bluuebunny/crossref_metadata_2025 huggingface dataset:
Combustion and Emission Performance of a Syngas-Diesel Dual-Fuel Generator
Authors: Arslan Aysegul , Dev Shouvik , Yousefi Amin , Stevenson David , Liko Brian , Butler James , Guo Hongsheng , Birouk Madjid
Published: November 2022

Remote or off-grid communities in Canada and across the world heavily rely on diesel-fueled generators to meet their electrical power and heating needs. Reducing diesel consumption of these generators with locally produced sustainable fuels such as syngas has the double benefit of reducing the greenhouse gas (GHG) emissions and the cost of transporting diesel to remote locations. In remote/off-grid areas, syngas can be produced from local biomass or waste through gasification or pyrolysis. The aim of this study was to investigate the combustion and emission performance of a syngas-diesel dual-fuel generator at a constant load condition under varying syngas flow rate and composition.

This experimental study was carried out using a 30-kilowatt (kW) generator with a four-stroke, four-cylinder, turbo-charged, and electronically controlled direct injection diesel engine. The intake manifold of the engine was modified to introduce syngas upstream of the engine’s turbocharger. Syngas was simulated using individually controlled flow rates of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2) and nitrogen (N2) from compressed gas cylinders before their mixing and introduction into the engine intake manifold. Two practical syngas compositions with varying CO/H2 ratios were evaluated. The engine was operated with a programmable engine control unit to control the diesel direct injection events. Electrical load on the generator was controlled by a load bank set to 11 kW (5.25 bar IMEP) and the engine speed was 1800 rpm.

The experimental results revealed that increasing the syngas flow rate at a fixed diesel injection timing and duration caused the indicated thermal efficiency (ITE) of the engine to decrease. NOx emissions decreased with increasing syngas flow rate but CO, particulate matter (PM) and CO2 emissions increased. Increasing the CO/H2 ratio in the syngas caused the ITE to decrease and the CO and CO2 emissions to increase. The laminar flame speed (LFS) and ignition delay (ID) of syngas-air mixture were calculated to develop a further insight into the experimental results.
Effects of Biogas Flow Rate and Composition on Combustion and Emissions of a Small Biogas-Diesel Dual-Fuel Generator
Authors: Missaghian Roya , Dev Shouvik , Stevenson David , Guo Hongsheng
Published: November 2022

Diesel fueled generators are widely used to provide electricity in off-grid locations in Canada. Transporting diesel fuel to such generally remote locations is often an expensive endeavor and the cost of the electricity may swell to as much as three times the Canadian national average. This also makes it challenging to reduce the greenhouse gas (GHG) emissions in such locations. One solution is to convert the locally available waste biomass into biogas which can subsequently be used in these diesel generators to offset the diesel use. The objective of this study is to demonstrate the use of biogas-diesel dual-fuel combustion in a small diesel generator and study the effects of the biogas flow rate and composition on its operation. The study is unique in highlighting the challenges associated with the application of biogas-diesel dual-fuel combustion in such small generators which typically operate at high engine speeds.

The study is conducted on a 4.0 kW diesel generator which is powered by a four-stroke, single-cylinder, direct injection diesel engine. The generator’s intake manifold is modified to introduce biogas, and the diesel supply and return lines are rerouted to a separate tank to measure fuel consumption. Tests are conducted at an electrical load of 3.3 kW with the engine running at 1800 rpm. Other measurements include in-cylinder pressure, exhaust temperature and exhaust emissions. Biogas is simulated by combining compressed natural gas (CNG – with ∼95% CH4) from pipeline supply and carbon dioxide (CO2) and nitrogen (N2) from high purity gas bottles.

Three common biogas compositions are evaluated with the biogas flow rate progressively increased. Increasing the biogas flow rate leads to higher hydrocarbon and carbon monoxide emissions in comparison to diesel-only operation, though emissions of nitrogen oxides are reduced. Distinct differences are observed in the performance of the engine when the composition of biogas is changed.
Impact of Ignition Assistant on Combustion of Cetane 30 and 35 Jet-Fuel Blends in a Compression-Ignition Engine at Moderate Load and Speed
Authors: Miganakallu Niranjan , Stafford Jacob , Amezcua Eri , Kim Kenneth S. , Kweon Chol-Bum M. , Rothamer David A.
Published: November 2022

This study investigates the use of a commercial-off-the-shelf (COTS) ceramic glow-plug to assist ignition of jet fuel blends with cetane numbers of 30 and 35, below the minimum cetane number of 40 for #2 diesel. Experiments were carried out on a single-cylinder compression-ignition engine operating at 1200 RPM for single and dual-injection (pilot + main) timing sweeps. The COTS glow-plug, termed the ignition assistant, was operated at varying input power levels between 0 and 70 W (stock maximum power input is 30 W) at each SOI. Results demonstrate that the use of an ignition assistant at the higher input powers (50 and 70 W) enables operation over a wider range of SOI timings where more advanced times are limited by high pressure-rise rates and more retarded times are limited by rapidly increasing coefficient of variation of gross indicated mean effective pressure. Use of the ignition assistant enables stable combustion at later injection timings increasing the operable range of SOI timings. For the CN 30 fuel, at earlier injection timings, pressure traces and heat release analysis demonstrated the advancement of start of combustion and combustion phasing with the ignition assistant on. At retarded injection timings where combustion would not otherwise occur completely for the CN 30 fuel, operating the ignition assistant at the higher powers enabled combustion phasing to be advanced and combustion to be stabilized at conditions where, with the ignition assistant off, misfire (flameout) would occur. Furthermore, the ignition assistant enabled combustion phasing to follow an approximately linear response with respect to SOI timing over a wider range of SOI times.
Combustion characteristics of F24 compared to Jet A in a Common Rail Direct Injection Research Compression Ignition Engine
Authors: Soloiu Valentin , Smith Richard Collins , Weaver Amanda , Parker Lily , Brock Dillan , Rowell Aidan , Ilie Marcel
Published: November 2022

Research was conducted to determine combustion characteristics such as: ignition delay (ID), combustion delay (CD), combustion phasing (CA 50), combustion duration, derived cetane number (DCN) and ringing intensity (RI) of F24, for its compatibility in Common Rail Direct Injection (CRDI) compression ignition (CI) engine. The first part of this study is investigating the performance of Jet-A, F24, and ultra-low sulfur diesel #2 (ULSD) using a constant volume combustion chamber (CVCC) followed by experiments in a fired CRDI research engine. Investigations of the spray atomization and droplet size distribution of the neat fuels were conducted with a Malvern Mie scattering He-Ne laser. It was found that the average Sauter Mean Diameter (SMD) for Jet-A and F24 are similar, with both fuels SMD droplet range between 25–29 micrometers. Meanwhile, ULSD was found to have a larger SMD particle size in the range of 34–40 micrometers. It was observed during the study, utilizing the CVCC, that the ID and CD for neat ULSD and Jet-A are nearly identical while the combustion of F24 is delayed. F24 was found to have longer durations of both ID and CD by approx. 0.5 ms. This results in a lower DCN for the fuel of 43.5, whereas ULSD and Jet-A have DCNs of 45 and 47 respectively. The peak AHRR for ULSD and Jet-A are nearly identical, whereas F24 has a peak magnitude of approx. 20% lower than ULSD and Jet-A. It was found that both aviation fuels had significantly fewer ringing events occurring after peak high temperature heat release (HTHR), a trend also observed in the CRDI research engine. Neat F24, Jet-A and ULSD were researched in the experimental engine at the same thermodynamic parameters: 5 bar indicated mean effective pressure (IMEP), 50°C (supercharged and EGR) inlet air temperature, 1500 RPM, start of injection (SOI) 16°BTDC, and 800 bar of fuel rail injection pressure as the baseline parameters in order to observe their ignition behavior, low temperature heat release, combustion phasing, and combustion duration. It was found that the ignition delay of F24 and Jet-A was greater than ULSD, approx. 5% for both aviation fuels. This ignition delay also affected the combustion phasing, or CA 50, of the aviation fuels. The CA 50 of the aviation fuels was delayed by approx. 2% compared to ULSD. Jet-A had a nearly identical combustion duration compared to ULSD, however F24 had an extended combustion duration which was approx. 3% longer than that of ULSD and Jet-A. It was discovered with the accumulations of these delays in ID, CD, CA50, that the RI of the aviation fuels were reduced. F24 was discovered to have more delays, and the RI correlates with these results having a 70% reduction in RI compared to ULSD.
Exploring the Benefits of Oxidative Coupling of Methane on Natural Gas Engine Efficiency Through One-Dimensional Simulation
Authors: Swift Evan , Wadkar Chaitanya , Lee Hyewon , Singh Satbir , Northrop William F.
Published: November 2022

Natural gas (NG), mainly composed of methane, is extremely resistant to autoignition. High efficiency premixed compression ignition (CI) combustion modes are therefore difficult to achieve in NG engines. One potential method for expanding the range of compression ignition operation in NG engines is to pretreat the fuel such that it becomes more reactive. This paper presents results from one-dimensional simulations of a medium duty multi-cylinder natural gas engine partially fueled by products from oxidative coupling of methane (OCM), a catalytic process by which methane is converted to C2 hydrocarbons like ethane and ethylene. First, the results of OCM reactor three-dimensional CFD simulations are presented to define the resulting product species distribution over a range of residence time. Using the reactor results, a one-dimensional model of an engine is implemented with and without OCM products to illustrate efficiency gains possible by operating in a compression ignition mode. Results of the modeling show that brake thermal efficiency improves by 1 to 7% with OCM-enabled CI combustion compared to spark ignition combustion of natural gas alone. The results also show that since the OCM reactor is exothermic, part of the incoming natural gas heating value is converted to sensible enthalpy. The OCM products therefore must be used to preheat the intake charge, thus avoiding an overall brake thermal efficiency (BTE) penalty. Overall, this study finds that OCM products have the potential to increase BTE of NG engines by allowing them to operate in premixed CI modes. Future work must look to improve OCM catalyst durability and reactor turndown ratio to provide a reliable high reactivity fuel stream for NG engines.
A Scoping Study on the Use of Direct Quantification of Fault Tree Using Monte Carlo Simulation in Seismic Probabilistic Risk Assessments
Authors: Kubo Kotaro , Fujiwara Keita , Tanaka Yoichi , Hakuta Yuto , Arake Daisuke , Uchiyama Tomoaki , Muramatsu Ken
Published: November 2022

After the Fukushima Daiichi Nuclear Power Plant accident, the importance of conducting probabilistic risk assessments (PRAs) of external events, especially seismic activities and tsunamis, was recognized. The Japan Atomic Energy Agency has been developing a computational methodology for seismic PRA, called the direct quantification of fault tree using Monte Carlo simulation (DQFM). When appropriate correlation matrices are available for seismic responses and capacities of components, the DQFM makes it possible to consider the effect of correlated failures of components connected through AND and/or OR gates in fault trees, which is practically difficult when methods using analytical solutions or multidimensional numerical integrations are used to obtain minimal cut set probabilities. The usefulness of DQFM has already been demonstrated. Nevertheless, a reduction of the computational time of DQFM would allow the large number of analyses required in PRAs conducted by regulators and/or operators. We therefore performed scoping calculations using three different approaches, namely quasi-Monte Carlo sampling, importance sampling, and parallel computing, to improve calculation efficiency. These were applied when calculating the conditional core damage probability of a simplified PRA model of a pressurized water reactor, using the DQFM method. The results indicated that the quasi-Monte Carlo sampling works well at assumed medium and high ground motion levels, the importance sampling is suitable for assumed low ground motion level, and that the parallel computing enables practical uncertainty and importance analyses. The combined implementation of these improvements in a PRA code is expected to provide a significant acceleration of computation and offers the prospect of practical use of DQFM in risk-informed decision-making.
Numerical investigation of particle erosion characteristics in supercritical carbon dioxide in elbow pipe channels
Authors: Xu Peng , Zhou Tao , Fu Zhongguang , Chen Juan
Published: November 2022

The erosion of pipe walls by particle in supercritical carbon dioxide (SCO2) has a significant impact on the safe operation of the reactor, therefore, a simulation study of the wall erosion pattern of particulate matter within the SCO2 in the bent pipe channel was carried out. The research results show that SCO2 is extruded to the outer wall side under the action of centrifugal force. At the same time, two symmetrical secondary flows are formed in the elbow area, in the range of angle 60°–75°, the flow line is the most intensive and the secondary flow phenomenon is the most obvious; the erosion of particulate matter on the pipe is mainly concentrated in the outer side of the elbow area; with the increase of mass flow velocity, the erosion rate of particulate matter on the wall surface gradually increases. And the effect of increasing mass flow velocity on the erosion rate is nearly linear; the increase of particle diameter will lead to the first increase and then decrease of erosion; when the density of particles increases, the erosion rate of particles on the wall decreases, but the effect is low.
Numerical Analysis of Heat Transfer Enhancement With Spiral Tube in the Passive Containment System
Authors: Chen Kai , Wang Ruiqi , Huang Chonghai , Qi Xiao , Wang Xiaoyan
Published: November 2022

In this paper, the condensation heat transfer characteristics of light tubes and spiral tube tubes are studied by numerical analysis. The condensation characteristics of vertical spiral tube containing non-condensing gas vapor were explored, and the distribution of steam velocity, pressure and temperature near the wall of the heat transfer tube was analyzed. The enhanced heat transfer method of non-condensing gas vapor was obtained, which provided a theoretical basis for the enhanced heat transfer of steam condensation. The results show that the spiral tube can increase the heat exchange performance. The spiral can effectively reduce the thickness of the liquid film, which can impressively enhance the heat transfer performance.
Investigation of the Fuel Element Damage Monitoring Technology in HTGRs and PWRs
Authors: Nie Rui , Wang Yu , Xie Feng , Qing Shan , Cao Jianzhu
Published: November 2022

Understanding the performance of fuel elements, particularly defective ones, in the reactor core quickly and accurately is essential as most radioactive nuclides are produced in the fuel elements and released into the primary circuit. Radioactivity in the primary circuit may result in potential radiation hazards to the maintenance workers and the environment near the nuclear power plant. Therefore, fuel element damage monitoring technology has received wide attention in the field of nuclear fission reactors. Few reviews focus on fuel element damage monitoring technology to facilitate the development of high-temperature gas-cooled reactors (HTGRs). In this study, we investigated the state of fuel element damage monitoring technology in HTGRs and pressurized water reactors (PWRs), summarized their characteristics and parameters, and compared their advantages and disadvantages. The radioactive source terms in HTGRs and PWRs were listed, and the typical nuclides in the primary circuit adopted for the fuel element damage monitoring were illustrated. This study can provide a good reference for developing fuel element damage monitoring technology in HTGRs in the future.
Discussion on Optimization of Protection Effect of Shielding Doors in High Level Waste Treatment Facilities
Authors: Shen Jingyi , Zhang Liying , Wang Bingheng , Gao Guiling
Published: November 2022

Due to the special nature of the radiation sources involved (high radioactivity and high penetration) in high discharge waste treatment facilities, several shielding doors are installed in the facilities to ensure staff safety. In the analysis of the radiation protection design of shielding doors, it is found that the type of radiation source, the relative position of the radiation source and the door, and the structure of the door all have an impact on the radiation shielding effect. In this paper, the shielding door of a hot room in a high discharge waste treatment facility is used as the research object, and the dose rate outside the shielding door is analyzed with the characteristics of radiation sources and their different locations, and with respect to the existing shielding door structure. The analysis results show that, under the premise of meeting the shielding requirements, when the radiation emitted by the source has a certain angle of incidence relative to the shielding door, the dose rate at a specific location outside the door will be significantly increased due to the scattering leakage of the door slit and the effect of the oblique penetration of the radiation. In addition, the characteristics of the radiation source, such as the type of nuclide, and the geometry can also influence the safety design of the shielded door. Therefore, in order to optimize the protection effect of shielded doors, considering that the characteristics of radiation sources are generally difficult to optimize, this paper proposes several solutions from two perspectives: door slit scattering and overlap length, and combining other influencing factors from different aspects. The optimization effects of each solution are also compared, and the corresponding adaptation sites are also outlined through their respective advantages and disadvantages. Through the analysis and research of this paper, the safety and effectiveness of the shielding door is improved, the safety of personnel is guaranteed, and the foundation for the future design of the shield door is laid.
Simulation Research on the New Electrode Structure of Ionization Chamber Detector
Authors: Chang Jiahao , Wang Zhentao , Xu Shuo
Published: November 2022

The gas ionization chamber can be used in the examination of the irradiated fuel assembly and online measurement of steel sheet thickness. Response time is an important parameter of gas ionization chamber detectors, which will affect the clarity of radiation imaging. Previous results show that in the ionization chamber of the traditional structure, the electric field intensity is relatively low in some areas, which will affect the response time of the gas detector. By modifying the structure of the electrode, the areas of the weak electric field can be reduced or even eliminated. In this paper, we propose a new electrode structure, and two software tools are used in this work. Solidworks is used to establish ionization chamber models with different electrode structures. The finite element analysis software Simcenter MagNet is adopted to obtain the electric field distribution. The results show that the area of the weak electric field inside the ionization chamber of the new electrode structure is significantly reduced. In addition, the average electric field strength inside the gas ionization chamber detector with the new electrode structure is also improved. Theoretical calculation results show that the drift time of ions is reduced by about 0.690ms. Therefore, the development of the new electrode structure can effectively reduce the response time of the detector.
Experimental Study and Intelligent Prediction on Pressure Fluctuation of Accumulator Under Ocean Conditions
Authors: Wei Tianyi , Xie Guanhui , Li Dongyang , Tan Sichao , Du Yangyang , Li Zhongyi , Wang Yuan
Published: November 2022

Liquid sloshing will occur in liquid storage tanks such as accumulator of floating nuclear power plant (FNPP) subjected to additional inertial forces under motion conditions. The study carried out measurement experiments based on the 6-DOF platform to study the sloshing characteristics and pressure variation rule of the accumulator. The results show that surging will induce many kinds of nonlinear free surface sloshing forms, it can be seen that the law of pressure variation is mainly dominated by natural frequency and excitation frequency based on time and frequency domain analysis. Then the study combines the automatic encoder and extreme learning machine to build the deep extreme learning machine (DELM) network to predict the pressure in time series. Based on the phase space reconstruction of the time sequence, the pressure results of the next time are output after the last 15 pressure data are input. The prediction results show that the DELM model has fast speed and high precision and the predicted value is in good agreement with the experimental data. So this study can provide a reference for the pressure monitoring and the artificial intelligence application of FNPP.
Sensitivity and Uncertainty Analysis of Molten Corium-Concrete Interaction (MCCI) for ALWR During Severe Accident
Authors: Wu Zijie , Chen Peng , Zhao Xinhao , Guo Chao , Zhan Dekui , Xia Shaoxiong
Published: November 2022

Molten corium-concrete interaction is an important phenomenon in the late phase of severe accident, threatening the integrity of containment and might causing potential large release of radioactivity. A sensitivity and uncertainty analysis of MCCI under severe accident of a 1000 MW advanced light water reactor (ALWR) was performed with ASTEC (MEDICIS) [1], a lumped parametric integral severe accident code developed by IRSN. Several representative phenomena were screened out referenced by EURSAFE severe accident Phenomena Identification and Ranking Table (PIRT) [2], including debris bed formation, layer configuration, heat sources, and convective heat transfer correlation. Related input parameters, sensitivity coefficients, and modeling options in ASTEC code were selected, such as convective correlations, layer stratifications, initial layer compositions, and the potential ranges of these parameters were identified. A simple sampling method was used to analyze the independent effect of each parameter/model. Key parameters were chosen to evaluate the impact of sensitivity parameters to the MCCI process. A large break loss of coolant accident scenario, where in-vessel melt retention is invalid is simulated as an initial event. The results emphasize the importance of layer configuration and fission product partition. However, it should be emphasized that analysis results may be quite uncertain due to the limitation of the physical models and the adequacy or validity of the selected range of input variables.
Flow Mixing Characteristics in Double Loop Reactor Pressure Vessel Under Accident Conditions
Authors: Xie Guanhui , Li Runcheng , Wei Tianyi , Lin Zhikang , Li Dongyang , Tan Sichao
Published: November 2022

In case of core emergency cooling safety injection, the boron containing coolant injected externally and dilution water mass will be mixed in the pressure vessel. The uneven mixing of boron containing coolant and dilution water mass may lead to the return of the core to criticality. Therefore, it is of great significance to accurately measure the boron concentration distribution in the pressure vessel and study the mechanism affecting the mixing process for the safe operation of the reactor. In this paper, combined with the structural characteristics of HPR1000 pressure vessel, a visual experimental device is built through proportional modeling design, and the flow mixing process of diluted water mass, safety injection solution and coolant in the pressure vessel under double loop operation is obtained by using plane laser-induced fluorescence technology, the effects of different Reynolds numbers on the diffusion of boric acid were experimentally studied. The experimental results show that under the condition of double loop, the two inlets divide the circumferential direction into good arc and bad arc. The velocity distribution of fluid flowing through the bad arc is more uniform, while the vertical flow of fluid flowing through the good arc is uneven; The fluid flows downward rapidly after the intersection on the inferior arc side, and the intersection height is positively correlated with the cold pipe flow, while the fluid on both sides shows obvious mixing after the intersection on the superior arc side; Clear water mass cannot be avoided at the core inlet, but increasing the cold pipe flow and safety injection flow can reduce the time of clear water mass flowing through the core.
Study on Aerosol Growth and Deposition Properties Affected by Steam Condensation
Authors: Xia Zhaoyang , Zhou Zhiwei
Published: November 2022

The MELCOR 2.1 computer code has been used to simulate the large-scale aerosol behavior experiment in the Containment System Test Facility (CSTF) vessel. The test LA2 of the Light Water Aerosol Containment Experiments (LACE) was designed to simulate the containment conditions and aerosol behaviors in the high-steam-concentration environment under a postulated severe accident. In this study, the Aerosol Condensation model’s (ACD) and Hygroscopic Model’s (HM) ability of the aerosol behavior prediction has been evaluated by the simulation of LA2 based on MELCOR 2.1 code. It has been found that the size distribution and depletion rate of dry aerosols are affected by the mass of water aerosol. The different masses of water aerosol in ACD and HM models are due to the different relative humidity calculated by these two models. The simulation models with different control volumes setup were evaluated to study the effect of water aerosol mass on aerosol depletion rate. The results show that higher water aerosol mass results are calculated and better airborne aerosol masses are predicted under the multi-control volume models. Based on this research①, it can be concluded that good results of aerosol deposition in the vessel are severely affected by the accuracy of water aerosol mass. The improvement of water aerosol mass results by the MELCOR code’s simulation should be thoroughly studied.
Prevention and Treatment of Network Storm in Control Station of Digital I&C System in Nuclear Power Plants
Authors: Dong Wang , Qiang Leng
Published: November 2022

In the design of non-safety I&C system of nuclear power plants, different safety classification and power supply sequence design need to meet the characteristics of system network redundancy and self-healing. Therefore, engineers often use ring network configuration in system network design. When the ring network design or network wiring is wrong, it is easy to cause a network storm, resulting in the abnormal operation of the main control unit of the first-floor control network control station, and the mis-operation of the control unit on the field equipment, resulting in nuclear power safety accidents. This requires that the main control unit of the control station could resist the attack of network storm. This paper provides a method to prevent network storm based on link layer. The abnormal packets are filtered in the network protocol layer of the control unit, and the network storm threshold detection algorithm is used to monitor the network storm attack in time, and the network loopback protection control unit is set. Experiments show that this method can effectively resist the attack of network storm. When the main control unit is attacked by network storm, it can normally complete the task of logic unit, ensure that the field instrument and control equipment is in safe working mode, and the system can automatically return to normal state after the network storm stops. At present, this technology has been realized and applied in the digital I&C system of nuclear power plants, which has good adaptability and broad development space.
Cause Analysis of Oil Leakage of the Skeleton Oil Seal for a Diesel Engine Pre-Lubricated Oil Pump
Authors: Lai Binsheng , Chen Zhi , Li Jianming , Zhou Xin
Published: November 2022

The shaft seal of the pre-lubricated oil pump for the emergency diesel engine in a nuclear power plant is a skeleton oil seal. After about one year of operation, oil will leak from the shaft seal and enter the drive motor, affecting the operation reliability of the emergency diesel engine. By building a numerical simulation platform, the thermal-structure coupling analysis of the skeleton oil seal were carried out and the contact pressure, deformation, Von Misses stress contour and temperature contour of the skeleton oil seal under actual working conditions were studied. Through the establishment of a sealing test device, sealing tests for the concentric smooth shaft, the concentric shaft with a groove on the sealing contact surface, and the eccentricity shaft with a groove on the contact surface were carried out under different shaft surface roughness and hardness. And the influence on the sealing performance of the oil seal was analyzed. The morphology of the sealing lip and the change of material functional groups before and after the trial were analyzed. The study results show that the accuracy and surface quality of the shaft where the oil seal is installed will affect the sealing performance of the oil seal; the main reason for the failure of the skeleton oil seal of the pre-lubricating oil pump is the long-term wear of the transmission shaft and oil seal, which forms grooves on the shaft; and the formation of the grooves will lead to increased leakage. Therefore, improving the wear resistance of the drive shaft is a key. The research results have high reference value for the exploration of the sealing principle of the same type of skeleton oil seal and the analysis of the reasons for the failure of the seal.
Analysis of Hydrogenation Properties of Nuclear Fuel Zirconium Alloy Cladding
Authors: Qin Lin
Published: November 2022

During the service of the reactor, the zirconium alloy will inevitably interact with hydrogen to form zirconium hydride, which will adversely affect its mechanical properties. In this paper, the first-principles software VASP is used to analyze the phase transition of zirconium hydride, and based on the results, the subprogram of MAAP4 integrated analysis for severe accidents is optimized to further analyze the interaction between zirconium alloy cladding and hydrogen. Verification. The results show that the diffusion equation has large calculation potential and high calculation accuracy for the effect of zirconium hydride with obvious phase transition, and can realize the hydrogen performance analysis of the cladding material in the reactor. At the same time, VASP shows that δ – ZrH1.5 is the main component of cladding material hydrogenation It is also the main reason for brittle transition.
Decommissioning Considerations for Layout Design of Nuclear Buildings
Authors: He Wei-ting , Jiang Wei-feng
Published: November 2022

Decommissioning for nuclear power plant is complex project, which is needed to be taken into account during the early phase of design stage. Many researches and practices have already done for nuclear decommissioning activities. The decommissioning chapter is defined in preliminary safety analysis report for new build nuclear project, which needs to describe the design and management activities. According to the preliminary research for decommissioning requirement and scheme, many activities are direct related to layout design of nuclear buildings. In this paper, the decommissioning factors for layout design of nuclear buildings are summarized, which can be used as reference and supply some practices for other project.
Heat Transfer Characteristics of Different Horizontal Wires in Pools of Liquid and Supercritical Carbon Dioxide
Authors: Liu Minyun , Xi Dapeng , Fei Junjie , Huang Yanping
Published: November 2022

The peculiar heat transfer mechanism of supercritical fluids has been studied for a long time, especially the flow and heat transfer in the tubes. Numerous experiments have demonstrated the three heat transfer modes of supercritical fluids: normal heat transfer, improved heat transfer and deteriorated heat transfer. The effects of the pressure, pipe diameter, mass flow rate, heat flux and flow direction also have been well studied in the experiments. From the perspective of theory, the pseudo-boiling theory noticed the similarities between the subcritical boiling and the supercritical fluid heat transfer, and explained the heat transfer mechanism. Another theory focuses the buoyancy and flow acceleration effect caused by the property change also made great success. However, the existing research still yields inconsistent results and more evidences are needed. In this work, the heat transfer characteristics from different horizontal wires immersed in both liquid and supercritical carbon dioxide are studied. For a wide range of bath temperatures (5 ∼ 60 °C) and pressures (5 ∼ 8 MPa), the heat transfer coefficients were measured with a quasi-steady increase and decrease of the heat generation rate. The surface temperature of the wires was derived from the measured resistance. Finally, the boiling curves of both the subcritical cases and supercritical cases were obtained. Meanwhile, the near-wall fluid fields were visualized using the high-speed camera. Different from the prior experiments, this pool-type experiment has avoided the complex turbulence flows, and provides clearer evidences of the different heat transfer modes of the supercritical fluids.
A Numerical Study of the Spray Cooling Effect on Improving the IVR Safety Margin
Authors: Yu Peng , Jia Ningxi , Guo Qiang , Liu Zhuo , Jin Yu , Yuan Yidan
Published: November 2022

In-vessel retention (IVR) is a widely adopted severe accident mitigation strategy in the advanced commercial PWRs. External water cooling on the outer surface of the reactor pressure vessel (RPV) is designed to efficiently remove the decay heat from the in-vessel corium, such that the RPV integrity can be kept and the radioactive corium retained inside. The effectiveness of the IVR strategy requires that the maximum heat flux along the RPV lower than the critical heat flux (the switch point from nucleate boiling to film boiling). In existing engineering design, water cooling is realized by flooding the RPV outer surface. Spray cooling on the outer vessel surface is considered to be a potential method to increase the safety margin. In this paper, we investigate the effect of spray cooling in the IVR applications with respect to the influences on the heat transfer and cooling capacity (limit). Molten pool heat transfer analysis is performed to analysis its influence on the thermal behavior of the melt pool and RPV. The cooling capability (limit) is also analyzed between the spray cooling and conventional cooling measurements. Results indicate that the spray cooling does not show significant influence on heat removal as the changes of the heat flux profile and the wall thickness (that are of interest in safety analysis) are insignificant; the main contribution to the enhancement of the safety margin by spray cooling would be from the expected significant improvement of critical heat flux (CHF).
Mixing and Stratification Phenomena Under Natural Convection in the Multi-Openings Compartment
Authors: Jiang Jinghua , Li Ying , Wang Tianlin , Tong Lili , Cao Xuewu
Published: November 2022

The mixing and stratification of hydrogen-vapor-air in the compartment is extensively studied under inertia jets and turbulent buoyant jets. The characteristics of buoyancy-driven flows during fission and fusion reactor accidents need to be further studied to provide a benchmark for the validation of computational procedures. In this paper, a large-scale facility of a vessel with multiple openings is established to study the mixing and stratification of the mixture driven by buoyancy under natural convection. The test is carried out with well-controlled boundary conditions, in which, a mixture of helium and vapor with a volume fraction of 1:10 is injected in the compartment filled with air. As the injection begins, the gas mixture is driven by the injection source and the buoyancy of the light gas. The gas is released through the top and bottom openings with the flow velocity of 5 m/s and 7.5 m/s, respectively. When the injection is stopped at 4600s, the density gradient induces the natural convection, air enters the vessel through the bottom opening with a relatively low velocity, and the low-density mixture is discharged through the top opening at the same time. During this period, the velocity of the mixture at the opening decreases due to the reduction of the drive force of natural convection.
Study on the Application of Electromagnetic Stepping CRDM at Tilted Environment
Authors: Lu Zhaohui , Li Zewen , Zhou Jianming , Liu Qingsong
Published: November 2022

Electromagnetic stepping control rod drive mechanism is most widely used in onshore pressurized water reactor in vertical direction. However, due to the bias load caused by long-term tilting, the wear and failure of the sliding block kinematic pair and carrier and buffer shaft kinematic pair are caused. The researchers carried out targeted research on the existing problems, and improved the design from the structural design, material improvement and surface treatment, and verified the rationality of the improvements through the full-size prototype tests, which also proved that the electromagnetic stepping control rod drive mechanism is feasible in tilted environment.
Weighted Data-Based Fault Detection Approach for Nonlinear Nuclear Power System
Authors: Chen Zhaoxu , Zhou Hongkuan , Ke Zhiwu , Qi Xiao , Qiu Zhiqiang
Published: November 2022

Mechanism-based and data-based methods are widely used in fault detection of nuclear power plant. Each method has its advantages and disadvantages. In this paper, we propose weighted data-based fault detection method based on data which we called Implicit Model Approach (IMA) for nuclear power plant. By introducing weighted factor and Takagi-Sugeno modeling method, we extend the IMA-based fault detection from linear system to nonlinear system. At local operating point, linear IMA is utilized to generate sub-system residual function. Inspired by Parallel Distributed Control (PDC) method, we generate overall residual function and overall residual evaluation mechanism. Simulation analysis has verified the validity of the proposed algorithm. The significance of the weighted IMA lies in establishing a data-based and mechanism-friendly approach. This work can provide new route for fault detection of nonlinear nuclear power system.
Detection Efficiency Fitting Method Research by Γ-Ray Spectroscopy for Quantitative Nuclear Material Holdup
Authors: Li Yurong , Wang Sijia , Wang Jing , He Lixia
Published: November 2022

The term “holdup” refers to nuclear material that has been deposited in the processing facility’s equipment, containers, pipelines, etc. Nuclear material control and accounting require the monitoring of nuclear material holdup in process. Holdup is useful for indicating the state of facility operations, critical radiation safety status, and so on. It is more difficulty to quantitative analyzed nuclear material holdup by destructive analysis method. So non-destructive analysis (NDA) technology for in-situ and on-line measurement satisfied to the actual situation are the most recommended nominator for holdup quantitative analysis. In order to get the detection efficiency of γ-ray spectroscopy for quantitative nuclear material holdup. The intrinsic detection efficiency, geometric detection efficiency, and self-absorption attenuation correction methods are researched in this paper by combining Monte Carlo simulation and experiment. Three-dimensional and the least square fitting methods, and the distribution of the nuclear material holdup in the simulation pipeline system of nuclear facilities’ production line is simplified. Resulted to the experiment, the deviation between declared and the measured value is less than 30%. Compared with the requirements of national nuclear safeguards supervision and the needs of facility operation, the detection efficiency fitting method research by γ-ray spectroscopy for quantitative nuclear material holdup is achievable. It also can be widely used to provide relevant data in radiation dose monitoring, decommissioning source item investigation, and so on.
Dynamic Modeling and Simulation of MHTGR Plant Start-Up and Shutdown System
Authors: Li Bowen , Dong Zhe , Li Junyi
Published: November 2022

The start-up and shutdown system is an important auxiliary subsystem for the low power level operation of once-through steam generator (OTSG) equipped coal-fired plants or nuclear power plants (NPPs). It is difficult to generate qualified steam through OTSG at a low power level or in the start-up and shutdown process. The start-up and shutdown system can carry out steam-water separation for the working fluid flowing out of OTSG and realize the recovery of mass and energy. It is necessary to maintain the stability of pressure, water level, and flowrate of each branch’s during the start-up and shutdown process, which enables coordination between OTSGs and thermal loads. A modular high-temperature gas-cooled reactor (mHTGR) is a typical small modular reactor (SMR) equipped with the OTSG. So as to realize the automatic start-up and shutdown function of mHTGR, it is necessary to carry out the modeling, simulation, and control design of the start-up and shutdown system. Driven by the above requirements, a lumped parameter dynamic model is proposed according to the conservation law of mass, energy, and momentum. In addition, a novel modeling method of the two-phase vessel is raised in the study which can describe the ‘swell and shrink’ phenomenon in the critical equipment of start-up and shutdown systems. Additionally, the open-loop response to external disturbances is to verify the accuracy of mechanism modeling with numerical simulation.
The Research and Simulation of Beyond Design Basis Accidents in PWR Nuclear Power Plant
Authors: Cheng Guo
Published: November 2022

Fukushima nuclear accident occurred due to earthquake and beyond-design-basis tsunami, which is beyond design basis accident (BDBA); it is necessary to carry out relevant research on pressurized water reactor (PWR) nuclear power plant (NPP). Starting from the relations between various types of operating and accident conditions, this paper summarizes the BDBAs in the accident control guideline. During simulator training exercises with BDBAs including total loss to the steam generator feedwater and total loss of on-site and off-site electrical power supplies incident conditions, the evolution of nuclear safety-related parameters is studied, and the rules and the reasons of the evaluation are summarized. All this is helpful for the operator to master the principle of the accident.
Codes Comparative Study on Mechanical Properties of Core Forgings of Reactor Pressure Vessel
Authors: Yu Hao , He Yinbiao , Wu Xinxin , Gu Shenjie , Liu Xin , Wang Hongchang
Published: November 2022

In this paper, the mechanical properties of core forgings in Pressurized Water Reactor (PWR )NPPs in China were studied according to different rules of minimum yield strength at room temperature stipulated in ASME codes and RCC-M codes. First, this paper investigates the origin of two different codes for core forgings, then analyses the effects of yield strength, tensile strength, tempering temperature and toughness on the mechanical properties of forgings in both of codes. And then the results showed that the acceptance value of minimum yield strength at room temperature materials does not correspond to the mechanical design and analysis value. Finally, some suggestions for compiling the c’ore area forgings mechanical properties codes suitable for China’s PWR NPPs were given. This work provided a feasible implementation path for guiding the formulation of China’s PWR NPP codes.
Research and Practice on Environmental Dose Reduction in Nuclear Power Plant Core Instrument Room
Authors: Tang Long , Gao Binghan , Yu Long , Zhao Dongdong , Luo Feihua
Published: November 2022

Qinshan Phase II Units 3 and 4 began to use the solvent cleaning technology for flux thimble tubes in 2017. In 2018, the environmental dose of the core instrument room increased significantly, resulting in higher radiation protection costs in the core instrument room during the overhaul and absorption dose of equipment maintenance person, etc. After the abnormality of the environmental dose of the core instrumentation room was found, the investigation into the reasons for the increase of the ambient dose in the core instrumentation room of Unit 3 found that because the room was only designed with an air inlet and no air outlet, a large amount of radioactive dust escaped from the room. The neutron flux detector was rusted for the first time and the material analysis of the radioactive dust found the activation products Fe-59 and Co-60. Aiming at this problem that has never occurred in the field of nuclear power, this paper firstly analyzes and studies the reasons for the increase of the environmental dose in the core instrument room. On this basis, the four environmental dose reduction measures adopted are described, including the improvement of the cleaning method of the flux thimble tubes, the decontamination of the equipment surface, the overall cleaning of the mechanical equipment, and all-round cleaning of room radioactive dust. From the practical results, the ambient dose in the core instrument room was reduced from nearly 1mSv/h to about 0.1mSv/h, and the room surface pollution and equipment radiation hot spots were almost eliminated.
Study on the Plutonium Holdup Measurement in Glove-Box
Authors: Cheng Yimei , Xu Xiaoming , Yin Honghe , Li Xinjun , Wang Sijia
Published: November 2022

Based on passive total neutron counting with the 3He detectors, an assay system that can define the plutonium holdup in glove-box directly had been established through optimization design by Monte-Carlo simulation. The subsequent debugging for the electronics of this system ensured the system staying in a good operation state. The carried out experimental measurements had defined a series of parameters for the system, including the optimal operation voltage, detection efficiency for neutrons, spatial efficiency distribution, and the relationship between sample mass and the counts. Finally, according to the on-site measurements, the RSD of the measurement system for the glove-box holdup was 0.2%, which indicates the excellent stability of this system.