bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of the Macroscopic Group Constant of Pebble Bed Fluoride Salt Cooled High Temperature Reactor Based on the Collision Probability Method
Authors: Zhang Dida , Jia Guobin , He Long , Shen Jiajie , Zhan Zhichao , Wang Hailing , Guo Wei
Published: October 2017

The pebble bed fluoride salt cooled high temperature reactor (PB-FHR) is one of the generation IV nuclear reactors, a lot of study has concentrated on PB-FHR neutronics all over the world. As the most important part in the study work, the macroscopic group constant must be well prepared. The fuel pebble was chosen for the candidate of PB-FHR due to its outstanding, but the double heterogeneous due to its complex structure causes much difficult in the calculation of macroscopic group constant. In this work, an analytical program named Z2D is written to calculate the macroscopic group cross section. In the program, the collision probability method (CPM) was applied to solve the slowing-down integral transport equation, and the macroscopic constant was evaluated with the obtained neutron flux. Also, the recurrence method was introduced to accelerate the computing speed of slowing-down source. The results were compared with those calculated by MCNP, and good agreements were obtained.
Optical Readout Characteristics in a New Gas Scintillation Chamber for Neutron Measurement
Authors: Hu Jing , Ouyang Xiaoping , Zhang Zhongbing , Liu Jinliang , Chen Liang , Ruan Jinlu
Published: October 2017

A novel neutron diagnostic method is presented based on optical readout from scintillation in gases excited by recoil charged particles for fusion research. According to the method, we have designed a new gas scintillation chamber filled with scintillation gas CF4 and installed with a multi-wires structure to provide strong electric field. The electric field distributions of cylindrical multi-wire structures with different geometrical parameters are analyzed systematically. By building up an optimal multi-wire structure, the optical readout characteristics are also studied with energetic charged particles. Electron-induced avalanche in the electric field excites gas molecules to emit numerous scintillation photons, which are readout using photomultiplier tubes, and measured using multichannel analysers. The results show that the light signals and charge signals are enhanced simultaneously and the rise time of the light signal hardly changes, approximately 12ns, as the applied voltage increases. More importantly, the typical pulse height spectrum from the light signals is acquired, and the obtained resolution is 8.8% for 6.5MeV protons.
RELAP5 STH and Fluent CFD Coupled Calculations of a PLOHS + LOF Transient in the HLM Experimental Facility CIRCE
Authors: Angelucci M. , Martelli D. , Forgione N. , Tarantino M.
Published: October 2017

This work describes the activity performed at the University of Pisa concerning the application of an in-house developed coupling methodology between a modified version of RELAP5/Mod.3.3 and the ANSYS Fluent commercial CFD code to a pool system. Mono-dimensional codes, like RELAP5, are commonly used for thermal-hydraulic analysis of entire complex systems. Nevertheless, their one-dimensional feature represents a limit in the analysis of such problems where significant 3D phenomena are involved. On the other hand, CFD codes standalone are usually employed to simulate relatively small domains. The use of System Thermal-Hydraulic + CFD coupled calculations can overcome these issues, allowing the simulation of a complete system, but with a part of the domain reproduced with the CFD code.

In this work, the coupled calculation technique was used to simulate a PLOHS + LOF transient in the HLM experimental facility CIRCE (CIRCulation Experiment), located at the ENEA Brasimone research centre. The paper initially calls up the coupling procedure adopted, consisting in a “two-way” coupling. MATLAB software, used as external interface, manages the exchange of data between the system and the CFD code. The numerical method adopted for the coupling is the implicit scheme. Then, the main features of the CIRCE facility are briefly described, so are the two computational domains employed in this study. In particular, the CFD code was used to model the CIRCE pool (8 m high) and the Decay Heat Removal (DHR) heat exchanger. Due to the long duration of the transient simulated, a 2D axial-symmetric domain was chosen in order to reduce the computational time. The test section, placed inside the pool and consisting in a heat source and a heat sink, and the secondary side of the heat exchanger, were modeled with RELAP5. The use of the coupling tool allowed to set realistic boundary conditions in the calculation, more representative of the experimental ones. The main numerical results obtained from the PLOHS + LOF coupled calculation were compared with experimental data. Calculated LBE mass flow rates in the test section and in the DHR showed good agreement with experimental data. Some discrepancies with respect to the experimental trends were noticed for LBE temperatures; these should be related to some simplifications introduced in the model. Nevertheless, obtained outcomes represent a preliminary guideline for the improvement of the modeling for future works.
Experimental Study on Structured Surfaces for Nucleate Pool Boiling Enhancement
Authors: Nirgude Vishal V. , Modak Mayank , Sharma Avadhesh K. , Sahu Santosh K.
Published: October 2017

In the present experimental study an attempt has been made to study the boiling heat transfer characteristics of variety of enhanced surfaces. Three different copper test surfaces: polished copper and two structured surfaces were used in the present investigation. The heat transfer performance of each surface is studied under saturated pool boiling conditions at atmospheric pressure by using water and isopropyl as pool liquid. The effect of intersecting tunnel geometry with 0.5 mm and 1 mm depth on heat transfer performance has been studied. The comparison of heat transfer coefficient indicates that the intersecting tunnel structure enhanced the boiling heat transfer performance and reduced the wall superheat at given heat flux inputs.
Liquid Inlet Boundary Effect on the Simulation of Liquid Waves in Vertical Air-Water Churn Flow
Authors: Tekavčič Matej , Končar Boštjan , Kljenak Ivo
Published: October 2017

The present study investigates the influence of liquid inlet modelling on the development of liquid waves in isothermal churn flow of air and water in a vertical pipe. The porous wall liquid inlet section, commonly used in experiments, is modelled as a simple inlet flow area in our simulation. Using the liquid mass flow rate from experiment, the magnitude of the wall normal velocity component is determined by the inlet area which is used as a modelling parameter. This parameter significantly affects the calculated liquid wave frequency. The inlet liquid velocity profile was not measured in available experiments and thus presents a major source of uncertainty in simulations. The parametric analysis shows that a suitable liquid inlet area can be determined over the range of liquid flow rates, leading to good agreement of simulated and measured wave frequencies. A three-dimensional simulation was performed using the multiphase solver interFoam from the open-source code OpenFOAM.
Experimental Study of Flow Regime Map in 5×5 Rod Bundle
Authors: Liu Hang , Ren Quanyao , Pan Liangming , Hibiki Takashi , Zhou Wenxiong , Ye Tingpu
Published: October 2017

In relation to development of the flow regime criteria for rod bundles, this paper provides an experimental flow regime map and compares the experimental map with the existing flow regime transition criteria for vertical rod bundles so far. An experiment of vertical adiabatic air-water flow was conducted under an atmosphere pressure conditions. The experiment facility was composed of 5×5 rod arranged on a square pitch in a square shell with 9.5 mm outside diameter and 12.6 mm pitch. A total of 242 data sets were acquired consisting of superficial gas flow rates, 0.02–8.69 m/s, and superficial liquid flow rates, 0.02–2.13 m/s. A new flow regime map was obtained and the flow regime transition model for rod bundles was validated by the measured flow regime map. A fairly good agreement with some discrepancies has been obtained between the existing flow regime transition criteria and measured flow regime maps for rod bundles.
The Rigorous SP3 Theory and Study on its Numerical Verification
Authors: Qingquan Pan , Haoliang Lu , Dongsheng Li , Kan Wang
Published: October 2017

On the premise of no mathematical approximation, the rigorous SP3 theory which is deduced from the theoretical basis of the 3rd-order spherical harmonic method and the simplified harmonic method has more definite physical meaning. Compared with the conventional SP3 theory, the interface and boundary conditions of the rigorous SP3 theory are obtained according to the continuity of angular flux, and the angular flux is also established a relationship with each order scalar flux, which provides the theoretical solution to the discontinuous factors applied to the SP3 equation. However, the interface and boundary conditions of the rigorous SP3 theory bring in the high-order partial derivative related to the transverse leakage, which makes the current nodal method difficult to solve the SP3 equation and easily leads to numerical instability. The rigorous SP3 theory is summarized and compared with the conventional SP3 theory. Combining the special modality of the rigorous SP3 equation and the current nodal method, three methods to verify the rigorous SP3 theory are proposed, each of which has advantages and disadvantages. Developing codes and analyzing the calculation process and the results, comprehension and assumptions are concluded for the implementation of the rigorous SP3 theory.
Planning the Selection and Assignment of Security Forensics Countermeasures
Authors: Bajramovic Edita , Bochtler Jürgen , Ben Zid Ines , Lainer Andreas
Published: October 2017

Cybersecurity incidents are stressful, complex in nature, and frequently are not systematically considered in daily tasks. When correctly managed, operational readiness procedures make sure the availability of data required to successfully and quickly recover from a security incident while lessening the adverse effect. Therefore, protective measures, such as implementation of data diodes, are playing an essential role in defending I&C systems. In addition, applicability of the newest forensic and digital evidence-related standards to the nuclear domain is being evaluated. Results of such evaluation are being considered in the 3D and 2D modeling of cybersecurity relevant assets. The development of the new IEC 63096, downstream standard of IEC 62645, will also support the proposed evaluation and modeling. However, IEC 63096 covers not only forensic and incident management-related security controls but also a broad range of cybersecurity controls. This paper will further explore the security degree-specific selection and overall assignment of forensic-related security controls for the nuclear domain. Results from ongoing prototype developments will be used to demonstrate possible alternative selections and assignments along with their contribution to different security metrics.
CFD Analysis of Thermal Mixing and Mass Flux Distribution in the PWR After MSLB
Authors: Xu Hong , Xu Yiban , Cao Liping , Sung Yixing , Kucukboyaci Vefa N. , Wright Richard F.
Published: October 2017

During a postulated main steam line break (MSLB) event of a Pressurized Water Reactor (PWR) initiated at the Hot Zero Power (HZP) condition, increased heat removal from the broken steam generator (SG) on the secondary side that significantly reduces the coolant temperature on the primary side, and cold primary coolant enters the reactor vessel through the affected loop resulting in asymmetric temperature and mass flux distributions into the reactor core. A plant safety analysis under the MSLB condition needs to account for the thermal and mass flux asymmetry effects on the reactor core response due to the colder water flowing from the affected SG and the reactor coolant system (RCS) to reactor vessel.

High resolution computational fluid dynamics (CFD) methodology with ANSYS CFX (Version 16.1) software was applied to analyze the flow behaviors and thermal-hydraulic phenomena and to study the thermal mixing and asymmetry effects in the downcomer and lower-plenum of a typical Westinghouse design four-loop PWR under the MSLB conditions. Two scenarios were considered for the CFD simulation distinct by reactor coolant pump status:

(1) Low-flow case: without offsite power where the reactor core is cooled through natural circulation

(2) High-flow case: with offsite power available and the reactor coolant pumps in operation

The CFX CFD modeling and simulation were based on the reactor vessel boundary conditions from a system code transient simulation at the limiting time steps with respect to thermal margin of the fuel design. The geometric model included the vessel downcomer and the lower internals up to the reactor core inlet below the fuel assemblies. The results of CFD simulation show the different flow patterns and temperature distributions at the reactor core inlet for the low-flow case and for the high-flow case. Thermal asymmetric effect exists in both cases, but in the low-flow case, cold flow enters into core inlets at the opposite side of faulted loop located, and in the high-flow case cold flow enters into core inlets at the same side of faulted loop located. A mass flux asymmetric effect exists in both cases, but for the low-flow case, the core inlet mass flow distribution is more uniform than that for the high-flow case. The reactor core inlet distributions under the MSLB condition were further evaluated through comparisons with the results from the STAR-CCM+ (Version 10.04.01) CFD modeling and simulation. The evaluation showed that the simulation results are in good agreement with the STAR-CCM+ predictions and consistent with the phenomenon observed in an experiment published in open literature and site engineer judgment based on the available detected data.
Investigation Into the Influence of Fuel Rods on the Anti-Seismic Mechanical Characteristics of Fuel Assembly Spacer Grid by FEM Method
Authors: Sun Jingya , Dang Yu , Liu Song , Liu Jiazheng , Zhu Libing
Published: October 2017

The anti-seismic performance of fuel assembly is mainly determined by the critical crush load and the stiffness of spacer grids. To comprehensive know about the influence of fuel rods on the spacer grid, a 5×5 spacer grid FEM model which including fuel rods is established. Basing the fact that the grid spring has remarkable influence on the grid crush strength which is found in experiment, some cases are carried out, which are used to analyze effects of grid with/without fuel rod, friction between the grid spring/dimple and the fuel rod, the deflection of grid spring on the static buckling strength. Results show that grids with fuel rods will have higher crush strength than those without fuel rods; at certain range, increasing grid spring deflection at working point will do help to increase the grid crush strength; higher friction coefficient of grid spring and fuel rod can enhance the crush strength. Comparing with experimental results in literatures, results from simulations show the same tendency with the experimental results. The conclusion and the simulation method involved in this paper can provide some guidelines to optimize the performance of spacer grid assembly.
A Prototype of Tomographic Gamma Scanner
Authors: Quanhu Zhang , Sufen Li , Suxia Hou , Lin Zhang , Wenming Zuo
Published: October 2017

Tomographic gamma scanning (TGS) method is one of the most advanced non-destructive assay (NDA) methods. TGS method can determine quantitatively with high accuracy transuranic nuclides in heterogeneously distributed media with medium- and high-density, and is thus widely used to assay the location and quantity of selected radioisotopes in scraps and wastes within sealed containers. In this paper, a prototype of tomographic gamma scanner which we designed is introduced. The TGS system is composed with four parts: external source with front collimator, radioactive material drum turning table, HPGe γ detector assembly including back collimator and cooling system, and computer. Successful implementation of the work has broken through the difficult problems or restraints to the development and applications of TGS, it will be applied widely to the non-destructive assay of nuclear materials within sealed container in the nuclear safeguards, radwaste measurement and arms control fields.
Investigation of Slug Flow Structure in Terms of Flow Regime Transition in Co-Current Two-Phase Flow
Authors: Zhang Muhao , PAN Liang-ming , Ju Peng , Ishii Mamoru
Published: October 2017

In order to investigate the structure parameters evolution characteristics during flow regime transition process in slug flow, the vertical upward slug flow experiment in a wide range of liquid superficial velocity (0.03 < jl < 1.6 m/s) were conducted in a tubular test section with the inside diameter of 25.4 mm. Impedance void meters were employed to measure the void fraction of separated two parts corresponding to Taylor bubble and liquid slug. The present research studied the evolution of length ratio and void fraction in slug unit by keeping the liquid superficial velocity constant while increasing gas flow rate. New structure of slug unit in strong relation with transition process was observed. In specific, it was realized that the proportion of such special structure unit played an important role in transition from slug flow to churn-turbulent flow. The existing transition criteria from slug flow to churn-turbulent flow in upward two-phase flow (entrance effects model, flooding model, wake effects model, bubble coalescence model and Helmholtz instability model) were compared with the experimental identified results obtained by a new objective flow regime identification method, ReliefF-FCM algorithm. The results indicate that the transition model based on the wake effects could be the most appropriate choice to describe the mechanism of transition from slug flow to churn-turbulent flow in present experimental conditions.
Tungsten Powder Filled Polymers for Flexible Radiation Shields in Nuclear Industries
Authors: Yan Binyou , Song Jiupeng , Wang Wei , Yu Yang
Published: October 2017

A novel type of flexible composite with tungsten powder filled in polymers (TPFP) homogeneously was developed as an alternative to lead (Pb) based radiation shields used in nuclear industries. TPFP had a density in the range of 4 to 11.3 g/cm3, which can be tailor-made according to the applications. In addition to the advantage of lower toxicity over Pb-based shielding, TPFP can be formed into various shapes, such as pipe shields, pipe wraps, safe floor shields, blankets, etc. The mechanical properties and attenuation of γ-ray was investigated for the developed TPFP.
Ultra Large Diameter Glass Reinforced Plastic Pipe Outsourcing of Concrete Structure for Conventional Island Construction Management Practices
Authors: Mengwu Wang , Hongjun Xia , Yong Yang , Xiaofei Zhang , Zhaopu Gao
Published: October 2017

It is very rare to adopt ultra large diameter glass reinforced plastic pipe in the Chinese nuclear power field. The construction techniques like safety and quality control, design tracking, construction organization, schedule control and other perspectives are still lacking of experiences. So the accumulation of construction experiences for this kind of structure became a key work in the nuclear power plant construction phase.
Fluid Dynamic Analysis on Hydrogen Deflagration in Vertical Flow Channel With Annular Obstacles
Authors: Matsumoto Toshinori , Sato Masatoshi , Sugiyama Tomoyuki , Maruyama Yu
Published: October 2017

Hydrogen combustion including deflagration and detonation could become a significant threat to the integrity of containment vessel or reactor building in a severe accident of nuclear power stations. In the present study, numerical analyses were carried out for the ENACCEF No.153 test to develop computational techniques to evaluate the flame acceleration phenomenon during the hydrogen deflagration. This experiment investigated flame propagation in the hydrogen-air premixed gas in a vertical channel with flow obstacles. The reactingFoam solver of the open source CFD code, OpenFOAM, was used for the present analysis. Nineteen elementary chemical reactions were considered for the overall process of the hydrogen combustion. For a turbulent flow, renormalization group (RNG) k-ε two-equation model was used in combination with wall functions. Three manners of nodalization were applied and its influences on the flame propagation acceleration were discussed.
Development of Security and Safety Fuel for Pu-Burner HTGR: Part 5 — Test and Characterization for ZrC Coating
Authors: Ueta Shohei , Aihara Jun , Goto Minoru , Tachibana Yukio , Okamoto Koji
Published: October 2017

To develop the security and safety fuel (3S-TRISO fuel) for Pu-burner high temperature gas-cooled reactor (HTGR), R&D on zirconium carbide (ZrC) directly coated on yttria stabilized zirconia (YSZ) has been started in the Japanese fiscal year 2015. As results of the direct coating test of ZrC on the dummy YSZ particle, ZrC layers with 18–21 microns of thicknesses have been obtained with 0.1 kg of particle loading weight. No deterioration of YSZ exposed by source gases of ZrC bromide process was observed by Scanning Transmission Electron Microscope (STEM) observation.
Application of GOTHIC8.0 3D Model to Simulate Heat Removal Process in Containment Safety Verification via Integral Test (CERT)
Authors: Wang Guodong , Wei Shengjie , Ni Chenxiao , Zhang Di , Wang Zhe
Published: October 2017

The purpose of this study is to establish a detailed three-dimensional (3D) model of containment safety verification via integral test (CERT) using the containment code GOTHIC 8.0. This paper presents the model construction and a typical CERT case for the model evaluation. In the typical CERT case, steam with high mass and energy is released to the test vessel to simulate the passive containment response during main steamline break (MSLB) accident. Heat removal process is accomplished primarily by absorption of energy by the gas volume and structures inside vessel, by condensation of steam on the inside shell surface, by heat conduction through the steel shell, and by evaporation of water film covered on the outer vessel shell surface. The main results of the typical CERT case are qualitatively compared with the results obtained from simulations with GOTHIC 8.0 code. From comparison, a verification of the code in terms of pressurization, temperature response, steam condensation and water film evaporation are carried out. The code analysis results are of significance on the research of thermal hydraulic phenomena which occur in the passive containment cooling system (PCS) during accidental sequences.
Melting Simulation Using a Particle Method With Angular Momentum Conservation
Authors: Kondo Masahiro , Ueda Shota , Okamoto Koji
Published: October 2017

To analyze the core degradation and relocation behavior of melts in a severe accident of nuclear power plant, the melting and solidification in the complexed geometry is to be calculated. For the calculation of such complexed behavior, a new particle method conserving angular momentum is proposed and applied for the melting simulation. When solid melts, it may move like a rigid body. The angular momentum conservation is important to capture such kind of motion. The potential of the new particle method was confirmed with a calculation of the melting in dam break geometry and cantilever geometry.
Thermo-Hydraulic Research for Supercritical Water Reactor During Power-Raising Phase of Startup
Authors: Zichao Li , Tao Zhou , Lanyu Zhou , Liang Liu , Juan Chen , Hongxing Yu
Published: October 2017

Thermal characteristics during startup of CSR1000 are directly related to the security of supercritical water reactors. The heat transfer model during power-raising phase is built according to the sliding pressure mode of CSR1000 and thermal characteristics of coolant and moderator are analyzed. The results show that, during the temperature-raising phase of startup, Coolant and moderator temperatures in inner assemblies increase with core power increase only. With increases of core power and feed-water flow rate, Coolant and moderator temperatures remain unchanged during power-raising phase. Thermal properties of the coolant change in the pseudo-critical temperature and the heat transfer deterioration occurs.
Assessment of the Turbulent Prandtl Number Effect on Simulating Heat Transfer Characteristics of Supercritical Water Flow in Bare Tubes
Authors: Farah Amjad , Harvel Glenn , Pioro Igor
Published: October 2017

Computational Fluid Dynamics (CFD) is a numerical approach to modelling fluids in multidimensional space using the Navier-Stokes equations and databases of fluid properties to arrive at a full simulation of a fluid dynamics and heat transfer system.

The turbulence models employed in CFD are a set of equations that determine the turbulence transport terms in the mean flow equations. They are based on hypotheses about the process of turbulence, and as such require empirical input in the form of constants or functions, in order to achieve closure. By introducing a set of empirical constants to a model, that model then becomes valid for certain flow conditions, or for a range of flows.

Of those constants, the turbulent Prandtl number appears in multiple equations; energy, momentum, turbulent kinetic energy, turbulent kinetic energy dissipation rate, etc. and the value it takes in each equation is different and chosen empirically to fit a wide range of flows in the subcritical region. The studies that attempt to find the effect of varying the turbulent Pr number on simulation results, often only mention one number; presumably the one that appears in the energy equation (although it is never explicitly explained). The rest of the constants are treated as universally acceptable for generalized flow and not tested for their effect on flow parameters.

A numerical study on heat transfer to supercritical water flowing in a vertical tube is carried out using the ANSYS FLUENT code and employing the Realizable k-ε (RKE) and the SST k-ε turbulence models. The 3-D mesh consists of a 1/8 slice (45° radially) of a bare tube. The study explored the effects of turbulent Pr numbers, and their variations, in order to understand their significance, and to build on previous knowledge to modify the turbulence models and achieve higher accuracy in simulating experimental conditions.

The numerical results of 3D flow and thermal distributions under normal and deteriorated heat transfer conditions are compared to experimental results. The distributions of temperature and turbulence levels are used to understand the underlying phenomena of the heat transfer deterioration in supercritical water flows.

Reducing the energy turbulent Pr number produced the most accurate prediction of the deterioration in heat transfer, by altering the production term due to buoyancy, which appears in the equations for turbulent kinetic energy as well as its dissipation rate. The buoyancy forces in upward flows act to reduce the turbulent shear stress, resulting in localized increase in wall temperatures.
Numerical Study on Mitigation of Heat Transfer Deterioration in Supercritical CO2 Heat Exchanger Application
Authors: Wong Kin Wing , Cheng Hui , Zhao Jiyun
Published: October 2017

With the advantages of the thermophysical property of supercritical carbon dioxide (SCO2), SCO2 has been proposed for being used as the coolant of the secondary system in a nuclear reactor to promote a higher thermal efficiency. However, heat transfer deterioration (HTD) in supercritical fluid became a potential operational problem for the supercritical heat exchanger. Understanding of HTD is importance to heat exchanger tube design.

In this paper, both circular and annular tube with the same sectional area is simulated using the ANSYS FLUENT 15.0 with Shear Stress Transport (SST) turbulence model. In general, the SST model can accurately predict the position of HTD peak as found in the experiment but with a difference between the simulated and experimental value of the peak. Nevertheless, the SST model is still regarded as the turbulence model in modeling supercritical carbon dioxide heat transfer in ANSYS FLUENT. Computational Fluid Dynamics (CFD) simulation was performed for SCO2 on 8.42 MPa with an inlet temperature of 312.15K under heat flux value of 110 kW/m2 to illustrate the effect of heat transfer deterioration in the circular and annular tube. Second, the effect of turbulence augmentation to wall temperature are investigated by placing the semi-circular obstacles at the heated wall of the circular tube. The result showed that the addition of Vortex Generator (VG) could lessen the HTD effect and followed by the smoothing effect of the wall temperature along the downstream of the tube.
Development of a Gel Type Dosimeter for X-Ray Fields
Authors: Aoki Yutaro , Harvel Glenn , Sakura Toshiharu , Sunagawa Takeyoshi
Published: October 2017

In recent years, use of radiation beams or particle beams have been put to practical use for cancer therapy. In cancer radiation therapy, visualization of radiation patterns is absolutely necessary for precisely evaluating the dose distribution. Therefore, gel type or Fricke type dosimeters [1] are considered useful for visualization. In this study, we developed a new type of gel dosimeter using a doped polyvinyl alcohol (PVA) based solution. This gel uses a red color based chemical reaction that occurs when the active agent is separated. Irradiation of the gel with X-rays is sufficient to break the chemical bonds of the active agent. We irradiated different gel samples with X-rays from a Hitachi MBR-1520R-3 source under different configurations to test the gel performance. We used UV-VIS spectrometry to measure the absorbance of transmitted light through the gel. For the active agent, the absorbance is at a peak wavelength of 490 nm. The amount of absorbance is proportional to the number of interactions with X-rays. We irradiated the gel between 0.5Gy-10Gy with visualization of the gel by photography and spectrometry between each irradiation. The spectrometry was performed using a StellarNet Black Comet system observing the absorbance between 300nm and 600nm. The results show that as the X-ray dose increases, the gel transitions from a clear gel to a light pink gel and then to a red gel. All colors are translucent and allow for the passage of light. The first samples were done in clear plastic containers of 250 ml size. The containers were filled with gel to eliminate air and possible oxygen contamination. The second set of experiments repeated the first study but used metallic coins as X-ray shields. The regions covered by the coins were protected from the dose and remained clear. A sharp edge was observed at the edge of the coin. This implies that the gel does not diffuse and hence can represent a dose distribution as long as it is not mixed. The third samples were placed in disposable cells for measurement of absorbance. The absorbance had a peak in the vicinity wavelength of 490nm. The results confirmed the absorbance to be proportional for increasing applied dose. In summary, a color transition gel was developed for use in detecting irradiation dose from X-rays. This technique has potential application for visualization of dose during medical procedures.
Pressure Drops and Model Modification for Two-Phase Flow in Porous Beds With Coarse Particles
Authors: Zou Xumao , Li Liangxing , Kong Liubo , Wang Huasheng
Published: October 2017

Motivated by reducing the uncertainties in coolability analysis of a debris bed, this paper proposed a modified model for the pressure drops of two phase flow through packed beds with coarse particles based on the experimental studies. The experiments are carried out on the test facility of DEBECO-LT (DEbris BEd COolability-Low Temperature), which was designed to investigate single / two-phase flow in porous beds. The coarse particles are packed in the cylindrical test section with the inner diameter of 120 mm and the height of 600 mm. Through single-phase flow tests in homogeneous beds, the reliability of the whole experimental system is ensured. Then two-phase flow tests are performed to investigate the flow characteristics, to provide basic data for verifying and modifying the existing models. The results show that, the interfacial drag in beds with coarse particles will result in a decreasing tendency in the pressure drop curves along with the fluid velocity, and the the effect of interfacial drag should be considered in the debris coolability analysis models for beds with coarse particles. Compared with the existing models, the new model shows relatively satisfactory forecasting ability, and the predictions have favorable agreement with existing experimental data under various conditions. This modified model could be applied to calculate the pressure drops of two-phase flow in coarse-particle beds.
Modeling and Experiments of a Passive Decay Heat Removal System for Advanced Nuclear Reactors
Authors: Bersano Andrea , De Salve Mario , Bertani Cristina , Falcone Nicolò , Panella Bruno
Published: October 2017

Within the field of research and development of innovative nuclear reactors, in particular Generation IV reactors and Small Modular Reactors (SMR), the design and the improvement of safety systems play a crucial role. Among all the safety systems high attention is dedicated to passive systems that do not need external energy to operate, with a very high reliability also in the case of station blackout, and which are largely used in evolutionary technology reactors.

The aim of this work is the experimental and numerical analysis of a passive system that operates in natural circulation in order to study the mechanism and the efficiency of heat removal. The final goal is the development of a methodology that can be used to study this class of systems and to assess the thermal-hydraulic code RELAP5 for these specific applications. Starting from a commercial size system, which is the decay heat removal system of the experimental lead cooled reactor ALFRED, an experimental facility has been designed, built and tested with the aim of studying natural circulation in passive systems for nuclear applications. The facility has been simulated and optimized using the thermal-hydraulic code RELAP5-3D. During the experimental tests, temperatures and pressures are measured and the experimental results are compared with the ones predicted by the code.

The results show that the system operates effectively, removing the given thermal power. The code can predict well the experimental results but high attention must be dedicated to the modeling of components where non-condensable gases are present (condenser pool and surrounding ambient). This facility will be also used to validate the scaling laws among systems that operate in natural circulation.
The Effect of Minor Actinide Transmutation on Temperature Coefficient in PWR
Authors: Zhang Wenxin , Yu Haoyang , Liu Bin , Cai Jin , Cui Shuangshuang
Published: October 2017

Minor actinides in the spent fuel have strong radiotoxicity and very long half-life, the the properly dispose of spent fuel is indispensible to the development of nucler energy. Generally,we dispose the spent fuel by geological burying. But it can not compeletly solve the problem. Neutron transmutation is the only way to shorten the half-life of radioactive nuclides, under the irradiation of neutron MA nuclide will capture neutron or fission, and translate into the short lived nuclide or something valued nuclide. Reactivity temperature coefficient is an improtant safety parameter in nuclear reactor physics.In the reactor design, for the safely operation of reactor, reactivity temperature coefficient must be be negative. The introduction of MA in the PWR must have interference to the temperature coefficient. This paper mainly studied the influence of PWR transmutation minor actinide on the temperature coefficient.
Research on Quantitative Safety Objectives of the Risk-Informed Management Activities in Nuclear Power Plants in China
Authors: Huwei Li , Yan Yi , Chuang Wang , Wenbin Xiong , Zhichao Huang , Yongyue Chu
Published: October 2017

In this paper, the quantitative safety objectives of the risk-informed management activities in nuclear power plants are discussed, which include core damage frequency (CDF) and large release frequency (LRF). It traces the base and source for setting these objectives and analysis their appropriateness and applicability briefly. In addition, this paper shows the risk level of current nuclear units in China which are different in type and generation, and introduces the status of risk-informed optimization activities in China. Finally, combining with the confusion and discussion which has been found out in the using of the safety guidelines previously, this paper summarizes and discusses the appropriateness and applicability of quantitative safety objectives in probabilistic risk analysis activities in nuclear power plants in China, and gives some suggestions.
Preparation and Co (II) Removal of ZnO/Poly-Piperazineamide Nanofiltration Membranes
Authors: Zhang Xiaoguang , Chen Xuexing , Chen Qingchun , Deng Zhaolong , Liu Yan , Chen Rong , Deng Huiyu
Published: October 2017

A series of nanofiltration membranes were prepared by interfacial polymerization of piperazine and terephthaloyl chloride on the surface of polyacrylonitrile (PAN) ultrafiltration membranes. ZnO nanoparticles were incorporated in the active separation layer to modify the performances of the membranes. The preparation conditions as the monomer concentration, dosage of nano-ZnO particles and the reaction time on removal of a simulated radioactive nuclide Co (II) were investigated.

Fourier transform infrared in attenuated total reflection mode verified the formation of polyamide on the PAN ultrafiltration membrane. The scanning electron microscope images showed that the nano-ZnO particles can homogeneously fixed on the membrane surface. The retention of Co (II) increased with increasing the dosage of nano-ZnO in the range of 0∼0.03 g. Further adding more nano-ZnO, the rejection rate of Co (II) first decreased and then increased. The concentration of piperazine and terephthaloyl chloride showed similar effect on removal of Co (II) ion. 5 minutes polymerization time was sufficient to form an active separation layer on the substrate membrane which changed the separation mechanism from ultrafiltration to nanofiltration. The separation performance of NF3 prepared by the following conditions was optimum: 0.03g nano-ZnO, 0.6 wt% piperazine, 0.5 wt% terephthaloyl chloride, and the reaction time was 15 min. The rejection rates of 1000 mg/L Na2SO4 and Co2+ in CoCl2 solution were 90% and 75% respectively. The Co (II) removal rate can be increased to nearly 90% by using ethylenediaminetetraacetic acid disodium salt. Increasing the operation pressure or the feeding concentration of Co (II) can also improve the performances of the membranes in this experiment.
Impact of Switching Time Interval for Dual Intakes on Workers in Main Control Room During Accidents
Authors: Na Xue , Hongtao Lin , Xinjian Liu , Yawei Mao , Lin Qiu
Published: October 2017

The main control room (MCR) ventilation system has been designed to maintain habitability of the control room envelope both under normal condition and accident condition. The system adopting dual air intakes adds one more air intake for accidents at suitable position. During accidents, the air intake with lower contamination will be selected and the other with higher contamination will be isolated, to reduce the amount of radioactive substances entering MCR extremely and enhance the habitability of MCR envelop. This paper is devoted to research on the impact of switching time interval (STI) for dual intakes on workers in main control room during accidents. As the contamination condition varies, the switching action will be happened. Switching time interval (STI) referred in this paper means the time between two switching actions. When accidents occur, the air intake will operate and switch between two intakes automatically. The action of switching will be influenced by several parameters: the meteorological conditions of the site, the response features of the monitoring instruments and the source term released to the environment after accidents. Analysis of these parameters and their sensitivity analysis are performed, which show that the ventilation system cannot afford too frequent switching actions resulted from instantaneous sudden changes of intake’s activity. That’s the reason why it is necessary to set a minimum STI which means the contamination of one intake have to be lower than the other intake and this dominant position should be kept longer than the minimum STI, if not, the switching action will not be happened. As it is essential to set a minimum STI to prevent frequent switching of system, the analysis of its impact on the atmospheric relative concentrations and the doses of the workers in main control room are performed on basis of specific site meteorological condition and the response characteristic of dose monitoring instruments. Three kinds of accident release conditions are considered, which are relief valve release, containment leakage and elevated funnel release. The atmospheric relative concentrations and the doses of the workers in MCR are evaluated for every case and compared with the dose limits. Finally an acceptable minimum STI of dual air intakes is recommended.
Preliminary Experimental Study on Erosion-Corrosion Behavior of Second Loop Pipeline in Nuclear Power Plant With Vapor Liquid Two Phase Flow
Authors: Liu Pengfei , Zhang Xian , Zhao Nan , Liu Junliang , Kuang Bo
Published: October 2017

Under the conditions of the actual operation of the nuclear power plant, especially in the drainage system of the heaters, water recycling system, and condensate pump recirculation system, there is a sudden pressure drop after the control valve in the pipeline, which will lead to serious vapor-liquid two-phase flow. Vapor liquid two phase flow can lead to accelerated corrosion in the pipeline. In order to study the influence of vapor liquid two phase flow on the accelerated corrosion of the pipeline, an experimental facility for simulating the operating conditions of the Second Loop was designed and completed. The experimental facility comprises a pressure regulator, high pressure water tank, circulating pump, power heater, low pressure water tank, condensing and cooling system, instrumentation and data acquisition system. The flow characteristics and the corrosion characteristics of the inner wall of the pipe in the flow channel after the control value were studied in the experiments. The flow characteristics include the distribution of water and vapor temperature, pressure drop distribution and void fraction along the flow channel. In the meanwhile, the corrosion rate and surface characteristics of inner wall at different locations were also studied by CCD and SEM. In addition, the influences of pipe material and pipeline geometry on the erosion-corrosion were also studied in the experiments.
Molecular Dynamics Simulation of the Sputtering of Graphite due to Bombardment With Deuterium and Tritium in Fusion Environment
Authors: Zhao Qiang , Li Yang , Zhang Zheng , Ouyang Xiaoping
Published: October 2017

The sputtering of graphite due to the bombardment of hydrogen isotopes is one of the critical issues in successfully using graphite in the fusion environment. In this work, we use molecular dynamics method to simulate the sputtering by using the LAMMPS. Calculation results show that the peak values of the sputtering yield are located between 25 eV to 50 eV. After the energy of 25 eV, the higher incident energy cause the lower carbon sputtering yield. The temperature which is most likely to sputter is about 800 K for hydrogen, deuterium and tritium. Before the 800 K, the sputtering rates increase when the temperature increase. After the 800 K, they decrease with the temperature increase. Under the same temperature and energy, the sputtering rate of tritium is bigger than that of deuterium, the sputtering rate of deuterium is bigger than that of hydrogen.
Transient Simulation Modeling of Condenser Based on Thermal System Dynamics
Authors: Jinrong Qiu , Yuansheng Lin
Published: October 2017

Complex process such as heat transfer, mass transfer and flow is occurring in the condenser, simulation analysis is an effective method of studying its dynamical character. Conventionally, simulation of condenser is modeled basing on thermal system static, the content and depth of research is not enough. Aiming at understanding its transient character deeply, condenser modeling is carried out basing on the view and method of thermal system dynamics, the parameter of the object is treated as coupling parameter. Adapting a set of ordinary differential equations, the model can reflect the transient character of condenser effectively. The model can reflect the coupling relationship between the parameters which can’t be obtained through the previous simulation model. The model has simple form and can be computed conveniently.