Volume Control System Research Articles

Flow Rate and Volume Control of Fluid Based on Arduino for Synthesis of Silver Nanowires

In this study, we have successfully developed a flow rate and volume control system based on Arduino. This system consists of a container containing liquid, dc motor, keypad, and Arduino UNO that serves as a controller. The principle of this system is to control pulse width modulation (PWM) and delay time of dc motor using Arduino. This fluid flow and volume rate control system aims to control how much the fluid volume enters a chamber for mixing the solution. This system has an accuracy rate of 0.5 ml and has a measurement range of up to 100 ml for one process. For forward, the system will be applied to the medical as a substitute for syringe pump and research laboratory for controlling the manufacture of solutions on the synthesis of nanomaterials, especially silver nanowires.

Transient Analysis of CVCS Malfunction in Large Passive PWR

The present work focuses on a simulation of increase of coolant inventory due to malfunction of chemical and volume control system (CVCS) in advance passive pressure water reactor 1000 (AP1000) operating at a 102% nominal power before transient start-up. The objective is to verify if this transient may induce any over pressure in the reactor coolant pressure boundary due to inadequate residual heat removal. RELAP5 system code was used to simulate the transient and the simulation result was compared with the simulation result by LOFTRAN code. The RELAP5 simulation result is well comparable with the simulation result by LOFTRAN and this transient does not endanger the AP1000 pressure boundary system.

Analysis of the impact of different scenarios on the simulation results of unauthorized dilution of boric acid in the coolant of the primary circuit of the NPP-2006

Abstract Unauthorized dilution of boric acid in the reactor coolant due to improper operation of the chemical and volume control system (KBA) is a project mode with the violation of normal operation. The operator is obliged to identify unauthorized dilution within half an hour and stop feeding with pure condensate. The power unit has automation, which stops feeding on EP (emergency protection) and ATWS (Anticipated transient without scram) signals. The situation without the intervention of the operator and the failure of automation to stop dilution can be considered as a beyond design basis accident. The article presents an analysis of unauthorized boric acid dilution process in the primary circuit coolant of the NPP-2006 power unit up to the controlled state, either considering the operator's intervention after a 30-minute period of process, i. e. with a forced cessation of dilution, or without the operator's intervention until the tanks with pure condensate are completely emptied.

Analysis of the dynamic performance of an electro-hydrostatic actuator and improvement methods

As a kind of actuation mechanism for power-by-wire (PBW) actuation systems of more/all electrical aircraft, an electro-hydrostatic actuator (EHA) is a highly integrated local hydraulic actuation system. It is a volume control system consisting of a motor, a pump, an actuator, etc., which has features of high efficiency and reliability. However, the poor dynamic characteristic is one of the main factors restricting its wide application in aircraft. In this paper, the reason for the poor dynamic characteristic of an EHA is revealed from the perspectives of the natural frequency characteristic and the power requirement, respectively. In other words, the insufficiency of the motor output power at a high frequency is the main factor causing the poor dynamic characteristic of the system, and methods which include increasing the maximum output torque of the motor, reducing the rotational inertia of the motor-pump group, and adopting a double-motor-pump group configuration are proposed in this paper, by which the dynamic characteristic of the system can be improved. The feasibility of those methods are verified by simulations. Finally, the dynamic characteristic is tested on an EHA prototype, and results show that saturation of the output torque of the motor is the main factor restricting the dynamic characteristic of the EHA system.

Reliability Analysis of CVCS with Extended GO-FLOW Methodology by Considering Automatic Control Functions

Automatic Control System (ACS) has been more widely applied in nuclear power plants (NPP) in order to achieve better performance, convenience and economics. Some new challenges are also emerging in reliability analysis of ACS because of its complexity and strict regulatory requirements of NPP. The dynamic behavior of ACS is difficult to be expressed by traditional system reliability analysis techniques such as fault tree analysis and/or event tree which are widely applied for probabilistic safety assessment in NPPs. This paper presents an extended GO-FLOW methodology by introducing several supplementary operators for modelling control logic generally used in NPP systems. A Chemical and Volume Control System (CVCS) in Pressurized Water Reactor (PWR) NPP is taken as an example to demonstrate the usage of improved GO-FLOW methodology in modeling and reliability estimation of a process system coupled with automatic control functions.

Effect of user interface layout on the operators’ mental workload in emergency operating procedures in nuclear power plants

The improved control interface designs in nuclear power plants (NPPs) have been constantly developed in order to satisfy actual requirements. In this article, the effect of user interface layout on mental workload (MWL) of operators in emergency operating procedures in NPPs is analyzed. The control circuit interface of the Chemical and Volume Control system (RCV) was redesigned based on some human factor criterions and it was compared to the original interface during the procedure of system boots. The multi-index evaluation method based on performance measures (i.e., time to complete and error rate), subjective rating (i.e., NASA Task Load Index (NASA-TLX)) and physiological measure (i.e., eye movement) was used to evaluate MWL of operators. Twenty-two engineering students tested both interfaces in randomized order. The results showed that interface design has a significant effect on operators’ MWL. Specifically, the redesigned interface was rated significantly lower in overall workload, time to complete, and fixation indices, but higher blink rate. The results suggested that human factor criterions have a significant effect on operators’ MWL so they should be considered during designing of interface, and using of NASA-TLX tool and eye movement technique is useful for assessing of human-computer interface (HCI) designs in NPPs.

Twofold application of nanofluids as the primary coolant and reactivity controller in a PWR reactor: Case study VVER-1000 in normal operation

The use of nanofluid as a dual heat transfer enhancer and excess reactivity controller in a typical pressurized power reactor (PWR) is the focus of this study. Presently, boric acid is the dominant method for reactivity control in PWRs and Chemical & Volume Control System (CVCS) controls the boric acid concentration during reactor operation. In this study, we have replaced the coolant fluid of the first loop with a nanofluid which act as coolant, neutron moderator and neutron absorber. A full core of VVER-1000 as a typical PWR system is modeled with coupled neutronics and fluid dynamic codes. Among five nanofluids investigated, 2% volume fraction silver oxide is found to satisfy both neutronics and thermohydraulics safety margins of VVER-1000 nuclear reactor.

Measurement of Boron Concentration with the Serpentuator System

An off-line boron meter in a pressurized water reactor (PWR) nuclear power plant has the disadvantages of lagging data measurements and a long response time. This paper aims to shorten the response time and enhance the measurement accuracy of this type of device. First, the shortcomings of off-line boron meters were analyzed and the serpentuator system was proposed to replace the typical container system. Then, both FLUENT and GEANT simulation tools were used to demonstrate the merits of the serpentuator system. FLUENT was used to simulate the fluid response, while GEANT4 was used to obtain the f(P) curve. The simulation results from FLUENT indicate that the residence time of the fluid in the container system was approximately 9.5 times that in the serpentuator system. The simulation results obtained from GEANT4 manifest that the f(P) curve of the rectangular section was steeper than for the circular section. When the polyethylene was 8 cm thick, the f(P) curve was the steepest. Compared with a serpentuator made of titanium alloy, stainless steel, and brass, a serpentuator made of zirconium alloy or aluminum alloy achieved a steeper f(P) curve. Therefore, the serpentuator system is more applicable for PWRs using an off-line boron letdown through a chemical and volume control system.

The research and test of the cavitation performance of first stage impeller of centrifugal charging pump in nuclear power stations

The safety production is the most important index for nuclear power development, and the CVCS (chemical and volume control system) occupies an important place in safety control system. The CCP (centrifugal charging pump) is an important component of CVCS system and its particularity decides the high requirements on the cavitation performance, so the research on CCP cavitation has great significance. Using the 3D Pro/E software, the paper makes models of the flow passage components of first stage prototype of CCP in nuclear power stations, and completes the cavitation steady-state computation in the case that the high flow rate of first stage prototype reaches Q=160m3/h using the numerical computation software ANSYS CFX. The cavitation is divided into the following five stages according to its development process: inception operating condition, development operating condition, critical operating condition, serious operating condition and fracture operating condition. The research analyze the flow field, static pressure fields and bubble distribution conditions in the impeller in different cavitation states, and selects the middle flow line, the front shroud flow line and the back shroud flow line from the same blade for the comparative analysis; to verify the reliability of computation, the researcher made a first stage cavitation prototype to verify its hydraulic performance and cavitation performance. After the comparative analysis on the flow field, pressure and bubble distribution conditions of CCP first stage impeller in different cavitation states, the research draws the following conclusions: (1) as the inlet pressure decreases, the cavitation degree increases, the bubble distribution area extends from impeller inlet to impeller outlet and shows different laws in different cavitation states; (2) the generation of cavitation is affected by the pressure changes in impeller passages, and when the inlet pressure decreases, the static pressure in impeller passage decreases, thus producing a local low-pressure area; (3) the comparison of computation and test results shows small errors, thus proving the accuracy of analog computation; besides, the research verifies the cavitation performance in different flow rates by test, and test results show that NPSH3 is smaller than the 7.8m stipulated in Technical Specifications in any flow rate condition, indicating that the design is reasonable. The research points out a direction for the further improvement of optimization design of CCP cavitation performance.

Pressure fluctuation analysis for charging pump of chemical and volume control system of nuclear power plant

Equipment Failure Root Cause Analysis (ERCA) methodology is employed in this paper to investigate the root cause for charging pump’s pressure fluctuation of chemical and volume control system (RCV) in pressurized water reactor (PWR) nuclear power plant. RCA project task group has been set up at the beginning of the analysis process. The possible failure modes are listed according to the characteristics of charging pump’s actual pressure fluctuation and maintenance experience during the analysis process. And the failure modes are analysed in proper sequence by the evidence-collecting. It suggests that the gradually untightened and loosed shaft nut in service should be the root cause. And corresponding corrective actions are put forward in details.

HMSCs from UCB: Isolation, Characterization and Determination of Osmotic Properties for Optimal Cryopreservation

In tissue engineering, storing of biological material represents a fundamental step to bring cell-based medical devices to market on demand Karlsson and Toner (2000) and more recently Fadda et al. (2009). Compared to other methods, freezing to cryogenic temperatures allows long shelf lives and genetic stability (Karlsson and Toner, 2000). Unfortunately, cryopreserved cells are damaged by the cryopreservation process itself (Mazur, 2004). This loss (up to 50 %) can be tolerated for some cell lineages, but it’s unacceptable for others, as the human Mesenchymal Stem Cells (hMSCs) from Umbilical Cord Blood (UCB), whose collection and isolation is known to be difficult (Bieback et al., 2004). In this case, an optimal cryopreservation protocol is mandatory. Due to the high number of trials actually required for experimental optimization, mathematical modelling is considered a practical solution. To this aim, the osmotic properties need to be first estimated in order to determine the volume of residual intra-cellular water left by osmosis to form lethal ice or glass. In this work, the hMSCs from UCB of three different donors, after informed consent, have been isolated by a density gradient centrifugation method. The successful isolation has been verified through phenotypic cytofluorimetric analysis, and adipogenesis/osteogenesis capability differentiations. Osmotic properties, namely inactive cell volume, water and CPA (DMSO) permeabilities, have been determined by means of experimental runs carried out under hypertonic conditions (obtained with the addition of sucrose or DMSO), at three different temperatures. Cells volumes excursions have been measured by a potenziometric device (Coulter Counter) under equilibrium and dynamic conditions. Linear and non-linear regression analyses have been carried out to determine the adjustable parameters by means of the two parameters bi-compartimental model by Kleinahns (1998), as applied to a single-sized cell population (i.e. identical cells with size equal to the average). It is found that, the inactive volume fraction of hMSC from UCB apparently changes (increase) when DMSO is used instead of sucrose, thus limiting cell volume excursion during swelling. It is hypothesized that, a cell volume control system is activated during swelling, probably due to the action of ion pumps.

Finalization of the conceptual design of the auxiliary circuits for the European test blanket systems

In view of the ITER conceptual design review, the design of the ancillary systems of the European test blanket systems presented in [1] has been updated and made consistent with the ITER requirements for the present design phase. Europe is developing two concepts of TBM, the helium cooled lithium lead (HCLL) and the helium cooled pebble bed (HCPB) one, having in common the cooling media, pressurized helium at 8MPa [2]. TBS, namely helium cooling system (HCS), coolant purification system (CPS), lead lithium loop and tritium extraction/removal system (TES–TRS) have the purpose to cool down the TBM and to remove tritium to be driven to TEP from breeder and coolant. These systems are placed in port cell 16 (PC#16), chemical and volume control system (CVCS) area and tritium building. Starting from the pre-conceptual design developed in the past, more mature technical interfaces with the ITER facility have been consolidated and iterative design activities were performed to comply with design requirements/specifications requested by IO to conclude the conceptual design phase.In this paper the present status of design of the TBS is presented together with the preliminary integration in ITER areas.

First principles calculations predict stable 50 nm nickel ferrite particles in PWR coolant

Thermodynamic calculations that combine experimental data with the results of first principles calculations yield negative free energies for {111} surfaces of nickel ferrite for the temperature, pressure and ion concentrations typical of Pressurized Light Water Reactor (PWR) coolant. When combined with a positive bulk free energy of formation, the negative surface energies predict that thermodynamically-stable octahedral nickel ferrite particles with diameters of ∼50nm should be present in PWR coolant during operation. These particles would not be removed by mixed bed demineralizers and would be below the filter pore sizes typically used in Chemical and Volume Control Systems. The calculations also predict that these particles are not thermodynamically stable in coolant under ambient conditions. Based on these results it is proposed that solvated nickel ferrite particles, which are predicted to be stable and likely long-lived in PWR primary coolant, contribute to the nucleation of metal oxide scale on PWR fuel rod cladding and that conventional methods for purifying the primary coolant may be ineffective in removing these species.

Optimization of the Dynamic Performance of the Direct Drive Volume Control System Based on Orthogonal Experiment

Direct drive volume control (DDVC) electro-hydraulic servo system has many advantages compared to the valve control system. However, its application scopes were restricted by its poor dynamic performance. To study the reason for the low dynamic response, mechanical model of DDVC electro-hydraulic servo system is established. Structure parameters influencing the dynamic performance are analyzed. To optimize the structure parameters, the methodology of orthogonal experiment is presented. The selection of factors and levels of the experiment and the choice of the evaluation index are also revealed. The proposed methodology is carried out by simulation software and an optimal configuration is obtained. The dynamic response of the DDVC system with the optimal parameters is simulated. The results show that the dynamic performances are improved. The cross-over frequencyincreases from 0.0046 rad/s to 0.0442 rad/s, and the rise time Tr decreases from 488.6s to 47.90s.

Simulation Research on Effects of Low Velocity Characteristics to Direct Drive Volume Control Systems

The Direct Drive Volume Control (DDVC) Electro-hydraulic Servo System is a new Electro-hydraulic Servo System. It has the advantages of flexibility of AC servo motor control and high power of hydraulic servo system. Compared with the traditional electro-hydraulic servo system, the DDVC system is efficient, miniaturized integrated, convenient operated and economical. It has been used in many domains, and made great economic benefits. So it is widely considered to be one of the most important developing directions of the hydraulic control system. It will be widely used in more and more areas in the future. With the development of its application, how to improve the trajectory tracking precision of the DDVC system in low velocity motions becomes more important in the field. So that, the level of the low velocity characteristic impacted the system become to an important subject. In this paper, the mathematical mode of AC asynchronism motor Direct Torque Control was established, and the simulation mode was built. In addition, the idealized model of the DDVC system which based on united simulation of AMEsim/Simulink was established, simulation was executed. In order to make the research available, the low velocity characteristic of the DDVC system was also analyzed, and the low velocity characteristic simulation model was built. Computer simulation validated that the friction, the leakage and the mechanical losses are seriously influenced the system performance when the system working on the low velocity mode.

Direct-Drive Differential Volume Control Electro-Hydraulic Servo Control System

Direct-drive volume control electro-hydraulic servo control system, derivation model of single-rod hydraulic cylinder system, pointed out that when the reciprocating motion characteristics are inconsistent. In order to solve this problem, proposed direct-drive differential volume control electro-hydraulic servo system design of its control system and analysis of system models. Through theoretical analysis, validate this proposed direct-drive bad dynamic volume control system, symmetric dynamic performance, improving control system reliability.

Example User Centered Design Process for a Digital Control System in a Nuclear Power Plant

The U.S. nuclear industry, like similar process control industries, has moved toward upgrading its control rooms. The upgraded control rooms typically feature digital control system (DCS) displays embedded in the panels. These displays gather information from the system and represent that information on a single display surface. In this manner, the DCS combines many previously separate analog indicators and controls into a single digital display, whereby the operators can toggle between multiple windows to monitor and control different aspects of the plant. The design of the DCS depends on the function of the system it monitors, but revolves around presenting the information most germane to an operator at any point in time. DCSs require a carefully designed human system interface. This paper centers on redesigning existing DCS displays for an example chemical volume control system (CVCS) at a U.S. nuclear power plant.

Thermal hydraulic feasibility analysis of the IBED PHTS for ITER

One of the main challenges of the ITER fusion reactor is to effectively remove large amount of heat deposited to the surface of the plasma facing components. The tokamak cooling water system (TCWS) will accomplish the objective of removing about 1GW of peak heat load from in-vessel components while maintaining pressures and temperatures of the coolant within acceptable and safe limits during different operational scenarios. A study of feasibility has been launched for the IBED PHTS (Integrated Blanket, Edge localized mode coils (ELMs) and Divertor Primary Heat Transfer System; it consists of five independent cooling trains (four operational and one in stand-by), one steam pressurizer, supply and return headers, ring manifolds and connections to the all in-vessel components (i.e. First Wall Blanket, Divertor, ELM, Diagnostics and other Ports clients).The dynamic behaviour of the IBED PHTS has been investigated by means of RELAP5® code to simulate the response of the system during plasma pulse and baking operations. Due to the plasma heat deposition on the surfaces of the in-vessel components and subsequent increase in hot leg temperature, a large amount of water volume is transferred from the hot legs of the circuit to the surge-line of the pressurizer during each burn cycle. This causes rapid increase of pressure and temperature of the system and the following actions are proposed to counteract these variations: spray injection in the upper dome of the pressurizer from the Chemical and Volume Control System (CVCS) to reduce the pressure and active control of flow rates through heat exchangers and their bypass loops to regulate the heat transfer from the primary system to the environment via secondary and tertiary loops.This paper focuses on the prediction of the thermal hydraulic behaviour of the IBED PHTS during plasma pulses and baking scenarios, describing the various activity of the analysis, the geometrical assessment of the circuit and the modelling with RELAP5® code. The results have been compared with design and operational requirement. Possible strategies to enhance the system performances have been formulated.

Numerical simulation of thermal stratification in an elbow branch pipe of a tee junction with and without leakage

Thermal stratification can cause thermal fatigue of the piping system of a nuclear power plant. One of the regions most at risk of suffering from thermal fatigue is a small elbow pipe branching off from the main pipe of the coolant loop for the drain or letdown system in the chemical and volume control system (CVCS). This work focuses on a fundamental description of the thermal stratification caused by turbulent penetration and buoyancy effects in the elbow branch pipe using large-eddy simulations (LESs). The LES results for the normalized temperature, mean temperature, and root-mean square (RMS) temperature were found to be in good agreement with the available experimental data which confirms that LES can predict the thermal stratification in a closed elbow branch pipe where cold fluids are stagnant. Subsequently, the flow and heat transfer were numerically predicted using LES when leakage occurred in the elbow branch pipe. The numerical results show that the thermal stratification region is pushed towards the horizontal part and may remain there for a long time for a leakage ratio of 1%. However, thermal stratification is quickly eliminated for a leakage ratio of 5%, although there is a higher power spectrum density (PSD) of the temperature in the early stages of the leakage. It may be concluded that a small leakage ratio can result in the elbow branch pipe being at high risk of thermal fatigue caused by thermal stratification.

Passive Properties of the Isolated Mouse Heart: Titin, Collagen and the Working Sarcomere Length Range

Understanding the passive properties of the left ventricle (LV) is important with the high and increasing prevalence of Diastolic Heart Failure. We examined the sources of passive pressure in the isolated mouse heart and its working sarcomere length (SL) range. A Langendorff perfused isolated heart system was used with a volume controlled balloon inserted in the LV of the mouse (C57BL/6). Hearts were paced and perfused with a Tyrode solution at constant perfusion pressure. The volume control system was used to measure Frank-Starling (FS) relationships. Hearts were then arrested and permeabilized by perfusing the heart with 1% triton in a relaxing solution followed by measurement of the FS relationship. The obtained passive pressure-volume curve for the permeabilizied heart was lower than that of the intact heart; analysis revealed that turgor from constant pressure perfusion of the intact heart is a major source of this difference. To determine the molecular basis of the passive pressure of the skinned heart, we used both myofilament extraction and trypsin degradation of titin and repeated FS measurements. Both methods suggest that titin produces ∼80% of the passive pressure of the heart. Additional intact hearts were glutaraldehyde fixed at passive and BaCl2 activated conditions at similar volumes to the permeabilized hearts. Mid-wall fibers were carefully dissected from the hearts and SL measured via laser diffraction. SL of activated hearts ranged from 1.8-2.0um; diastolic SL from 1.95-2.15 um. Consistent with the isolated heart experiments, isolated muscle work shows that in this SL range, titin is the main contributor to passive tension. In conclusion, in the mouse LV diastolic sarcomere lengths exists in a relatively tight range and in this range titin is the major contributor to diastolic pressure of the intact heart.