Role of the Nonrotating Decay Heat Removal Blower Pressure Loss in ALLEGRO Reactor

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
G. Mayer ◽  
A. Guba
Keyword(s):  
Pressure Loss ◽  
Natural Circulation ◽  
Reactor Core ◽  
Heat Removal ◽  
Loss Coefficient ◽  
Normal Operation ◽  
Pressure Loss Coefficient ◽  
Decay Heat ◽  
Accident Conditions ◽  
Core Cooling

Abstract ALLEGRO is a helium-cooled fast reactor, which is being developed by the Czech Republic, France, Hungary, Slovakia, and Poland. It will be the demonstrator of the GFR-2400-MWth Generation IV gas-cooled fast reactors. In ALLEGRO, a three-loop safety system is designed to remove decay heat during accident conditions. The nonrotating blower blades may represent a huge pressure loss in the decay heat removal loop (DHR), which hinders natural circulation. The lower the pressure loss coefficient of the DHR blower blades is, the better cooling is available during natural circulation. On the other hand, a large core bypass develops if a DHR valve is opened inadvertently during normal operation. In this case, the higher DHR blower pressure loss is better from core cooling point of view. Consequently, the low pressure loss of the DHR blower is advantageous for core cooling in station blackout (SBO) event but disadvantageous for inadvertent DHR valve opening event. Both the above-mentioned cases may lead to insufficient core cooling in accident conditions, which threatens the integrity of the reactor core. In this study, we present CATHARE thermohydraulic calculations to assess the sensitivity of the DHR blower pressure loss coefficient for the above-mentioned two cases.

Transient Analysis for the Case of Changes in Coolant Inventory for Advanced Heavy Water Reactor

2004 ◽  
Author(s):  
H. G. Lele ◽  
A. Srivastava ◽  
B. Chatterjee ◽  
A. J. Gaikwad ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Heavy Water ◽  
Nuclear Reactor ◽  
Natural Circulation ◽  
Reactor Core ◽  
Two Phase ◽  
Decay Heat ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Heavy Water Reactor ◽  
Core Cooling

Safety of nuclear reactor needs to be assessed against different categories of Postulated initiating events. Advanced Heavy Water Reactor is natural circulation light water cooled and heavy water moderated pressure tube type of reactor. Inventory of the system is important parameter in determination of flow characteristics of this natural circulation reactor. In view of this, various events that cause changes in PHT system inventory are analysed in this paper. One of the reason for decrease in coolant inventory is hypothetical Loss of coolant accident (LOCA) This event is of very low probability but important from designing engineered safeguard system of a reactor. Loss of coolant accident in a nuclear reactor can cause voiding of the reactor core due to expulsion of primary coolant from break. In such, a situation the reactor core experiences very low heat removal rate from the nuclear fuel though the decay heat generation continues even after tripping of the reactor. Heat generation in the reactor core is due to various sources such as decay heat, stored heat etc, can lead to heating of fuel elements. However, Emergency core cooling systems of the reactor are actuated and prevent undesirable temperature rise. These events are called design basis events and focus is on adequacy of Emergency Core Cooling System (ECCS) and fuel integrity. The scenarios, phenomena encountered and consequences depend upon size and location of break, system characteristics, and actuation and capability of different protection and engineered safeguard systems of the reactor system. Moreover, this reactor has several passive features to ensure safety of this reactor. which are considered in analyzing these events. Events under category of decrease in coolant inventory includes loss of coolant accidents due to break at different locations of different sizes. Various locations considered in this paper are steam line, inlet header, inlet feeder, ECCS header, downcomer, pressure tube, Isolation condenser inlet header, instrument line break at inlet header and steam drum. The paper also considers scenario emerging due to malfunctions like relief valve stuck open. Causes for events under category of increase in coolant inventory are Increase in Drum level controller set point, Inadvertent valving in of Accumulators and Inadvertent valving in of Gravity driven water pool (GDWP). Last two events are not analysed as they are not possible. The analysis for the above events is complex due to various complex and wide ranges of phenomena involved during different pies under this category. It involves single and two phase natural circulation at different power levels, inventories and pressures, two-phase natural circulation under depleted inventory conditions. Coupled neutronics and thermal hydraulics behaviour, Phenomena under LOCA, phenomena during ECCS injection, direct injection into fuel rod, advanced accumulator injection., vapour pull through and coupled controller and thermal hydraulics. Modelling of these phenomena for each event is discussed in this paper. In this paper summary of analyses for representive event is presented.

scholarly journals Modeling the Ambient Condition Effects of an Air-Cooled Natural Circulation System

2017 ◽  
Author(s):  
Rui Hu ◽  
Darius D. Lisowski ◽  
Matthew Bucknor ◽  
Adam R. Kraus ◽  
Qiuping Lv
Keyword(s):  
Experimental Data ◽  
Natural Convection ◽  
Empirical Model ◽  
Natural Circulation ◽  
Heat Removal ◽  
Normal Operation ◽  
Scale Model ◽  
Ambient Conditions ◽  
Flow Rates ◽  
Decay Heat

The Reactor Cavity Cooling System (RCCS) is a passive safety concept under consideration for the overall safety strategy of advanced reactors such as the High Temperature Gas-Cooled Reactor (HTGR). One such variant, air-cooled RCCS, uses natural convection to drive the flow of air from outside the reactor building to remove decay heat during normal operation and accident scenarios. The Natural convection Shutdown heat removal Test Facility (NSTF) at Argonne National Laboratory (“Argonne”) is a half-scale model of the primary features of one conceptual air-cooled RCCS design. The facility was constructed to carry out highly instrumented experiments to study the performance of the RCCS concept for reactor decay heat removal that relies on natural convection cooling. Parallel modeling and simulation efforts were performed to support the design, operation, and analysis of the natural convection system. Throughout the testing program, strong influences of ambient conditions were observed in the experimental data when baseline tests were repeated under the same test procedures. Thus, significant analysis efforts were devoted to gaining a better understanding of these influences and the subsequent response of the NSTF to ambient conditions. It was determined that air humidity had negligible impacts on NSTF system performance and therefore did not warrant consideration in the models. However, temperature differences between the building exterior and interior air, along with the outside wind speed, were shown to be dominant factors. Combining the stack and wind effects together, an empirical model was developed based on theoretical considerations and using experimental data to correlate zero-power system flow rates with ambient meteorological conditions. Some coefficients in the model were obtained based on best fitting the experimental data. The predictive capability of the empirical model was demonstrated by applying it to the new set of experimental data. The empirical model was also implemented in the computational models of the NSTF using both RELAP5-3D and STAR-CCM+ codes. Accounting for the effects of ambient conditions, simulations from both codes predicted the natural circulation flow rates very well.

Study on a Small Power Reactor With Compact Pressure Vessel and Natural Circulation

2014 ◽  
Author(s):  
Kenya Takiwaki ◽  
Shungo Sakurai ◽  
Yutaka Takeuchi ◽  
Yasushi Yamamoto
Keyword(s):  
Power Reactor ◽  
Natural Circulation ◽  
Reactor Core ◽  
Cooling Water ◽  
Heat Removal ◽  
Small Power ◽  
Control Rod ◽  
Decay Heat ◽  
Heat Removal System ◽  
Removal System

There is movement which is developing the small reactor for the small electricity grid in place of a big power reactor which requires the high capital cost. This paper introduces a small power reactor whose purpose is to achieve high economic competitiveness and advanced safety. In order to attain high economic competitiveness, it is designed to be small and simple and uses natural circulation and high pressure. A steam generator is integrated into the reactor pressure vessel (RPV), thus dispensing with a primary system and preventing radiation leakage from the reactor core. The small core is designed to have a high power density (100 MW/m3, almost twice that of a conventional boiling water reactor). The concept of a 300 MWt (100 MWe) core design is established by introducing a boiling heat transfer system. By boiling cooling water, the cooling-water circulating flow quantity in a reactor core is enlarged. By increasing a flow, the minimum critical power ratio is improved, which is an important core characteristic. Furthermore, using a burnable poison (Gd2O3), the excess reactivity of a reactor core is reduced and excess reactivity is controlled only by the control rod. Moreover, the maximum linear power density is improved and the critical power ratio is minimized by optimizing the burnable poison arrangement and the control rod pattern. In order to attain high safety, our small reactor has an advanced decay heat removal system that can cool the core without external support. This decay heat removal system is part of the secondary cooling system and combined with a cooling tower. As a result, the quantity of cooling water stored in the decay heat removal system is reduced, and longtime decay heat removal is possible by small equipment.

scholarly journals Decay Heat Removal and Transient Analysis in Accidental Conditions in the EFIT Reactor

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
Giacomino Bandini ◽  
Paride Meloni ◽  
Massimiliano Polidori ◽  
Maddalena Casamirra ◽  
Francesco Castiglia ◽  
...  
Keyword(s):  
Natural Circulation ◽  
Thermal Power ◽  
Heat Removal ◽  
Normal Operation ◽  
Steam Generators ◽  
Flow Paths ◽  
Decay Heat ◽  
Driven System ◽  
Accelerator Driven System ◽  
Relap5 Code

The development of a conceptual design of an industrial-scale transmutation facility (EFIT) of several 100 MW thermal power based on accelerator-driven system (ADS) is addressed in the frame of the European EUROTRANS Integral Project. In normal operation, the core power of EFIT reactor is removed through steam generators by four secondary loops fed by water. A safety-related decay heat removal (DHR) system provided with four independent inherently safe loops is installed in the primary vessel to remove the decay heat by natural convection circulation under accidental conditions which are caused by a loss-of-heat sink (LOHS). In order to confirm the adequacy of the adopted solution for decay heat removal in accidental conditions, some multi-D analyses have been carried out with the SIMMER-III code. The results of the SIMMER-III code have been then used to support the RELAP5 1D representation of the natural circulation flow paths in the reactor vessel. Finally, the thermal-hydraulic RELAP5 code has been employed for the analysis of LOHS accidental scenarios.

Vibration suppression investigation and parametric design of tri-axle straight heavy truck with pitch-resistant hydraulically interconnected suspension

2021 ◽  
pp. 107754632110396
Author(s):  
Fei Ding ◽  
Jie Liu ◽  
Chao Jiang ◽  
Haiping Du ◽  
Jiaxi Zhou ◽  
...  
Keyword(s):  
Surface Area ◽  
Dynamic Load ◽  
Pressure Loss ◽  
Vibration Suppression ◽  
Parametric Design ◽  
Suspension System ◽  
Loss Coefficient ◽  
The Body ◽  
Impedance Matrix ◽  
Pressure Loss Coefficient

The vibration suppression of the proposed pitch-resistant hydraulically interconnected suspension system for the tri-axle straight truck is investigated, and the vibration isolation performances are parametrically designed to achieve smaller body vibration and tire dynamic load using increased pitch stiffness and optimized pressure loss coefficient. For the hydraulic subsystem, the transfer impedance matrix method is applied to derive the impedance matrix. These hydraulic forces are incorporated into the motion equations of mechanical subsystem as external forces according to relationships between boundary flow and mechanical state vectors. In terms of the additional mode stiffness/damping and suspension performance requirements, the cylinder surface area, accumulator pressure, and damper valve’s pressure loss coefficient are comprehensively tuned with parametric design technique and modal analysis method. It is found the isolation capacity is heavily dependent on installation scheme and fluid physical parameters. Especially, the surface area can be designed for the oppositional installation to separately raise pitch stiffness without increasing bounce stiffness. The pressure loss coefficients are tuned with design of experiment approach and evaluated using all conflict indexes with normalized dimensionless evaluation factors. The obtained numerical results indicate that the proposed pitch-resistant hydraulically interconnected suspension system can significantly inhibit both the body and tire vibrations with decreased suspension deformation, and the tire dynamic load distribution among wheel stations is also improved.

The Characteristics Study of Helium-Xenon Mixture in Closed Brayton Cycle for Space Nuclear Reactor Power

2018 ◽  
Author(s):  
Xie Yang ◽  
Lei Shi
Keyword(s):  
Physical Properties ◽  
Pressure Loss ◽  
Nuclear Reactor ◽  
Reactor Power ◽  
Loss Coefficient ◽  
Working Fluid ◽  
System Efficiency ◽  
Pressure Loss Coefficient ◽  
Molar Weight ◽  
Xenon Mixture

Differing from the adoption of helium as working fluid of closed Brayton cycle (CBC) for terrestrial high temperature gas cooled reactor (HTGR) power plants, helium-xenon mixture with a proper molar weight was recommended as working fluid for space nuclear reactor power with CBC conversion. It is essential to figure out how the component of helium-xenon mixture affects the net system efficiency, in order to provide reference for the selection of appropriate cycle working fluid. After a discussion of the physical properties of different helium-xenon mixtures, the related physical properties are studied to analyze their affection on the key parameters of CBC, including adiabatic coefficient, recuperator effectiveness and normalized pressure loss coefficient. Then the comprehensive thermodynamics of CBC net system efficiency is studied in detail considering different helium-xenon mixtures. The physical properties study reveals that at 0.7 MPa and 400 K, the adiabatic coefficient of helium-xenon mixture increases with increased molar weight, from 0.400 (pure helium) to 0.414 (pure xenon), while recuperator effectiveness firstly increases and then decreases with the increase of molar weight, and the normalized pressure loss coefficient increases monotonically with molar weight increases. The thermodynamic analysis results show that the adiabatic coefficient has less effect on the net system efficiency, while the net system efficiency increases with increased recuperator effectiveness, and the net system efficiency decreases with normalized pressure loss coefficient increases. Finally, the mixture of helium-8.6% xenon was adopted as working fluid, instead of pure helium, for ensuring less turbine mechanicals (turbine and compressor) stages, and resulting maximum recuperator effectiveness. At the given cold / hot side temperature of 400 / 1300 K, the net system efficiency can reach 29.18% theoretically.

Rotating Annulus Component Performance Characterisation Based on CFD Analyses

2018 ◽  
Author(s):  
Youming Yuan ◽  
David Hunt
Keyword(s):  
Test Data ◽  
Pressure Loss ◽  
Model Performance ◽  
Internal Flow ◽  
Loss Coefficient ◽  
Performance Data ◽  
Pressure Loss Coefficient ◽  
1D Model ◽  
Torque Coefficient ◽  
Secondary Air

FloMASTER is a 1-D thermo-fluids system simulation tool and its component models depend on the characterisation data of the component performance. Such performance data is mainly based on data banks established from extensive tests exemplified by the books like “Internal Flow” by Miller [1] and “Handbook of Hydraulic Resistance” by Idelchik [2]. One of the key components of the gas turbine secondary air system is the rotating annulus. However, reliable data and correlations for performance characteristics like pressure loss coefficient, torque coefficient, windage and heat transfer for this component are rare and non-existent in the open literature for the case of both walls rotating simultaneously, which is becoming more common in today’s multi-spool military aero engines. To overcome this challenge of lack of reliable performance data and correlations, in this paper the Mentor Graphics 3D CFD tool “FloEFD” is used to model both inner wall rotating and outer wall rotating annulus flow, and to verify the 3D CFD results of performance data in terms of pressure loss coefficient and torque coefficient versus some published test data in the open literature. It is shown that the CFD gives results on pressure loss and torque coefficients that are in good agreement with test data based correlations used in FloMASTER. This demonstrates that 3D CFD can be used as a powerful tool for verifying the existing 1D model, extending the 1D model performance data range and generating new performance data for developing new components where such data is not available from open literature. A future project is to extend this approach to provide performance data for rotating annuli with both walls rotating. Such data will form the basis for developing a new component model for a rotating annulus with both walls rotating.

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