Results of the QUENCH-L2, DISCO-L2, and COMET-L2 experiments performed within the LACOMERA project at the Forschungszentrum Karlsruhe

The LACOMERA project at the Forschungszentrum Karlsruhe, Germany (FZK) is a 4-year action within the 5th Framework Programme of the EU which started in September 2002. Overall objective of the project is to offer research institutions from the EU Member Countries and Associated States access to four large-scale experimental facilities QUENCH, LIVE, DISCO, and COMET. These facilities are being used to investigate core melt scenarios from the beginning of core degradation to melt formation and relocation in the vessel, possible melt dispersion to the reactor cavity, and finally corium concrete interaction and corium coolability in the reactor cavity. The paper summarizes the main results obtained in the following three experiments:QUENCH-L2: boil-off of a flooded bundle. The test is of a generic interest for all reactor types, provided a link between the severe accident and design basis areas, and would deliver oxidation and thermal hydraulic data at high temperatures.DISCO-L2: fluid-dynamic, thermal, and chemical processes during melt ejection out of a breach in the lower head of a pressure vessel of the VVER-1000/320 type of reactor.COMET-L2: investigation of long-term melt-concrete interaction of metallic corium in a cylindrical siliceous concrete cavity under dry conditions with decay heat simulation of intermediate power during the first test phase, and subsequently at reduced power during the second test phase.     

Structural studies of the phase separation in the UO2–PuO2–Pu2O3 ternary system

In the oxygen hypo-stoichiometric range of (U_1?yPu_y)O_2?x mixed oxide MOX fuels, the U–Pu–O phase diagram is known to exhibit a large biphasic domain depending on the Pu content. However, the phase equilibria are still to be fully described as various representations are proposed in the literature.In the present work, we notify new insights into the phase separation occurring in the UO₂–PuO₂–Pu₂O₃ domain at room temperature. Our microstructural and X-ray diffraction results are compared to the different representations reported in the literature. We provide, for the first time in the hypo-stoichiometric domain, an indisputable experimental observation of a triphasic region at high Pu content, composed of two fluorite-type structures and of one α-Pu₂O₃ sesquioxyde type structure. These results are in contradiction with previous experimental representations of the U–Pu–O ternary system.     

Relative Population of the Levels of the 1s2s2p and 1s2p2 Configurations of Argon from Three Electron Excited Atoms

The possible contributions of the cascading from higher excited states to the states which can deexcite by the x-ray and Auger processes are investigated for Li-like argon. A model is developed to calculate the probability that a given excited state will eventually populate a particular lower excited state. The model requires the calculation of the transition rates of the cascading levels. Numerical results are presented for the cascade feeding of the levels of the ls2s2p and ls2p2 configurations. The cascading levels considered belong to the ls2snl and ls2pnl configurations with nl = 3s,3p,...4f.     

Thermodynamics of the Pu-O2 system

Translated from Atomnaya Énergiya, Vol. 65, No., 4, pp. 265–268, October, 1988.     

常温催化氢氧化合过程研究

采用本实验室制备的Pt-SDB(聚乙烯-二乙烯苯)疏水催化剂，研究了在管式反应器中氢气和氧气的化合反应。考察了冷却方式、惰性填料、温度、空速和催化剂用量等因素对常温催化氢氧化合过程的影响，并进行了宏观动力学研究，测定了表观活化能。实验结果表明：疏水催化剂Pt-SDB在常温下高效催化氢氧化合反应，而且具有良好的疏水性。建立了反应物氢气的连续性方程。     

水-氢同位素液相催化交换反应过程

描述了水氢同位素液相催化交换反应的模型,并从动力学和反应过程的角度对模型进行了实验验证。验证结果表明:水氢同位素液相催化交换是一个较复杂的传质反应的串联过程,主要包括汽液相间转化和氢同位素催化交换两个反应。     

Study of the Recombination of H_2 and O_2 at Ambient Temperature

The hydrophobic catalysts was developed at Chalk River Nuclear Laboratories and was used in the recombiner operated at ambient conditions. The advantage of operating a recombiner at ambient temperature were recognized by several researchers. It is clear that significant savings can be realized if the recombiner is operated at ambient temperature without the need for costly heaters and coolers. And the process is safer and more uncomplicated than conventional processes.The experimental conditions as followings: carrier gas is Ar; concentration of H2 is 1%;     

Radiation experiments with hydrogen-containing materials on the URAM-2 cryogenic irradiation facility at the IBR-2 reactor

The URAM-2 irradiation system facility at the IBR-2 reactor is described. The results of experiments performed with this facility to study the behavior of water ice, solid methane, aromatic hydrocarbons, and other materials exposed to fast neutrons and rays are presented. The rate of energy accumulation in these materials under irradiation and the amount of accumulated hydrogen and the temperature at which the hydrogen leaves the material matrices are determined. Recommendations are made for the working temperature of these materials for use in cold neutron moderators.Translated from Atomnaya Énergiya, Vol. 97, No. 3, pp. 183–189, September, 2004.     

添加Al2O3和SiO2的大晶粒UO2芯块制备研究

研究了Al2O3和SiO2添加剂对UO2芯块晶粒尺寸的影响.结果表明:加入少量的Al2O3和SiO2,可有效促进烧结过程中UO2芯块的晶粒度长大,过量加入则会阻碍烧结过程中UO2芯块的致密化;在添加量一定的情况下,添加不同比例的Al2O3和SiO2,对芯块晶粒尺寸有较大影响,只添加SiO2,对芯块晶粒尺寸影响不大,Al2O3添加量增加,芯块晶粒尺寸随之增加;添加Al2O3和SiO2促进UO2芯块晶粒长大的机制是在烧结期间发生了液相烧结.     

The chlorination of La_2O_3 by MgCl_2 in the LiCl-NaCl melts

The chlorination of rare earth oxides by MgCl2 was investigated in the molten chlorides. To reduce the solvent salt volatility, the LiCl-NaCl mixture was selected as a solvent by comparing the mass loss of the Li ClNaCl with LiCl-KCl melts after the addition of MgCl2 in the temperature range of 873 K to 1073 K. The dissolution behavior of La2O3 was investigated in the LiCl-NaCl-MgCl2 melts by XRD measurements and ICP-AES analysis of the melts, which indicated that La2O3 was chlorinated by Mg Cl2 to produce La Cl3. The reduction peak of La(Ⅲ) in the LiCl-Na Cl-MgCl2-La2O3 melts was observed from cyclic voltammogram and square wave voltammogram. The Mg-La alloy obtained by galvanostatic electrolysis in the LiCl-NaCl-MgCl2-La2O3 melts was characterized by XRD and SEM-EDS, indicating that the Mg-La alloy consisted of Mg and La2Mg17 phases.