The development of the crack growth model in zirconium claddings in iodine environment

The theoretical model of iodine induced stress corrosion cracking of zirconium claddings which takes into account the cladding texture has been developed. The process of quasistationary crack growth is considered. In the model the crack is described with the set of brittle and ductile regions which are alternating along the crack front. The cladding material has polycrystalline structure and mechanical behavior of the grains depends on their orientation relative to the applied stresses. Chemical potential of dissolved iodine has minimum in the places with maximum tensile stresses which occur in the brittle region of the crack tip. Iodine weakens interatomic bonds in the crack tip and leads to growth of the crack. The stresses in the brittle region relax and the redistribution of the stresses causes the crack growth in the ductile region. In the model the stresses in both regions are calculated self-consistently. Critical iodine concentration in the gaseous phase near the tip determines the condition of crack growth This criterion can be presented in the form that the stress intensity factor exceeds some threshold value. The value of iodine flux to the crack tip has been calculated. The comparison of calculated rate of crack growth with the experimental results has demonstrated a satisfactory agreement. The model predicts the decrease of the threshold SIF for the increase of the tangential component of texture factor that is in a good agreement with the experimental observations.     

Methyl iodide as a promoter of the SCC of zirconium alloys in iodine vapour

The presence of organic-iodine contaminants, or specifically methyl iodide, in the iodine environment during stress corrosion tests leads to an increased frequency of crack nucleation, and possibly a more rapid crack propagation process. The unusual fractographic features associated with these impurities suggest that they enhance the reduction in the surface energy of zirconium, cause an instability in the propagating crack front, and possibly enhance the rate of reaction to form zirconium iodides. These impurities are the most potent catalysts of iodine-induced cracking so far identified, although methyl iodide alone cannot initiate cracking.     

A new method for coating microspheres with zirconium carbide and zirconium carbide-carbon graded coats

A new method for the chemical vapor deposition of ZrC and C-ZrC alloys has been developed. This process has been applied to the fabrication of coated particle nuclear fuels of the type used in the large High Temperature Gas-Cooled Reactor. A powder feeder is used to supply ZrCl₄ to the fluidized bed coating furnace where it undergoes reaction with a hydrocarbon to form ZrC. Quantitative metering of the ZrCl₄ makes it possible to control the deposition of the ZrC and the codeposition of the C-ZrC alloys on the fuel particles. Examples of both types of coats made using the described technique are discussed and illustrated.     

Phosphate-hydroxyquinoline method for separation and volumetric determination of zirconium

The proposed method consists of a combination of the well-known phosphate method for separation of zirconium, and determination of zirconium as the hydroxyquinolate. The separation of zirconium hydroxyquinolate from an oxalate medium after solution of the phosphate preccipitate in oxalic acid has been used for the first time. The conditions of separation of zirconium from titanium and thorium in the phosphate precipitation, and from niobium and tantalum in precipitation of the hydroxyquinolate, have been studied. By this method it is possible to separate zirconium in practice from all accompanying elements (except hafnium), and to determine small amounts of zirconium (2–5 mg) by a volumetric method to an accuracy of ± 2–4%.     

Nondestructive nuclear-physical method of determining hydrogen in zirconium hydride

A. A. Bochvar All-Union Scientific-Research Institute of Inorganic Materials (VNIINM). Translated from Atomnaya Énergiya, Vol. 74, No. 5, pp. 448–450, May, 1993.     

Phosphate-hydroxyquinoline method for separation and volumetric determination of zirconium

The proposed method consists of a combination of the well-known phosphate method for separation of zirconium, and determination of zirconium as the hydroxyquinolate. The separation of zirconium hydroxyquinolate from an oxalate medium after solution of the phosphate preccipitate in oxalic acid has been used for the first time. The conditions of separation of zirconium from titanium and thorium in the phosphate precipitation, and from niobium and tantalum in precipitation of the hydroxyquinolate, have been studied. By this method it is possible to separate zirconium in practice from all accompanying elements (except hafnium), and to determine small amounts of zirconium (2–5 mg) by a volumetric method to an accuracy of ± 2–4%.     

Droplet impingement method to measure the surface tension of molten zirconium oxide

ABSTRACT

Measuring the surface tension of molten ZrO2 is critical to determine the progression of a severe accident in a nuclear power plant. However, no experimental reports have been published pertaining to the surface tension of liquid ZrO2 because of its high melting point, high reactivity, and high vapor pressure, among other factors. Thus, in this study, the surface tension of ZrO2 was measured by using the droplet impingement method, which can help determine the surface tension of molten oxides in an extremely short time. The impingement behavior could be determined to analyze the surface tension from the image. The surface tension was approximately 0.91 N/m at 2988 K, which is the melting point of ZrO2, and this value was consistent with the data estimated using the oscillation droplet method. Compared with a past report regarding the surface tension of the molten Zr-O system, the surface tension of molten Zr was noted to reduce with oxidation.     

锆合金包壳二次氢化破损模拟方法研究

压水堆燃料锆包壳管一旦出现破口,流入包壳内的水会在内外壁压差的作用下闪蒸为水蒸汽,在包壳管内壁引发锆水反应,使包壳管内壁由于大量吸氢而产生破损,称为二次氢脆。为了模拟压水堆一回路运行工况与锆包壳管的二次氢脆发生过程,通过理论强度计算与热工验证,自主设计锆合金包壳管二次氢脆实验堆外模拟装置,并针对ZIRLO合金包壳管开展双热源模拟实验。该装置实现了在一回路工况水平下的长期稳定运行,模拟结果显示ZIRLO合金管内外壁氧化并生成沿轴向自下而上浓度增加的氢化物。表明该装置解决了窄缝空间热分层现象带来的影响,可模拟包壳管二次氢脆过程中的一次破口失水、冷却水闪蒸及间隙蒸汽腐蚀行为,验证了该装置技术手段可行性。     

碘吸附器的现场试验——放射性甲基碘法

放射性甲基碘法是碘吸附器现场试验的重要方法之一.本文不仅介绍其试验原理及试验过程,同时也对我们设计研制的放射性甲基碘法主要设备进行介绍.几年来的实践证明,该放射性甲基碘法及其设备可靠、有效,可进一步推广.     

Mechanism of formation of zirconium sponge in zirconium production by the magnesothermic process

The mechanism of formation of zirconium sponge in the production of zirconium by the magnesothermic process has been investigated by introducing into the reducing agent a very soluble but not very volatile additive (aluminum, tin) acting as marked atoms. It was found that the growth of the zirconium sponge on the wall of the reaction crucible above the level of the molten bath is the result of the reaction of zirconium chloride vapor with molten magnesium as the latter ascends by capillary action through the previously formed sponge. The amount of zirconium chloride reacting with magnesium in unit time depends more upon the perimeter of the crucible than upon the surface area of the bath. To intensify the reduction of zirconium chloride by magnesium, it is recommended that partitions be placed in the crucible to act practically in the same way as the crucible wall.     

The dilatational misfit of zirconium hydrides precipitated in zirconium

The unconstrained misfit strains, $\text{δ}{}_{\mathrm{[uvtw]}}$, associated with the formation of zirconium hydride precipitates in zirconium have been calculated with respect to directions [uvtw]_Zr. Both the δ-hydride, (normally produced by slow cooling) and the γ-hydride (formed after fast cooling) are considered. The results are shown to be self-consistent and predict the correct volume change caused by the transformation.     

The clarification and purification of radioactive waste water by the flotation method

The method of flotation of ferric and aluminum hydroxides was used to study the clarification and purification of radioactive waste water containing large amounts of detergent and complex-forming substances. It was shown that flotation produced precipitates with a smaller volume at a higher clarification rate than the settling method.Translated from Atomnaya Énergiya, Vol. 16, No. 1, pp. 48–51, January, 1964