ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V007T00A001. doi:10.1115/PVP2018-NS7.

This online compilation of papers from the ASME 2018 Pressure Vessels and Piping Conference (PVP2018) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Monitoring, Diagnostics, and Inspection

2018;():V007T07A001. doi:10.1115/PVP2018-84036.

Internal valve leakage in a natural gas pipeline not only brings huge economic losses to the petroleum enterprises, but also causes immeasurable environmental pollution. Therefore, the diagnosis of internal valve leakage and the prediction of leakage rates are the basis to ensure the safe operation of natural gas pipeline. In this paper, based on acoustic emission detection system, the internal valve leakage signals were collected, which were analyzed and processed to diagnose the internal valve leakage and predict the leakage rates. Due to the complex work environment and serious noise interference, the collected acoustic emission signals contain a large amount of environmental noise. Therefore, singular spectrum analysis was proposed to reduce the environmental noise in acoustic emission signals. Radial basis function neural network was used to predict the leakage rates. Experimental results demonstrate that pure internal leakage source signals can be obtained via singular spectrum analysis. The prediction accuracy of leakage rates based on the characteristic parameters of pure AE signals is better than the accuracy without signals denoising. Therefore, singular spectrum analysis is an effective denoising method for acoustic emission signals, which can improve the prediction accuracy of internal valve leakage rate.

Commentary by Dr. Valentin Fuster
2018;():V007T07A002. doi:10.1115/PVP2018-84137.

This paper discusses a specially developed semiconductor strain cell that allows sensitive measurement of surface strain in environments with temperatures up to 1050F (566C). There is an unmet industry-wide need in the manufacturing and power generation fields for monitoring material mechanics and component degradation at temperatures exceeding the maximum working temperature of traditional strain gage technologies. This technology advances attachment methodology of the semiconductor gage to allow field deployment and a physically reliable interface with structural strain. Measuring strain at these temperatures is useful both in the laboratory and in practical monitoring applications. The technology provides a way to monitor changes in materials exposed to heat and stress and give plant engineers tools to predict and avoid critical failures.

Commentary by Dr. Valentin Fuster
2018;():V007T07A003. doi:10.1115/PVP2018-84268.

During present offshore gas-condensate production, flow meters, due to its exceedingly high cost, are being substituted by Virtual Flow Metering (VFM) Technology for monitoring total and single-well flow rates through sensor measurements and physical models. In this work, the inverse problem is solved by Data Reconciliation (DR), minimizing weighted sum of errors with constraints integrating multiple two-phase flow models. The DR problem is solved by Parallel Genetic Algorithm, without complex calculations required by conventional optimization. The newly developed VFM method is tested by data from a realistic gas-condensate production system. The results show good accuracy for the total mass flow rate with model calibration. Meanwhile, recommended single-well flow rate can be provided without physical meters. The method is proved of good robustness with individual pressure sensor invalid, even total flow rate measurements unavailable. The time cost of each reconciliation process can meet the demand of engineering application.

Commentary by Dr. Valentin Fuster
2018;():V007T07A004. doi:10.1115/PVP2018-84529.

The pressure pipeline in line inspection technology is the most effective nondestructive testing method to detect the quality of buried oil and gas pipelines at present. In line inspection tool usually uses magnetic flux leakage (MFL) technology to detect the change of leakage magnetic field to detect pipeline defects. Permanent magnets magnetize the wall of the pipeline as an excitation. During the detection process, the magnetic field performance of permanent magnets is required to be high. At the same time, the magnetic performance of the permanent magnet in the magnetic cleaning pipe also determine the cleaning effect inside the pipeline. In this paper, the magnetic distribution of permanent magnets is studied and the Nd-Fe-B permanent magnets with the best magnetic properties are taken as the objects. The finite element simulation is used to optimize the shape of the permanent magnets with better magnetic distribution, and the magnetic intensity factors of the preferred cylindrical permanent magnets are analyzed. In addition, three experiments of the influence of temperature, the influence of the ferromagnetic combination, and the influence of the environment medium are conducted.

As a result, the relationship between the magnetic intensity of the Nd-Fe-B permanent magnets and the factors is obtained. The conclusion is of great significance to the design and research of permanent magnetic circuit in line inspection magnetization device.

Commentary by Dr. Valentin Fuster
2018;():V007T07A005. doi:10.1115/PVP2018-84598.

This paper presents a new method for monitoring systems with direct coupling of measurement data and a finite element model of a mechanical component. In the presented first case study the measurement data received from a monitoring system is coupled with a finite element model developed in Code_Aster, showing the possibility of minimizing the efforts of data-model coupling on complex components.

A thermo-mechanical calculation of a generic regenerative heat exchanger of a nuclear power plant will be used as an example to describe the opportunities and the limitations of the use of numerical simulation in modern monitoring systems. The experimental measurements and the thermo-mechanical numerical simulation process will be presented. The projection hypothesis that allows the transition from locally measured temperature to the numerical model will be described. The relation between computing time, sampling rate of the data acquisition system and refinement of the numerical mesh will be analyzed and discussed in terms of computation perspective.

The paper explains how the measurement data can be projected on the mesh of a mechanical component with Code_Aster and how the numerical simulation can be fed on the measurement data. In an outlook, the use of this method in future monitoring systems will be discussed under consideration of real world problems and applications in nuclear power stations.

Commentary by Dr. Valentin Fuster
2018;():V007T07A006. doi:10.1115/PVP2018-84651.

One of the most challenging aspects when performing on-site piping troubleshooting is to obtain the most pertinent information possible regarding piping behavior: acceleration, stress, pressure levels, etc. This last parameter is always difficult to obtain because when pressure taps are available on the line, they are rarely in the area of interest.

PVDF (PolyVinyliDene Fluoride) wire makes it possible to perform non-intrusive pressure measurements but needs to be calibrated in order to have a good representation of phenomenon occurring inside the pipe. After development of a dedicated calibrator and calculation of the fluid/structure coupling coefficient, VibraTec is able to assess PVDF sensor sensitivity according to client’s installation characteristics.

Non-intrusive measurements provide a good accuracy regarding phenomenon amplitude and frequency localization even though some temperature restrictions apply to PVDF measurements.

Although PVDF sensors seem to be simple to implement, particular attention must be paid during installation as this has a direct influence on the PVDF response.

Commentary by Dr. Valentin Fuster
2018;():V007T07A007. doi:10.1115/PVP2018-85159.

Creep failure of the pressure vessels operated at high temperatures in power and petrochemical industry is a frequent reason of its collapse. Some ultrasonic properties, as the ultrasonic waves’ velocity, are sensitive to change of material properties due to thermally induced degradation processes, especially plastic deformation. The article discusses possible applications of ultrasonic testing to detect creep degradation process based on results of measurements performed on collapsed membrane wall from P265GH pressure purpose steel. The methodology may help with selection of potentially critical areas on pressure equipment under operation prior its further investigation while performing e.g. residual life assessment.

Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Operations and Maintenance of Pressure Vessels, Heat Exchangers, Piping, and Structures

2018;():V007T07A008. doi:10.1115/PVP2018-84091.

As supercritical carbon dioxide (sCO2) is emerging as a potential working fluid in power production Brayton cycles, fluid purity within the power cycle loops has become an issue impacting commercialization. Sandia National Laboratories has been evaluating the longevity of sCO2 recompression closed Brayton power cycles to quantify the advantages of sCO2 over other fluids as utilizing sCO2 yields comparatively greater efficiencies. Hydrocarbon plugging has been observed in the small printed circuit heat exchanger channels of our high temperature recuperator, increasing pressure drop across the heat exchanger. As pressure drop is a critical factor in the overall efficiency of sCO2 recompression closed Brayton cycles, in this paper we report on our investigation into heat exchanger efficiency reduction from hydrocarbon plugging induced pressure drop.

Commentary by Dr. Valentin Fuster
2018;():V007T07A009. doi:10.1115/PVP2018-84107.

This paper explores new analysis techniques and mitigation concepts developed to extend the current state of the art acoustic induced vibrations (AIV) analyses. These new methods are intended to provide more accurate evaluations of this phenomenon in an attempt to solve AIV problems found in blowdown and piping systems. Current screening methods for AIV are based on pass/fail data with minimal or undesired options for reducing the likelihood of failure for AIV events. Computational fluid dynamics simulations and finite element analysis in combination with lab testing of novel mitigation options using accelerometers, dynamic pressure transducers, and strain gages were performed to better understand the phenomenon and develop possible solutions to reduce the impact of AIV on piping systems.

Results of the testing and analyses performed at the Southwest Research Institute (SwRI) indicate that there is a possible correlation with acoustic modes, structural modes, and elevated stresses during AIV events. Minor reductions in dynamic pressure fluctuations throughout piping during AIV events can be made by changes in valve geometry and piping configurations. Results of CFD modeling and analysis demonstrate that computational analysis can be used to evaluate mitigation strategies and suggest that the use of a dampener as a mitigation technique may be successful in reducing the amplitudes of dynamic pressure waves in piping systems caused by AIV events.

Commentary by Dr. Valentin Fuster
2018;():V007T07A010. doi:10.1115/PVP2018-84123.

Efficient refinery start-up and shutdown durations are vital in establishing prolonged productivity in refineries operating hydrotreating reactors. The benefits of efficient start up and shutdown cycles are extensive, and include considerable operational and cost reduction. Reduced start-up and shutdown cycles, however, require increased heating and cooling rates, which cause higher temperature gradients throughout the reactor vessel, consequently leading to higher thermal stresses, which may affect damage mechanisms and limit reactor’s life. The equipment’s OEM has defined guidelines for the reactor heating and cooling during start-up and shutdown cycles and any attempt to reduce the start-up and shutdown duration is usually limited by these guidelines. It is therefore necessary to carry out an engineering assessment to determine the effect of changing the start-up and shutdown procedures beyond the OEM guidelines on reactor’s life.

Multiple thermo-mechanical Finite Element analyses for a series of different start-up/ shutdown procedures, including the current procedure, were carried out to determine the through-wall thermal gradient and stresses, and identify the most critical locations. In order to estimate convective heat transfer coefficients, Computational Fluid Dynamic (CFD) analysis was utilized to describe the complex fluid flow behavior of the feedstock in the presence of catalysts and internal geometry features. Low Cycle Fatigue (LCF) was adopted as a main damage mechanism to quantify the damage as a result of the changed operating conditions. It was determined that the LCF life calculated in the reactor vessel’s critical damage locations was found to be sufficiently long with respect to the frequency of start/shutdown cycles, even with operating conditions exceeding the OEM limit. Therefore, alternative guidelines were suggested to achieve the time reduction in startup/shutdown operation by increasing ramp rates without compromising structural integrity of the vessel.

Commentary by Dr. Valentin Fuster
2018;():V007T07A011. doi:10.1115/PVP2018-84285.

The three-phase separator has a wide range of applications in oil production industry. For the purpose of studying the effect of heating temperature, demulsifiers and water content on the separation of oil-water mixture in the three-phase separator, eight kinds of oil samples were taken from different oil transfer stations in Changqing Oilfield and the mixtures were prepared by stirring method. To simulate the two-stage dehydration process, the first stage dehydration experiments without any heating were performed on mixtures at the dose of 100ppm demulsifer at 20°C, and the water cut of these mixtures is the same as that of the gathering pipeline in each oil transfer station. The water cut of the upper crude oil was measured after 40 minutes, and the values of them ranged from 0.5 vol% to 65.2 vol%. No visual stratification was observed for the sample most difficult to separate, so it was selected to conduct the second stage dewatering process. Three bottles of the same mixture were prepared and heated to 30°C, 40°C and 50°C, respectively. The results showed that all of them stratified in 10 minutes, and the water-cut values of the upper oil layer were 1.4 vol%, 0.5 vol% and 0.3 vol%, respectively, compared to 65.2 vol% at 20°C. When the concentration of demulsifier was changed to 200ppm and 300ppm, the results exhibited almost no differences. So it is deduced that the further improvement of heating temperature and demulsifier dose have limited enhancement on oil-water separation. At Last, 35 vol%, 50 vol%, 70 vol% and 85 vol% water cut mixtures of the special oil sample were made to experiment as previously. In consequence, the 35 vol% water-cut emulsions presented a relatively slow rate of oil-water stratification at low heating temperature, and the oil content of the lower separated water was improved by the addition of demulsifier dosage above 100ppm when the water cut was 90 vol%. It is indicated that high heating temperature is necessarry for low water-cut mixtures oil-water separation and can be appropriately reduced to save energy consumption as the water cut continues to rise. The demulsifier dosage is also neccessary be controlled in high water cut period. These experimental data provide the basis for the further optimization operation of the three-phase separator.

Commentary by Dr. Valentin Fuster
2018;():V007T07A012. doi:10.1115/PVP2018-84545.

One of the vacuum column made of Carbon steel (SA 285 Gr. C) was found with severe corrosion under insulation during turnaround inspection. The equipment was in service for the past 46 years. The corrosion was around the full circumference of the column at a location immediately above the stiffener ring. The wall loss was extensive, which mandated a welded full circumferential patch to encapsulate the corroded region. A full circumferential lap patch with reinforcement plug welds was designed as per ASME PCC-2 [2], fabricated and installed at site. During the dye penetrant examination of the patch plate welds, fine cracks were noted at the toe of the fillet welds. A subsequent PAUT (Phased Array Ultrasonic Testing) of patch plate welds, showed that the cracks were in column shell (base material) surface initiating from toe of the fillet weld of the patch and beneath the fillet weld.

The cracks found in first few sections of welds were ground and re-welded with appropriate pre-heating and post-heating. However, some cracks were still observed in base material, although with reduced magnitude compared to previous welding. Despite proper controls in place during the welding, the challenge was, some minor cracks were re-occurring at the base material surface below fillet welds. A multi discipline review was carried out to understand the potential root cause for the cracks, detailed assessment of risks and impact due to the cracks. A risk based approach was followed, in evaluating cracks for acceptance based on API 579-1/ASME FFS-1 [1], for continued service of the column and to minimise the extension of turn around duration. Later, a long-term plan was made to replace the equipment.

Commentary by Dr. Valentin Fuster
2018;():V007T07A013. doi:10.1115/PVP2018-85038.

When inspecting a piping system, injection points should receive specific attention because they are sometimes subject to accelerated or localized corrosion. If metal loss is found at the location of such injection points during the inspection, a Fitness-For-Service (FFS) assessment can be used to evaluate whether the component can continue to operate safely without a plant shutdown. A more practical method for assessing the integrity is needed to provide specific procedures for the FFS assessment of a piping branch, e.g., an area-replacement rule.

This paper will present a practical example of an FFS assessment of an injection point in a boiler feed-water line in which internal corrosion was found using ultrasonic testing. We outline a way to characterize the metal-loss shape and assess the integrity of the injection point. We also present a quill-type injection design as a permanent countermeasure.

Commentary by Dr. Valentin Fuster
2018;():V007T07A014. doi:10.1115/PVP2018-85064.

In the damage evaluation (and analysis) of the bolted flange joints, it is most important to evaluate the reduction in the sealing performance. Although the marginal nut height found by Alexander’s theory [1] serves as a value smaller about 20% than standard nut height, even if it becomes thin 20% or more on a track record and experience, leakage does not occur. In this study the effects of nut thinning due to corrosion on the sealing performance in 3-inch bolted flange joints under internal pressure by use of FEM calculations. The following results are obtained the relationship between stripping bolt load and nut height is developed, and the marginal nut height for the sealing performance is calculated.

Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Plant Life Extension: Aging and Life Management

2018;():V007T07A015. doi:10.1115/PVP2018-84025.

Pressure testing of pressurised equipment is crucial in establishing confidence that it is capable of performing the duty for which it has been designed and fabricated.

A pressure test is usually mandated by pressurised equipment design codes for newly fabricated equipment.

Also many regulations or industry codes for the design and fabrication of pressurised equipment require that a pressure test is performed on any modified in-service pressurized equipment to verify that the integrity of the equipment has not been compromised after such modifications.

Although the usual and normally the preferred method of pressure testing is conducting a full hydrostatic test on the entire equipment (i.e. using a liquid medium, typically water), there may be occasions that a hydrostatic test is simply not practical.

As an alternative to a full hydrostatic test, the designer may consider performing a localized pressure test or sometimes a full pneumatic test on modified equipment.

It must be emphasized that a full pneumatic test can create extreme hazards to a facility and nearby personnel and therefore needs a careful and methodological assessment prior to being attempted on any equipment.

This article is structured primarily as an attempt to assist the organizations in charge of design and inspection of newly fabricated or in-service equipment to identify general hazards associated with pneumatic test of pressurised equipment in a structured manner.

An analysis of a simple cylindrical pressure vessel is presented to provide a better understanding of hazards associated with pneumatic test.

Two tables in the paper provide the recommended exclusion zones from the equipment being pneumatically tested in order to reduce hazards associated with shock waves and/or projectile fragments.

The paper also briefly explains alternative methods of testing in lieu of a full hydrostatic or pneumatic test. [1, 2]

Topics: Hazards
Commentary by Dr. Valentin Fuster
2018;():V007T07A016. doi:10.1115/PVP2018-84541.

This study concerns the long-term operation (LTO) of a boiling water reactor (BWR) reactor pressure vessel (RPV) and its internals. The main parts of this study are: survey on susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs).

The ageing of nuclear power plants (NPPs) emphasises the need to anticipate the possible degradation mechanisms. The BWR survey on susceptibility to these uses the OL1/OL2 RPVs and significant internals as a pilot project.

It is not necessary to carry out the TLAAs for all components. Some components were excluded from the TLAAs with a screening process. To do this, it was necessary to determine the component specific load induced stresses, strains and temperature distributions as well as cumulative usage factor (CUF) values.

For the screened-in components, the TLAAs covered all significant time dependent degradation mechanisms. These include (but are not limited to):

• irradiation embrittlement,

• fatigue,

• stress corrosion cracking (SCC), and

• irradiation accelerated SCC (IASCC).

For the components that were screened-in, the potential to brittle, ductile or other degradation was determined. Only some of the most significant cases and results are presented. According to the analysis results, the operational lifetime of the OL1/OL2 RPVs and internals can safely be extended from 40 to 60 years.

Commentary by Dr. Valentin Fuster
2018;():V007T07A017. doi:10.1115/PVP2018-84687.

Attention to be paid to the aging of industrial facilities has been growing in the last ten years, both by public authorities and industrial executives. Many process plants, operating in Europe, have reached or exceeded their project nominal life and the safe management of aging is an urgent question. Failures, due to aged chemical process plants, cause the release of hazardous materials with severe consequences for people and workers. To counteract this phenomenon, plant operators carry out many technical activities, including non-destructive controls on piping and vessels, by adopting sophisticated methods (e.g. Risk Based Inspection RBI).

The European Directive 2012/18/UE (Seveso III) for the control of Major Accident Hazard (MAH) introduced a few requirements for the safe aging of critical equipment, which must be verified during mandatory audits. The aim of this work is to present a synthetic methodology that can be useful for both Seveso auditors and industrial managers for evaluating the adequacy of the measures to control the aging of critical equipment.

To achieve a synthetic assessment of the adequacy of the aging management programs, a compensated index method has been developed, which is a simple and easy-to-use tool. The use of an index method inevitably introduces a degree of uncertainty. However, if it is compared to other qualitative methods, such a tool offers the advantage of a major clarity in the assessment process. This paper discusses a practical application of the method within inspection programs, as required by the art. 27 of Seveso III Directive.

Commentary by Dr. Valentin Fuster
2018;():V007T07A018. doi:10.1115/PVP2018-84831.

The Electric Power Research Institute (EPRI) with Électricité de France (EDF) developed the Integrated Life Cycle Management (ILCM) computer code to provide a standard methodology to support effective decision making for the long-term management of selected nuclear station components. In 2016, a Likelihood of Replacement (LoR) expert elicitation was developed to provide reliability curves for determination of replacement options for components that were not initially included in ILCM. The LoR methodology required expert’s to estimate future replacement probabilities which were then combined with historical failures using Bayesian analysis. Although this methodology was effective, parts of the industry were accustomed to providing a High/Medium/Low (HML) probability categorization for selected periods of operation. This paper presents an approach for calculating Weibull replacement probability curves from HML categorical replacement probability estimates. Additional questions beyond the initial HML categorization were developed. These focused on the timing of category transitions to refine parameter likelihood functions, reduce parameter uncertainty, and offset the significant Weibull parameter uncertainty introduced by using categorical estimates.

Topics: Failure , Probability
Commentary by Dr. Valentin Fuster
2018;():V007T07A019. doi:10.1115/PVP2018-85138.

This paper presents a methodology for identifying blunt flaws in piping using in-service data from ultrasonic inspection tools. The method is applicable to data obtained from predetermined inspection grids, or directly from bracelet or array type inspection tools. The flaw edge and size are identified by calculating the three-dimensional slope vector (i.e., magnitude and direction) of each point in the kriging interpolated wall thickness profile. The transition from a steeper slope to a relatively flat profile is then used by a search algorithm to determine the flaw edge.

The method is applied to the flaw assessment of feeder piping in CANDU nuclear reactors. The results show that in addition to identifying blunt flaws, the developed methodology also provides a convenient way for characterizing the flaw dimensions for structural integrity assessment. The uncertainty in the results is mainly attributed to the signal loss and coverage error associated with the inspection data.

Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Pumps and Valves

2018;():V007T07A020. doi:10.1115/PVP2018-84118.

In a pressurized water reactor the high pressure system vent lines from the pressurizer and reactor are routed to a common header that can be emptied to the refueling water storage tank or a drain tank. During plant testing the valves are operated in the following sequence: the pressurizer isolation valve is opened to pressurize the common header, the pressurizer isolation valve is closed, then the drain tank isolation valve is opened. This sequence of valve operation verifies that the valves open and close properly — opening the pressurizer isolation valve allows steam to enter the common header and is verified by pressure indication via a pressure transducer, and opening the drain tank isolation valve decreases the pressure in the common header and verifies that the pressurizer isolation valve closed properly. During this sequence of valve actuation, the other solenoid valves in the system are subject to transient steam pressures. During one test sequence an isolation valve to the refueling water storage tank indicated that it was not closed for a period of several seconds. Since there is only one pressure transducer in the common header, a systemlevel analysis was performed to obtain a more detailed understanding of the transient pressures in the common header, and how that might affect solenoid valve performance.

Topics: Valves , Solenoids
Commentary by Dr. Valentin Fuster
2018;():V007T07A021. doi:10.1115/PVP2018-84208.

In recent years, the number of imported Chinese pressure pipeline valves has been increasing, and the Administration of Quality Supervision Inspection and Quarantine (AQSIQ) issued Circular No. 151 in 2012 to clarify that the imported pressure piping valves need to have type test by the bodies approved by the type testing administration verified by AQSIQ. This paper makes a comparative study on the differences of the valve test and the test standard commonly used in China and in the foreign countries, as well as on the relevant requirements of the valve manufacturing standards involved in the imported valve type test. Through the comparison on above test standards and type test requirements, the foreign manufacturers will understand the standard differences, inspection requirements and precautions when importing China’s pressure pipeline valve. Combined with imported valve inspection and type test case analysis to help foreign enterprises fully understand our laws and regulations to ensure that when they import Chinese valve, they can meet our requirements to ensure the use security.

Commentary by Dr. Valentin Fuster
2018;():V007T07A022. doi:10.1115/PVP2018-84293.

Wellhead choke valves, frequently used to control oil and gas flow rates from producing wells in the petroleum industry, may experience loss of material due to the impingements of solid particles within the extraction fluids. This phenomenon, called impact erosion, is a serious concern to engineers, as it can result in loss of performance or even failure of the devices. Being capable to identify the valve components which are most vulnerable to impact erosion and provide quantitative estimation of the useful life of the chokes under actual production conditions may open the way to improved design and maintenance. The present contribution focuses on the use of Computational Fluid Dynamics techniques for predicting the impact erosion of a choke valve working in severe slurry conditions. The in-house erosion prediction library E-CODE, developed within the authors’ research group and illustrated in previous works, was employed to model the complex phenomena occurring in the valve. The good agreement between the numerical estimates and the outcomes of a test performed in the Hydraulic Laboratory of Politecnico di Milano indicated that, given the composition of the slurry environment and the operation condition of the valve, it is possible to estimate with reasonable accuracy the erosion characteristics of the device. This will allow gathering useful information for improving the scheduled maintenance of the production systems and the design of heavy-duty equipment.

Topics: Erosion , Slurries , Valves , Damage
Commentary by Dr. Valentin Fuster
2018;():V007T07A023. doi:10.1115/PVP2018-84672.

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an extension of paper PVP2017-66269, “Check Valve Flow and Disk Lift Simulation Using CFD” [1], and utilizes some of the same concepts to characterize flow through piston-lift check valves. The previous example considered a swing check valve involving rotational movement; this example considers a vertical lift piston check valve involving translational movement. Specifically, CFD was used to determine valve flow coefficients (CV) as a function of disk lift position as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The CFX application, which is part of the ANSYS suite of finite element software, was used to determine the flow characteristics. As presented in PVP2017-66269, balancing flow-induced forces on the check element and considering the disk assembly weight, the valve lift behavior can be predicted. Results from the CFX analysis were compared to recent test results of a skirted disk-piston check valve and previous test results of a standard disk-piston check valve. The results showed good agreement in most cases. This validates that flow characteristics across valves with different types of check elements at different disk lift positions can be reliably predicted using CFD analysis. It is important to note that while the test results and CFD analysis showed good agreement, it was vital that actual testing be performed in order to validate the approach. This follows the recommendation outlined in the previous paper.

Commentary by Dr. Valentin Fuster
2018;():V007T07A024. doi:10.1115/PVP2018-84757.

During the pre-operational blowdown testing of the AP1000® Automatic Depressurization System (ADS), it was observed that several ADS Stage 1-3 balanced globe valves did not fully open; however, the valves did sufficiently open to provide adequate ADS flow to meet the ADS System depressurization safety function. Since the Main Control Room did not receive a full-open signal indicating that the ADS valves fully completed the valve stroke, the valves were disassembled to determine the potential cause and scoring was observed on the valve disk and valve body guide surfaces. A technical design review team was formed and determined that the primary cause was unequal thermal expansion between the thin walled valve disk and the thicker valve body resulting in interference during valve stroking. Classical thermal and CFD analyses were used to confirm that, once a normally closed globe valve received its signal to open, there was not sufficient “soak time” for the thicker valve body to reach thermal equilibrium with the thinner valve disk; thus, as the valve disk stroked open as it moved along the guide surfaces, there was not sufficient clearance resulting in scoring between the disk and the guides preventing the disk from stroking fully open. The solution was to maximize the clearance between the disk and body guides to allow for thermal growth during the ADS blowdown event. However, changing the clearances between the body guides and disk may compensate for thermal growth but may also impact the valve’s “balancing” function; therefore. disk piston rings were added to restore the tight clearance needed for “balancing” yet sufficiently provide relief from the effects of thermal growth. A prototype valve was retrofitted, and small scale validation tests were performed using air to challenge the changes. The preliminary performance test results were utilized by system designers to better understand the valve function in the event of an ADS blowdown. Although no full-scale retrofit testing was practical using high temperature saturated steam, as no suitable test facility was available within the plant operational test schedule time frame, the quality of the recovery effort yielded a high degree of confidence that the system retest would be successful. The project came to a successful conclusion upon two successful operational ADS blowdown tests with the retrofits installed.

Topics: Valves , Failure
Commentary by Dr. Valentin Fuster
2018;():V007T07A025. doi:10.1115/PVP2018-85040.

Safety related valves in nuclear power plants are required to be qualified in accordance with the ASME QME-1 standard. This standard describes the requirements and the processes for qualifying active mechanical equipment that are used in nuclear power plants. It does not cover the qualification of electrical components that are addressed using IEEE standards; however, QME-1 recognizes that both mechanical and electrical components must be qualified when they are interfaced as an assembly. Qualifying both mechanical and electrical valve assemblies can be challenging. Considerable amount of judgment is used when developing the plan to qualify any valve with an electric motor actuator. If the wrong steps are taken in planning the tests, the results from the tests may not be useful thus triggering the need to perform additional tests to comply with QME-1 requirements. This paper presents lessons learned in the process of qualifying valve assemblies to meet QME-1 requirements. The lessons include the decision processes associated with planning and executing valve testing, analysis of the valve assemblies for natural frequency determination, and missed opportunities to capture relevant test data during the tests. Finally, the paper will discuss challenges associated with justifying the tests and extending the results of the tests to cover untested valve assemblies.

Topics: Safety , Engines , Motors , Valves
Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Safety, Reliability, and Risk Management

2018;():V007T07A026. doi:10.1115/PVP2018-84144.

During the drilling process, the non-linear contacts between the bit and the bottom hole, the drill string and the borehole wall can cause the bit’s stick-slip vibration, which will shorten the life of the bit and even endanger the safety of the drill string. The severity of stick-slip vibration of a bit can be identified by the rotary speed of a bit, the triaxial accelerations of the drill string, the wellhead torque and other parameters measured by the measuring while drilling (MWD) tools in the downhole and devices on the surface. To evaluate the level of stick-slip vibration, this paper proposes a risk assessment method of sick-slip vibration based on backpropagation neural network (BPNN). According to the time and frequency domain analysis of the data collected from simulation, the feature parameters of the time and frequency domains of signals are extracted, and then the kernel principal component analysis (KPCA) is applied to reduce dimensions. Consequently, the feature vectors can be obtained, which become the input parameters of the BPNN. Based on BPNN algorithm, the stick-slip vibration of the bit is determined, and the classification of stick-slip vibration strength is carried out. The results show that this method can effectively identify the severity of stick-slip vibration of a bit. Therefore, this method is valid to evaluate the stick-slip vibration of a bit, which will help drillers adjust the drilling parameters practically according to the severity of vibration, so as to reduce the risks of stick-slip vibration during drilling and improve the efficiency and safety of drilling operation.

Commentary by Dr. Valentin Fuster
2018;():V007T07A027. doi:10.1115/PVP2018-84362.

Three-dimensional large eddy simulations of high-pressure jets at the same nozzle pressure ratio of 5.60 but issuing from different nozzles are conducted. Four different nozzle geometries, i.e., the circular, elliptic, square, and rectangular nozzles, are used to investigate the effect of the nozzle geometry on the near-field jet flow behavior. A high-resolution, hexahedral, and block-structured grid containing about 31.8 million computational cells is applied. The compressible flow solver, astroFoam, which is developed based on the OpenFOAM C++ library, is used to perform the simulations. The time-averaged near-field shock structures and the mean axial density are compared with the experiment data to validate the fidelity of the LES results, and the reasonable agreement is observed. The results indicate that the remarkable differences exist in the near-field flow structures of the jets. In particular, the circular and square jets correspond to a three-dimensional helical instability mode, while the elliptic and rectangular jets have a two-dimensional lateral instability in their minor axis planes. A subsonic flow zone exists after the Mach disk in the circular and square jets, but is lacking in the elliptic and rectangular jets. The intercepting shocks in the circular jet originate near the nozzle exit, and appear to be circular in cross-section. The intercepting shocks in the square jet originate at the four corners of the nozzle exit at first, and then are observed along the major axis plane some distance downstream of the nozzle exit. However, the formation of the intercepting shock is observed in the major axis planes but is lacking in the minor axis planes for the elliptic and rectangular jets. In addition, the real mass flow rates and discharge coefficients for different jets are computed based on the LES modeling, and their differences are explored.

Commentary by Dr. Valentin Fuster
2018;():V007T07A028. doi:10.1115/PVP2018-84617.

Accidental releases of oil and oil products will cause extensive damage to environment, if timely and effective measures are not available. Predicting the consequences of spilled oil is of significant importance for emergency management. Although software for risk assessment of gas pipelines is very popular, few are available for hazardous liquid pipelines, due to the difference in behaviors of accidental releases of gases and liquids in the same situation. The major differences are that the spread of released oil is mainly affected by the topography of the land and may result in pollution of soil or waterways, while gas pipeline failure may form gas clouds or explosions and merely pose environmental pollution problems. An integrated model was developed in order to analyze the environmental consequences of spills from oil pipelines. The method presented in this paper allowed to predict the flow trajectory of released liquid from a pipeline and other relevant parameters, including the extent of spread of the oil and the proportion of release reaching any important location, such as a river, in any given topography. The methodology has been applied to a release, which occurred in Marshall, Michigan, in 2010. The results obtained are of the correct order of magnitude compared with realistic data. A case-study is presented and discussed to illustrate the features of the methodology. The results confirmed that the proposed model may be considered an important tool within a comprehensive approach to the management of risk related to onshore oil pipelines.

Commentary by Dr. Valentin Fuster
2018;():V007T07A029. doi:10.1115/PVP2018-84832.

The EPRI Preventive Maintenance Basis Database (PMBD) has become a standard in the industry to develop, validate, or examine the impact of custom changes to maintenance strategies for common power plant equipment. The PMBD provides failure modes and an indication of frequency of occurrence. Recent feedback from PMBD users has made it clear that including a “Cost Module” to work with PMBD data would be a useful addition to the PMBD program and allow users to view the cost impacts associated with alternate custom maintenance strategies. This paper presents a methodology for the merging of maintenance information extracted from PMBD with cost estimates and additional expert-provided reliability data to estimate a maintenance cost distribution. Additional expert information includes missing data and PM type: monitoring, wear-rate reducing (e.g. oil change), or life-restoring (e.g. refurbishment). The cost distribution is calculated via Monte Carlo simulation and is dependent on the PM plan currently considered. Value-based optimization of the PM plan is performed through Bayesian optimization of the mean PM cost by varying the various PM frequencies. Bayesian optimization iteratively uses Gaussian Process Regression (GPR) to fit a non-parametric meta-model to a noisy objective function. As a part of GPR it is necessary to fit a covariance function that describes the spatial correlation or smoothness of the objective cost function. The meta-model with the covariance function effectively produces a built-in sensitivity analysis for the optimization as well.

Commentary by Dr. Valentin Fuster
2018;():V007T07A030. doi:10.1115/PVP2018-84833.

Électricité de France (EDF) has developed the Investment Portfolio Optimal Planning (IPOP) software tool [1] to be released with the Integrated Life Cycle Management (ILCM) software tool developed by the Electric Power Research Institute (EPRI) [2]. IPOP is an extremely powerful tool that uses genetic algorithms to provide an optimal strategy for investment in spare components and preventive replacements of multiple components at multiple power plant stations across an entire fleet. A drawback of IPOP is that it requires an extensive amount of user information to run even a single component. In response, Component Optimization Analysis Tools (COATs) was developed to simplify the process of deriving an optimal strategy for purchasing spares and replacements for a single component. This paper describes a two-layer algorithm used in the replacement strategy optimization in COATs. The inner layer consists of a Monte Carlo simulation that estimates the Expected Net Present Value (ENPV) of a given replacement strategy. A strategy consists of: the age of a component at which it needs to be replaced, the age of a component at which a spare should be purchased, years left in the plant at which to skip a scheduled replacement, and the end of life at which the scheduled replacement is skipped; and the years left in the plant at which no more spares are purchased. The Monte Carlo analysis uses these four strategy inputs with component costs, acquisition times, and reliability curves with plant downtime costs to calculate an ENPV for that strategy. The outer layer of the algorithm is an optimization layer that can use either Bayesian optimization or genetic algorithms to maximize the ENPV. These optimization algorithms are routinely available in various software packages and effectively treat the ENPV Monte Carlo as a black box function. An efficiency comparison is given between the two optimization algorithms to demonstrate under which conditions each algorithm out performs the other.

Topics: Optimization
Commentary by Dr. Valentin Fuster
2018;():V007T07A031. doi:10.1115/PVP2018-84986.

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage.

Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

Commentary by Dr. Valentin Fuster
2018;():V007T07A032. doi:10.1115/PVP2018-85113.

Natural Gas is becoming an important energy source option and the capacity of the world to produce it is surging. Natural gas is usually liquefied for shipping and storage. Fire and explosion are among the most dangerous accidents in facilities at LNG Depot; especially pool fire is the most frequent incidents. At the same time the chain of accidents may lead to extremely severe consequences. In order to avoid such calamity a detail study on accident inversion technology is required to save human lives and prohibit the destruction of LNG Depot. In this thesis a topological network based fire accident inversion method for LNG tank fire accident is proposed. Firstly, analyze the LNG depot with the STAMP/STPA method. Then, the topology model of LNG tank fire inversion is established, and the optimal estimator of the shortest path is proposed according to the weighted edge topological network structure, based on which the fire location can be determined. Case study is applied to a LNG Depot. The results show that the position of the fire source calculated by the proposed method is the same as that of the simulated accident by FDS, which proves the feasibility of the method and provides a basis for reducing the fire losses and preventing accidents of LNG.

Commentary by Dr. Valentin Fuster

Operations, Applications, and Components: Storage and Transportation of Radioactive Materials

2018;():V007T07A033. doi:10.1115/PVP2018-84089.

The containment systems of transport and storage casks for spent fuel and high level radioactive waste usually include bolted lids with metallic or elastomeric seals. The mechanical and thermal loadings associated with the routine, normal and accident conditions of transport can have a significant effect on the leak tightness of such containment system.

Scaled cask models are often used for providing the required mechanical and thermal tests series. Leak tests have been conducted on those models.

It is also common practice to use scaled component tests to investigate the influence of deformations or displacements of the lids and the seals on the standard leakage rate as well as to study the temperature and time depending alteration of the seals.

In this paper questions of the transferability of scaled test results to the full size design of the containment system will be discussed.

Topics: Safety , Leakage , Containment
Commentary by Dr. Valentin Fuster
2018;():V007T07A034. doi:10.1115/PVP2018-84260.

KORAD-B/II shipping packages are used to transport C4 concrete packages that are temporarily stored at the HANUL nuclear power plant. These packages must therefore satisfy the requirements prescribed in the Korea Nuclear Safety Security Commission Act 2014-50, the IAEA Safety Standards No. SSR-6, and US 10 CFR Part 71. These regulatory guidelines classify a KORAD-B/II shipping package as a Type B package, and state that this type of package must be able to withstand a temperature of 800 °C for a period of 30 min. It is desirable to conduct a test using a full-scale model of a shipping package when performing tests to evaluate its integrity. However, it is costly to perform a test using a full-scale model. Therefore, to evaluate the thermal integrity of a KORAD-B/II shipping package, thermal tests were conducted using a slice model. For comparison purposes, a thermal test was also carried out using a half-scale model. In the first thermal test using a slice model, the maximum surface temperature of the cask body was higher than the permitted maximum temperature limits owing to incomplete combustion. In the second thermal test using a slice model and in the thermal test using a half-scale model, the maximum temperature of the cask body was lower than the permitted maximum temperature limit. Therefore, the thermal integrity of the KORAD-B/II shipping package could be considered to be maintained. The temperature results from the thermal test using a slice model were higher than those of the thermal test using a half-scale model. Therefore, the effect of flame on a single-layer shipping package without neutron shielding, such as the KORAD-B/II shipping package, seems to be affected by the reduction in the time rather than the size reduction.

Commentary by Dr. Valentin Fuster
2018;():V007T07A035. doi:10.1115/PVP2018-84429.

Impact limiters are attached near to the top and the bottom of a spent fuel containment body as shock absorbers to maintain the structural integrity of the containment not only in normal condition but also in hypothetical accident condition of 9m falling. Ellipsoidal-head-like metallic impact limiters are used for a spent fuel containment which is designed to carry 26 spent fuel assemblies. Main geometry dimensions of the limiters, such as diameter, thickness of the shell, length of straight flange and fillet radius, are design variables. The LS-DYNA software is applied to simulate the acceleration of containment in a falling accident. Sensitivity analyses of the variables on acceleration of spent fuel containment in the 9m falling accident are carried out. By response surface method, the best geometry dimensions which minimize the acceleration of the containment in falling accident are achieved. As showed in results, ellipsoidal head shaped metallic impact limiters work very well in the 9m falling accident. They could significantly decrease load factor and provide more safety margin.

Commentary by Dr. Valentin Fuster
2018;():V007T07A036. doi:10.1115/PVP2018-84584.

The Bundesanstalt für Materialforschung und –prüfung (BAM) runs an investigation program on the long-term behavior of multi-component metal seals. Such seals are used in a wide area of applications including transport and storage casks for spent nuclear fuel and high level radioactive waste. The seal function is mainly based on the compression of the inner helical spring, which generates the necessary seal force to keep the sealing surfaces in close contact. This in turn leads to a plastic deformation of the outer jacket of the seal, comprised of highly ductile aluminum or silver that adapts to the sealing surfaces of cask body and bolted lid, thus providing high level leak tightness. In Germany, those casks are licensed for interim storage periods of up to 40 years or more if extended interim storage would become necessary before a final repository is available. Thus, the sealing performance has to be evaluated, including factors like elevated temperature due to decay heat or mechanical loads due to transport under normal as well as accident conditions. Long-term investigations at BAM have been running over the last nine years to identify and evaluate the seal performance by measuring the remaining seal force, the useable resilience and the leakage rate after various time intervals at temperatures ranging from room temperature up to 150 °C. It was found that the seal force and useable resilience decrease with time and temperature, caused by creep deformation of the outer jacket. In order to obtain an analytical description for the seal behavior and to achieve more information on the material behavior under application conditions a comprehensive investigation program with focus on aluminum as outer jacket material was launched. The program includes material investigations such as compression and tension creep tests with representative basic materials. An additional test setup allows for the continuous measurement of the remaining seal force at temperatures of up to 150 °C. Furthermore, seal segments are compressed and stored in heating chambers, thus producing segments at different stages of the aging process. The segments are investigated regarding the development of the contact area width, jacket thickness and microstructural changes. This data will be used to develop material models and an analytical description of the time and temperature dependent long-term sealing behavior. This paper explains the current status of gained test results and modelling approaches and closes with an outlook to the future project plans.

Commentary by Dr. Valentin Fuster
2018;():V007T07A037. doi:10.1115/PVP2018-84614.

Among other mechanical tests the 1 meter drop onto a steel puncture bar shall be considered for accident safe packages for the transport of radioactive material. According with the IAEA regulations “the bar shall be of solid mild steel of circular section, 15.0 ± 0.5 cm in diameter and 20 cm long, unless a longer bar would cause greater damage ...”. The most damaging puncture bar length can be estimated by iterative processes in numerical simulations. On the one hand, a sufficient puncture bar length has to guarantee that shock absorbers or other attachments do not prevent or reduce the local load application to the package, on the other hand, a longer and thus less stiff bar causes a smaller maximum contact force. The contrary influence of increasing puncture bar length and increasing effective drop height shall be taken into account if a shock absorber is directly placed in the target area. The paper presents a numerical approach to identify the bar length that causes maximum damage to the package. Using the example of two typical package masses the sensitivity of contact forces and puncture bar deformations to the initial length are calculated and assessed with regard to the international IAEA package safety requirements.

Commentary by Dr. Valentin Fuster
2018;():V007T07A038. doi:10.1115/PVP2018-84631.

Elastomers show a high versatility which makes them ideal materials for sealing applications in various fields. Especially under changing application conditions the high recovery potential of this class of material is beneficial to compensate temperature or pressure fluctuation, and geometrical changes resulting from mechanical loads in e.g. accident conditions. Out of these reasons elastomers are also used in containers for low and intermediate level radioactive waste and for spent fuel transportation casks. In casks designed for low and intermediate level waste elastomer seals can act as primary seal responsible for the containment function whereas in spent fuel storage and transportation casks (dual purpose casks (DPC)) elastomer seals are used as auxiliary seals to allow leakage rate measurements of metal barrier seals. An inherent prerequisite for this kind of application is the long time-scale of operation without or with limited possibility of seal replacement. In Germany an interim storage license for DPC’s is typically issued for 40 years, a timeframe which might increase in the future due to challenges of the final repository siting procedure. For low and intermediate level waste, also long time periods are required before final disposal can be achieved. Therefore, the performance of elastomer seals over extended time periods is, as for other applications, of high importance.

A typical approach to ensure long-term functionality is to perform accelerated aging tests to calculate an estimated lifetime by assuming e.g. Arrhenius like equations for the timetemperature relationship. This approach requires a suitable end of life criterion considering the application of interest. This often can represent a challenge on its own.

As BAM is involved in most of the cask licensing procedures and especially responsible for the evaluation of cask-related long-term safety issues we initiated several test programs for investigating the behavior of elastomer seals. Experiments concerning the low temperature performance down to −40 °C and the influence of gamma irradiation have been started first. Currently the thermal aging behavior of elastomer seals, which is the topic of this contribution, is examined.

For our aging investigations we use a broad approach to first determine the property changes in different elastomer materials due to thermo-oxidative aging at elevated temperatures and secondly, we test how the typical methods of lifetime extrapolation can be applied to these results. This approach enables us to detect and exclude undesired side effects which very often influence lifetime estimations. In this contribution, our recent results are extended. The results show that lifetime estimation based on single material properties can be misleading and therefore a combination of several methods is recommended.

Topics: Elastomers
Commentary by Dr. Valentin Fuster
2018;():V007T07A039. doi:10.1115/PVP2018-84714.

Accident safe packages for the transport of spent nuclear fuel and high-level waste shall fulfil international IAEA safety requirements. Compliance is shown by consecutive mechanical and thermal testing. Additional numerical analysis are usually part of the safety evaluation. For damage protection some package designs are equipped with wood filled impact limiters encapsulated by steel sheets. The safety of these packages is established in compliance with IAEA regulations. Cumulative mechanical and fire tests are conducted to achieve safety standards and to prevent loss of containment. Mechanical reliability is proven by drop tests. Drop testing might cause significant damage of the impact limiter steel sheets and might enable sufficient oxygen supply to the impact limiter during the fire test to ignite the wood filling. The boundary conditions of the fire test are precisely described in the IAEA regulatory. During the test the impact limiter will be subjected to a 30 minute enduring fire phase. Subsequent to the fire phase any burning of the specimen has to extinguish naturally and no artificial cooling is allowed. At BAM a large-scale fire test with a real size impact limiter and a wood volume of about 3m3 was conducted to investigate the burning behaviour of wood filled impact limiters in steel sheet encapsulation. The impact limiter was equipped with extensive temperature monitoring equipment. Until today burning of such impact limiters is not sufficiently considered in transport package design and more investigation is necessary to explore the consequences of the impacting fire. The objective of the large scale test was to find out whether a self-sustaining smouldering or even a flaming fire inside the impact limiter was initiated and what impact on the cask is resulting. The amount of energy, transferred from the impact limiter into the cask is of particular importance for the safety of heavy weight packages. With the intention of heat flux quantification a new approach was made and a test bench was designed.

Commentary by Dr. Valentin Fuster
2018;():V007T07A040. doi:10.1115/PVP2018-84763.

An ENUN 32P cask supplied by Equipos Nucleares S.A. (ENSA) was transported 9,600 miles by road, sea, and rail in 2017 in order to collect shock and vibration data on the cask system and surrogate spent fuel assemblies within the cask.

The task of examining 101,857 ASCII data files — 6.002 terabytes of data (this includes binary and ASCII files) — has begun. Some results of preliminary analyses are presented in this paper.

A total of seventy-seven accelerometers and strain gauges were attached by Sandia National Laboratories (SNL) to three surrogate spent fuel assemblies, the cask basket, the cask body, the transport cradle, and the transport platforms. The assemblies were provided by SNL, Empresa Nacional de Residuos Radiactivos, S.A. (ENRESA), and a collaboration of Korean institutions. The cask system was first subjected to cask handling operations at the ENSA facility. The cask was then transported by heavy-haul truck in northern Spain and shipped from Spain to Belgium and subsequently to Baltimore on two roll-on/roll-off ships. From Baltimore, the cask was transported by rail using a 12-axle railcar to the American Association of Railroads’ Transportation Technology Center, Inc. (TTCI) near Pueblo, Colorado where a series of special rail tests were performed. Data were continuously collected during this entire sequence of multi-modal transportation events. (We did not collect data on the transfer between modes of transportation.)

Of particular interest — indeed the original motivation for these tests — are the strains measured on the zirconium-alloy tubes in the assemblies. The strains for each of the transport modes are compared to the yield strength of irradiated Zircaloy to illustrate the margin against rod failure during normal conditions of transport.

The accelerometer data provides essential comparisons of the accelerations on the different components of the cask system exhibiting both amplification and attenuation of the accelerations at the transport platforms through the cradle and cask and up to the interior of the cask. These data are essential for modeling cask systems.

This paper concentrates on analyses of the testing of the cask on a 12-axle railcar at TTCI.

Commentary by Dr. Valentin Fuster
2018;():V007T07A041. doi:10.1115/PVP2018-84844.

In this work, a geometrically-accurate two-dimensional (2D) computational fluid dynamic (CFD) model of a used nuclear fuel cask, that can contain up to 32 pressurized water reactor (PWR) used nuclear fuel (UNF) assemblies, is constructed. This model is similar to the TN-32 cask employed in the ongoing high-burnup (HBU) Spent Fuel Data Project lead by the Electric Power Research Institute (EPRI). This model is used to predict the peak cladding temperature under vacuum drying conditions. Due to the symmetry of the cask, only one-eighth of the cross-section is modeled. Steady-state simulations that include the temperature-jump boundary conditions at the gas-solid interfaces are performed for different heat generation rates in the fuel regions and a range of dry helium pressures, from ∼105 to 100 Pa. These simulations include conduction within solid-gas regions and surface-to-surface radiation across all gas regions. The peak cladding temperatures are reported for various heat generation rates and rarefaction conditions, along with the maximum allowable heat generation that brings the cladding temperatures to the radial hydride formation limit. The results showed that the decrease of helium pressure significantly increased the temperature of the cladding material compared to the atmospheric pressure condition.

Commentary by Dr. Valentin Fuster
2018;():V007T07A042. doi:10.1115/PVP2018-84848.

Vacuum drying of nuclear fuel canisters may cause the temperature of fuel assemblies to considerably increase due to the effect of gas rarefaction at low pressures. This effect may induce a temperature-jump at the gas-solid interfaces. It is important to predict the temperature-jump at these interfaces to accurately estimate the maximum temperature of the fuel assemblies during vacuum drying.

The objective of this work is to setup a concentric cylinders experimental apparatus that can acquire data to benchmark rarefied gas heat transfer simulations, and determine the temperature-jump coefficient at the interface between stainless steel surface and helium gas. The temperature-jump is determined by measuring the temperature difference and heat flux across a 2-mm gap between the concentric cylinders that contains rarefied helium and compare the results to analytical calculations in the slip rarefaction regime.

Commentary by Dr. Valentin Fuster

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