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Estimation of radionuclide transfer times in the geological layers of saligny site

01 Jan 2009-

AbstractLucrarea descrie evaluarea timpului de transfer pentru 60Co si 137Cs in straturile geologice ale amplasamentului Saligny care este selectat pentru construcţia unui depozit de deseuri radioactive. Sunt prezentate aspectele geologice ale amplasamentului Saligny necesare pentru evaluarea timpului de transfer al radionuclizilor. In lucrare este prezentat modelul conceptual si modelul matematic asociat care descrie transferul radionuclizilor din sistemul de depozitare deseuri radioactive in acvifer, si este utilizat pentru calcularea variaţiei concentraţiilor 60Co si 137Cs in fiecare compartiment al sistemului de depozitare. Timpii de transfer al 60Co si al 137Cs sunt derivaţi din diferenţa dintre timpul când un radionuclid atinge concentraţia maxima in doua compartimente adiacente. Timpii de transfer al 60Co si al 137Cs sunt comparaţi cu timpii de injumataţire al radionuclizilor in scopul evaluarii rolul straturilor geologice ale amplasamentului sa intârzie transferului radionuclizilor si in acelasi timp sa permita dezintegrarea naturala a radionuclizilor. This paper describes the assessment of 60 Co and 137 Cs transfer times in the geological layers of Saligny site which is selected for the construction of a radioactive waste repository. The geological aspects of Saligny site necessary to assess the transfer time of radionuclides are presented. The conceptual model of the repository as well as the associated mathematical model which describes the transfer of radionuclides from the radioactive waste disposal system to the aquifer is used to calculate the variation of 60 Co and 137 Cs concentrations into each compartment of the disposal system are presented in the paper. The 60 Co and 137 Cs transfer times are derived from the time difference of a radionuclide reaching the highest pick value of concentration into two adjacent compartments. The 60 Co and 137 Cs transfer times are compared with the half life of radionuclides in order to asses the role of the geological layers of the site in delaying the transfer of radionuclides, allowing as well the natural decay of radionuclides. more

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Proceedings ArticleDOI
01 Jan 2003
Abstract: The Saligny Site, situated in the vicinity of the Cernavoda Nuclear Power Plant in Romania, has been chosen as a repository site for placement of future Low and Intermediate Level Nuclear Waste. Scientific investigations are on going to help assess the long-term performance of the nuclear waste repository and include the development of a site conceptual model, geochemical characterization of the proposed liner material and the geologic formations surrounding the repository. Geochemical characteristics of the proposed waste site and of repository liner material are essential information in providing key model parameters needed to determine the mechanisms and rates for the potential release and transport of radionuclides in the environment. A series of laboratory sorption and diffusion experiments in support of the site conceptual model were run at Los Alamos National Laboratory, USA and Institute for Nuclear Research, Romania. These experiments compared responses of cesium-137 and tritiated water as radionuclides, and included natural soil samples from Saligny site and cement liner material. Sorption experiments focused on studying the affinity of cesium-137 for soil samples from: a clay rich loess horizon, a compacted red clay horizon and a Portland type cement, proposed as liner for the repository. A Saligny synthetic water was used for the soil sorption experiments. For the cement sorption and diffusion experiments, NaCl 10mM water was necessary in order to avoid insolubility problems at the high pH (around 12) when in contact with the cement. Preliminary studies of the geochemistry for radionuclide-soil matrix and radionuclide-concrete liner interactions were obtained through the sorption and diffusion experiments. The sorption isotherms were linear for all samples with high Kd values for soil samples and low values for the cement. Mineralogical information obtained through quantitative X-ray diffraction (QXRD) analysis, for the studied soil samples were in agreement with the sorption results. The high amount of clay present in the soil samples was determined to be the main contributor for the strong sorption. Diffusion cells were prepared for comparing hydrologic response characteristics for tritiated water and cesium-137, through the measurement of diffusion coefficients as influenced by the soil and cement matrices. Tritiated water and cesium-137 diffusion coefficients were determined from the change in radionuclide concentration profile over time while diffusing through the soil or cement matrix, and were found in agreement with the values listed in literature findings.Copyright © 2003 by ASME

2 citations

01 Jan 2007
Abstract: Estimarea activitaţii combustibilului nuclear uzat depozitat in bazinele cu apa, este importanta pentu analiza degradarii tecii de combustibil datorita coroziunii. Aceasta estimare permite personalului de operare sa coreleze valoarea activitaţii apei din bazine cu numarul de elemente care prezinta defecte de teaca. Prezentul articol prezinta rezultatele obţinute in estimarea activitaţii combustibilului nuclear uzat EK-10 si C-36 ce este depozitat la Magurele. Pentru estimarea starii termenului sursa s-au utilizat de coduri de calcul ce valorifica istoria exploatarii combustibilului. Calculele sunt importante pentru estimarea nivelului radionuclizilor (produsi de fisiune, gaze de fisiune, produsi de activare) din interiorul combustibilui uzat atsfel incât sa poata fi luate masurile necesare pentru protecţia impotriva radiaţiei si prevenirea eliberarii de material radioactiv din combustibil in mediu. An estimate of spent fuel activity in storage ponds is important to any analysis of actual cladding failure due to corrosion. This allows the operator the possibility to correlate the estimated values of the activity to the actual values in water samples, thereby predicting the number of failing fuel elements. This paper presents the obtained results in estimation of activity of spent fuel activity, EK-10 and C-36, which is in wet storage at Magurele in Romania. Validated computer codes and history of fuel exploitation have been used to estimate the actual state fuel source term. Also the computation is important for estimation of radionuclides level (fission products, fission gasses, activation products) presents in spent fuel inside so for establishing of the necessary measures which could be taken for radiation protection and for prevention of radionuclides release into the environment.

1 citations