The Ki-Jang research reactor (KJRR), a new research reactor in Korea, is being planned to fulfill multiple purposes. In this study, as an assessment of the environmental radiological impact, we characterized the atmospheric dispersion and deposition of radioactive materials released by an unexpected...
The Ki-Jang research reactor (KJRR), a new research reactor in Korea, is being planned to fulfill multiple purposes. In this study, as an assessment of the environmental radiological impact, we characterized the atmospheric dispersion and deposition of radioactive materials released by an unexpected incident at KJRR using the weather research and forecasting-mesoscale model interface program-California Puff (WRF-MMIF-CALPUFF) model system. Based on the reproduced three-dimensional gridded meteorological data obtained during a 1-year period using WRF, the overall meteorological data predicted by WRF were in agreement with the observed data, while the predicted wind speed data were slightly overestimated at all stations. Based on the CALPUFF simulation of atmospheric dispersion (${\chi}/Q$) and deposition (D/Q) factors, relatively heavier contamination in the vicinity of KJRR was observed, and the prevailing land breeze wind in the study area resulted in relatively higher concentration and deposition in the off-shore area sectors. We also compared the dispersion characteristics between the PAVAN (atmospheric dispersion of radioactive release from nuclear power plants) and CALPUFF models. Finally, the meteorological conditions and possibility of high doses of radiation for relatively higher hourly ${\chi}/Q$ cases were examined at specific discrete receptors.
The Ki-Jang research reactor (KJRR), a new research reactor in Korea, is being planned to fulfill multiple purposes. In this study, as an assessment of the environmental radiological impact, we characterized the atmospheric dispersion and deposition of radioactive materials released by an unexpected incident at KJRR using the weather research and forecasting-mesoscale model interface program-California Puff (WRF-MMIF-CALPUFF) model system. Based on the reproduced three-dimensional gridded meteorological data obtained during a 1-year period using WRF, the overall meteorological data predicted by WRF were in agreement with the observed data, while the predicted wind speed data were slightly overestimated at all stations. Based on the CALPUFF simulation of atmospheric dispersion (${\chi}/Q$) and deposition (D/Q) factors, relatively heavier contamination in the vicinity of KJRR was observed, and the prevailing land breeze wind in the study area resulted in relatively higher concentration and deposition in the off-shore area sectors. We also compared the dispersion characteristics between the PAVAN (atmospheric dispersion of radioactive release from nuclear power plants) and CALPUFF models. Finally, the meteorological conditions and possibility of high doses of radiation for relatively higher hourly ${\chi}/Q$ cases were examined at specific discrete receptors.
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제안 방법
For this reason, the ground-level concentration and the deposition of radioactive materials were computed independently under all meteorological conditions from September 2014 to August 2015. Because the amount released from the facility in an unexpected severe accident might be difficult to accurately predict, the simulation focused on an evaluation of the dispersion direction, the dilution factor, and the possibility of a high dose of radiation in the study area. The dispersion (χ/Q) and deposition (D/Q) factors, which correspond to the average concentration or deposition by using a unit release rate (Q), were calculated using three dimensional gridded meteorological data over a 1-year period.
Extended periods of the meteorological field, over a 1-year period, were sequentially extracted from WRF and MMIF, and field measurements were carried out onsite at KJRR. To estimate the ability of the WRF–MMIF to reproduce the meteorological data, the simulated data were compared with the measurement data at KJRR onsite, especially for wind patterns.
In this study, the WRF–MMIF–CALPUFF model system was used to produce high-resolution meteorological fields and to estimate the dispersion of radioactive materials.
In this study, to evaluate the meteorological conditions and spatial regions of high-dose radiation exposure to the public, we attempted to characterize the atmospheric dispersion and deposition of radioactive materials released by an unexpected incident at KJRR. Also, a model system for realistic dispersion characteristics as a means of practical safety assessment for new research reactor was presented.
In this study, we attempted to characterize the atmospheric dispersion and deposition of radioactive materials released by an unexpected incident at KJRR. In this study, the WRF–MMIF–CALPUFF model system was used to produce high-resolution meteorological fields and to estimate the dispersion of radioactive materials.
Pasquill–Gifford (PG) and McElroy–Pooler dispersion coefficients were used for rural areas and urban areas, respectively, and the complex terrain algorithm of the partial plume path adjustment was applied in this study.
The atmospheric dispersion (c/Q) and deposition (D/Q) factors, which correspond to the average concentration or deposition by using a unit release rate (Q), were calculated using three-dimensional gridded meteorological data collected during a 1-year study period using the weather research and forecasting–mesoscale model interface program–California Puff (WRF–MMIF–CALPUFF) model system.
The meteorological data, including temperature, humidity, wind pattern, and precipitation values re-produced by the WRF–MMIF were also compared using statistical approaches. The determination coefficient (R2), mean bias (MB), normalized mean error (NME), and root mean square error (RMSE) were used to evaluate the consistency at all observation points. The R2, MB, NME, and RMSE were calculated using the following equations:
kr/). The field measurement data and archive data in the modeling grid were then inputted and interpolated in the WRF model simulation to improve the prediction accuracy. To obtain the field measurement, the objective analysis technique (OBSGRID) provided by the WRF model was applied.
The joint frequency function of wind speed and direction for 16 sectors according to atmospheric stability class at the KJRR site were reproduced using the WRF–MMIF simulation output.
To estimate the ability of the WRF–MMIF to reproduce the meteorological data, the simulated data were compared with the measurement data at KJRR onsite, especially for wind patterns.
대상 데이터
A meteorological station was installed at the north-east edge of the KJRR boundary (35.3251°N, 129.2474°E).
2474°E). The collected meteorological data, including wind speed, direction, temperature, pressure, and humidity at 65 m, 10 m, and 1.5 m, were recorded every 10 minutes beginning on 1 September 2014 and separately stored in a data logger (CR1000, Campbell). Additionally, hourly meteorological data (e.
The modeling system is currently the US EPA's preferred long-range dispersion model and is composed of three main modules: CALMET, CALPUFF, and CALPOST.
, Mo-99, I-131, and Ir-192), and (3) conducting neutron transmutation silicon doping to help meet growing global demand. The planned location for the KJRR is in a suburb of Busan City (35.3251 N,129.2474 E) in the south-east region of South Korea. According to regulatory requirements, various assessments of the environmental radiological impacts have been carried out, including potential air dispersion release of radionuclides during an unexpected accident.
Note that the cumulus parameterization scheme is not used in the 1-km grid model, for which convective rainfall generation is assumed to be explicitly resolved. To improve the prediction accuracy of the WRF model, high-resolution input data for the geological parameters (e.g., 90 m resolution (3s) obtained from the shuttle radar topography mission data from the National Aeronautics and Space Administration and a 30 m resolution medium division land cover map from the Korea Ministry of Environment, http://egis.go.kr) were used in the finest nested domain. The details of the physics and grid configuration in the WRF and modeling conditions in CALPUFF are summarized in Table 1.
4. Wind rose plots extracted from observations (left) and WRF-MMIF (right) at five observation stations; (A) On site, (B) Ulsan, (C) Busan, (D) Kimhae, and (E) Yangsan.
이론/모형
Since these models are simple to use and appear to overestimate environmental concentrations, they are widely used to estimate air dispersion characteristics, although the Lagrangian dispersion model can provide more complete and realistic dispersion characteristics [29]. Accordingly, the PAVAN model, one of the conventional Gaussian type dispersion models which estimates ground level concentrations downwind of accidental radionuclide releases from nuclear facilities into the atmosphere, was also applied in this study. The joint frequency function of wind speed and direction for 16 sectors according to atmospheric stability class at the KJRR site were reproduced using the WRF–MMIF simulation output.
Also, a model system for realistic dispersion characteristics as a means of practical safety assessment for new research reactor was presented. For these main objectives, the weather research and forecasting (WRF) model from National Center for Atmospheric Research was used to produce high resolution meteorological fields. The meteorological model output from WRF was statistically compared to field measurement data in the study area.
The field measurement data and archive data in the modeling grid were then inputted and interpolated in the WRF model simulation to improve the prediction accuracy. To obtain the field measurement, the objective analysis technique (OBSGRID) provided by the WRF model was applied. By performing an objective analysis in meteorological modeling, we can improve meteorological analyses on the mesoscale grid by incorporating information from observations, and thus better model reproducibility can be expected [16].
성능/효과
58 for Yangsan station. Based on these comparison results, rainfall data reproduced from WRF and MMIF in this study were in moderate agreement with the values observed for all stations.
Heavy contamination in the vicinity of KJRR was observed; the χ/Q values at up to 50 km distance from the source dramatically decreased (by more than 106 orders of magnitude).
64 at Yangsan station. Systematic overestimation, evaluated in terms of NME%, was observed for all stations; it was 52.7% onsite, 46.1% for Ulsan, 72.0% for Busan, 50.8% for Kimhae, and 39.9% for Yangsan. Although this overestimation of wind speed pattern might affect the dispersion of radionuclides in the model output, leading to subsequently underestimated results due to wide dispersion from the source region, using a three-dimensional gridded wind vector still offers notable advantages.
2, between the values from these two models. Therefore, based on the results of this study, the Gaussian type dispersion models (e.g., PAVAN), which lead to a conservative dose for preliminary safety analysis estimates, can result in unnecessary and costly facility design changes. Under moderately unstable conditions and with wind blowing from the N and NNW at a relatively low wind speed (1.
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