Assessment of the relevance of Coffinite formation within the near-field environment of spent nuclear fuel geological disposals

2006 ◽  
Vol 932 ◽  
Author(s):  
V. Robit-Pointeau ◽  
C. Poinssot ◽  
P. Vitorge ◽  
B. Grambow ◽  
D. Cui ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Thermodynamic Data ◽  
Spent Nuclear Fuel ◽  
Near Field ◽  
New Mineral ◽  
Short Term ◽  
Geological Disposal ◽  
Field Environment ◽  
Permanent Presence

ABSTRACTExperiments were performed in anoxic gloves box in an attempt to synthesise Coffinite both in representative near-field conditions, and in conditions which were expected to favour its precipitation according to thermodynamic calculations. The experimental results did not confirm the predictions. However, a new mineral was observed instead of Coffinite. In addition, accurate characterization of various natural samples demonstrate the permanent presence of U(VI) within Coffinite contradictory to its theoretical composition. Our observations raise the question on the validity and applicability of available –actually estimated- thermodynamic data of Coffinite. Based on kinetic hindrance of Coffinite formation, coffinitization of spent nuclear fuel in geological disposal is not anticipated to be a dominant short term process.

Preliminary Calculations of Radionuclide Release From Near-Field to Biosphere Using Computer Code Goldsim

2003 ◽  
Author(s):  
S. Prva´kova´ ◽  
Juraj Dˇu´ran
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Slovak Republic ◽  
Near Field ◽  
Compartment Model ◽  
Computer Code ◽  
Geological Disposal ◽  
Rock Formations ◽  
Groundwater Supply ◽  
Radionuclide Release

This paper presents preliminary calculations for the performance assessment of the hypothetical disposal facility for spent nuclear fuel in the Slovak Republic. In the concept of geological disposal, two host rock formations are under consideration: granite and clay. Slovakia is now in site selection phase therefore the lack of input data for calculations is compensated from the international reports [1, 2]. The calculations of radionuclide release were made for the spent nuclear fuel disposed in a hypothetical underground repository situated in clay host formation. One-dimensional mathematical model of the radionuclide release through the engineered and natural barrier system up to one million years was simulated using a flexible compartment model tool Goldsim. Both deterministic and probabilistic calculations have been applied. The input parameters for probabilistic calculations are selected from the probability density functions (PDF) using Monte Carlo method. Radionuclide release to the biosphere is considered via contaminated groundwater supply taken from a deep well. Three different exposure pathways were considered: consumption of the root vegetables, consumption of meat and drinking of water from well. The results of preliminary assessment of radiological consequences are expressed in terms of release rates on the aquifer-well interface together with the corresponding individual annual doses for average member of the critical group of adults living in the vicinity of the repository. The regulatory limits regarding the annual doses for the concept of geological disposal in Slovakia are under preparation.

scholarly journals Nuclear Data Uncertainty Quantification in Criticality Safety Evaluations for Spent Nuclear Fuel Geological Disposal

2021 ◽  
Vol 11 (14) ◽  
pp. 6499
Author(s):  
Matthias Frankl ◽  
Mathieu Hursin ◽  
Dimitri Rochman ◽  
Alexander Vasiliev ◽  
Hakim Ferroukhi
Keyword(s):  
Uncertainty Quantification ◽  
Nuclear Fuel ◽  
Evaluation Method ◽  
Spent Nuclear Fuel ◽  
Nuclear Data ◽  
Data Uncertainty ◽  
Evaluation Methodology ◽  
Geological Disposal ◽  
Fuel Assemblies ◽  
Criticality Safety

Presently, a criticality safety evaluation methodology for the final geological disposal of Swiss spent nuclear fuel is under development at the Paul Scherrer Institute in collaboration with the Swiss National Technical Competence Centre in the field of deep geological disposal of radioactive waste. This method in essence pursues a best estimate plus uncertainty approach and includes burnup credit. Burnup credit is applied by means of a computational scheme called BUCSS-R (Burnup Credit System for the Swiss Reactors–Repository case) which is complemented by the quantification of uncertainties from various sources. BUCSS-R consists in depletion, decay and criticality calculations with CASMO5, SERPENT2 and MCNP6, respectively, determining the keff eigenvalues of the disposal canister loaded with the Swiss spent nuclear fuel assemblies. However, the depletion calculation in the first and the criticality calculation in the third step, in particular, are subject to uncertainties in the nuclear data input. In previous studies, the effects of these nuclear data-related uncertainties on obtained keff values, stemming from each of the two steps, have been quantified independently. Both contributions to the overall uncertainty in the calculated keff values have, therefore, been considered as fully correlated leading to an overly conservative estimation of total uncertainties. This study presents a consistent approach eliminating the need to assume and take into account unrealistically strong correlations in the keff results. The nuclear data uncertainty quantification for both depletion and criticality calculation is now performed at once using one and the same set of perturbation factors for uncertainty propagation through the corresponding calculation steps of the evaluation method. The present results reveal the overestimation of nuclear data-related uncertainties by the previous approach, in particular for spent nuclear fuel with a high burn-up, and underline the importance of consistent nuclear data uncertainty quantification methods. However, only canister loadings with UO2 fuel assemblies are considered, not offering insights into potentially different trends in nuclear data-related uncertainties for mixed oxide fuel assemblies.

scholarly journals XANES characterization of UO2/Mo(Pd) thin films as models for ϵ-particles in spent nuclear fuel

2013 ◽  
Vol 430 ◽  
pp. 012113 ◽  
Author(s):  
M A Denecke ◽  
T Petersmann ◽  
R Marsac ◽  
K Dardenne ◽  
T Vitova ◽  
...  
Keyword(s):  
Thin Films ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel

Radionuclide behaviour in the near-field of a geological repository for spent nuclear fuel

2012 ◽  
Vol 100 (8-9) ◽  
pp. 699-713 ◽  
Author(s):  
Volker Metz ◽  
Horst Geckeis ◽  
Ernesto Gonzáles-Robles ◽  
Andreas Loida ◽  
Christiane Bube ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Near Field ◽  
Geological Repository

Fracture smectite as a long-term sink for natural radionuclides – indications from unusual U-series disequilibria

2000 ◽  
Vol 88 (9-11) ◽  
Author(s):  
N. Marcos ◽  
J. Suksi ◽  
H. Ervanne ◽  
K. Rasilainen
Keyword(s):  
Nuclear Fuel ◽  
Chemical Stability ◽  
Spent Nuclear Fuel ◽  
Activity Ratio ◽  
Near Field ◽  
Natural Radionuclides ◽  
Mineral Component ◽  
Considerable Part ◽  
Preferential Loss

Occurrence of natural U in fracture smectite (main mineral component of bentonite) was studied as an analogue to radionuclide behaviour in the near-field of spent nuclear fuel repository. Elevated U content (57 ppm) was observed in fracture smectite sampled from the surface of water-carrying fracture in granite pegmatite at a depth of 70 m. The current groundwater conditions are oxidising at the sampled point. The U-234/U-238 activity ratio (AR) measured in the bulk U and in its sequentially extracted phases, displays unusually low value (around 0.30). Low AR indicates preferential loss of the U-234 isotope from the system. Because the U-234 loss can also be seen in the Th-230/U-234 activity ratio (clearly over 1), the selective removal of the U-234 isotope must have taken place more recently than what is needed to equilibrate Th-230/U-234 pair (i.e. 350000 a). To explain the selective U-234 loss from the smectite we postulate that bulk U is in reduced +4 form and a considerable part of the U-234 isotope in easily leachable oxidised +6 form. This study suggests that the long-term chemical stability of the bulk U in the smectite is due to irreversible fixation of U in the reduced +4 form.

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