Pipe Break Research Articles

Validation study of sodium pool fire modeling efforts in MELCOR and SPHINCS codes

Discharge of sodium coolant into containment from a sodium-cooled fast reactor vessel can occur in the event of a pipe leak or break. In this situation, some of the liquid sodium droplets discharged from the coolant system will react with oxygen in the air before reaching the containment. This phase of the event is normally termed the sodium spray fire phase. Unreacted sodium droplets pool on the containment floor where continued reaction with containment atmospheric oxygen occurs. This phase of the event is normally termed the sodium pool fire phase. Both phases of these sodium-oxygen reactions (or fires) are important to model because of the heat addition and aerosol generation that occur. Any fission products trapped in the sodium coolant may also be released during this progression of events, which if released from containment could pose a health risk to workers and the public. The paper describes progress of an international collaborative research in the area of the sodium fire modeling in the sodium-cooled fast reactors between the United States and Japan under the framework of the Civil Nuclear Energy Research and Development Working Group. In this collaboration between Sandia National Laboratories and Japan Atomic Energy Agency, the validation basis for and modeling capabilities of sodium spray and pool fires in MELCOR of Sandia National Laboratories and SPHINCS of Japan Atomic Energy Agency are being enhanced.This study documents MELCOR and SPHINCS sodium pool fire model validation exercises against the JAEA’s sodium pool fire experiments, F7-1 and F7-2. The proposed enhancement of the sodium pool fire models in MELCOR through addition of thermal hydraulic and sodium spreading models that enable a better representation of experimental results is also described.

On‐Line Warning System for Pipe Burst Using Bayesian Dynamic Linear Models

AbstractPipe breaks are a recurrent problem in water distribution networks and detecting them quickly is crucial to minimize the economic and environmental costs for municipalities. This study presents a burst detection methodology applying Bayesian dynamic linear models (DLMs) on water flow time series combined with an outlier monitoring tool. The model is used to characterize the actual flow and, for each time, a one‐step ahead forecast distribution is obtained recursively before moving onto the next observation. The outlier detection method consists of comparing the main model with an alternative one wherein the mean flow is shifted to a higher value (as bursts tend to increase flow) to evaluate which model best fit the observed data. If the alternative model is favored, a burst alarm is issued. To verify the performance of this approach, the DLM and monitoring tool were applied on 2 yr of flow data from two district meter areas (DMAs) in Halifax (Canada), and a historical break data set is used to assess model accuracy. The model was able to detect up to 75% and 71.2% of the pipe breaks, with a false alarm rate of 5.15% and 12% in the first and second DMA, respectively. Finally, the proposed model allows for straightforward interpretation of model parameters, nonlinear relationship between flow and predictors of interest, naturally describes the uncertainty for future predictions, can easily accommodate missing values and can be tuned to maximize break detection or minimize false alarm rates to adapt to specific objectives of water infrastructure managers.

Progress in Drainage Pipeline Condition Assessment and Deterioration Prediction Models

The condition of drainage pipes greatly affects the urban environment and human health. However, it is difficult to carry out economical and efficient pipeline investigation and evaluation due to the location and structure of drainage pipes. Herein, the four most-commonly used drainage pipeline evaluation standards have been synthesized and analyzed to summarize the deterioration and breakage patterns of drainage pipes. The common pipe breakage patterns are also summarized by integrating the literature and engineering experience. To systematically describe the condition of drainage pipes, a system of influencing factors for the condition of pipes, including physical, environmental, and operational factors, has been established, and the mechanism of action of each influencing factor has been summarized. Physical, statistical, and AI models and their corresponding representative models have been categorized, and the research progress of current mainstream drainage-pipe deterioration and breakage prediction models are reviewed in terms of their principles and progress in their application.

Plant-scale experiments of an air inflow accident under sub-atmospheric pressure by pipe break in an open-pool type research reactor

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

BEPU analysis of a CANDU LBLOCA RD-14M experiment using RELAP/SCDAPSIM

A key element of the safety analysis is Loss of Coolant Analysis (LOCA) which must be performed using system thermal-hydraulic codes. These codes are extensively validated against separate effect and integral experiments.RELAP/SCDAPSIM is one such code that may be used to predict LBLOCA response in a CANDU reactor. The RD-14M experiment selected for the Best Estimate Plus Uncertainty study is a 44 mm (22.7%) inlet header break test with no Emergency Coolant Injection. This work has two objectives first is to simulate pipe break with RELAP and compare these results to those available from experiment and from comparable TRACE calculations. The second objective is to quantify uncertainty in the fuel element sheath (FES) temperature arising from model coefficient as well as input parameter uncertainties using Integrated Uncertainty Analysis package.RELAP calculated results are found to be in good agreement with those of TRACE and with those of experiments. The base case maximum FES temperature is 335.5 °C while that of 95% confidence 95th percentile is 407.41 °C for the first order Wilk's formula. The experimental measurements fall within the predicted band and the trends and sensitivities are similar to those reported for the TRACE code.

Experimental Bench-Scale Study on Cuttings-Bed Erosion in Horizontal Wells

Abstract Cuttings-beds formation while drilling wellbores is a common challenge, especially for horizontal wells, as drilled particles have higher area to be deposited and form cuttings-beds, which can cause several problems such as increased torque and drag, pipe sticking or pipe breakage, among others. Removal of the drilled cuttings is done by circulating a suitable drilling fluid through the wellbore. This paper presents results from laboratory tests with deposited cuttings-bed and the flow of a fluid to erode the bed. The simulated cuttings-bed is a 1 m long deposited sand-bed in a horizontal section. Three different types of fluids are being used in the tests. To investigate how the rheological properties can affect the erodibility of the cuttings-bed, water (as a Newtonian fluid), a xanthan gum solution, and a water-based drilling fluid prepared for an offshore field operation (as a non-Newtonian fluids) are applied. Ultrasound measurements together with differential bed weight have been used to analyze the fluid–bed interaction. Results have shown that the cuttings-bed is eroded by dune movement. Saltation and dragging of sand particles due to the fluid flow appear to create a crest and then avalanche them down. The different types of fluids undergo different shear rates from the same pump power as the viscosity changes, as well as flow rates dependency along the dune extent.

Bayesian geoadditive water pipe failure forecasting model by optimizingthe updating period

Abstract Municipal water managers rely on pipe deterioration models to plan maintenance, repair, and replacement. Although efforts have been made to increase their accuracy, these models are subject to uncertainties in the predictions. In this paper, an optimization procedure of the Bayesian updating period of the parameters of an existing deterioration model is proposed to sequentially reduce the uncertainty in the prediction of the water pipe breakage rate variable. This latter is modeled using a structured geoadditive regression technique where covariates are allowed to have linear (e.g., categorical) and nonlinear (e.g., continuous) relationships with the response variable. Unknown and unobserved covariates are included in the model through a geospatial component that captures spatial auto-correlations and local heterogeneities. The optimization procedure searches through the time series data to identify the optimal updating period horizon that corresponds to the minimum error between the predicted coefficient of determination between predictions and observations using the unupdated and updated models. The process is repeated until the entire time series data is covered. The application of this approach to failure data of large Canadian urban water systems shows a significant reduction in the uncertainty of the parameters and increases the accuracy in the prediction of the output response variable.

Isolated pressure zones based on GIS as a solution for water network problems

Abstract One of the most important accidents for water transmission lines occur by air entrance due to water hammer into the water pipeline at sub-atmospheric transient pressure. The air can be sucked into the water system causing repeated pipe breaks in sub-atmospheric transient pressure. This work aimed to improve the advanced techniques including remote sensing (RS), and the internet of things (IoT) to control the repeated pipe breaks. According to the geospatial information systems (GIS), the relationship classes between the spatial and non-spatial data were defined for the scaled model. By GIS the location of pipe breaks and sucking air into water pipeline was recognized during fluid instabilities. The location of pipe breaks was defined by the numerical modelling based on GIS. According to numerical analysis, the Courant number was equal to 0.977. In the field test, the surge velocity was 1084 m/s. The pressure wave was detected in 0.005 s by RS facilities equipped with water hammer sensors, advanced modems, and data loggers referring to the IoT technique. The result of this work led to a reduction of the non-revenue water (NRW) and the saving of drinking water.

Design for ACP100 long term cooling flow resistance with random forests and inverse quantification

The ACP100 is an integrated small modular reactor with passive designs, and core cooling in the long-term cooling phase of the double-ended direct vessel injection (DEDVI) pipe break accident relies on the natural circulation in the sump recirculation pipeline. Therefore, the design of the recirculation pipeline flow resistance is very important. The ARSAC was used in the study to carry out the design for the recirculation pipeline flow resistance of the ACP100. The surrogate model of the accident simulation was constructed using the random forests algorithm, followed by using an inverse quantification method to determine the flow resistance distributions of the filter and related pipe, and finally the forward uncertainty propagation was performed for validation. The resistance design method utilized in the study has a high degree of freedom and is able to take the manufacturing uncertainty into consideration, which could facilitate the subsequent geometry design.

Numerical and experimental investigation of the effect of the optimal usage of pump as turbine instead of pressure-reducing valves on leakage reduction by genetic algorithm

The leakage, caused by design problems, pipe breakage, and fittings' failure, is a critical challenge that the beneficiaries face in the water distribution networks (WDNs). Control and management of the network pressure have always been considered helpful solutions to reduce the leakage in these systems. In the present study, locating and setting of the five pressure reducer valves (PRVs) have been optimized using GA (genetic algorithm) to minimize the leakage and make uniform pressure. Results show that the network leakage has reduced 21% from 34.53 lit/s to 27.26 lit/s. In the next step, the PRVs are replaced by two pumps as turbines (PATs) at two desirable points for converting extra elevation head of the real gravity WDN to generate electricity. It is also found that the performance of PATs in reducing the amount of leakage is similar to PRV, and there are slight differences. Therefore, nearly 153 MW/year is generated using two PATs that resulted in 15,000 $/year in cost-saving. As estimated, the cost for installing and operating two PATs is $14,000, so the return on capital will be at least one year.

Pressure Driven analysis of water distribution systems for preventing siphonic flow

The analysis of the water distribution network is complicated and requires several assumptions to simplify its problem definition. Demand Driven Analysis (DDA) is typically used to analyse the network assuming that all network nodes can deliver the required demand regardless of the available pressure. In the case of analysing an existing network under deficit condition such as pipe breakage or extra demand required for firefighting, assumptions used to simulate the network with DDA is not valid. Node Head Flow Relationship (NHFR) should be considered through Pressure Driven Analysis (PDA) to analyse the network. Most PDA methods assume that the networks are airtight which means that if the pressure at any demand node is negative, delivered demand will be equal to zero and the flow is permitted in the connected pipes (Siphonic flow). This assumption is hydraulically incorrect since the air is allowed to get into the connected pipes and prevent their flow leading to node isolation. In this paper, a new Pressure Driven Analysis to Prevent Siphonic Flow (PDA-SF) approach is proposed to analyze the network under deficit conditions and consider isolating the nodes that show available head less than node elevation. The PDA-SF was tested and compared to previous methods in four case studies under steady state analysis or extended period simulation. The case studies cover also different network conditions whether node isolation is needed or not. The PDA-SF was able to solve different networks where other methods failed to achieve the required demand or service pressure. The new PDA-SF method shall enable peers and modelers to better simulate and analysis water distribution networks.

Experimental Investigation on Flow Behavior of Paste Slurry Transported by Gravity in Vertical Pipes

In order to dispose of large quantities of mineral tailings, paste backfill is proposed and widely adopted. Paste backfill, which has high concentration and yield stress and behaves as a non-Newtonian fluid, is prepared at the surface plant and then transported underground. Vertical pipelines are more likely to suffer various failures, such as pipe breaks, wear and plugging, during the transport process. Few present studies focus on the flow behavior of paste slurry flowing in vertical pipes. In this work, two L-shaped pipeline systems with internal diameters (ID) of 40 mm and 65 mm with electrical resistance tomography (ERT) were manufactured to visualize flow regimes and measure the axial velocity and pipe pressure of slurry flowing in the upper and lower zones of vertical pipes. Flow regimes were extracted from ERT-reconstructed images stacked by time-series. Based on this, four typical flow regimes were summarized, and the characteristics of velocity and pressure change with vertical pipe depth were discussed.

Active Air-borne noise suppression for pipe break early warning in smart water networks

Acoustic alarm systems using IoT (internet of things) smart sensors (e.g. accelerometers) for leak detection in water networks are rapidly gaining popularity. One of the issues for such systems is the false alarms which often occur as a result of signal contamination by environmental noise, especially by air-borne noise resulting in additional vibration. This research proposes a dual-sensor concept for active air-borne noise suppression in accelerometer signals that are excited by both fluid-borne noise (including the leak signal) and air-borne environmental noise. In the proposed arrangement, a microphone adjacent to the measurement station is used to measure the air-borne noise simultaneously to the accelerometer mounted to the pipe. Three methods have been applied in this paper: 1) using the non-coherent output power (NCOP) between the accelerometer and microphone signals; 2) using a Wiener filter; and 3) using adaptive least mean square (LMS) filters together with adaptive infinite impulse response (IIR) filters. Field tests have been carried out on a cast iron water main embedded in a water distribution system. A speaker was used to generate air-borne noise around the measurement station and to excite unwanted vibrations in the pipe. The results show that all three methods can effectively suppress air-borne noise from the accelerometer signals mounted to the pipe. A noise reduction of 30 dB can be achieved using the NCOP in the frequency domain or using the Wiener filter in the time domain. The adaptive filters are relatively less effective and the effectiveness reduces with the increase in bandwidth of the air-borne noise. However, the adaptive filters have the potential to be applied online for real-time processing.

Sensitivity-based adaptive procedure (SAP) for optimal rehabilitation of sewer systems

ABSTRACT Urban flood resilience requires high-performance sewer systems, and multi-objective optimization methods are widely used to improve sewer system efficiency. A non-polynomial complete (NP complete) optimization problem may exist in urban sewer rehabilitation, which may cause low efficiency in optimizing large network systems. In this research, a sensitivity-based adaptive procedure (SAP) is proposed, which can be integrated with optimization algorithms. SAP was integrated with Non-dominated Sorting Genetic Algorithm II (NSGA-II) and Multiple Objective Particle Swarm Optimization (MOPSO) methods. We further used the Hydraulics and Risk Combined Model (HRCM), which is a risk-informed multi-objective optimization model designed for drainage system rehabilitation to validate the performance of SAP procedure. Results showed that SAP can improve the optimizing performance, and SAP-NSGA-II exhibited superior performance in solving the combined problems of pipe breakage and overflooding.

Vibration detection method for core loosening degree of high‐voltage direct current converter valve saturable reactor based on variational mode decomposition‐symmetrized dot pattern and image matching

Saturable reactor is the key equipment in converter valves; it is important to evaluate the core condition. In this paper, a recognition model of saturable reactor core loosening based on variational mode decomposition (VMD)-symmetrized dot pattern (SDP) feature fusion images and scale-invariant feature transform (SIFT) was proposed. Firstly, the saturable reactor vibration test under high frequency pulse excitation was carried out, and the vibration signals in different core loosening degrees were collected. Secondly, the VMD algorithm was used to decompose the broadband vibration signal into multiple narrowband functions, which were used to reflect the characteristics of each frequency band. Thirdly, each function and the original signal were transformed by SDP, the generated spiral arms were fused into a new image, and the typical templates in different loosening degrees were selected. Finally, the improved SIFT algorithm was used to obtain the matching results between test sets and templates. The results show that the recognition accuracy of the proposed model for core loosening is 97.5%, which is better than traditional algorithms. It can find the core loosening defect early and avoid further failures such as water pipe break and discharge, which can provide an important basis for saturable reactor monitoring.

Acoustic Signal Classification by Support Vector Machine for Pipe Crack Early Warning in Smart Water Networks

Uncontrolled pipe breaks are a challenge for water utilities all over the world. This paper describes a technique that enables pipe cracks to be identified at an early stage before they become uncontrolled breaks by utilizing a permanent acoustic monitoring system as part of a smart water network. Multiple acoustic features are selected and extracted from recorded wave files that are associated with proactive repair and uncontrolled pipe break events. The extracted acoustic features and the associated wave file labels (as either crack/leak noise or no crack/leak noise) are used to train a support vector machine model. The trained model has been operationalized in the South Australia Water Corporation’s smart water network analytics platform to process incoming new acoustic wave files in a near-real-time manner. If the acoustic wave file is classified as a pipe crack/leak, an alarm is sent to an investigation crew such that leak localization can be conducted and repairs started. The successful detection of multiple pipe cracks/leaks by the developed model after its implementation proves that it is an effective tool to enable proactive management of pipe breaks in water distribution systems.

Joint maintenance planning of deteriorating co-located road and water infrastructures with interdependencies

Due to co-location and spatial proximity, deteriorating water infrastructure (WI) and transportation infrastructure (TI) have complex interdependencies, including both physical dependency from road to pipe, and operational dependency from pipe to road. On one hand, traffic load is not only a dominant factor for the physical degradation of road but may also be an important contributing factor to the sudden failure of the pipe underneath the co-located road due to the extreme propagated stress. On the other hand, the water pipe breaks and repairs will also cause traffic blockage, lane closure, and repaving of road surface, which influence both road user costs and road maintenance costs. Most of the existing maintenance work mainly considered WI and TI separately but neglected their complex interdependencies. This study proposes a joint proactive maintenance planning framework for the co-located road and pipe under their degradation uncertainties by explicitly taking into account both their physical and operational dependencies. In particular, the competing failure modes of both the traffic-induced sudden failure and the corrosion-induced gradual failure are simultaneously considered for the pipe to capture the physical dependency. Road maintenance costs and road user costs in the presence of pipe maintenance disruption are also formulated for the road to capture the operational dependency. A case study is further provided to comprehensively evaluate the performance of the proposed joint maintenance planning strategy over several existing benchmark strategies and demonstrate the cost-saving benefit of the proposed work. The impacts of interdependencies on the proposed maintenance planning decisions are also thoroughly investigated.

Performance Evaluation of Pipe Break Machine Learning Models Using Datasets from Multiple Utilities

Performance Evaluation of Pipe Break Machine Learning Models Using Datasets from Multiple Utilities

Preliminary accident analyses of ex-vessel LOCA and TES pipe break for CFETR HCCB blanket system

Safety analysis is one of the most important parts in the design of nuclear power reactor. It is a necessary step for China Fusion Engineering Test Reactor (CFETR) to make the research in safety accidents analysis of main coolant systems and tritium systems. The consequences of nuclear accidents can be used to prove the safety of plant and optimize the systems design. Now, the main design parameters of CFERR have been determined, and the conceptual design of the main systems have been done. This paper presents two design basis accidents (ex-vessel loss of coolant accident (LOCA) and TES pipe break) analysis results in primary helium cooling system (HCS), and tritium extraction system (TES). According to the accident analysis results, the radioactive release assessments are given. The analysis results can provide reference for the following parameter optimization design of CFETR systems.

A Coupled Thermal‐Hydraulic‐Mechanical Approach to Modeling the Impact of Roadbed Frost Loading on Water Main Failure

AbstractSubsurface pipe failures in cold regions are generally believed to be exacerbated by differential strain in shallow soils induced by seasonal freeze and thaw cycles. The transient stress–strain fields resulting from soil water phase change may influence the occurrence of local buried pipe breaks including those related to urban water mains. This work proposes that freezing‐induced frost loading results in uneven stress–strain distributions along the buried water mains placing them at risk of bending, breaking, and/or leaking. A coupled thermal‐hydraulic‐mechanical (THM) model was developed to illustrate the interactions among moisture, temperature, and stress–strain fields within variably saturated freezing soils. Several typical cases involving highly frost‐susceptible and lower frost‐susceptible soils underlying roadbeds were examined. Results show that the magnitude of frost‐induced compressive stress and strain changes between different frost‐susceptible soils can vary significantly. Such substantial differences in stress–strain fields would increase the breakage risk of water mains buried within different types of soils. Furthermore, even water mains buried within soils with low frost‐susceptibility are at risk when additional sources of soil water exist and are available to migrate to the freezing front. To reduce the risk of damage to buried pipe‐like infrastructure, such as municipal water mains, from soil freezing phenomena, the selected backfill material should have fairly consistent frost susceptibility or a broad zone of transition should be considered between materials with significantly different frost susceptibility. In addition, buried pipes should be kept as far away from external sources of subsurface water as possible considering the potential for the water source to exacerbate the level of risk to the pipe.