Data Assimilation for Fukushima Nuclear Accident Assessments

2017 ◽  
Author(s):  
Mei Xu ◽  
Biao Yuan ◽  
Liangyu Wang ◽  
Lijun Zhang
Keyword(s):  
Data Assimilation ◽  
Dose Rate ◽  
Radiation Field ◽  
Nuclear Power ◽  
Nuclear Accident ◽  
Radioactive Material ◽  
Fukushima Nuclear Accident ◽  
The Real ◽  
Kalman Filter Algorithm ◽  
Good Agreement

In order to investigate the feasibility of data assimilation in a real nuclear accident environment, measurements of Fukushima nuclear accident were considered. The data assimilation system was constructed by using the Lagrangian puff model as the radioactive material diffusion model, and 86 group real dose rate data from the accident as the observations, and the Ensemble Kalman Filter algorithm as the assimilation algorithm. The experimental results show that the assimilated nuclear accident radiation field is in good agreement with the actual measurements, the land contaminated areas are concentrated in the northwest of the nuclear power plant. With the increase of the real measurements, the error of the radiation field decreases with time. Compared with the results with no assimilation, the uncertainty of assimilated dose rate was reduced more than 80%. Through the data assimilation, the whole error of the radiation field is about 30%. The utilization of the real measurements can reduce the uncertainty of the model prediction.

Unit Dose Factors for Transportation of Radioactive Materials

2015 ◽  
Author(s):  
Kevin J. Connolly ◽  
Elena Kalinina
Keyword(s):  
Dose Rate ◽  
Nuclear Power ◽  
Large Scale ◽  
Spent Nuclear Fuel ◽  
Radioactive Material ◽  
Unit Distance ◽  
The Public ◽  
Environmental Impact Statements ◽  
Unit Dose ◽  
Interim Storage

It will be necessary in the future to transport spent nuclear fuel on a large-scale basis from nuclear power plant sites to interim storage and/or a repository. Shipments of radioactive material are required to comply with regulations limiting the dose rate to no more than 0.1 mSv (10 mrem) per hour at 2 meters from the sides of the vehicle transporting the package. Determining the resulting dose to the public will be necessary for a number of reasons (e.g., stakeholder concerns, environmental impact statements). In order to understand the dose consequence of such a transportation system, this paper describes a method for determining unit dose factors. These are defined as the dose to the public per unit distance traveled along a road, rail, or waterway from one shipment assuming unit values for the other route specific parameters. The actual dose to the public is calculated using unit dose factors, the dose rate due to the radiation field emanating from the package, and characteristics of the route itself. Route specific parameters include the speed of the conveyance, the population density, and characteristics of the environment surrounding the route; these are provided by a routing tool. Using these unit dose factors, in conjunction with a routing tool, it will be possible to quantify the collective dose to the public and understand the ramifications of choosing specific routes.

Fukushima Nuclear Accident Implications for the Nuclear Power Development in China

2011 ◽  
Vol 347-353 ◽  
pp. 3810-3814
Author(s):  
Zi Ying Jiang
Keyword(s):  
Nuclear Power ◽  
Nuclear Energy ◽  
Nuclear Accident ◽  
Fukushima Nuclear Accident ◽  
Energy Structure ◽  
Power Development ◽  
Fukushima Accident ◽  
Safety Standards ◽  
Nuclear Power Development ◽  
Nuclear Development

The Fukushima nuclear accident is prompting countries around the world to reassess the safety of nuclear power plant and their nuclear development aspirations. The course of Fukushima nuclear accident, the accident status to date are summarized, the global support for nuclear energy after Fukushima are stated, and the nuclear power development in China, China responses to Fukushima accident are analyzed. Nuclear energy plays an important role as means to adjust the energy structure, to avoid environmental pollution, and to address climate change in China, while the development speed of nuclear power should be reasonable and appropriate. Drawing lessons from Fukushima crisis, China insists on the safety-first principle in nuclear power development, hence China should be cautions in NPP sites selection, reviews its nuclear power development speed, lifts the safety standards, and improve the nuclear emergency response capabilities.

Assessing Sensitivity of Observations in Source Term Estimation for Nuclear Accidents

2012 ◽  
Author(s):  
Yuanwei Ma ◽  
Dezhong Wang ◽  
Wenji Tan ◽  
Zhilong Ji ◽  
Kuo Zhang
Keyword(s):  
Data Assimilation ◽  
Source Term ◽  
Dynamic Models ◽  
Source Parameters ◽  
Nuclear Accident ◽  
Fukushima Nuclear Accident ◽  
Observation Data ◽  
Source Terms ◽  
Highly Nonlinear ◽  
Assimilation System

In the Fukushima nuclear accident, due to the lack of field observations and the complexity of source terms, researchers failed to estimate the source term accurately immediately. Data assimilation methods to estimate source terms have many good features: they works well with highly nonlinear dynamic models, no linearization in the evolution of error statistics, etc. This study built a data assimilation system using the ensemble Kalman Filter for real-time estimates of source parameters. The assimilation system uses a Gaussian puff model as the atmospheric dispersion model, assimilating forward with the observation data. Considering measurement error, numerical experiments were carried on to verify the stability and accuracy of the scheme. Then the sensitivity of observation configration is tested by the twin experiments. First, the single parameter release rate of the source term is estimated by different sensor grid configurations. In a sparse sensors grid, the error of estimation is about 10%, and in a 11*11 grid configuration, the error is less than 1%. Under the analysis of the Fukushima nuclear accident, ahead for the actual situation, four parameters are estimated at the same time, by 2*2 to 11*11 grid configurations. The studies showed that the radionuclides plume should cover as many sensors as possible, which will lead a to successful estimation.

An Inverse Method to Estimate Emission Rates of Multi-Radionuclides Based on an Ensemble 4DVar Method With Local Gamma Dose Rate Measurements

2018 ◽  
Author(s):  
Xiaobing Geng ◽  
Mei Xu ◽  
Lijun Zhang ◽  
Biao Yuan
Keyword(s):  
Data Assimilation ◽  
Transfer Coefficient ◽  
Dose Rate ◽  
Emergency Response ◽  
Estimation Method ◽  
Coefficient Matrix ◽  
Gamma Dose ◽  
Nuclear Accident ◽  
Gamma Dose Rate ◽  
Emission Rates

An inverse source estimation method is proposed to reconstruct emission rates of multi-radionuclides using local gamma dose rate measurements under the data assimilation framework. It involves the Proper Orthogonal Decomposition (POD)-based ensemble four-dimensional variational data assimilation (PODEn4DVar) algorithm and a transfer coefficient matrix (TCM) created using FLEXPART, a Lagrangian atmospheric dispersion model. PODEn4DVar is a hybrid data assimilation method that exploits the strengths of both the ensemble Kalman filter (EnKF) and the 4DVar assimilation method. With an explicit expression of control (state) variables in the cost functional, the data assimilation process is substantially simplified than traditional 4D variational method. By setting a unit emission rate and running the ATDM model (FLEXPART in this article) driven by meteorological fields forecasted with WRF, we get the transfer coefficient matrix with the progression of nuclear accident. TCM not only acts as observation operator in PODEn4DVar, but also eliminates the control run in traditional data assimilation framework. The method is tested by twin experiments with ratios of nuclides assumed to be known. With pseudo observations based on Fukushima Daiichi nuclear power plant (FDNPP) accident, most of the emission rates were estimated accurately, except under conditions when wind blew off land toward the sea and at extremely slow wind speeds near the FDNPP. Because of the long duration of accident and variability of meteorological fields, measurements from land only in local area is unable to offer enough information to support emergency response. With abundant measurements of gamma dose rate, emission rates can be reconstructed sequentially with the progression of nuclear accident. Therefore, the proposed method has the potential to be applied to nuclear emergency response after improvement.

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