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[en] The progression of a severe accident in a CANDU type reactor is slow because the core is surrounded by a large quantity of heavy and light water which acts as a heat sink to remove the decay heat. Therefore, the source term formation is a complex and long process involving fission products transport and releasing in the fuel matrix, thermal hydraulics of the transport fluid in the primary heat system and containment, deposition and transport of fission products, chemistry including the interaction with the dousing system, structural materials and paints, etc. The source term is strongly dependent on initial conditions and accident type. The paper presents chemistry aspects for a severe accident in a CANDU type reactor, in terms of the retention in the primary heat system. After releasing from the fuel elements, the fission products suffer a multitude of phenomena before they are partly transferred into the containment region. The most important species involved in the deposition were identified. At the same time, the influence of the break position in the transfer fractions from the primary heat system to the containment was investigated. (orig.)
Journal
[en] An important approach aiming to build sustainable solutions in radioactive waste management is a continuous dialogue among stakeholders. Most European countries encourage the construction of national arenas involving public participation and transparency. Different national and local contexts have contributed to the development of a quite broad set of approaches and tools. The paper addresses to the context of Cernavoda and Saligny communities. The Saligny site is currently under investigation and debate to host the repository for low and intermediate level waste produced by Cernavoda NPP. A methodology to catalyze the participation of citizens is discussed based on social characterization of the community and evaluation of different tools and methods. (author).
Journal
Journal of Nuclear Research and Development; ISSN 2247-191X; 
; (no.3); p. 22-28
; (no.3); p. 22-28
[en] The final disposal of irradiated graphite is a topical issue and urgently seeks for favourable solutions, but no firm decision has been taken so far concerning conditioning and packaging the graphitic waste although these materials impose major challenges due to big volumes and associated radionuclide inventory. In Romania, irradiated graphite does not exceed 10 tones and comes partly from the thermal column of the TRIGA reactor at INR Pitesti and partly from decommissioning of the VVSR reactor in Bucharest. The total radionuclide inventory is low and mainly dominated by 3H, 14C, 152Eu, 60Co and 36Cl, depending on the position in the thermal column and irradiation history. However, an optimal solution for its final disposal is envisaged for the national radioactive waste management plan. An alternative may be disposal in a surface repository. 14C and 36Cl are radioisotopes which may exhibit long term impact, both with potential to be released from graphitic material. In this context, the paper proposes a GoldSim model for the performance assessment of irradiated graphite disposal in a surface repository with characteristics borrowed from the Saligny site, considering only 14C and 36Cl radioisotopes. As there are still a lot of uncertainties and a lack of some relevant input parameters, the model is rather a support on which adjustments are still to be made as soon as new data become available regarding this topic. (author).
Journal
Journal of Nuclear Research and Development; ISSN 2247-191X; ; (no.4); p. 29-34
; (no.4); p. 29-34
[en] Romania operates in open fuel cycle two CANDU 600 units. The spent fuel is foreseen to be disposed off in a geological repository starting with 2055. In-house safety assessments of a generic disposal concept in granite similar to the Canadian one showed that C-14 plays an important role in the total annual dose. In order to decrease the uncertainty on C-14 radiologic impact, experimental tests on the C-14 amount, speciation and release from Zy-4 irradiated claddings from Cernavoda NNP have been performed under CAST project. The results have been used in updating the C-14 input data in order to test the sensitivity of the model to the following parameters: instantaneous release fraction from UO2 and Zy-4, the organic/inorganic ratio of the C-14 released from Zy-4 claddings, the C-14 diffusivity coefficient and Kd in bentonite and granite. GOLDSIM simulations, which accounted for the radiologic impact of CO2 and CH4, indicated that the most sensitive parameters are the instantaneous release fraction from the UO2 pellets and the Kd in bentonite. (author)
Journal
Journal of Nuclear Research and Development; ISSN 2247-191X; ; (no.16); p. 14-20
; (no.16); p. 14-20
[en] Short communication
Journal
[en] The Dirac bracket for gauge-fixed two and one-forms with Stueckelberg coupling is derived along an irreducible manner. The inferred results coincide with those from the reducible, hence our method puts on equal footing the irreducible and reducible second-class constraints. (authors)
Journal
Romanian Journal of Physics; ISSN 1221-146X; ; v. 45(1-2); p. 41-49
; v. 45(1-2); p. 41-49
[en] The knowledge and understanding of water flow and solute transport in the unsaturated zone is becoming increasingly important especially in mitigation of groundwater pollution. Fate of radionuclide in the geological environment is a topic to address in performance and safety assessment studies for nuclear waste disposal and may be modeled considering flow and transport in porous media. However, often, due to the heterogeneity and anisotropy of the real systems, the computer simulations may be difficult to render the real behavior. This paper addresses the simulation of a tracer transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on experimental data and was performed with the Alliances platform, a numerical tool developed by French organizations CEA, ANDRA and EDF. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, the dispersivity coefficients of iodine were investigated in order to match the experimental concentration determined on samples from different locations of the site. A close fit of the simulation over experimental data for the water saturation profile at a depth of 0.5 m in transient state was targeted by taking into account evapotranspiration in order to obtain a realistic estimation of the water infiltration in the porous media. Dispersivity coefficients obtained from the simulation of the tracer transport are in good order of magnitude for the unsaturated area and allow to have a good preview of the tracer plume. However, further investigations are recommended on new samples in order to validate the migration of the tracer plume as expected. (orig.)
Journal
[en] Diagrams were plotted from electromagnetic data that were recorded at Muntele Rosu Observatory during December 1996 to January 1997, and December 1997 to September 1998. The times when Vrancea earthquakes of magnitudes M ≥ 3.9 occurred within these periods are marked on the diagrams.The parameters of the earthquakes are given in a table which also includes information on the magnetic and electric anomalies (perturbations) preceding these earthquakes. The magnetic data prove that Vrancea earthquakes are preceded by magnetic perturbations that may be regarded as their short-term precursors. Perturbations, which could likewise be seen as short-term precursors of Vrancea earthquakes, are also noticed in the electric records. Still, a number of electric data do cast a doubt on their forerunning nature. Some suggestions are made in the end of the paper on how electromagnetic research should go ahead to be of use for Vrancea earthquake prediction. (authors)
Journal
Romanian Journal of Physics; ISSN 1221-146X; ; v. 44(7-8); p. 833-850
; v. 44(7-8); p. 833-850
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