Mercury Loop Research Articles

A Compact Gas Liquid Separator for the Spallation Neutron Source Mercury Process Loop

Abstract Upgrades at the spallation neutron source (SNS) accelerator at Oak Ridge National Laboratory are underway to double its proton beam power from 1.4 to 2.8 MW. About 2 MW will go to the current first station while the rest will go to the future Second Target Station. The increase of beam power to the first target station is especially challenging for its mercury target. When the short proton beam hits the target, strong pressure waves are generated, causing cavitation erosion and challenging stresses for the target's weld regions. SNS has successfully operated reliably at 1.4 MW by mitigating the pressure wave with the injection of small Helium bubbles into the mercury. To operate reliably at 2 MW, more gas will be injected into mercury to mitigate the pressure wave further. However, the mercury process loop was not originally designed for gas injection, and the accumulation of gas in the pipes is a concern. Due to space constraints, a custom gas liquid separator (GLS) was designed to fit a 90-deg horizontal elbow space in the SNS mercury loop. Simulations and experiments were performed, and a successful design was developed that has the desired efficiency while keeping the pressure losses acceptable.

Buoyancy effects in vertical rectangular duct with coplanar magnetic field and single sided heat load – Downward and upward flow

The effects specific for downward and upward flows of liquid metal (LM) in a vertical rectangular duct in a coplanar magnetic field (MF) are investigated. The experiments were performed in the JIHT's test facility with a closed magnetohydrodynamic (MHD) mercury loop. The temperature and velocity fields were measured in the duct with single-side heating in a coplanar magnetic field. The averaged temperature fields, wall temperature distributions, statistical characteristics of temperature fluctuation and longitudinal velocity profiles were obtained. The results for the downward and the upward flow under different flow conditions are compared.

Experimental investigations of heat transfer and temperature fields in models simulating fuel assemblies used in the core of a nuclear reactor with a liquid heavy-metal coolant

The aim of this experimental investigation is to obtain information on the temperature fields and heat transfer coefficients during flow of liquid-metal coolant in models simulating an elementary cell in the core of a liquid heavy metal cooled fast-neutron reactor. Two design versions for spacing fuel rods in the reactor core were considered. In the first version, the fuel rods were spaced apart from one another using helical wire wound on the fuel rod external surface, and in the second version spacer grids were used for the same purpose. The experiments were carried out on the mercury loop available at the Moscow Power Engineering Institute National Research University’s Chair of Engineering Thermal Physics. Two experimental sections simulating an elementary cell for each of the fuel rod spacing versions were fabricated. The temperature fields were investigated using a dedicated hinged probe that allows temperature to be measured at any point of the studied channel cross section. The heat-transfer coefficients were determined using the wall temperature values obtained at the moment when the probe thermocouple tail end touched the channel wall. Such method of determining the wall temperature makes it possible to alleviate errors that are unavoidable in case of measuring the wall temperature using thermocouples placed in slots milled in the wall. In carrying out the experiments, an automated system of scientific research was applied, which allows a large body of data to be obtained within a short period of time. The experimental investigations in the first test section were carried out at Re = 8700, and in the second one, at five values of Reynolds number. Information about temperature fields was obtained by statistically processing the array of sampled probe thermocouple indications at 300 points in the experimental channel cross section. Reach material has been obtained for verifying the codes used for calculating velocity and temperature fields in channels with an intricately shaped cross section simulating the flow pass sections for liquid-metal coolants cooling the core of nuclear reactors.

Why Can’t We Retire Codeine?

Some remedies have long outlived their usefulness and have thankfully been relegated to historical archives, supplanted by safer, more effective drugs. We no longer prescribe mercury loop diuretics or antisyphilitic arsenicals. Yet, the use of codeine-containing products persists for cough relief and analgesia in children. As Kaiser et al1 report in their study “National Patterns of Codeine Prescriptions for Children in the Emergency Department” in this month’s issue, prescriptions for codeine-containing products barely edged down in frequency between 2001 and 2010, despite convincing studies documenting their lack of benefit and serious adverse effects. Using data from the National Hospital and Ambulatory Medical Care Survey database, they found codeine prescribed in the pediatric emergency department at the incredible rate of 558 805 to 876 729 prescriptions per year with only a small statistical decline over that period. Additionally, the US Food and Drug Administration reported that >1.7 million children aged 17 years and younger had a prescription for a codeine product filled at a pharmacy in 2011.2 These high numbers continue despite guidance from professional societies discouraging the use of codeine in children. Why do pediatric practitioners continue to write prescriptions for codeine? Kaiser et al … Address correspondence to Alan D. Woolf, MD, MPH, FAAP, Pediatric Environmental Health Center, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail: alan.woolf{at}childrens.harvard.edu

Gas Bubble Size Measurements in Liquid Mercury Using an Acoustic Spectrometer

A properly dispersed population of small bubbles can mitigate cavitation damage to a spallation neutron source target. In order to measure such a bubble population, an acoustic device was developed and implemented in a mercury loop at ORNL. The instrument generated pulses of various frequencies and measured their acoustic propagation in the bubbly medium. It then deduced sound speed and attenuation at the various frequencies and used an inverse problem solver to provide near real-time measurements of bubble size distribution and void fraction. The measurements were then favorably compared with an optical method.

Structural-hydraulic test of the liquid metal EURISOL target mock-up

Structural-hydraulic tests of the European Isotope Separation On-Line (EURISOL) neutron converter target mock-up, named MErcury Target EXperiment 1 (METEX 1), have been conducted by Paul Scherrer Institut (PSI, Switzerland) in cooperation with Institute of Physics of the University of Latvia (IPUL, Latvia). PSI proceeded with extensive thermal-hydraulic and structural computational studies, followed by the target mock-up tests carried out on the mercury loop at IPUL. One of the main goals of the METEX 1 test is to investigate the hydraulic and structural behaviour of the EURISOL target mock-up for various inlet flow conditions (i.e. mass flow rates) and, in particular, for nominal operating flow rate and pressure in the system. The experimental results were analysed by advanced time–frequency methods such as Short-Time Fourier Transform in order to check the vibration characteristics of the mock-up and the resonance risk. The experimental results (obtained in METEX 1), which include inlet flow rate, pressure of the cover gas, total pressure loss, structural acceleration, sound and strain data, were jointly analysed together with numerical data obtained from Computational Fluid Dynamics (CFD).

Two-phase flow model for energetic proton beam induced pressure waves in mercury target systems in the planned European Spallation Source

Two-phase flow calculations are presented to investigate the thermo-hydraulical effects of the interaction between 300 kJ proton pulses (2 ms long, 1.3 GeV) with a closed mercury loop which can be considered as a model system of the target of the planned European Spallation Source(ESS) facility. The two-fluid model consists of six first-order partial differential equations that present one dimensional mass momentum and energy balances for mercury vapour and liquid phases are capable to describe quick transients like cavitation effects or shock waves. The absorption of the proton beam is represented as instantaneous heat source in the energy balance equations. Densities and internal energies of the mercury liquid-vapour system are calculated from van der Waals equation, and the general method how to obtain such properties is also presented. A second order accurate high-resolution shock-capturing numerical scheme is applied with different kinds of limiters in the numerical calculations. %Our two-fluid model is very similar to the RELAP5 thermo-hydraulical code %which is used in the nuclear industry to simulate nuclear power plant accidents. Our analysis show that even 75 degree temperature heat shocks cannot cause considerable cavitation effects in mercury in 2ms long pulses

SNS Target Systems initial operating experience

The SNS mercury target started operation with low beam power when commissioned on April 28, 2006. The beam power has been following a planned ramp up since then and has reached 340 kW as of February 2008. The target systems supporting neutron production include the target and mercury loop, the cryogenic and ambient moderator systems, reflector and vessel systems, bulk shielding and shutters systems, utility systems, remote handling systems and the associated instrumentation and controls. Availability for these systems has improved with time and reached 100% for the first 2000 hour neutron production run in fiscal year 2008. An overview of the operating experience and the planning to support continued power increases to 1.4 MW for these systems will be given in this paper.

Mitigation Technologies for Damage Induced by Pressure Waves in High-Power Mercury Spallation Neutron Sources (II)—Bubbling E.ect to Reduce Pressure Wave—

Liquid mercury was suggested to be used as target material for high-power pulsed spallation neutron sources. In order to realize the high-power target, however, the pressure wave is a critical issue, which is caused by the thermal shock in mercury and causes cavitation at the moment when highly intense proton beams bombard mercury. R&D on pressure wave mitigation technologies is carried out for Japan Spallation Neutron Source (JSNS; 1MW/25 Hz). Microbubble injection into the mercury is one of prospective technologies to mitigate the pressure wave. The microbubble effect was experimentally investigated from the viewpoint of pitting damage due to the cavitation in the mercury loop with an electro-magnetic impact testing machine (MIMTM) and numerically examined from the viewpoint of bubble dynamics. In the present study, we confirmed that the microbubble injection is very effective to reduce pitting damage and the amplitude of negative pressure, which causes explosive growth of cavitation bubble.

Numerical study on pressure wave propagation in a mercury loop

On-beam tests were carried out at the Los Alamos Neutron Science Center–Weapons Neutron Research (LANSCE–WNR) facility in June 2005 to investigate pressure wave mitigation in mercury targets for the MW-class spallation neutron sources under international collaboration between US Spallation Neutron Source (SNS) and Japanese Spallation Neutron Source (JSNS). A mercury loop was used for the target, a so-called In-Beam Bubbling Test Loop (IBBTL). The loop consists of the rectangular pipe of 25 mm × 50 mm 2 in cross section, 1.5 mm in wall thickness and 2 m in total length approximately. The SNS team set 8 strain sensors on the pipe wall to measure the strain propagation caused by the pressure wave. The maximum strain appeared at 350 mm apart from the proton-bombarded point at 5.5 ms after the proton bombardment. It is known that the propagation velocity of the pressure wave in mercury is ca. 1500 m/s and that of the stress wave in stainless steel is ca. 5000 m/s. However, the apparent wave propagation velocity in the IBBTL was lower than those velocities and was observed to be 65 m/s. Numerical analysis was carried out to understand the strain propagation in the pipe wall of the IBBTL. Numerical results showed that the maximum strain at 350 mm apart from the beam spot appeared at 5.5 ms after proton bombardment in good agreement with experimental results.

Overview of the SNS target system testing and initial beam operation experience

The Spallation Neutron Source (SNS) construction project has been completed including initial beam operation with the mercury target, moderators and associated systems. The project was initiated in 1999, with groundbreaking in December of 1999. Final integrated system testing for the mercury target, cryogenic moderators, shutter systems, water and other utility systems and all control and safety systems were completed in April 2006 and first beam on target was delivered April 28, 2006. This paper will give an overview of the system testing conducted in preparation for beam operation and initial operating experience with low power beams. One area of testing was extensive remote handling testing in the target service bay to demonstrate all key operations associated with the target and mercury loop. Many improvements were implemented as a result of this experience. Another set of tests involved bringing the supercritical cryogenic moderator systems on line. Again, lessons learned here resulted in system changes. Testing of the four water loops was very time consuming because of the complexity of the systems and many instrumentation issues had to be resolved. A temporary phosphor view-screen was installed on the front of the target which has been extremely useful in evaluating the beam profile on the target. Initial profile results will be presented. Target system performance for initial beam operation will be discussed. In general, all systems performed well with excellent availability. There were some unexpected findings. For example, xenon spallation gas products are believed to have deposited on a downstream gold amalgamation bed designed to remove mercury vapor and this disposition increased the local dose rate. A summary of findings and plans for ramping up in power will be given.

Conducting Pulsed Target

Conducting pulsed target scheme has been studied as an alternative targetry solution used for a dedicated high-intense and bright muon source (PRISM). We made a conceptual design and have developed a pulse power supply and a mercury loop to be used for the proof-of-principle test.

水銀循環用ギアポンプシール材の損耗劣化

A gear pump will be used in mercury target system for JSNS (Japan Spallation Neutron Source). A seal element of the gear pump is a key component to safely operate the mercury target system. The gear pump was operated in the experimental mercury loop in JAERI. After several hundreds hours operation, certain leakage of mercury was observed from the sealing part of the gear pump. In order to develop a sound seal element and structure for the pump, as the first step, the surfaces of the seal elements were observed precisely by a laser microscope. It was confirmed that the surface degradation was correlated to the amount of leakage; the largest leakage occurred from the seal surface set on a drive shaft on pulley side that was most damaged.

502 水銀ターゲットシステムのソースターム評価

Source term methodology for radioactive nuclides generated by spallation reaction between proton beam and mercury was proposed for a safety concept construction of a MW-class mercury target system. The methodology was considered the effects of all mercury leakage from main mercury loop, mercury evaporation, transportation by ventilation air flow, filter and atmospheric dispersion as well as the decrement of mercury temperature and chemical form such as amalgam. From the analytical results obtained under the conditions expecting high safety margin, the maximum level of the public exposure was approximately 7μSv, which is negligible in comparison with the 1 mSv of one-year natural radiation exposure.

Recherches récentes sur la cavitation à l'Institut de mécanique de Grenoble

Two themes combining two various test means are covered: The developed cavitation studied in the IMG's hydrodynamic tunnel and the cavitation erosion studied on a mercury loop. The developed cavitation study includes: the analysis relating to the separation of a cavity from a wall, the unsteady cavitation per pocket, the interaction between germs, the boundary layer and the cavity (this study is dealt wilh in a separate report), and the experimental study of partial cavitation. Erosion tests were carried out in collaboration with the CERG and EDF with a view to clarifying the rules of similarity. Finally, a special effort has been made so as to develop and calibrate miniaturized pressure sensors specially adapted to measure instantaneous excess pressures due to structural implosion.