Ryutaro Hino

R & D on mercury target pitting issue

Abstract A technical issue in mercury spallation target development is pitting, which appears on the target vessel in conjunction with the pressure wave. Pitting has been found in off-beam line test by split Hopkinson pressure bar (SHPB) test as well as in the on-beam test of mercury target at WNR of LANSCE. In SHPB tests pressure in mercury was reduced from 80 to 40, 20 and 10 MPa. Specimens made of type 316 stainless steel were inspected before and after the impacting test at ×450 magnification. Results show that over 20 MPa pitting was generated. But at the lowest pressure in mercury, the number of pits was very limited and substantial damage was small. Substantial damage by pitting is characterized by holes where mass is removed from the wall. Depression itself may not be a substantial damage as long as it is not accompanied by holes.

Bubble dynamics in the thermal shock problem of the liquid metal target

The thermal shock stress in a mercury target vessel was analyzed. The target receives the incident proton beam at an energy of 1 MW with a pulse duration of 1 μs. A negative pressure of 61 MPa was generated following the dispersion of the compression field at 52 MPa which was generated by the proton beam injection. It is expected that cavitation may be caused by the negative pressure. In order to evaluate the cavitation behavior and the following material damage mechanism, a simulation study was carried out using the equation of motion based on bubble dynamics for a single bubble, and fundamental parameter analysis was carried out. It is found that a bubble has a volume expansion of more than 1000 times with a change of the pressure at the window of the target vessel. Consequently wave propagation will be affected. Theoretical consideration was given to the wave motion of propagation in a bubbly liquid. The equation of state in a bubbly liquid can be approximated by polynomials. The diameter of a bubble and the bubble volume fraction inherent in mercury can be estimated if the critical pressure, the sound velocity, and resonance frequency are measured by static and dynamic experiments.

Thermal and hydraulic tests of test sections in the helium engineering demonstration loop

Abstract The helium engineering demonstration loop (HENDEL) has been constructed and operated to test the large-scale components of the high temperature engineering test reactor (HTTR) under simulated reactor operating conditions. The fuel stack test section (T 1 ) of HENDEL simulates the fuel stack of the HTTR core and is used to investigate thermal and hydraulic performance. Hot tests with 1000°C helium gas have been conducted using simulated fuel rods having uniform, exponential and cosine axial heat flux distributions. The test results agreed with previously proposed correlations, although the simulated fuel rods had various heat flux distributions and high heat flux rates. The in-core structure test section (T 2 ) also was installed in the HENDEL to verify the performance of the core bottom structure of the HTTR. The tests show that good performance was obtained. Examination of the thermal mixing characteristics indicated that mixing started at the location where the hot helium gas flowed into the hot plenum and that complete mixing was achieved during the downward flow in the outlet hot gas duct. The seal performance testing indicated no change of the leakage flow rate after 4000 hours of operation. The temperature of the metal portion of the structure was below 500°C and uniform around circumferential cross-sections due to the good performance of the thermal insulation blocks.

Experiments on mercury circulation system for spallation neutron target

A construction of the spallation neutron source is in progress under the Japan Proton Accelerator Research Complex (J-PARC) Project. A mercury circulation system has been designed to supply mercury to the target stably. In the design of the mercury circulation system, it was necessary to test a mercury pump performance. An erosion rate under the mercury flowing condition and an amount of remaining mercury after draining mercury from the system also must be made clear from viewpoints of evaluating life time of mercury piping. In addition, these data play essential roles in establishing remote handling scenario of components used in the system, because mercury would be highly activated. The mercury pump performance, the erosion rates and the amount of remaining mercury were investigated by using a mercury experimental loop with an experimental gear pump. As a result, it was demonstrated that the discharged flow rates of the pump were sufficient. The flow rate increased linearly with the rotation speed as expected. With conservative assumption, a decreased amount of piping wall thickness was estimated 660 mm after 30-year operation under the rated mercury velocity of 0.7 m/s based on the obtained erosion rate. For the amount of remaining mercury in the loop, remaining rates of weight was estimated to be 50.7 g/m2.

Analytical Study of Volumetric Scroll Pump for Liquid Hydrogen Circulating System

The paper presents analytical results of suction process of a volumetric scroll pump, which will be developed for circulating liquid hydrogen in a cold moderator system. The multi-block grid generation approach has been applied to generate a moving boundaries computational model. The finer mesh patterns have been generated in the near-wall regions. The Low-Reynolds number k-ε turbulence model has been solved for predicting Reynolds stresses and turbulent scalar fluxes. The analysis has been carried out under liquid hydrogen flow conditions. The heat transfer effect is neglected to simplify the study. The analytical results show that at the end of suction process the relative pressures increase significantly in a pocket while decrease continuously in another pocket. This phenomenon might damage scroll pump components if the high-pressure side is too high and/or the low-pressure side is too low until the cavitations occur. Therefore, the pocket should open to the discharge chamber before it closes and separates from the suction chamber in order to prevent the cavitations and extremely high-pressure regions.

Water flow experiments and analyses on the cross-flow type mercury target model with the flow guide plates

Abstract A mercury target is used in the spallation neutron source driven by a high-intensity proton accelerator. In this study, the effectiveness of the cross-flow type mercury target structure was evaluated experimentally and analytically. Prior to the experiment, the mercury flow field and the temperature distribution in the target container were analyzed assuming a proton beam energy and power of 1.5 GeV and 5 MW, respectively, and the feasibility of the cross-flow type target was evaluated. Then the average water flow velocity field in the target mock-up model, which was fabricated from Plexiglass for a water experiment, was measured at room temperature using the PIV technique. Water flow analyses were conducted and the analytical results were compared with the experimental results. The experimental results showed that the cross-flow could be realized in most of the proton beam path area and the analytical result of the water flow velocity field showed good correspondence to the experimental results in the case when the Reynolds number was more than 4.83×10 5 at the model inlet. With these results, the effectiveness of the cross-flow type mercury target structure and the present analysis code system was demonstrated.

Inertia effect on thermal shock by laser beam shot

A stress wave generates and propagates in a beam window, a target container and solid target plates of the target system for neutron spallation source because of a thermal shock induced by an injection of a high-intensity proton beam. In this study, a thermal shock experiment was carried out using a ruby laser to investigate the behavior of the stress wave propagation. Numerical analyses on the stress waves induced by the thermal shock were carried out. It was confirmed that tensile stress waves were generated at the border of the heated area because of the inertia effect of the propagation of compressive stresses to outside of the heated area associated with the thermal shock. Subsequently the tensile stress waves concentrate at the center of the non-heated surface to become large. These trends are adequately supported by the numerical results.

Prediction of Flow Patterns and Pressure Distributions in Suction Process of Volumetric Scroll Pump

Prediction of Flow Patterns and Pressure Distributions in Suction Process of Volumetric Scroll Pump Phichai KRITMAITREE a , Mitsunobu AKIYAMA a , Ryutaro HINO b , Masanori KAMINAGA b & Atsuhiko TERADA b a Mechanical Engineering Department , Utsunomiya University , Ishii-cho , Utsunomiyashi , Tochigi , 321-0912 b System Engineering Group, Tokai Research Establishment , Japan Atomic Energy Research Institute , Shirakata , Tokai-mura , Naka-gun , Ibaraki , 319-1195 Published online: 07 Feb 2012.

Mercury Target and Its Peripheral Devices for 1 MW Spallation Neutron Source

The Japan Atomic Energy Research Institute (JAERI) and the High Energy Accelerator Research Organization (KEK) are promoting a plan to construct a 1MW neutron source facility at the Tokai Research Establishment, JAERI, under the Japan Proton Accelerator Research Complex (J-PARC) Project. In the facility, 1 MW pulsed proton beam from a high-intensity proton accelerator will be injected into a mercury target in order to produce high-intensity pulse neutrons for use in the fields of life and material sciences. In order to realize such a high-power neutron source, the design activity of a cross flow type (CFT) mercury target and its peripheral devices has continued and the results is reflected in the ordering specifications of the facility construction. The arrangement of each component and their structure was optimized through experimental and analytical studies. In this paper, the present design of the mercury target components for 1MW spallation neutron source including the target vessel, a mercury circulation system, and a target trolley will be reported.Copyright

Stress waves due to deposited heat in mercury and lead spallation targets

Stress waves resulting from deposited heat in mercury and lead spallation targets were studied. A computation was carried out with the following conditions: —the incident proton energy and current are 1.5 GeV and 3.3 mA, respectively: the total proton energy is 5 MW in short pulses at a frequency of 50 Hz —targets are mercury and lead —proton beam profile has a Gaussian distribution. The following results are obtained: 1. It is found that the cylindrical part of the container expands due to stress waves with periods of 180 μs for mercury and 130 μs for lead. The periods are roughly evaluated by D/V, where D is the diameter of target container, 0.2 m, and V the speed of sound in fluid materials. 2. Membrane components of stress control large amplitude stress waves, whilst bending stress components induce high frequency stress waves in both targets. 3. A fitting function describing deposited energy as, a function of position in the target was proposed. The ratio of deposited energy to the projectile energy is under 50% for 1.5 GeV protons for both targets.