The valve assembly used in nuclear power plants is important safety-related equipment. In the new standard, the physical attributes are measured using a valve diagnosis test, which is used in the ...expansion to other non-tested valves using a quantitative test-basis methodology. With a motor-operated actuator, the state of stem's lubrication is related to physical attributes such as the stem factor and the friction coefficient. This study analyzed the numerical transient of fluid and solid lubrication with a squeeze film effect due to the loading rate on the stem and the stem nut using the experimental data. The differential equation that governs the motion mechanism of the stem and stem nut is established and analyzed. The flow rate, the fluid and the solid contact forces are calculated with the friction coefficient. Finally, we found that a change in the friction coefficient results from a change of the shear force in the solid contact mode during the interchange process between the solid contact mode and the fluid contact mode. The qualitative understanding of the squeeze film effect is expanded quantitatively for forces, thread surface distance, velocity, and acceleration, with consideration of the metal solid contact and fluid contact.
An interval type-2 fuzzy logic (IT2FL)-based technique is proposed to control the operation of an in-conduit hydropower generator for recapturing waste energy in water pressure reducing valves (PRVs) ...and generating maximum power. Using an experimental setup, an actual water supply station is simulated for testing the operation and control of the in-conduit generator. The test system includes one hydro-powered generator, two PRVs, and two motor-operated valves (MOVs). An IT2FL method developed in MATLAB is used to control MOVs in order to adjust the customer pressure and maximize the generator efficiency. A prototype hardware setup is developed to produce the voltage set points that control the MOV actuators using the pressures, which are measured by transducers and transferred to the IT2FL algorithm via a data acquisition and control system. The generator operational limit is met to avoid any possible damage. The IT2FL control-based algorithm is tested on the hardware-in-the-loop (HIL) setup under various flow and pressure values and compared to type-1 fuzzy logic (T1FL) and existing pseudo algorithms. Also, an economic analysis is carried out using real data of a water booster section in Northern Nevada for justifying the economic benefits of the proposed scheme.
This paper presents a systematic optimal design algorithm to design the shape of rotor slot to get a specific speed-torque characteristic in three-phase squirrel cage induction motor for the ...application to motor operated valve (MOV) actuator. The developed method consists of three steps: design based on equivalent circuit method (ECM) utilizing multi-objective formulation, selection of the strongly influential geometric parameters of rotor slot, and precise design based on finite element method (FEM). The validity of the suggested design method is demonstrated through applications to rotor slot design of three-phase induction motor to achieve a NEMA class D speed-torque characteristic.
This paper proposes a flexible and secure control scheme for recapturing the waste energy across water pressure reducing valves using an in-conduit hydro-powered generator. A laboratory scaled ...platform for investigating the hydropower generator is established to model the water supply stations. The wasted energy is used by the in-conduit generator to generate electricity. A fuzzy-based control scheme is designed to maximize the generator efficiency such that the required water pressure and flow on the customer side are not affected due to this waste energy recapturing. In the proposed scheme, the generator operating characteristics are taken into consideration to prevent any damage. The effectiveness of the proposed scheme for different flow and pressure scenarios is evaluated.
Safety related valves within the nuclear power plant were governed by the Inservice Testing Program (IST) for scheduling tests or maintenances during the plant normal operation. Based on the program ...definitions, series of tests for these valves have to be performed and conducted periodically. Safety functions of safety related valves such as Motor Operated Valve (MOV), Air Operated Valve (AOV) and Check Valve (CV) under the event of Design Basis Accident (DBA) could be performed properly. IST program plays an important role for constantly maintaining these safety related valves under operable conditions; therefore safety functions such as emergency reactivity control, post-accident residue heat removal, post-accident radioactivity removal and containment isolation could be performed and satisfied during the DBA event or abnormal plant operation occurrences.
This study performed the Risk-informed evaluations for safety related valves in the IST program for BWR and PWR nuclear power plants in Taiwan. Outcome from this study, safety classifications for the safety related valves under IST program could be categorized, HSSC category valves could be identified, testing frequency relieves for the LSSC category could be suggested, systematic comparison of the safety significant classification between BWR and PWR nuclear power plants was presented and finally, due to the advantages of the RI-IST, both dose exposure for the plant staffs and outage cost reductions for the utility managements could be achieved.
Pumping stations are used to increase water pressures in supply mains for fire fighting, high rise building, and to maintain water supply in water towers and storage tanks. Water pressure reducing ...valves (PRV) are needed on domestic systems where the municipal water main's pressure is more than 80psi. Some of the energy loss across the PRV can be converted to electricity by replacing the existing PRV with small hydroelectric turbines and generators. Decreasing the water pressure from 150 psi to 50 psi also reduces the water flows through the system and wastewaters. There is a need to develop a scheme to control the operation of the in-conduit hydro-powered generator for maximum efficiency which is the subject of this paper.
Safety related valves such as Motor Operated Valves (MOV), Air Operated Valves (AOV) or Check Valves (CV) play an important role in nuclear power plant. Functioning of these valves mainly aim at ...emergency reactivity control, post-accident residue heat removal, post-accident radioactivity removal and containment isolation when a design basis accident occurred. In order to maintain these valves under operable conditions, an Inservice Testing Program (IST) is defined for routine testing tasks based on the ASME Boiler & Pressure Vessel Code section XI code requirements.
Risk based Inservice Testing Programs have been studied and developed extensively in the nuclear energy industry since the 1990s. Risk Based evaluations of IST can bring positive advantages to the licensee such as identifying the vulnerability of the system, reducing unnecessary testing burden, concentrating testing resources on the critical pass oriented valves and saving plant’s personnel dose exposure. This risk evaluation is incorporated with quantitative and qualitative analyses to the Motor Operated Valves under current Inservice Testing Program for PWR nuclear power plant in Taiwan.
With the outcome of the risk classifications for the safety related MOVs through numerical or deterministic analyses, a risk based testing frequency relief is suggested to demonstrate the benefits received from the risk based Inservice Testing Program. The goal made of this study, it could be as a reference and cornerstone for the licensee to perform overall scope Risk-Informed Inservice Testing Program (RI-IST) evaluation by referring relevant methodologies established in this study.
Implementing a risk-informed inservice testing (RI-IST) program provides a good aspect to the nuclear power plant licensee as an alternating program in the current ASME Section XI and 10 CFR 50.55a ...relevant testing programs. RI-IST concentrates testing resources on highly significant components, reduces excess testing burden, increases plant's availability, decreases dose rate on the plant's staff and also reduces cost on plant's operation and maintenance under nuclear safety expectations. Furthermore, RI-IST also gives a feature on prospective licensing change basis to a nuclear power plant's licensee.
This study will focus on safety-related and PRA-molded motor-operated valves (MOVs) and air-operated valves (AOVs) under the inservice testing program in boiling water reactor (BWR)-type nuclear power plant. As MOVs and AOVs have crucial safety functions throughout the nuclear power plant's safety systems, the steady operation and performance of MOVs and AOVs will definitely ensure that the nuclear power plant operates under safety expectations; therefore, this is the key reason to implement risk-informed evaluation for MOVs and AOVs in this study and being able to provide the safety significance classification for MOVs and AOVs under the current IST program to the plant's management. As a pilot study of RI-IST, the methodology of qualitative assessment will incorporate with probabilistic risk assessment (PRA) analyzing MOVs’ and AOVs’ safety significance within the current PRA model. The evaluating result will then classify its safety significance into a high-safety significant component (HSSC) and a low-safety significant component (LSSC) for MOVs and AOVs based on relevant regulatory criteria. With this initiating achievement, it can provide a cornerstone for further studies on the other types of valves and pumps in RI-IST program and also provide a valuable reference as proposing license change to the licensee.
When the maintenance program for components in a nuclear power plant is drawn up, it is important to evaluate and optimize the overhaul interval of components based on operation and maintenance ...experiences. Motor-operated valve (MOV) data in safety systems for BWRs are selected from the operation and maintenance database for Japanese nuclear power plants called NUClear Information Archives (NUCIA). The time dependence of the failure occurrence rate of MOV is analyzed by Baysian inference using a log-linear and regression model of nonhomogeneous Poisson process. Then, its optimal overhaul interval of MOV is evaluated based on the time-dependent failure occurrence rate as determined by Bayes analysis. This Bayes analysis is found to be effective for estimating the optimal decision for the overhaul interval of MOV in an actual nuclear plant. This analysis will also contribute to optimizing the overhaul interval of any components in a nuclear power plant by using the data in NUCIA.
When the maintenance program for components in a nuclear power plant is drawn up, it is important to evaluate and optimize the overhaul interval of components based on operation and maintenance ...experiences. Motor-operated valve (MOV) data in safety systems for BWRs are selected from the operation and maintenance database for Japanese nuclear power plants called NUClear Information Archives (NUCIA). The time dependence of the failure occurrence rate of MOV is analyzed by Baysian inference using a log-linear and regression model of nonhomogeneous Poisson process. Then, its optimal overhaul interval of MOV is evaluated based on the time-dependent failure occurrence rate as determined by Bayes analysis. This Bayes analysis is found to be effective for estimating the optimal decision for the overhaul interval of MOV in an actual nuclear plant. This analysis will also contribute to optimizing the overhaul interval of any components in a nuclear power plant by using the data in NUCIA.
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