scholarly journals Improvement of Reliability and Ecological Safety of NPP Reactor Coolant Pump Seals

2020 ◽  
pp. 47-55
Author(s):  
S. Shevchenko ◽  
O. Shevchenko
Keyword(s):  
High Pressure ◽  
Flow Characteristics ◽  
Environmental Safety ◽  
Mechanical Seal ◽  
Ecological Safety ◽  
Mechanical Seals ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Optimal Value ◽  
Contact Surfaces

The paper presents the analysis of existing designs of NPP reactor coolant pumps (RCP) rotor sealing systems. The most common design solutions of sealing units that provide the necessary tightness, reliability and service life under high pressure, temperature and sliding speeds typical for RCP, as well as trends for their improvement to increase tightness and environmental safety of activities were identified. Designs of impulse seals with a self-adjusting clearance are presented as the most promising assemblies for sealing pump shafts with high parameters. A computer model of impulse mechanical seal as an automatic control system is proposed. A framework for calculating impulse mechanical seals has been developed, allowing the choice of their main geometric parameters to ensure the optimal value of the mechanical clearance and the friction moment on the sealing contact surfaces. Expressions are obtained for constructing the static and flow characteristics of a impulse mechanical seal, the condition for its dynamic stability is determined. The paper presents the shaft sealing system of RCP, main nodes of which are several stages of impulse mechanical seals with a self-regulating clearance.

The Demonstrated Function of PLR Pump Mechanical Seal Under SBO Conditions

2017 ◽  
Author(s):  
Toshiyuki Yoshioka ◽  
Takashi Motani ◽  
Atsushi Fujimaru ◽  
Koji Yamada ◽  
Kunihiro Hasegawa ◽  
...  
Keyword(s):  
Nuclear Power ◽  
The Other ◽  
Leak Rate ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Reactor Coolant ◽  
Seal Failure ◽  
Coolant Injection ◽  
Regulatory Standards ◽  
Fukushima Daiichi

Generic Safety Issue 23 (GSI-23) by the U.S. Nuclear Regulatory Commission (NRC) was identified in 1980 as a result of staff concerns about reactor coolant pump (RCP) seal failure during Station Blackout (SBO), that is, seal degradation leading to a significant loss of reactor coolant in pressurized-water reactor (PWR) plants. Resolutions of GSI-23 have been considered at PWR plants. In 2000, NRC decided to close GSI-23 and issue Regulatory Issue Summary00–002 (RIS 00–002)[1], based on considerations such as; for example, the improvement of RCP seal performance[2], and the reduction of the risk of RCP seal failure in certain plants by the addition of alternate power sources. After the closure of GSI-23, some licensees were planning to make other associated improvements under their individual plant program. In Japan, the RCP seal was showed that leakage rate was low under SBO testing conditions[3] in licensing safety reviews conducted according to new nuclear regulatory standards after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. On the other hand, a boiling-water reactor (BWR) is not included in GSI-23 because operating experience indicates that seal failures in BWRs result in smaller leak rates than seal failures in PWRs and, BWRs have the reactor coolant injection capability under SBO conditions, such as the reactor core isolation cooling (RCIC) and the high-pressure coolant injection (HPCI) system. In addition, for the particular BWR-2 type plants that do not have emergency makeup systems, the pump mechanical seal was tested under SBO conditions and successfully showed minimal leakage[4]. However, for the BWR-5 type plants which have the reactor coolant injection capability, such as the RCIC and HPCI systems, the pump seal had not been tested. In Japan, after the nuclear accident at the Fukushima Daiichi Nuclear Power Plant, licensing safety reviews of BWRs and PWRs are being conducted according to new nuclear regulatory standards. We took this opportunity to test the leak rate from Primary Loop Recirculation (PLR) pump mechanical seals under SBO condition. The peak of leak rate was approximately 0.6ton/h (2.6gpm) during the 24 hours of SBO testing condition. Despite damage of O-rings in the mechanical seal by heated water which were ovserbed at post-inspection test, a very low leak rate was realized because the leakage path after passing through the damaged parts of the O-rings was limited by the other restricting pathway in the mechanical seal. This seal leakage was very low, compared with the reactor coolant makeup capability of the RCIC system and the reactor coolant release capability from main steam safety relief valve (SRV). Therefore, we reconfirmed that the result of this leak rate does not affect the safety evaluation for the reactor. It is shown in this paper that the leak rate from PLR pump mechanical seals is low under SBO condition by our demonstration test.

scholarly journals Characteristics of the Waviness End-Face Mechanical Seal in Reactor Coolant Pump Considering the Viscosity-Temperature Effect

2021 ◽  
Vol 9 ◽  
Author(s):  
Yu Ma ◽  
Ya-Hui Wang ◽  
Hai-Chun Zhou ◽  
Wen-Tao Su
Keyword(s):  
Liquid Film ◽  
Temperature Effect ◽  
Temperature Rise ◽  
Structural Parameters ◽  
Thermal Characteristics ◽  
Mechanical Seal ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Study Results ◽  
Operational Safety

Mechanical seals prevents flow leakages in reactor coolant pumps thus playing an important role in their operational safety. However, their operational performance depends on different parameters, the seal geometrical design and the sealing medium characteristics among others. This study investigates the main performances of the waviness end-face mechanical seal, considering the effect of fluid flow and thermal characteristics. The involved coupled thermal-hydraulic process is simulated using the OpenFOAM, based on the coupled Navier-Stokes and energy balance equations. Study results showed that the viscosity-temperature effect may increase the flow leakage, and decrease both the opening force and the liquid film stiffness. The later may be decreased to negative values under specific conditions. It’s therefore generally found that visco-thermal characteristics of the sealing medium may negatively affect mechanical seal’s operational stability. On the other hand, from the perspective of liquid film temperature rise, the visco-thermal effect may lead to the regulation of the temperature rise in the liquid film, which improves the mechanical seal’s operational safety in some aspects. Through a comprehensive analysis, the optimal structural parameters of the waviness mechanical seal investigated in this study are found to be hi = 2.5μm, β = 900μrad (Rd-Ri)/(Ro-Ri) = 0.2, α = 0.8, and k = 9.

scholarly journals Leakage Characteristic of Helical Groove Seal Designed in Reactor Coolant Pump

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Meng Zhang ◽  
Xiao-fang Wang ◽  
Sheng-li Xu ◽  
Shuo Yin
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Friction Factor ◽  
Helix Angle ◽  
Operation Condition ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Friction Factors ◽  
Helical Groove ◽  
Groove Seal

Helical groove seal is designed in reactor coolant pump to control the leakage along the front surface of the impeller face due to its higher resistance than the circumferentially grooved seal. The flow and the friction factors in helical groove seals are predicted by employing a commercial CFD code, FLUENT. The friction factors of the helical groove seals with helix angles varying from 20 deg to 50 deg, at a range of rotational speed and axial Reynolds number, were, respectively, calculated. For the helically grooved stator with the helix angle greater than 20 deg, the leakage shows an upward trend with the helix angle. The circumferentially grooved stator has a lower resistance to leakage than the 20 deg and 30 deg stators. It can be predicated that, for a bigger helix angle, the friction factor increases slightly with an increase in high axial Reynolds number, which arises from the high-pressure operation condition, and the friction factor is generally sensitive to changes in the helix angle in this operation condition. The study lays the theoretical foundation for liquid seal design of reactor coolant pump and future experimental study to account for the high-pressure condition affecting the leakage characteristic.

Analysis of Mechanical Seal Leakage within Hydrostatic on Nuclear Reactor Coolant Pump

2014 ◽  
Vol 496-500 ◽  
pp. 990-994 ◽  
Author(s):  
Hai Yang Zhang ◽  
Wei Bing Zhu ◽  
Zhou Gang
Keyword(s):  
Centrifugal Force ◽  
Nuclear Reactor ◽  
Hydrodynamic Lubrication ◽  
Structural Characteristics ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Coolant Pump ◽  
Turning Angle ◽  
Hydrodynamic Lubrication Theory ◽  
Turning Radius

According to the fluid hydrodynamic lubrication theory, and the structural characteristics of the convergence gap seal is combined, the effect of differential pressure and centrifugal force should be considered, then the convergent wedge gap mechanical seals flow field numerical model is established and the influence of the leakage factors are researched, including the geometric parameters and operating parameters. Research has shown that the amount of leakage and the seal clearance were positively correlated. And the larger turning Angle is, the bigger correlation becomes, however, it is negatively correlated with speed and turning radius, the seal leakage is impeded by the centrifugal force and the larger turning radius is, the smaller leakage becomes.

Flow Field Analysis of the Reactor Coolant Pump Internal Cooling Circulation

2017 ◽  
Author(s):  
Jie Qin ◽  
Qingmu Xu ◽  
Junkai Yuan ◽  
Kun Cai
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Distribution ◽  
Internal Cooling ◽  
Shaft Seal ◽  
Flow Area ◽  
Coolant Pump ◽  
Reactor Coolant

Reactor coolant pump (RCP) is one of the most critical devices in third generation of pressurized water reactor nuclear power plant. EMD shield pump and KSB wet winding pump are two representative kinds of RCPs without complex shaft seal system. Due to cancellation of shaft seal system, the entire rotors (including the flywheel) are immersed in the coolant. The losses in RCPs take one third of the total power including rotation loss caused by rotor in the water, electromagnetic loss in the shielding sleeve,the heat transferred through high temperature coolant, and heat generated by bearing.Because of the losses listed above, bearing and winding are heated,and the losses make temperature rise. in order to ensure that the motor is working properly at low temperatures, the company EMD and KSB design the RCP internal cooling circulation which brings the heat out to ensure the normal operation of the RCPs. The RCP internal cooling circulation includes inlet flow area, auxiliary impeller, thrust bearing, the lower flywheel, motor can, upper radial bearing, upper flywheel, outlet flow area, and external heat exchanger,etc. Flow characteristics in every flow path determine the flow distribution and heat transfer, and the flow distribution determines whether the cooling performance of RCP internal cooling circulation meets the requirements. In order to control operating temperature of motor and bearing, and to optimize heat transfer, adjusting the size of flow area and changing the flow characteristics arecritical. flow field and temperature field in RCP internal cooling circulation need overall analysis. Flow distribution can be obtained theoretically through the calculation of an overall three-dimensional model.But on the one hand, the calculation time is long due to a complex three-dimensional model with a large quantity of grids, on the other hand, it is easier to casue errors in local processing and the errors are difficult to find or correct. For rapid analysis and optimization of flow and heat transfer in RCP internal cooling circulation, ensure the motor winding and bearing operate at an appropriate temperature, the local characteristics of RCP internal cooling circulation are studied, one-dimensionalanalysis method of RCP internal cooling circulation is developed. This one-dimensional analysis method can be used to predict the flow distribution of each part of RCP internal cooling circulation according to change of the channel geometry parameters, key dimensions, boundary conditions and rotor speed. The geometric parameters are optimized by analyzing the flow distribution, and the purpose of design guidance are achieved.

scholarly journals Numerical and Experimental Study on Waviness Mechanical Seal of Reactor Coolant Pump

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1611
Author(s):  
Xiaodong Feng ◽  
Wentao Su ◽  
Yu Ma ◽  
Lei Wang ◽  
Heping Tan
Keyword(s):  
Liquid Film ◽  
Coupling Effect ◽  
Hydrodynamic Lubrication ◽  
Leakage Rate ◽  
Numerical Results ◽  
Force Balance ◽  
Mechanical Seal ◽  
Deformation Method ◽  
Coolant Pump ◽  
Reactor Coolant

Based on the fluid hydrodynamic lubrication theory, a mathematical model of liquid film lubrication was established for the waviness hydrodynamic mechanical seal of a reactor coolant pump. The influences of the waviness amplitude and pressure on the sealing performance were investigated by the numerical simulation. The numerical results showed that the leakage rate increases linearly as the pressure and waviness amplitude increase under the force balance condition. The minimum liquid film thickness decreases first and then increase as the pressure increases. Stationary slide rings with three different waviness amplitudes were processed using the pre-deformation method and tested at different pressure and temperature. The experiments showed that all the three kinds of seal have good stability under different pressure conditions. The experimental results showed that the leakage rate is influenced by the pressure, waviness amplitude, and temperature, and the leakage rate increases as the pressure increases. The comparison between experimental and numerical results showed that both the temperature and pressure affect the seal performance, and tends to a smaller leakage rate, which is quite different from the numerical values. Therefore, the multi-physics coupling effect should be considered in the numerical analysis of seal performance, and this will be studied in the further works.

scholarly journals Effect of eccentricity on radial force and cavitation characteristics in the reactor coolant pump

2020 ◽  
pp. 312-312
Author(s):  
Yuanyuan Zhao ◽  
Xiuli Wang ◽  
Rongsheng Zhu
Keyword(s):  
Nuclear Power ◽  
Nuclear Reactor ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Radial Force ◽  
Asymmetric Structure ◽  
Two Phase ◽  
Coolant Pump ◽  
Cavitation Inception ◽  
Reactor Coolant

Nuclear reactor coolant pump as one of the most critical equipment is the only one rotating equipment in first loop system of nuclear power plant. Due to the asymmetric structure of the pump body, especially the existence of outlet segment lead to a certain of radial force, the magnitude of radial force directly affects the work stability of the reactor coolant pump. The nuclear reactor coolant pump could stability work under those transient complex conditions is an important index of its performance. To study the cavitation characteristics and radial force of reactor coolant pump on transient cavitation, a prototype pump and those exhibiting different gravity center offsets are analyzed numerically with CFD software ANSYS CFX by employing RNG k-? model and two-fluid two-phase flow model. Through the experiment-combined simulation, the variations of cavitation characteristics and radial force of the reactor coolant pump under different eccentricities are characterized. As revealed from the results, the flow characteristics of the internal flow field of the nuclear main pump change after the axis is offset by different distance. The influence of eccentricity on the cavitation of the nuclear main pump is mainly manifested at the impeller inlet from cavitation inception to severe cavitation. When the eccentricity is 5mm, the cavitation performance is improved. The effect of eccentricity on the radial force of impeller is reflected in the variation of force direction. Compared with other plans, the radial force is superior in transient cavitation under the eccentricity of 5mm.

Influence of structural parameters on wavy-tilt-dam hydrodynamic mechanical seal performance in reactor coolant pump

2020 ◽  
Vol 166 ◽  
pp. 210-221
Author(s):  
Wen-Tao Su ◽  
Yang Li ◽  
Ya-Hui Wang ◽  
Ya-Ning Zhang ◽  
Xiao-Bin Li ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Mechanical Seal ◽  
Coolant Pump ◽  
Reactor Coolant

Improving of quality of gate assembly contact surfaces of high-pressure fi ttings by diamond burnishing

2020 ◽  
pp. 99-104
Author(s):  
S.A. Zaydes ◽  
A.N. Mashukov ◽  
T.Ya. Druzhinina
Keyword(s):  
Surface Roughness ◽  
High Pressure ◽  
Main Part ◽  
Conical Surface ◽  
The Real ◽  
Metal Seal ◽  
Diamond Burnishing ◽  
Air Tightness ◽  
Contact Surfaces

The contact belt of the gate assembly is the main part of high pressure fittings. The serviceability of the fittings assembly as whole depends on the air-tightness and quality of the mating surfaces. The technology of diamond burnishing allows to increase the interface of the nodes by red ucing the surface roughness of the metal-to-metal seal. The real experience for improving of the fittings contact belt due to the use of diamond burnishing of the nozzles seats and the conical surface of the rods.

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