Liquid metals with high thermal conductivity, high boiling point and adequately high specific heat are used to enhance heat transfer.
The coolant of a fast neutron reactor should possess low neutron absorption cross section and be a poor moderator for achieving high neutron economy and for sustaining the hard neutron spectrum. Liquid sodium has been the coolant of choice for the fast neutron reactors.
The process governing the contamination by Activated Corrosion Products (ACPs) of a nuclear cooling system involves many different mechanisms that react with each other including corrosion-release, dissolution-precipitation, erosion, deposition, convection, purification, activation and radioactive decay. One of the most important mechanisms is the dissolution-precipitation mechanism, which governs the behavior of soluble corrosion products and which is related to water chemistry specifications (pH, dissolved hydrogen concentration, zinc injection…). The dissolution-precipitation model has been improved inthe new version of OSCAR, OSCAR V1.4, released at the end of 2017.
d CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Aqueuse, F-91191 Gif-sur-Yvette, France.
Tel: +33(0)169081640, Fax: +33(0)169081586, Email: firstname.lastname@example.org
Abstract –Zirconium is used as material for various applications in spent nuclear fuel
reprocessing plants involving concentrated nitric acid medium under highly corrosive oxidizing conditions. In such conditions, zirconium can show two different oxidation regimes as a function of potential. At high potentials, the oxidation current is relatively important (few µA/cm 2 ) and
The long-term safety assessment of the geological repository has to take into account the degradation of the carbon steel used for the waste overpacks and the cell disposal liners, which are in contact with the claystone formation. This degradation is mainly caused by generalized corrosion processes which form a passive layer on the metal surface consisting of a dense oxide inner layer and a porous hydroxide outer layer in contact with the groundwater inthe pore space of the claystones. The processes take place under anaerobic conditions, since the groundwater is anoxic. The neighboring geochemical environment (pH, concentrations) and groundwater flow trends induce changes of thecorrosion conditions, which, in turn, influence the geochemical and thermo-hydro-mechanics of the claystones. The temperature also affects thecorrosion conditions. Indeed, the waste canisters are a source of heat. At the beginning of the repository development, the temperature is estimated to be about 90 ◦ C. Later, it is supposed to reach its steady- state value near 40 ◦ C.
remains to be directly determined, although the concentration of defects on steel pile bends has been identi ﬁed as a factor. 47 The formation of anoxic microenvironments behind macro-bio ﬁlms (algae; sea squirts, barnacles) due to the decomposition of organic matter is one possible initiation point, and bacterial adhesion is facilitated by the initial formation of extracellular polymeric substances ( ‘slime’) inthe bioﬁlm. 48 Minor colonies of SRBs also develop in oxygen depleted pore space within normal marine corrosion, 49 , 50 as indicated by the generation of sul ﬁdes within more typical corrosion samples. The generation of anoxic microenvironments leads to H 2 S generation by sulfate-reducing bacteria against the steel surface. The subsequent oxidation of iron sulﬁdes, via a range of reactive intermediate compounds, generates protons at every stage. This increases thecorrosion potential of the process and generates an environment conducive to SRB metabolism. The generation of H 2 S by sulfate-reducing bacteria and its mineralisation against the steel surface is a key factor inthe enhanced corrosion rate, both as iron is oxidised as an electron donor in electrochemical reactions, and by iron sul ﬁde mineralisation. The generation of an oxidised layer by sulfur- and sul ﬁde-oxidising bacteria protects the SRB colonies from the atmosphere and oxic water column, allowing the process to continue. The ultimate development of high concentrations of H 2 S and its oxidation to sulfuric acid results inthe die off of the macrobiota forming the bio ﬁlm, exposing the ALWC blister at the surface. The mineral paragenesis developed during this process is in contrast to that proposed by Jeffrey and Melchers, 25 where iron oxyhydroxides were proposed to be converted to sul ﬁde phases by bacterial processes and highlights the importance of determi- nation of iron and sulfur oxidation state in phase identiﬁcation.
The diagram is compared with that obtained for a reference sample (same conditions without ODA). The impedance modulus (Fig. 4 a) at 10 −3 Hz shows a signi ﬁcant increase after the ODA treatment (more than two decades) compared to the reference sample. In addition, the phase angle (Fig. 4 b) reveals a very well de ﬁned time constant inthe high frequency range, which is not visible on the reference sample, and related to the ODA ﬁlm formation on the sample. Thus, the ODA is able to form a ﬁlm on the carbon steel surface at 120 °C inthe representative thermochemical conditions of the secondary circuit. The signi ﬁcant increase of the impedance modulus after the ODA treatment could be due to the deposition condition (temperature and treatment time inthe autoclave) and could also reveal a synergistic effect between the magnetite layer formation and the ODA adsorption.
EIS measurements. The impedance measurements were per formed with a conventional three electrode cell with a mercury sulfate electrode (MSE) in a saturated potassium sulfate solution and a platinum grid, as reference electrode and counter electrode, respectively. The working electrode consisted of the carbon steel RDE or the carbon steel plate, depending on the temperature of the ODA ﬁlms formation. In both cases, the surface area in contact with the electrolyte was 1 cm 2 . The electrolytic solution was prepared from deionized water by adding 10 −3 M Na 2 SO 4 (analytical grade). The choice of this medium was based upon its low electrical conductivity, close to that encountered in industrial water circuits, its low corrosiveness toward carbon steel and because it is an easily reproducible baseline solution. The pH was ﬁxed at 10 with ammonia. A high pH value (around 10) is currently considered for secondary circuit conditioning to limit ﬂow accelerated corrosion of carbon steels and to decrease the magnetite solubility. 29 31
diffusion of OH - inthe oxide layer
F. Jambon & al., Solid State Ionics, 231 (2013) 69-73
SIMS profiles of the isotopic tracers through the oxide scale as a function of the recalculated depth (the oxide scale, represented by the 16 O profile is displayed as a
Importance of the metallurgy (minor elements) Role of phosphorous found on the votive columns of India
from the 6th century and on other artifacts
Delhi iron pillar from R. Balasubramaniam & al. in EFC 36, published by Maney (2002), pp 261-280 (1rst workshop)
24 AOÛT 2017
1953: Stress Corrosion Cracking
occurred inthe stainless steel tubing of the steam generator of the prototype for the Nautilus. SCC failures occurred on the secondary surfaces of the tubes. By 1957, H. Copson at INCO had demonstrated that the Stress corrosion cracking of Fe-Cr-Ni alloys would stop above about 40% Ni, when exposed to boiling MgCl 2 .
M. Hélie and G. Plante, MRS 1985, Stockholm
SCC likely to occur in granitic solutions on nickel base alloys provided local pH be sufficiently low (<3 as in a pit) and a sufficient stress level be applied (such as by the host rock after recovery of the geological formation)
After reprocessing occurs, existing fast reactors receive their fuel from the now-separated TRU stockpile. This is mostly a straightforward calculation. There are scenarios, however, where the amount of separated TRU inthe stockpile is not sufficient to meet the fuel demands of
operating reactors. CAFCA suffers from the same idiosyncrasy, which is kept in both codes in order to maintain simplicity of the reactor ordering algorithm. A lack of fuel happens most often for EUFR scenarios, when reprocessing capacity builds are not keeping pace with the needs of FR fuel (reactor builds can outpace reprocessing capacity expansion because EUFR startup is not constrained by TRU availability). For most scenarios, a maximum of about 10% of the fuel is “missing.” Were these situations to occur inthe actual fuel cycle system, the “missing” fuel could be replaced by enriched uranium, or perhaps by TRU or SNF purchased or taken for free from a foreign country under a nonproliferation-based fuel take-back agreement. There would be a cost for this fuel, although it would likely be very small (especially if the U.S. were taking title to another country’s SNF). Another alternative to keep FRs fueled would be to increase the TRU yield of the FR fleet by increasing the conversion ratio, so that more TRU would be produced per kg of FR SNF reprocessed. A final option involves lifting restrictions on the pace of reprocessing plant builds. Whatever action is taken to ensure reliable refueling for FRs, the cost penalty for missing fuel at a system-wide level is likely to be relatively small and is not likely to impact fuel cycle decisions. The only major impact of fuel availability is inthe prediction of how many FRs can be built, and because the missing fuel never “builds up,” the pace of reactor builds still tracks with those of other fuel cycle codes.
can explain high concentration of Si inthe ICP. Silicon may come from glass alteration (under matrix hydrolysis) or from COx water. Si-K edge absorption spectrum obtained in ICP differs from the amorphous one and was also struc- tured. It seems to correspond to mix of several phases (non- tronite, greenalite, chamosite, or others silicate phases), although best fits were obtained with trioctahedral phyllosili- cates. Indeed nontronite has already been detected as the only
Damien Féron | February 17, 2016 | PAGE 35
Results included in this document are CEA’s property. They cannot be disclosed without prior authorization .
Corrosion products on a 450 year-old archaeological iron nail in anoxic
environment were investigated at the nanometer level using STXM Interfacial layer of 100nm to few µm at the interface metal/oxide
Materials 2021, 14, 2017 2 of 16
be considered, such as NaF that favors the formation of fluorine phases, e.g., Mg(OH) 2−x F x ,
MgF 2 , Na(K)MgF 3 , as proposed or characterized in [ 13 – 17 ], and that not modifies the
geopolymer properties. These fluorine phases also limit the MgZr corrosion and thus the hydrogen production [ 18 – 20 ]. Recently, using electrochemical experiments, thecorrosion of MgZr alloy embedded within the geopolymer with various NaF contents have shown that thecorrosion rate and the nature of the fluorine phases formed are dependent of NaF concentration within geopolymer [ 21 ]. This result is in line with our recent experiments of natural MgZr alloy corrosionin poral solutions extracted from geopolymers with and without NaF [ 17 ]. The identification of thecorrosion products (CP) formed has highlighted that the amounts of fluoride species and dissolved silica inthe solution set the nature of the CP, i.e., Brucite, fluorine phases, and magnesium silicates, and probably their protective properties regarding the MgZr corrosion. However, the origin of these protective properties probably in relation with the CP porous texture have not been investigated. Moreover, in our experiments, magnesium silicates precipitation was observed within the CP layer contrary to the electrochemical experiments of Barros et al. [ 21 ].
“Chemistry and Electrochemistry of Corrosion and Stress Corrosion Cracking: A
symposium Honoring the Contribution of R.W. Staehle” ,TMS 2001.
F.P. Ford, P.L. Andresen, “CorrosioninNuclear Systems: Environmentally Assisted
Cracking in Light Water Reactors”, inCorrosion Mechanisms in Theory and Practice, Marcel Deker, 2002.
Finally, in section 6.2.4, we study a transition scenario (scenario D, which is based on scenario C), which models SFR deployment with americium only transmutation in americium bearing blankets. First, we calculate nuclear data and burnup uncertainties propagation on several scenario results: global actinides inventories, natural uranium consumption, fuel fabrication needs and spent fuel inventory. Then, we analyze the contribution of nuclear data and burnup to total variance on different types of results. After that, we perform a feasibility study for scenario D, which consists in calculating the probability that fissile material lacks at a certain point. We also provide several sensitivity studies to parameters such as reprocessing plant recovery rate and front-end durations, and analyze the impact of decay heat uncertainty on the scenario feasibility.
6. Partitioning and transmutation (P&T)
Alternative technologies to decrease the amount of high level radioactive waste to be stored in deep geological repositories are being developed, such as P&T using either critical or subcritical fast reactor systems. The development of P&T technology has the potential of minor actinides separation using either aqueous and pyroprocessing, demonstrating high separation factors at laboratory scale. In order to give experts a forum to present and discuss state-of-the-art developments inthe P&T field, the NEA has been organizing biennial information exchange meetings on actinide and fission product partitioning and transmutation since 1990. The meetings covered scientific, as well as strategic/policy developments inthe field of P&T, such as fuel cycle strategies and transition scenarios, radioactive waste management strategies (including secondary wastes), progress in fuels and materials, related physics and experiments, system design and economics of P&T. The last NEA Information Meeting on Actinide and Fission Product Partitioning and Transmutation was held inthe San Diego (US) where more of 100 papers were presented covering all aspects of P&T (fuels, scenarios, advanced recycling, waste management)
The results presented here are obtained on samples (mix of nuclear glass and iron powder) altered inthe underground Laboratory of Bure (France). Micro and Nanoscale investigations (Transmission Electron Microscopy, Scanning Transmission X-Ray Microscopy, nanoAuger electron spectroscopy) show presence of neoformed nanocristallized phases (iron silicates) inside GAL and inthe iron corrosion products (ICP). Several families of structured Si-Fe-O phases are identified (e.g. smectite in ICP, chlorite and iron sulfide in GAL) according to the localization and the valence of iron in CP. Moreveor study of the provenance of silicium and iron found in phyllosilicates was carried out in mass spectroscopy (TOF-SIMS). Thereby it is possible to know the proportion of silicon and iron arising from the glass, initially substituted for 29-silicium and 5-iron, to form these silicates.