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1

Source term estimation for the MARIA research reactor and model of atmospheric dispersion of radionuclides with dry deposition

Lipka Maciej

Nukleonika

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2020

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Vol. 65, No. 3

173--179

EN

Source term is the amount of radionuclide activity, measured in becquerels, released to the atmosphere from a nuclear reactor, together with the plume composition, over a specific period. It is the basis of radioprotection- -related calculation. Usually, such computations are done using commercial codes; however, they are challenging to be used in the case of the MARIA reactor due to its unique construction. Consequently, there is a need to develop a method that will be able to deliver useful results despite the complicated geometry of the reactor site. Such an approach, based upon the Bateman balance equation, is presented in the article, together with the results of source term calculation for the MARIA reactor. Additionally, atmospheric dispersion of the radionuclides, analysed with the Gauss plume model with dry deposition, is presented.

2

Założenia metodyczne w zakresie modelowanie migracji radionuklidów w środowisku geologicznym w sąsiedztwie składowisk nisko- i średnioaktywnych odpadów promieniotwórczych

Lankof L., Pająk L.

Technika Poszukiwań Geologicznych

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2014

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R. 53, nr 1

85--97

PL

Modelowanie migracji radionuklidów w środowisku geologicznym w sąsiedztwie powierzchniowych składowisk promieniotwórczych odpadów nisko- i średnioaktywnych jest jednym z istotniejszych elementów wpływającym na ocenę długotrwałego bezpieczeństwa tych składowisk. Poza opisem zagadnień związanych z numerycznym modelowaniem migracji radionuklidów w środowisku geologicznym artykuł przedstawia również w skrócie metodykę oceny bezpieczeństwa polegającą na: określeniu scenariuszy uwalniania radionuklidów do środowiska, sformułowaniu modeli koncepcyjnych migracji radionuklidów w środowisku geologicznym, stworzeniu modelu geologicznego i hydrogeologicznego oraz implementacji tych modeli do obliczeń numerycznych i oceny narażenia człowieka na promieniowanie.

EN

Radionuclide migration modelling in geosphere in vicinity of near surface low and intermediate radioactive waste is one of the most important components of long term safety assessment of this type facility. In addition to the issues related to the numerical modelling of radionuclides migration in geosphere also methodology for safety assessment scenarios involving the determination of radionuclides release into geosphere as well as formulating conceptual models of radionuclides migration and geological and hydrogeological models and implementation of these models for numerical calculations allowing assessment of human exposure to radiation were briefly presented in this article.

3

Assessment of radionuclide migration and radiological human exposure at the closed near-surface radioactive waste repository

Gudelis A., Nedveckaite T., Prokopčiuk N., Filistovič V., Remeikis V., Motiejunas S.

Nukleonika

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2010

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Vol. 55, No. 2

251-259

EN

The near-surface “RADON” type radioactive waste repository, installed in 1963 and designed to store radioactive waste formed in industry, medicine and scientific investigations, was closed in 1989 because it did not meet the requirements imposed on the radioactive waste disposal. A comparatively small amount of radioactive waste is stored in this repository, but the inventory comprises various kinds of waste: short-lived low-level radioactive waste, short-lived low and intermediate radioactive waste, long-lived intermediate and high-level radioactive waste. The possible site-specific radionuclide migration through the groundwater pathway as well as the human exposure are considered by the computer program RESRAD-OFFSITE in this paper. The analysis of the obtained data shows that out of all stored radionuclides only H-3, C-14 and Cl-36 exceeding the dose constraint of 0.2 mSv can be considered as dangerous. The monitoring carried out in the repository environment has shown the contamination of groundwater with radioactive tritium and a significant reduction of contamination after construction of additional protective engineering barriers. For the assessment of the contribution of separate site-specific parameters of the model taking into account uncertainties of the model and parameters to the annual effective dose, the computer code RESRAD-OFFSITE provides the possibility of applying the regression analysis. It has been determined that the aquifer lateral dispersion as well as the hydraulic gradient, the radionuclide activity concentration in the repository together with the rate of penetration into the environment and the precipitation amount have the largest influence on the assessment accuracy of annual effective doses.

4

Impact of repository depth on residence times for leaking radionuclides in land-based surface water

Wörman A., Marklund L., Xu S., Dverstorp B.

Acta Geophysica

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2007

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Vol. 55, no. 1

73-84

EN

The multiple scales of landscape topography produce a wide distribution of groundwater circulation cells that control the hydro-geological environments surrounding geological repositories for nuclear waste. The largest circulation cells tend to discharge water into major river reaches, large freshwater systems or the nearby Baltic Sea. We investigated numerically the release of radionuclides from repositories placed in bedrock with depths between 100 to 2000 meters in a Swedish coastal area and found that leakage from the deeper positions emerges primarily in the major aquatic systems. In effect, radionuclides from the deeper repositories are more rapidly transported towards the Sea by the stream system compared to leakage from more shallow repositories. The release from the shallower repositories is significantly retained in the initial stage of the transport in the (superficial) landscape because the discharge occurs in or near low-order streams with high retention characteristics. This retention and residence time for radioactivity in the landscape control radiological doses to biota and can, thus, be expected to constitute an essential part of an associated risk evaluation.