Dose Estimates from the Chernobyl Accident

Länge, R.; Dickerson, M.H.; Gudiksen, P.H.

doi:10.13182/nt88-a34132

Cited by 33 publications

(12 citation statements)

References 5 publications

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“…Albergel et al (1988) and Gudiksen et al (1989) reported that the first release must have reached 2000 m or more. A similar profile of the Chernobyl emissions was proposed by Lange et al (1988) and Hass et al (1990).…”

Section: Earlier Estimates Of the Source Term And Purpose Of The Papersupporting

confidence: 74%

Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements

et al. 2017

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Abstract. This paper describes the results of an inverse modeling study for the determination of the source term of the radionuclides 134 Cs, 137 Cs and 131 I released after the Chernobyl accident. The accident occurred on 26 April 1986 in the Former Soviet Union and released about 10 19 Bq of radioactive materials that were transported as far away as the USA and Japan. Thereafter, several attempts to assess the magnitude of the emissions were made that were based on the knowledge of the core inventory and the levels of the spent fuel. More recently, when modeling tools were further developed, inverse modeling techniques were applied to the Chernobyl case for source term quantification. However, because radioactivity is a sensitive topic for the public and attracts a lot of attention, high-quality measurements, which are essential for inverse modeling, were not made available except for a few sparse activity concentration measurements far from the source and far from the main direction of the radioactive fallout.For the first time, we apply Bayesian inversion of the Chernobyl source term using not only activity concentrations but also deposition measurements from the most recent public data set. These observations refer to a data rescue attempt that started more than 10 years ago, with a final goal to provide available measurements to anyone interested. In regards to our inverse modeling results, emissions of 134 Cs were estimated to be 80 PBq or 30-50 % higher than what was previously published. From the released amount of 134 Cs, about 70 PBq were deposited all over Europe. Similar to 134 Cs, emissions of 137 Cs were estimated as 86 PBq, on the same order as previously reported results. Finally, 131 I emissions of 1365 PBq were found, which are about 10 % less than the prior total releases.The inversion pushes the injection heights of the three radionuclides to higher altitudes (up to about 3 km) than previously assumed (≈ 2.2 km) in order to better match both concentration and deposition observations over Europe. The results of the present inversion were confirmed using an independent Eulerian model, for which deposition patterns were also improved when using the estimated posterior releases. Although the independent model tends to underestimate deposition in countries that are not in the main direction of the plume, it reproduces country levels of deposition very efficiently. The results were also tested for robustness against different setups of the inversion through sensitivity runs. The source term data from this study are publicly available.

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Section: Earlier Estimates Of the Source Term And Purpose Of The Papersupporting

confidence: 74%

Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements

et al. 2017

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“…From the experience of the author and colleagues (Davoine and Bocquet (2007), referred to hereafter as DB07), a rough, conservative estimation of the uncertainty in the total activity released is a standard deviation of about 50% of the estimate for 131 I, 137 Cs and 134 Cs. The plumes of these radionuclides have been simulated by several teams, with a focus on choosing the right resolution for Eulerian models and the right parametrizations for the removal of the species (Lange et al, 1988;Hass et al, 1990;Brandt et al, 2002;Quélo et al, 2007).…”

Section: The Chernobyl Accidentmentioning

confidence: 99%

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Bocquet

2011

Quart J Royal Meteoro Soc

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Atmospheric chemistry and air-quality numerical models are driven by uncertain forcing fields: emissions, boundary conditions, wind fields, vertical turbulent diffusivity, kinetic chemical rates, etc. Data assimilation can help to assess these parameters or fields of parameters. Because such parameters are often much more uncertain than the fields diagnosed in meteorology and oceanography, data assimilation is much more of an inverse modelling challenge in this context. In this article these ideas are experimented with by revisiting the Chernobyl accident dispersion event over Europe. A fast four-dimensional variational scheme (4D-Var) is developed, which seems appropriate for the retrieval of large parameter fields from large observation sets and the retrieval of parameters that are nonlinearly related to concentrations. The 4D-Var, and especially an approximate adjoint of the transport model, is tested and validated using several advection schemes that are influential on the forward simulation as well as on the data-assimilation results. Firstly, the inverse modelling system is applied to the assessment of the dry and wet deposition parameters. It is then applied to the retrieval of the emission field alone, the joint optimization of removal-process parameters and source parameters and the optimization of larger parameter fields such as horizontal and vertical diffusivities or the dry-deposition velocity field. The physical parameters used so far in the literature for the Chernobyl dispersion simulation are partly supported by this study. The crucial question of deciding whether such an inversion is merely a tuning of parameters or a retrieval of physically meaningful quantities is discussed. Even though inversion of parameter fields may fail to determine physical values for the parameters, it achieves statistical adaptation that partially corrects for model errors and, using the inverted parameter fields, leads to considerable improvement in the simulation scores.

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“…In earlier papers (Gudiksen et al, 1989;Albergel et al, 1988), it was stressed that the first release must have reached 2000 m and more. A profile was proposed by Lange et al (1988) and by Hass et al (1990).…”

Section: Vertical Profilementioning

confidence: 99%

Inverse modelling-based reconstruction of the Chernobyl source term available for long-range transport

Davoine

Bocquet

2007

Atmos. Chem. Phys.

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Abstract. The reconstruction of the Chernobyl accident source term has been previously carried out using core inventories, but also back and forth confrontations between model simulations and activity concentration or deposited activity measurements. The approach presented in this paper is based on inverse modelling techniques. It relies both on the activity concentration measurements and on the adjoint of a chemistry-transport model. The location of the release is assumed to be known, and one is looking for a source term available for long-range transport that depends both on time and altitude. The method relies on the maximum entropy on the mean principle and exploits source positivity. The inversion results are mainly sensitive to two tuning parameters, a mass scale and the scale of the prior errors in the inversion. To overcome this hardship, we resort to the statistical L-curve method to estimate balanced values for these two parameters. Once this is done, many of the retrieved features of the source are robust within a reasonable range of parameter values. Our results favour the acknowledged three-step scenario, with a strong initial release (26 to 27 April), followed by a weak emission period of four days (28 April-1 May) and again a release, longer but less intense than the initial one (2 May-6 May). The retrieved quantities of iodine-131, caesium-134 and caesium-137 that have been released are in good agreement with the latest reported estimations. Yet, a stronger apportionment of the total released activity is ascribed to the first period and less to the third one. Finer chronological details are obtained, such as a sequence of eruptive episodes in the first two days, likely related to the modulation of the boundary layer diurnal cycle. In addition, the first two-day release surges are found to have effectively reached an altitude up to the top of the domain (5000 m).

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Dose Estimates from the Chernobyl Accident

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Cited by 33 publications

References 5 publications

Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements

Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Inverse modelling-based reconstruction of the Chernobyl source term available for long-range transport

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