Criticality Characteristics and Sensitivity Analysis of Fukushima Debris Beds Containing MCCI Products

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
María Freiría López ◽  
Michael Buck ◽  
Jörg Starflinger
Keyword(s):  
Sensitivity Analysis ◽  
Nuclear Power ◽  
Realistic Model ◽  
Power Station ◽  
Wide Range ◽  
Core Meltdown ◽  
Erosion Factor ◽  
The Impact ◽  
Control Rods ◽  
Core Concrete

Abstract This study investigates the criticality characteristics of debris beds that may have been formed through the molten–core–concrete-interaction (MCCI) at the pedestal floor of the damaged reactors in Fukushima Daiichi Nuclear Power Station. These were modeled as UO2-concrete systems submerged in water. First, a conservative model was used to evaluate the impact that the presence of concrete has on the neutron multiplication factor (keff) of debris beds. The good moderation capacities of concrete were proved, and it was found that recriticality would be possible under the considered conservative assumptions. Second, a more realistic model was used to perform an uncertainty and sensitivity analysis of a wide range of debris parameters (debris porosity, core meltdown grade, debris size, debris composition, concrete erosion factor, etc.). In this case, the results indicate that the probability of a recriticality event is very remote. It was also found that the presence of boron (B4C) from the control rods within debris has by far the highest influence on keff.

Sensitivity Analysis of External Exposure Dose for Future Burial Measures of Decontamination Soil Generated Outside Fukushima Prefecture

2020 ◽  
Author(s):  
Asako Shimada ◽  
Takuma Sawaguchi ◽  
Seiji Takeda
Keyword(s):  
Sensitivity Analysis ◽  
Nuclear Power ◽  
Soil Depth ◽  
Exposure Dose ◽  
External Exposure ◽  
Large Area ◽  
Power Station ◽  
Cover Soil ◽  
Evaluation Point ◽  
Fukushima Daiichi

Abstract A large area of east Japan was contaminated by radiocesium following a nuclear accident at the Fukushima Daiichi Nuclear Power Station. Following decontamination of the soil, external effective dose conversion factors were calculated by changing the volume of decontamination soil, depth of cover soil, and distance of the evaluation point from the decontamination soil. The decrement of the factors with an increase of the distance was larger for the smaller volume of decontamination soil. The factors decrease exponentially with an increase of the depth of cover soil in all cases. When there was no cover soil, annual external exposure doses for residents at 1 m from the repository site and public entry were over 10 μSv/y, even for the smallest size (2m × 2m × 1m) and 50 percentile value of radiation concentration (700 Bq/kg). When the surface was covered by 30 cm of non-contaminated soil, the annual external exposure doses were less than 10 μSv/y for the largest size (200m × 200m × 10m) and 95 percentile concentration (2500 Bq/kg).

scholarly journals Sensitivity of Characterizing the Heat Loss Coefficient through On-Board Monitoring: A Case Study Analysis

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3322 ◽  
Author(s):  
Marieline Senave ◽  
Staf Roels ◽  
Stijn Verbeke ◽  
Evi Lambie ◽  
Dirk Saelens
Keyword(s):  
Sensitivity Analysis ◽  
Steady State ◽  
Data Analysis ◽  
Heat Loss ◽  
Input Data ◽  
Loss Coefficient ◽  
Wide Range ◽  
Board Monitoring ◽  
The Impact

Recently, there has been an increasing interest in the development of an approach to characterize the as-built heat loss coefficient (HLC) of buildings based on a combination of on-board monitoring (OBM) and data-driven modeling. OBM is hereby defined as the monitoring of the energy consumption and interior climate of in-use buildings via non-intrusive sensors. The main challenge faced by researchers is the identification of the required input data and the appropriate data analysis techniques to assess the HLC of specific building types, with a certain degree of accuracy and/or within a budget constraint. A wide range of characterization techniques can be imagined, going from simplified steady-state models applied to smart energy meter data, to advanced dynamic analysis models identified on full OBM data sets that are further enriched with geometric info, survey results, or on-site inspections. This paper evaluates the extent to which these techniques result in different HLC estimates. To this end, it performs a sensitivity analysis of the characterization outcome for a case study dwelling. Thirty-five unique input data packages are defined using a tree structure. Subsequently, four different data analysis methods are applied on these sets: the steady-state average, Linear Regression and Energy Signature method, and the dynamic AutoRegressive with eXogenous input model (ARX). In addition to the sensitivity analysis, the paper compares the HLC values determined via OBM characterization to the theoretically calculated value, and explores the factors contributing to the observed discrepancies. The results demonstrate that deviations up to 26.9% can occur on the characterized as-built HLC, depending on the amount of monitoring data and prior information used to establish the interior temperature of the dwelling. The approach used to represent the internal and solar heat gains also proves to have a significant influence on the HLC estimate. The impact of the selected input data is higher than that of the applied data analysis method.

scholarly journals The Nuclear Legacy Today of Fukushima

2020 ◽  
Vol 70 (1) ◽  
pp. 257-292
Author(s):  
Kai Vetter
Keyword(s):  
Nuclear Power ◽  
Information Technologies ◽  
Radiation Detection ◽  
Imaging Systems ◽  
Human Society ◽  
Nuclear Power Generation ◽  
Power Station ◽  
Recent Developments ◽  
The Impact ◽  
Detection Technologies

The accident at the Fukushima Daiichi Nuclear Power Station (FDNPS) following the Great East Japan Earthquake and the subsequent tsunami in March 2011 changed people's perceptions regarding nuclear power generation in Japan and worldwide. The failure to prevent the accident and the response to it had an enormous impact specifically on the communities close to the site but also across Japan and globally. In this review, I discuss radiation detection technologies, their use and limits in the immediate assessment and response, and improvements since then. In particular, I examine recent developments in radiation detection and imaging systems that, in combination with the enormous advances in computer vision, provide new means to detect, map, and visualize radiation using manned and unmanned deployment platforms. In addition to smarter and more adaptable technologies to prevent and minimize the impact of such events, an important outcome of this accident is the need for informed and resilient citizens who are empowered by knowledge and technologies to make rational decisions. The accident at FDNPS leaves a legacy concerning the importance of historical information, technologies, and resilience as well as challenges regarding powerful technologies that can provide substantial benefits to human society but that are also associated with risks of which we must be aware.

R&D of JAEA for the decommissioning of TEPCO’s Fukushima Daiichi nuclear power station

2021 ◽  
pp. 014664532110108
Author(s):  
Koichi Noda
Keyword(s):  
Remote Control ◽  
Nuclear Power Station ◽  
Nuclear Power ◽  
Technology Development ◽  
Radioactive Wastes ◽  
Research Centre ◽  
Radiological Protection ◽  
Power Station ◽  
Wide Range ◽  
Fukushima Daiichi

This paper does not necessarily reflect the views of the International Commission on Radiological Protection. Since the accident at Fukushima Daiichi nuclear power station in March 2011, Japan Atomic Energy Agency (JAEA) has been contributing actively to the environmental recovery of Fukushima and the decommissioning of Fukushima Daiichi nuclear power station from a technical aspect, through a wide range of research and development (R&D) activities including fundamental research and applicational technology development. JAEA has been conducting R&D such as the characterisation of fuel debris, and treatment and disposal of radioactive wastes based on the ‘Mid-and-Long-Term Roadmap’ authorised by the Japanese Government. This R&D is mainly promoted by Collaborative Laboratories for Advanced Decommissioning Science (CLADS) in Tomioka Town, and CLADS has also been promoting cooperation with domestic and foreign research institutes, related companies, universities, etc. In addition, Naraha Centre for Remote Control Technology Development in Naraha Town commenced full operation in April 2016 for the development and demonstration of remote control technologies planned for use in the decommissioning of Fukushima Daiichi nuclear power station and disaster response. Okuma Analysis and Research Centre in Okuma Town is under construction for the analysis and characterisation of fuel debris and various radioactive wastes. Ten years have passed since the Great East Japan Earthquake and the accident at Fukushima Daiichi nuclear power station, and environmental conditions in Fukushima have been improving. The evacuation zone has been lifted, and preparation of specific recovery areas in the difficult-to-return zone has progressed. However, the reconstruction of Fukushima and the decommissioning of Fukushima Daiichi nuclear power station are still in progress, and JAEA will continue its R&D for the decommissioning of Fukushima Daiichi nuclear power station with domestic and international expertise in order to further contribute to the reconstruction of Fukushima.

scholarly journals Sensitivity of Direct Runoff to Curve Number Using the SCS-CN Method

2019 ◽  
Vol 5 (12) ◽  
pp. 2738-2746
Author(s):  
Abdul Ghani Soomro ◽  
Muhammad Munir Babar ◽  
Anila Hameem Memon ◽  
Arjumand Zehra Zaidi ◽  
Arshad Ashraf ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Water Availability ◽  
Curve Number ◽  
Resource Planning ◽  
Model Parameters ◽  
Rainfall Runoff ◽  
Direct Runoff ◽  
Wide Range ◽  
The Impact ◽  
Scs Cn

This study explores the impact of runoff curve number (CN) on the hydrological model outputs for the Morai watershed, Sindh-Pakistan, using the Soil Conservation Service Curve Number (SCS-CN) method. The SCS-CN method is an empirical technique used to estimate rainfall-runoff volume from precipitation in small watersheds, and CN is an empirically derived parameter used to calculate direct runoff from a rainfall event. CN depends on soil type, its condition, and the land use and land cover (LULC) of an area. Precise knowledge of these factors was not available for the study area, and therefore, a range of values was selected to analyze the sensitivity of the model to the changing CN values. Sensitivity analysis involves a methodological manipulation of model parameters to understand their impacts on model outputs. A range of CN values from 40-90 was selected to determine their effects on model results at the sub-catchment level during the historic flood year of 2010. The model simulated 362 cumecs of peak discharge for CN=90; however, for CN=40, the discharge reduced substantially to 78 cumecs (a 78.46% reduction). Event-based comparison of water volumes for different groups of CN values—90-75, 80-75, 75-70, and 90-40 —showed reductions in water availability of 8.88%, 3.39%, 3.82%, and 41.81%, respectively. Although it is known that the higher the CN, the greater the discharge from direct runoff and the less initial losses, the sensitivity analysis quantifies that impact and determines the amount of associated discharges with changing CN values. The results of the case study suggest that CN is one of the most influential parameters in the simulation of direct runoff. Knowledge of accurate runoff is important in both wet (flood management) and dry periods (water availability). A wide range in the resulting water discharges highlights the importance of precise CN selection. Sensitivity analysis is an essential facet of establishing hydrological models in limited data watersheds. The range of CNs demonstrates an enormous quantitative consequence on direct runoff, the exactness of which is necessary for effective water resource planning and management. The method itself is not novel, but the way it is proposed here can justify investments in determining the accurate CN before initiating mega projects involving rainfall-runoff simulations. Even a small error in CN value may lead to serious consequences. In the current study, the sensitivity analysis challenges the strength of the results of a model in the presence of ambiguity regarding CN value.

Analysis of a CRDM Nozzle Break LOCA Without Scram Using the U.S. NRC Coupled Code TRAC-M/PARCS

2002 ◽  
Author(s):  
A. Cuadra ◽  
J. Ragusa ◽  
T. Downar ◽  
K. Ivanov
Keyword(s):  
Nuclear Power ◽  
Cold Water ◽  
Three Dimensional ◽  
Control Rod ◽  
Operation Conditions ◽  
Wide Range ◽  
Core Conditions ◽  
The Impact ◽  
Power Response ◽  
The U.S

Recently, through-wall circumferential cracks in several control rod drive mechanism (CRDM) nozzle penetrations were detected at the Oconee-3 nuclear power plant. The presence of these cracks was seen as a potential precursor to a small break loss of coolant accident. In order to assess the impact of a postulated failure of a CRDM housing, analyses were performed using the U.S. NRC coupled thermal-hydraulics and neutronics code TRAC-M/PARCS. Although deemed highly unlikely, it was assumed that no control rods inserted in order to bound any possible reactivity transient associated with the break. The thermal-hydraulic model used to perform the study is based on an existing model of Oconee, built for PTS analysis, which models the whole plant and some of its control systems. A refined vessel model based on a TMI model was used to increase the resolution of the results and facilitate coupling to PARCS. All relevant ECCS systems were modeled and the control system allowed for, in addition to automatic actions, some assumed operator intervention. In particular, HPI throttling was modeled to maintain the hot leg subcooled at 42 +/- 7 K, and prevent an excessive amount of cold water from being injected into the system. A spatial kinetics analysis of this event was necessary because of the wide range of core conditions which occurred during the transient, from hot full power operation conditions to the cold zero power shutdown state. Analysis of the event with point kinetics and “best estimate” reactivity coefficients resulted in significant miss-prediction of the core power response. Conversely, the three-dimensional kinetics solution with cross section data generated over the entire range of the event led to a more accurate calculation of the power response and the overall analysis of the system transient response. This paper will describe the analysis of the control rod drive nozzle break event without scram using TRAC-M/PARCS.

Training of Technical Staff for Nuclear Power Station Operation

1981 ◽  
Vol 195 (1) ◽  
pp. 207-214
Author(s):  
T P Haire ◽  
P B Myerscough
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Power Station ◽  
Training Requirements ◽  
Technical Staff ◽  
Mechanistic Approach ◽  
Training Programmes ◽  
The Impact ◽  
Nuclear Processes

The paper discusses the statutory training requirements covering the technical staff in the CEGB (Central Electricity Generating Board). Details of the training programmes emphasize the importance of the staff having a thorough understanding of the nuclear processes involved in the station operation and not relying solely upon a mechanistic approach to operating procedures. The paper also examines the impact of this philosophy on the design of training simulators and makes a brief comparison with the training philosophies in other countries.

Special Issue on Structural Engineering of Nuclear Related Facilities

2010 ◽  
Vol 5 (4) ◽  
pp. 339-339
Author(s):  
Katsuki Takiguchi
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Nuclear Energy ◽  
Structural Engineering ◽  
Radioactive Waste Disposal ◽  
Radioactive Material ◽  
Plant Design ◽  
Special Issue ◽  
Power Station ◽  
Wide Range

Since it was first used, nuclear energy’s control has been an important issue. With the generation of electricity as a major nuclear energy application, the improvement of nuclear power generation technology has been required by society, including power plant design, construction, and maintenance and radioactive waste disposal. Nuclear facilities must also take into account disaster prevention, as in the case of earthquakes and terrorist attacks, particularly because of the extensive potential and actual range of effects. This has made nuclear energy issues important considerations in JDR editorial meetings. In the July 16, 2007, case of the Niigataken Chuetsu-oki Earthquake, quake ground motion equaled or exceeded that presumed in the design of the Tokyo Electric Power Company’s Kashiwazaki-Kariwa Nuclear Power Station, the world’s largest nuclear power station. Specific safety objectives for nuclear power plants include stopping the nuclear reaction, cooling the nuclear reactor, preventing radioactive material emission, and shielding surroundings from radiation - all of which were almost completely achieved in this case. Many problems were also revealed, however. JDR examined a special issue on Kashiwazaki-Kariwa Nuclear Power Station earthquake resistance at an editorial meeting but determined that such a topic remains premature. In its stead, we have planned a number featuring the structural engineering of nuclear related facilities as a first step in a series of special issues on nuclear energy. The papers for this number were submitted mainly by the presenters of 20th International Conference on Structural Mechanics in Reactor Technology, held in Espoo, Finland, in 2009 with the catch phrase “Challenges Facing Nuclear Renaissance.” We greatly appreciate the many contributions to this issue, and would like to thank the reviewers, without whose cooperation this number could not have been published. Please note that, independent of special numbers such as this one, JDR looks forward to receiving papers on a wide range of fields related to disaster.

Macromolecule/Polymer-Iodine Complexes: An Update

2019 ◽  
Vol 12 (3) ◽  
pp. 174-233
Author(s):  
Saad Moulay
Keyword(s):  
Graphene Oxide ◽  
Nuclear Power ◽  
Power Plants ◽  
Molecular Iodine ◽  
Poly Vinyl Alcohol ◽  
Complexing Agents ◽  
Iodine Doping ◽  
Wide Range ◽  
The Impact ◽  
Iodine Complexes

The great chemical affinity of molecular iodine towards several macromolecules and innumerable polymers allows the formation of macromolecule/polymer-iodine complexes, usually commensurate with the desired uses and applications. In many instances, the formation of such complexes occurs through a charge-transfer mechanism. The strength of the ensued complex is more accentuated by the presence of heteroatoms (nitrogen, oxygen, sulfur) and the π-conjugation induced moieties within the chemical structure of the polymer. A wide range of polymers with high specific surface areas and large total pore volumes are excellent candidates for iodine adsorption, suggesting their use in the removal of radioactive iodine in nuclear power plants. The recent results of iodine uptake by polysaccharides such as starch, chitin, chitosan, alginate, and cellulose are but novelties. Complexing vinyl polymers such as poly(N-vinyl-2-pyrrolidone), poly(vinyl pyridine), poly(vinyl alcohol), poly(vinyl chloride), poly(acrylonitrile), and polyacrylics, with molecular iodine revealed special chemistry, giving rise to polyiodide ions (In -) as the actual complexing agents. Carbon allotropes (graphene, graphene oxide, carbon nanotubes, amorphous carbons) and polyhydrocarbons are prone to interact with molecular iodine. The treatment of a broad set of polymers and macromolecules with molecular iodine is but a doping process that ends up with useful materials of enhanced properties such conductivity (electrical, ionic, thermal); in some cases, the obtained materials were of engineering applications. Complexation and doping materials with iodine are also aimed at ensuring the antimicrobial activity, particularly, for those intended for medical uses. In several cases, the impact of the iodine doping of polymer is the alteration of its morphology, as is the case of the disruption of the graphitic morphology of the graphene or graphene oxide.

Sensitivity Analysis on Safety Functions of Engineered and Natural Barriers for Fuel Debris Disposal

MRS Advances ◽  
2017 ◽  
Vol 2 (12) ◽  
pp. 687-692
Author(s):  
Taro Shimada ◽  
Yuki Nishimura ◽  
Seiji Takeda
Keyword(s):  
Sensitivity Analysis ◽  
Nuclear Power ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Radionuclide Migration ◽  
Power Station ◽  
Safety Function ◽  
Fukushima Daiichi ◽  
Physical And Chemical ◽  
And Chemical Properties

ABSTRACTA disposal measure for fuel debris generated at the accident in the Fukushima Daiichi Nuclear Power Station has been studied so far. However, physical and chemical properties of the fuel debris located in reactor containment vessels have not yet been obtained. In order to investigate the safety function of barriers required for disposal of fuel debris, sensitivity analysis for radionuclide migration was carried out, considering with uncertainty of the properties. As a result, it is indicated that it was important for evaluation of fuel debris disposal to obtain the physical and chemical properties of 14C and 129I during release to groundwater, in addition to 238U.

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