The U.K. nuclear accident model

Maryon, R. H.; Smith, F. B.; Conway, B. J.; Goddard, D. M.

doi:10.1016/0149-1970(91)90043-o

Cited by 70 publications

(26 citation statements)

References 11 publications

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“…The typical time scale for this depletion from gaseous to particulate form is, however, large (about 47 days (Maryon et al, 1991)) compared to the length of the model simulation (12 days in this study), so this effect is not taken into account here. Because of these uncertainties, both comprehensive and simple parameterizations of wet-and dry deposition are tested in this study.…”

Section: Parameterizations Of Dry-and Wet Depositionmentioning

confidence: 99%

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Modelling transport and deposition of caesium and iodine from the Chernobyl accident using the DREAM model

Brandt¹,

Christensen²,

Frohn³

2002

Atmos. Chem. Phys.

118

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Abstract. A tracer model, DREAM (the Danish Rimpuff andEulerian Accidental release Model), has been developed for modelling transport, dispersion and deposition (wet and dry) of radioactive material from accidental releases, as the Chernobyl accident. The model is a combination of a Lagrangian model, that includes the near source dispersion, and an Eulerian model describing the long-range transport. The performance of the transport model has previously been tested within the European Tracer Experiment, ETEX, which included transport and dispersion of an inert, non-depositing tracer from a controlled release. The focus of this paper is the model performance with respect to the total deposition of 137 Cs, 134 Cs and 131 I from the Chernobyl accident, using different relatively simple and comprehensive parameterizations for dry-and wet deposition. The performance, compared to measurements, of using different combinations of two different wet deposition parameterizations and three different parameterizations of dry deposition has been evaluated, using different statistical tests. The best model performance, compared to measurements, is obtained when parameterizing the total deposition combined of a simple method for dry deposition and a subgrid-scale averaging scheme for wet deposition based on relative humidities. The same major conclusion is obtained for all the three different radioactive isotopes and using two different deposition measurement databases. Large differences are seen in the results obtained by using the two different parameterizations of wet deposition based on precipitation rates and relative humidities, respectively. The parameterization based on subgrid-scale averaging is, in all cases, performing better than the parameterization based on precipitation rates. This indicates that the in-cloud scavenging process is more important than the beCorrespondence to: J. Brandt (jbr@dmu.dk) low cloud scavenging process for the submicron particles and that the precipitation rates are relatively uncertain in the meteorological model compared to the relative humidity. Relatively small differences are, however, seen in the statistical tests between the three different parameterizations of dry deposition.

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Section: Parameterizations Of Dry-and Wet Depositionmentioning

confidence: 99%

“…131 I is released in its gaseous form, but tends to attach to other particles as e.g. sulphur (Maryon et al, 1991). The effective dry deposition velocity for 131 I therefore tends to decrease with time.…”

Section: Parameterizations Of Dry-and Wet Depositionmentioning

confidence: 99%

Modelling transport and deposition of caesium and iodine from the Chernobyl accident using the DREAM model

Brandt¹,

Christensen²,

Frohn³

2002

Atmos. Chem. Phys.

118

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“…We use typical values for 131 I and 137 Cs that are found in the literature: the dry deposition velocity of gasphase 131 I is 0.5 (cm s −1 ) (Baklanov and Sorensen, 2001), the dry deposition velocity of particulate 131 I is 0.1 (cm s −1 ) (Baklanov and Sorensen, 2001) and the dry deposition velocity of 137 Cs is 0.05 (cm s −1 ) (Maryon et al, 1991) (the units of all deposition velocities are converted to m s −1 for use in WRF-Chem). One could also use other typical values as the dry deposition velocity for both 131 I and 137 Cs (e.g., as reported by Sportisse (2007), the dry deposition velocity of gas-phase 131 I could range from 0.1 to 0.5 cm s −1 , while the dry deposition velocity of 137 Cs could range from 0.04 to 0.31 cm s −1 ).…”

Section: The Constant Deposition Velocity Methodsmentioning

confidence: 99%

Modeling and sensitivity analysis of transport and deposition of radionuclides from the Fukushima Dai-ichi accident

Huang

et al. 2014

Atmos. Chem. Phys.

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Abstract. The atmospheric transport and ground deposition of radioactive isotopes 131 I and 137 Cs during and after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident (March 2011) are investigated using the Weather Research and Forecasting-Chemistry (WRF-Chem) model. The aim is to assess the skill of WRF in simulating these processes and the sensitivity of the model's performance to various parameterizations of unresolved physics. The WRF-Chem model is first upgraded by implementing a radioactive decay term into the advection-diffusion solver and adding three parameterizations for dry deposition and two parameterizations for wet deposition. Different microphysics and horizontal turbulent diffusion schemes are then tested for their ability to reproduce observed meteorological conditions. Subsequently, the influence of emission characteristics (including the emission rate, the gas partitioning of 131 I and the size distribution of 137 Cs) on the simulated transport and deposition is examined. The results show that the model can predict the wind fields and rainfall realistically and that the ground deposition of the radionuclides can also be captured reasonably well. The modeled precipitation is largely influenced by the microphysics schemes, while the influence of the horizontal diffusion schemes on the wind fields is subtle. However, the ground deposition of radionuclides is sensitive to both horizontal diffusion schemes and microphysical schemes. Wet deposition dominated over dry deposition at most of the observation stations, but not at all locations in the simulated domain. To assess the sensitivity of the total daily deposition to all of the model physics and inputs, the averaged absolute value of the difference (AAD) is proposed. Based on AAD, the total deposition is mainly influenced by the emission rate for both 131 I and 137 Cs; while it is not sensitive to the dry deposition parameterizations since the dry deposition is just a minor fraction of the total deposition. Moreover, for 131 I, the deposition is moderately sensitive (AAD between 10 and 40 % between different runs) to the microphysics schemes, the horizontal diffusion schemes, gas-partitioning and wet deposition parameterizations. For 137 Cs, the deposition is very sensitive (AAD exceeding 40 % between different runs) to the microphysics schemes and wet deposition parameterizations, but moderately sensitive to the horizontal diffusion schemes and the size distribution.

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“…Isotopic variables were replaced with radioactive tracers (i.e., 131 I and 137 Cs), and dry and wet deposition processes caused by gravity and precipitation processes, respectively, were introduced. Saya et al (2013) proposed a wet deposition process wherein the deposition is proportional to the ratio of the amount of condensed water to the total amount of water, whereas a traditional method (e.g., Maryon et al, 1991) considers only the amount of condensed water. In this study, the radioactive tracer mode of IsoRSM is used as an original framework.…”

Section: Introductionmentioning

confidence: 99%

A semi-Lagrangian advection scheme for radioactive tracers in the NCEP Regional Spectral Model (RSM)

Chang

Yoshimura

2015

Geosci. Model Dev.

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Abstract. In this study, the non-iteration dimensional-split semi-Lagrangian (NDSL) advection scheme is applied to the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM) to alleviate the Gibbs phenomenon. The Gibbs phenomenon is a problem wherein negative values of positive-definite quantities (e.g., moisture and tracers) are generated by the spectral space transformation in a spectral model system. To solve this problem, the spectral prognostic specific humidity and radioactive tracer advection scheme is replaced by the NDSL advection scheme, which considers advection of tracers in a grid system without spectral space transformations. A regional version of the NDSL is developed in this study and is applied to the RSM. Idealized experiments show that the regional version of the NDSL is successful. The model runs for an actual case study suggest that the NDSL can successfully advect radioactive tracers (iodine-131 and cesium-137) without noise from the Gibbs phenomenon. The NDSL can also remove negative specific humidity values produced in spectral calculations without losing detailed features.

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The U.K. nuclear accident model

Cited by 70 publications

References 11 publications

Modelling transport and deposition of caesium and iodine from the Chernobyl accident using the DREAM model

Modelling transport and deposition of caesium and iodine from the Chernobyl accident using the DREAM model

Modeling and sensitivity analysis of transport and deposition of radionuclides from the Fukushima Dai-ichi accident

A semi-Lagrangian advection scheme for radioactive tracers in the NCEP Regional Spectral Model (RSM)

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