선택한 단어 수는 입니다.
최소 단어 이상 선택하여야 합니다.
최소 단어 이상 선택하여야 합니다.
선택한 단어 수는 30입니다.
최대 10 단어까지만 선택 가능합니다.
최대 10 단어까지만 선택 가능합니다.
제안 방법
- As a best deterministic estimation, with a bias toward conservatism, as suggested in the NEI (Nuclear Energy Institute, U.S.) report [16], the empirical formulas employed in this study can predict the minimum RC wall thickness required to prevent local damage caused by the normal impact of an aircraft engine and its residual velocity. Impact speeds and compressive strengths of concrete are treated probabilistically as major sources of uncertainty.
- However, no risk assessment with a scenario of a realistic aircraft crash into an ISF has yet been completed. Development of a comprehensive and systematic framework that comprises several elements of risk evaluation would make it possible to determine the feasibility of using such a framework to predict the expected hazard posed to the public, in addition to enhancing the reliability of facility/cask designs under possible severe impact loadings from aircraft crash. Further, this approach will enable the development of a so-called risk-informed regulatory framework, which is more reasonable than conventional approaches that rely more on conservatism.
- Subsequently, the radiological consequences for a hypothetical site were calculated, and individual risks for each possible sequence were obtained through a quantitative event tree analysis. From the probability analysis, which takes into account parameter uncertainties with assumptions for three different facility capacities, the conclusion is that an AI on a single fully loaded storage cask is not expected to cause a radiological impact that exceeds regulatory limits under the worst-case scenario for the three sets of design structures studied here. To achieve the final goal of complete risk assessment, as detailed in the Introduction, a fire scenario and a secondary mechanical impact scenario on multiple casks can be added to the proposed framework in order to evaluate accurately the overall associated radiological consequences to the public and the environment following an aircraft crash.
- The wind speed reference height is 80 m and the release height is ground level. Hourly information from 1-year meteorological data, including wind speeds and directions, was utilized for a hypothetical site to determine the wind speed frequency groups in the scenario. In this study, three boundaries of interest surrounding the accident location are considered: an exclusion area boundary at 560 m, a low-population zone at 5.
- Since it is difficult to justify the impact orientations, it is assumed that the impact angle is equally distributed between 0° and 90° on the cask body; this is done in order to provide a comprehensive and systematic evaluation of all the impact cases without the need for an exact clue of the possibility of occurrence.
- Table 1 provides the model specifications that are employed in the analysis. Specifications of concrete strength class, wall thickness, elastic recovery of seal, and U-235 burnup rate are separated into three sets and analyzed accordingly. These parameters are regarded as safety relevant components, categorized in respect to increasing or decreasing potential risk.
- In addition, a best-estimate structural analysis, including fuel assembly damage, has been incorporated using practical FE modeling techniques to simulate accurately and efficiently the structural response under energetic loading. Subsequently, the radiological consequences for a hypothetical site were calculated, and individual risks for each possible sequence were obtained through a quantitative event tree analysis. From the probability analysis, which takes into account parameter uncertainties with assumptions for three different facility capacities, the conclusion is that an AI on a single fully loaded storage cask is not expected to cause a radiological impact that exceeds regulatory limits under the worst-case scenario for the three sets of design structures studied here.
- The aim of the present article has been to confirm the flexibility of the proposed framework, which was developed in the authors' previous research via an examination of three combinations of design structures of facility and cask for a hypothetical reference facility that presents integrated damage sequences from an aircraft crash scenario.
- The structural response analysis of this study is divided into three parts. The first part is a fragility analysis of the facility wall based on an empirical model, followed by a structural response analysis of the cask lid closure, with the last part investigating the fuel rod failure under a mechanical impact load. Detailed methodologies and information related to the fragility analysis of the facility wall and the lid gap analysis are not covered in this paper, as details of these analyses can be found in the authors' previous work [12,15].
- The impact analysis studied five impact orientations: lateral impacts on the lower (Case 1), center (Case 2), and upper parts of the cask (Case 3); an impact on an upper corner (Case 4); and a vertical impact on the lid closure (Case 5). The impact loading as a function of time is tabulated, evenly distributed, and perpendicularly directed to the nodes at the impact area.
- The other basket cells, which include 20 fuel assemblies, are filled with solid dummy bodies to correct the package weight. The purpose of this model is to analyze the dynamic response of the fuel assembly and estimate the fraction of rods that fail during the impact as an essential parameter of the radiological consequences. All the materials are modeled as isotropic elastic-plastic with hardening; material properties are listed in Table 4.
- 7; this model consists of a carbon steel cask body with one bolted upper lid closure without impact limiters, and a solid inner dummy weight representing the interior structure and spent fuel assemblies. The purpose of this model was to analyze the dynamic response of the lid closure system in order to calculate the leakage path area between the lid and the flange, since the lid seal plays an essential role in preventing the escape of fine particulates and radioactive gases from the cask. Therefore, unnecessary details of the cask system, such as the interior structures, were not modeled.
- 2, which addresses the structural response and radiological consequence analyses with inputs and outputs. The results of this study are intended to act as a basis of discussion and to provide comparisons between the three sets of specification levels.
- 25 mm [14]. Thus, this study defines the elastic recovery distances for the low- (L), median- (M), and high-performance (H) seals as 0.03 mm, 0.15 mm, and 0.25 mm, respectively. Three burnup rates are also considered in the consequences analysis, as follows: a low burnup rate at 25 GWd/MTU, an intermediate burnup rate at 45 GWd/MTU, and a high burnup rate at 60 GWd/MTU.
- Further, this approach will enable the development of a so-called risk-informed regulatory framework, which is more reasonable than conventional approaches that rely more on conservatism. Thus, under the frame of a probabilistic approach, this study attempts to integrate more elements into the development of a realistic aircraft crash scenario, including possible damage consequences and associated release of fission products to the environment.
- From the probability analysis, which takes into account parameter uncertainties with assumptions for three different facility capacities, the conclusion is that an AI on a single fully loaded storage cask is not expected to cause a radiological impact that exceeds regulatory limits under the worst-case scenario for the three sets of design structures studied here. To achieve the final goal of complete risk assessment, as detailed in the Introduction, a fire scenario and a secondary mechanical impact scenario on multiple casks can be added to the proposed framework in order to evaluate accurately the overall associated radiological consequences to the public and the environment following an aircraft crash.
대상 데이터
- Since it is difficult to justify the impact orientations, it is assumed that the impact angle is equally distributed between 0° and 90° on the cask body; this is done in order to provide a comprehensive and systematic evaluation of all the impact cases without the need for an exact clue of the possibility of occurrence. The jet engine of a B747 was chosen for this study to provide an upper bound impact load on the cask body. Whereas the scenario itself is a general impact scenario that can represent both commercial airplanes and military or hobby aircrafts.
이론/모형
- The computer code HOTSPOT v.3.0.2 [27], which was developed based on the Gaussian dispersion plume model, is used in this study to estimate the radionuclide spread from the accident. The reference person is presumed to have a breathing height of 1.
- The dynamic impact characteristics of a fuel assembly inside the cask are analyzed using the explicit nonlinear FE code ABAQUS [21]. Any method to evaluate fuel assembly response under mechanical impact load requires a detailed FE model.
- The mathematical model of the probability density function, as proposed by Oztemel and S € ‚ ensoy [19] using the lognormal distribution model, is applied to represent the uncertainty in the compressive strength of concrete for the three classes (C16, C20, and C25) shown in Fig. 4.
- Descriptions of the estimation process for associated radioactive material releases from the release fraction coefficients and the source term of radioactive inventory are described in the authors' previous work [12]. Three inventories for the radionuclides involved in the scenario that dominate the inhalation dose for all the chemical elements classes (volatiles, fission gases, and solid particles) are calculated using the ORIGEN-ARP of SCALE v.6.1.3 code [24] and presented in Fig. 13.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.