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The performance of heat exchangers in the pressurized water test loop is a critical factor in ensuring the achievement of irradiation parameters for fuel assemblies and the safety of experimental operations. The effect of the heat exchange area margin on the heat exchangers in the pressurized water test loop for the fuel assembly during the steady-state irradiation is analyzed. Additionally, optimization methods for determining the margin of heat exchange area and corresponding design strategies are further investigated. It shows that the effect of the heat exchange area margin on the heat exchange power is less affected by the inlet temperature of the primary water and is primarily influenced by the flow rate of the primary water. A decrease in the flow rate of the primary water reduces the compensatory effect of the cooling section on power and enhances the weakening effect of the regeneration section on power. Meanwhile, the correspondence between the margin of the regeneration section and the cooling section, established based on design conditions, can be applicable when there are changes in the inlet temperature of the primary water, but it is not suitable when there are changes in the flow rate of the primary water. When the flow rate of the primary water decreases, the cooling section margin required to compensate for the decrease in power caused by the regeneration section margin will increase significantly. In addition, short-circuiting the heat exchange tubes in the regeneration section can effectively enhance the heat transfer capability. Furthermore, setting the heat exchange area margins of the regeneration and cooling sections to zero can serve as a termination condition for iterative calculations in the verification of regenerative heat exchangers under off-design conditions. [ABSTRACT FROM AUTHOR]

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A neutron irradiation test of static random access memories (SRAMs) was performed using a spallation neutron source at Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). The probability of neutron-induced single-event upsets (SEUs) was measured for 65-nm bulk and silicon on thin buried oxide (SOTB) SRAMs under neutron irradiation at the BL10 experimental facility. The measured SEU data were compared with the previous data of the same SRAMs which were measured at other irradiation facilities having different neutron spectra. The differences in the operating voltage dependence of the measured SEU probabilities are discussed with particular attention to the impact of irradiation side on SEUs. The particle and heavy ion transport code system (PHITS) simulation based on the simple sensitive volume model qualitatively reproduced the operating voltage dependence seen in the measured ratio of SEUs for the Bulk SRAM between the resin side and board side irradiations under different neutron fields. [ABSTRACT FROM AUTHOR]

Negative and positive muon irradiation tests of static random access memories (SRAMs) were performed at Muon Science Innovation Channel (MuSIC) of Research Center for Nuclear Physics (RCNP), Osaka University. The muon-induced single event upset (SEU) cross sections for 65-nm bulk SRAMs were measured. The SRAM device was irradiated by the muon beams with average momenta ranging from 37.8 to 41.0 MeV/c at the beam exit. The incident muon fluence was measured using a one-by-one muon detection system with a plastic scintillator by taking advantage of the direct current (dc) muon beam and reliable absolute values of SEU cross sections were obtained. In addition to the measurement of the SEU cross sections, we measured muonic X-rays from the irradiated device to investigate the relation between the measured SEU cross section and the emission rate of muonic X-rays associated with the stopping position of the muons as a function of incident muon momentum. The result suggested that negative muons have a significant effect on SEUs by the emission of secondary light ions via negative muon capture reaction when negative muons stop near sensitive volumes (SVs) in SRAMs. [ABSTRACT FROM AUTHOR]

To measure the heat generation rate of nuclear fuel rods during an irradiation test, the temperature deviation of the coolant that passes by the fuel rod and its flow velocity need to be measured. Although the temperature of the coolant can be measured by thermocouples instrumented in the nuclear fuel test rig, the flowrate of the coolant is difficult to measure owing to the narrow space of the test rig. Therefore, a noise analysis technique using fluctuation signals from thermocouples installed at both end parts of the fuel rod has been developed by several advanced groups. Although the noise analysis technique was also developed at the Korea Atomic Energy Research Institute, out of pile test results showed that the accuracy of the coolant flow measurement was more than 40%. In this study, the ground pattern of the control board and earth connection are enhanced to eliminate external noise. In addition, a heater unit is installed in the coolant flow simulator to obtain a strong fluctuation signal from the coolant. Thus, the coolant flow simulator is improved, and the accuracy of the coolant flow measurement shows an error of less than 5%. [ABSTRACT FROM AUTHOR]

The heat generation rate is one of the most important characteristics in evaluating the performance of nuclear fuel. The heat generation rate of a nuclear fuel rod can be measured indirectly by calculating the heat flux that coolant absorbs while passing by the nuclear fuel rod. To calculate the heat flux from the fuel rod, it is necessary to measure the temperature deviation and flow velocity at both end parts of the fuel rod. Thus, measuring the flow velocity in the test rig during the irradiation test of nuclear fuel is important to measure the heat generation rate. In this study, a cross correlation technique that uses signals obtained from two thermocouples instrumented at both end parts of the fuel rod has been developed to measure the flow velocity of coolant in the test rig. [ABSTRACT FROM AUTHOR]

Irradiation test results demonstrate the validity of a scan FF technology for separately evaluating SET and SEU soft error rates (SERs) in logic VLSI systems. The SET and SEU soft errors mean the upset caused by latching an SET pulse that originates in combinational logic cell blocks and the upset caused by a direct ion hit to the FF, respectively. A test chip is fabricated using a 0.2-μm fully-depleted silicon-on-insulator standard cell library and irradiated under an LET of 40 MeV-cm2 /mg. The SET and SEU soft error rates are successfully measured by the scan FFs on the test chip. A theoretical SET SER estimation from measured SET-pulse widths is also experimentally validated. [ABSTRACT FROM AUTHOR]

A scan flip-flop (FF) is designed to observe both single event transient (SET) and single event upset (SEU) soft errors in logic VLSI systems. The SET and SEU soft errors mean the upset caused by latching an SET pulse that originates in combinational logic blocks and the upset caused by a direct ion hit to the FF, respectively. An irradiation test method using the scan FF is proposed to obtain SET and SEU soft-error rates at each FF distributed in logic VLSI systems. A test chip is designed using a 0.2-µm fully-depleted silicon-on-insulator standard cell library. The basic concepts have been validated with Verilog timing simulations. The cell-level implementation costs of the proposed scan FF are estimated to be reasonable. [ABSTRACT FROM AUTHOR]

Monitored Drift Tube chambers (MDT) are the precision tracking detectors in the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC). From simulations of the LHC operating conditions, the count rate in the inner barrel chamber of the muon spectrometer is expected to reach 500 Hz/cm² and can be ten times higher in the luminosity upgrade under discussion (SLHC). A degradation of the performances of drift tube chambers after extended operation in high-rate environment is usually caused by the formation of deposits on the anode wire. To study MDTs aging, three bundles of short tubes equipped like a final MDT chamber were irradiated in different periods with neutrons and photons using the TAPIRO nuclear reactor and the CALLIOPE gamma facility at the ENEA-Casaccia Research Center (Italy). The MDT performances with respect to accumulated dose were studied with cosmic rays and results on drift and tracking properties are presented. [ABSTRACT FROM AUTHOR]

Nuclear robots must be hardened against radiation for effective operation in high-radiation environments. These robots require special components that usually have few functions, high costs and long delivery times. In the present study, we propose a modulated and hierarchical electrical circuit system for robot components such as actuators. The hierarchical system is set into a design that can withstand radiation without reducing or limiting the functionality of the robot. The hierarchical system is achieved by minimizing the variety of integrated circuit (IC) components to be used and selecting specific ICs that require radiation testing. These ICs are defined by spotted ICs with regard to the integration density and operational speed. In some cases, it is possible to select off-the-shelf IC components, but certain key IC components are needed for on-line irradiation tests, depending on robot operation reliability and the radiation environment. Since the serial numbers of off-the-shelf IC components are random, it is important that a sufficiently large number of IC components are tested under the operating conditions for statistical evaluation. If the radiation lifetime is random, then the radiation lifetime of the sorted IC components can be estimated statistically. Here, the robot user decides the operation based on this lifetime. By doing so, the experimental cost can be minimized in accordance with the proposed method at the user's operational risk. Of course, if on-line irradiation tests are performed for various types of IC components, the radiation lifetime of the robot can be predicted with a relatively high accuracy. As a result, the design of a robot that operates under certain radiation conditions, while having a certain lifetime and cost, is possible. This design technique was applied to a nuclear disaster prevention robot and the radiation lifetime of the spotted IC components was shown to be distributed randomly, indicating the validity of the proposed method. [ABSTRACT FROM AUTHOR]

We present the results of a global irradiation test of full size triple-GEM detectors operated with a CF4-based gas mixture. This study has been performed in the framework of an R&D activity on detectors for the innermost region of the first muon station of the LHCb experiment. The prototypes have been irradiated at the Calliope facility of the ENEA-Casaccia with a high intensity 1.25 MeV gamma from a 60Co source. After the irradiation test the detectors' performances have been measured with X-rays and with a 3 GeV pion beam at CERN. A SEM analysis on several samples of the detectors has been performed to complete the understanding of the physical processes occurring in the GEM detector during the strong irradiation [ABSTRACT FROM PUBLISHER]

Rotating disk centrifugal atomization technology has been utilized to fabricate uranium silicide (U3Si, U3Si2) and U-Mo nuclear fuel powders having high uranium content per unit volume for high performance research reactor fuels. Atomized nuclear fuel powders have characteristics of a spherical shape with narrow size distribution, small specific surface area and high purity. The heat treatment time for the formation of U3Si by a peritectoid reaction was reduced from about 72 hours for comminuted powders to about 6 hours for atomized powders due to more rapid solidification of atomized powder with a finer microstructure. The homogeneity of fuel particles in fuel meats was improved by mixing atomized fuel powders with Al powders using a V-shaped tumbler mixer. The atomized powders with a spherical shape and smooth surface were extruded under lower force than the comminuted powders with angular rough surfaces. The dispersed fuel meat with atomized powders resulted in an increased fuel powder loading density and higher thermal conductivity in the heat flow direction. The thermal swelling of dispersed fuel meat decreased due to the reduced specific surface area of spherical atomized nuclear powder. The atomized U-10wt.%Mo dispersion fuel showed less bubble formation than the comminuted fuel after an irradiation test with 40% burnup. [ABSTRACT FROM AUTHOR]