[en] Outline: • Simulation with VSOP • Simulation with TINTE • Conclusion

[en] Air ingress, one of the beyond design basis accidents for high temperature gas-cooled reactors, receives high attention during the design of the 250 MW pebble-bed modular high temperature gas-cooled reactor (HTR-PM), because it may result in severe consequence including the corrosion of the fuel element and graphite reflector. The diffusion process and the set-up time of the stable natural convection after the double-ended guillotine break of the hot-gas duct are studied in the paper. On the basis of the preliminary design of the HTR-PM and its DLOCA analysis results, the diffusion process, as well as the influence of the core temperature distribution and the length of the hot-gas duct, is studied with the DIFFLOW code, which adopts a one-dimension variable cross-section diffusion model with fixed wall temperature. To preliminarily estimate the influence of chemical reaction between oxygen and graphite, which will change the gas component of the mixture, the diffusion processes between the He/N₂, He/O₂, He/CO and He/CO₂ are calculated, respectively. Furthermore, the code has been improved and the varying wall temperature can be simulated. The more accurate analysis is carried out with the changing temperature distribution from the DLOCA calculation. The analysis shows that there is enough time to adopt appropriate mitigation measures to stop the air ingress and the severe consequence of fuel element damage and large release of fission product can be avoided

[en] A seedling growth test for the identification of gamma irradiated edible vegetable seeds was described. The identification of gamma irradiated grape and the other seeds has been investigated. The purpose of this study was to develop an easy, rapid and practical technique for the identification of irradiated edible vegetable seeds. Seven different irradiated edible vegetable seeds: rice (Oryza sativa), peanut (Arachis hypogaea), maize (Zeamays), soybean (Glycine max), red bean (Phaseolus angularis), mung bean (Phaseolus aureus) and catjang cowpea (Vigna cylindrica) were tested by using the method of seedling growth. All of the edible vegetable seeds were exposed to gamma radiation on different doses, O(CK), 0.5, 1.0, 1.5, 2.0, 3.0, 5.0 kGy. After treatment with above 1.0 kGy dose to the seeds, the seedling rate was less than 50% compared with the control. Although the seedling rate of rice seeds reached 58%, the seedling growth was not normal and the seedling leaves appeared deformed. The results by this method were helpful to identify gamma treatment of the edible vegetable seeds with above 1.0 kGy dose. (author)

[en] A 2 x 250 MWth High temperature gas-cooled Pebble Bed Modular reactor (HTR-PM) is under development in China. The work being performed includes design and safety analyses. High temperature gas-cooled reactor (HTGR), especially the pebble-bed core type reactor, will inevitably cause the wear the graphite components and generate graphite dust during operation. The graphite dust is taken away by helium coolant and deposited throughout the primary system. Furthermore, the dust will become radioactive due to sorption of fission products released, although in very small quantities, during normal operation. Since it is possible that the fission products are released with dust under the accident conditions such as depressurization events, they have a potential hazard of radiation exposure to the environment. This paper presents a model and analyses of the dust transport in HTR-PM. The purpose of the work is to estimate the amount and distribution of deposited dust during plant life time, which was assumed to be 40 full-power years. The result will lay the foundation for further studies of fission products releasing and interaction with dust under accident conditions. (authors)

[en] Short communications only

[en] The high pressure helium and water/steam are respectively used as the primary and secondary coolant for the pebble-bed modular high temperature gas-cooled reactor (HTGR). Loss-of-water accident is one of the typical design basis accident (DBA), which would be caused by malfunction or current failure of the feed water pump, as well as the false action of the feed water valve. During the loss-of-water accident, due to the loss of the secondary heat sink, the temperature and pressure of primary coolant will increase. Subsequently, the reactor scram will be triggered by the protective signal of the “high flow rate proportion of primary circuit and secondary circuit” or the “high core inlet helium temperature”. For this type of the accident, the earlier open of the safety valve of the primary circuit should be avoided by reactor design. Based on the preliminary design of the 250 MW pebble-bed modular high temperature gas-cooled reactor (HTR-PM), with the coupled analysis code TINTE-BLAST, accidents with different slowdown rate of the feed water supply have been studied. The important parameters, including the reactor power, fuel element temperature, inlet/outlet helium temperature of the core, and especially the primary pressure, are analyzed. The consequences with first scram signal succeeding or failing are compared. The results can prove that, according to the current design of the protection system, this kind of accident can be detected in time. The scram signal will trigger the reactor shut down quickly, without causing the earlier open of the safety valve. After the reactor is successfully shut down, due to the inherent safety feature of the HTGR, the temperature and the pressure in the primary circuit will increase very slowly. The temperature of the fuel element, as well as that of the components, will not exceed the design limitations. (author)

[en] Hohlraums are one of the main types of indirect drive targets for inertial confinement fusion (ICF). Hohlraums are made by combining precision turning micromachining and electroplating processes

[en] Highlights: • Eu³⁺ have been successfully incorporated in multisites of cubic CaCO₃ nanocrystals. • Different PL intensity of CaCO₃:0.02Eu³⁺ was realized by introducing Eu³⁺ at different growth stages of CaCO₃. • Two sites of Eu³⁺ located in CaCO₃: One is located at disordered site near the surface. The other is located at the inner lattice. Eu³⁺ has been successfully incorporated in multisites of cubic CaCO₃ nanocrystals via carbonation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflection spectra (DRS) and photoluminescence (PL) spectroscopy were utilized to characterize the properties of all samples. PL spectra show that the intensity of CaCO₃:0.02Eu³⁺ nanoparticle is different when Eu³⁺ is introduced at different growth stages of CaCO₃. The different PL intensity is attributed to the different sites of Eu³⁺ located in CaCO₃ nanocrystals, which was identified by the analysis of Judd-Ofelt parameters, site-selective spectroscopy and decay curves. One site of Eu³⁺ at disordered site near the surface is analogous to Eu³⁺ located in a glasslike environment. The other site is located at the inner lattice associated with an ordered crystalline environment.

[en] A series of Tb³⁺, Eu³⁺ singly or doubly doped CaCO₃ phosphors have been synthesized by carbonation method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) spectroscopy. The results show that the synthesized samples are all pure calcite CaCO₃. The obtained samples have a cubic morphology with about 20 nm length. Under UV excitation, CaCO₃:Tb³⁺, CaCO₃:Eu³⁺ nanoparticles exhibit strong green and red emission, respectively. By adjusting the relative doping concentration of Tb³⁺ and Eu³⁺ ions in the CaCO₃ host, the different color hues of green, red, and white light can be obtained. It has been verified through the luminescence spectra and decay curves that there exists an effective energy transfer from the Tb³⁺ to Eu³⁺ ions in CaCO₃:Tb³⁺/Eu³⁺ and the form of energy transfer from Tb³⁺ to Eu³⁺ is dipole–quadrupole mechanism.

[en] The demonstration power plant of Chinese 250 MW high temperature gas-cooled reactor pebbled-bed module (HTR-PM) which is being under construction in the Shidao Bay of Shandong province has made breakthrough in all of the critical technologies, and is willing to operate in 2017. HTR-PM does not have the risk of large amount of hydrogen generation resulted from the zirconium water reaction due to its special design of graphite core structure and helium coolant of the primary circuit, however, considering that the HTR-PM has a small containment and does not design the deliberate ignitions which is the main hydrogen management measure in light water reactors, it is still necessary to study the hydrogen behavior in the water-ingress accident in which hydrogen will probably be generated. In this paper, the hydrogen generation amount and its distribution in the HTR-PM containment are analyzed with the TINTE code and GASFLOW code respectively in the water ingress accident caused by the steam generator heating tubes rupture. The calculation results indicate that there are total about 16.6 kg and 21 kg hydrogen produced due to graphite corrosion in the typical design basis water ingress accident and beyond design basis accident. The containment sub-pressure ventilation system makes sure the hydrogen concentration in the containment is less than 0.2% during the accident. There is no hydrogen explosion risk in the HTR-PM. (authors)