture in the enterprise has to be managed and the organization has to be prepared for the future. Here the methods of Change-Management offer a systematic and effective approach. Confidence in the employee's competencies is one of the key success factors for the change into the future.

Analyzing different HPCI operation modes simulated with ATHLET-CD regarding possible core degradation phenomena in Fukushima-Daiichi Unit 3

Christoph Bratfisch and Marco K. Koch

For extented application and analyses of the severe accident code ATHLET-CD, the course of the in-vessel accident in Unit 3 of Fukushima-Daiichi is simulated in the frame of the research project SUBA as a part of the BMBF sponsored collaborative project WASA-BOSS (Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen). Investigations, car-ried out by TEPCO, had shown that the High-Pressure Coolant Injection system (HPCI) might have stopped earlier than expected. A parameter variation was per-formed to analyze the impact of the tripped HPCI injection regarding the thermohy-draulic behaviour as well as the core degradation phenomena.

Large-scale Heat Transfer Experiments with Supercritical R134a Flowing Upward in a Circular Tube

Florian Feuerstein, Alexandre Coelho Silva, Denis Klingel and Xu Cheng

Heat transfer experiments with supercritical Freon R134a flowing upward in a circular tube with inner diameter of 10 mm and a heating length of 2,495 mm were conducted with a wide range of parameters: mass fluxes of 300 to 2,000 kg/m2s, heat fluxes of 10 to 200 kW/m2, bulk fluid temperature of 50 to 124 °C and pressures of 4.22 to 5.51 MPa. Effects of heat flux, mass flux, pressure and inlet temperature on heat transfer behavior are analyzed. Significant heat transfer deterioration is observed above a critical heat flux to mass flux ratio. Six representative correlations were selected and compared with the test data.

Simulation and Verification Studies of Reactivity Initiated Accident by Comparative Approach of NK/TH Coupling Codes and RELAP5 code

Salah Ud-Din Khan, Minjun Peng, Song Yuntao and Sajjad Haider

The objective is to analyze the safety of small modular nuclear reactors of 220 MWe power. Reactivity initiated accidents (RIA) were investigated by neutron kinetic/thermal hydraulic (NK/ TH) coupling approach and thermal hydraulic code i.e., RELAP5. The results obtained by these approaches were compared for validation and accuracy of simulation. In the NK/TH coupling technique, three codes (HELIOS, REMARK, THEATRe) were used. These codes calculate different parameters of the reactor core (fission power, reactivity, fuel temperature and inlet/outlet temperatures). The data exchanges between the codes were assessed by running the codes simultaneously. The results obtained from both (NK/TH coupling) and RELAP5 code analyses complement each other, hence confirming the accuracy of simulation.

As UK Inches Towards Chinese Reactor Project, China Sets Sights on New World Markets

John Shepherd

Early in January, as many of us in Europe were getting back into the routine of returning to work following the festive period, a new chapter in the history of nuclear energy was already starting to be written in the UK. The UK government asked the country’s nuclear regulators, the Office for Nuclear Regulation (ONR) and the Environment Agency, to start a generic design assessment (GDA) of what is now known as the ‘UK HPR1000 reactor’ – which is set to be the first deployment of Chinese reactor technology outside China. If the UK HPR1000 is eventually built in the UK, which would be at a designated site adjacent to the country’s former Bradwell nuclear power plant in Essex, on the eastern coast, the project will not only be a first for the use of Chinese nuclear technology in any other country, it will ironically make UK ties with France stronger – at a time when the UK is preparing to break away from the European Union.


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