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This paper presents the study of the impact caused by a liquid Cargo on a railway infrastructure. The dynamic behavior of a tank car corresponds to a multibody dynamic system with several degrees of freedom. This study’s data were obtained from a scale experimental fixture consisting of a track and a railcar with a tank. The track was instrumented with strain gauges and the railcar with accelerometers. The data showed non-periodic and periodic terms; therefore, the results were analyzed with the Empirical Mode Decomposition method (EMD).
It was found that the EMD identified the signal components that were related to the sloshing. These components represent the mode shapes of the original signal.
The location of the sloshing in the track was found applying spectrograms to the accelerometer data. This paper’s experimental outputs suggest that the sloshing effect is detectable at the track and in the vehicle dynamics.
A simplified methodology is proposed to estimate the dynamic pressures developed within partially filled cylindrical vertical tanks when subjected to earthquake-related horizontal accelerations. The total pressure at the bottom of the tank is calculated as the superposition of vertical and horizontal pressures. While the magnitude of the vertical pressure depends on the free surface height of the liquid, the horizontal pressure depends on the magnitude of the horizontal acceleration and on the diameter of the tank. The liquid free surface oscillation angle is simulated based upon the principles of the simple pendulum analogy for sloshing. The length of the pendulum, however, is set on the basis of a methodology to calculate the free sloshing frequency of partially filled containers. Such a methodology is experimentally verified in this work. The outputs of the model for full scale situations, suggest that the lateral perturbation - sloshing phenomenon (earthquake effect) can generate an increase in the total pressure of 56% above the no lateral perturbation situation, further suggesting that such an overpressure should be taken into account when designing tanks that could be potentially subjected to earthquake-related perturbations.
Spent nuclear fuel which is generated in the operation of nuclear reactors needs to be safely managed following its removal from the reactor core. On-site power reactor storage pools were designed on the assumption that after a short period of time spent nuclear fuel would be removed for reprocessing and disposal or further storage elsewhere. The amount of highly radioactive spent fuel that needs to be stored over longer periods of time is growing and additional storage capacity is required. One of the widely used options for additional storage capacity is the use of casks for dry storage of spent fuel. Among various existing dry storage concepts, several Member States are utilizing a concept of dual purpose casks (DPCs). This publication provides practical advice on the structure and contents of a DPC integrated safety case with reference to existing IAEA requirements relevant to the licensing and use of transport and storage casks for spent fuel.
This publication summarizes the work carried out during an IAEA coordinated research project (CRP) on safe and reliabe management of spent nuclear fuel. This work contributes to the overall goal of demonstrating the performance of spent nuclear fuel and related storage systems components over long durations, and facilitates the transfer of this knowledge to Member States. The technical areas addressed by the CRP participants were related to potential degradation mechanisms in metal casks and concrete overpacks, such as stress corrosion cracking; long term integrity and performance of the fuel cladding; thermo-mechanical behaviour of the metal seals; and long term gamma and neutron shielding capability. The participants also considered past and ongoing demonstration programmes. For each technical topic addressed the main conclusions have been drawn, including information on the development of specific monitoring and inspection techniques as well as future opportunities for closing relevant data gaps. A major achievement is also the establishment of a worldwide network of experts working on current research projects to demonstrate the long term performance of spent fuel in dry storage systems.
Braking-in-a-turn maneuvers represent a critical operational condition for any vehicle, due to the associated longitudinal and lateral perturbations to which it is subjected, which maximize the load transfer among the different wheels, and result in vehicle´s poor lateral stability and deficient braking performance.
In this paper, a suspended vehicle supporting a partially filled 10 litter-capacity container, is set on a tilt table at oblique angles, in order to simulate a braking-in-a-turn maneuver. The measurements are assessed in the time and frequency domains, on the basis of the lateral load transfer ratio and the infrastructure fatigue damage. The outputs from the experiment show that the Minimum fill level (one-quarter), generates the larger lateral load transfer (0.45). Such fill level also causes the greatest ratios for the alternate stress over the mean stress on the infrastructure. The spectral analysis reveals the dominance of one of the sloshing frequencies during such combined perturbation condition.
The magnitude of the steering forces at the wheel-track Interface depends on different properties and operational conditions linked to the vehicle and to the track, with the bogie´s yaw stiffness/resistance and the friction at the centre plate being recognized as the most influential vehicle factors. In this respect, the negative consequences of high values for yaw resistance have been recognized in terms of the railway accelerated deterioration and on the possibility for derailment. While some theoretical models have been proposed to simulate the effects of the centre plate friction on the railway damage, and experimental measurements have been reported of the turning resistance, no experimental data is available regarding the effect of the friction at the centre plate on the wheel-track forces. In this paper the conceptual design of a testing rig is presented for assessing such forces as a function of the center plate friction. The testing rig quantifies the effects of the friction forces developed at the centre plate, in terms of the loss of potential energy when a scaled-down vehicle travels downwards and tries to return upwards in a “U turn” maneuver. A simplified mathematical model is also proposed in this paper, whose Outputs suggest a significant effect of the dry friction on the magnitude of the steering forces.
Turning maneuvers performed by railway cars, imply the development of steering forces at the wheel-track interface, whose magnitude depends on a set of properties and operating conditions related to the vehicle and to the infrastructure, including track´s turning radius and vehicle´s yaw resistance.
Yaw resistance integrates two components. On the one hand, there is the yaw stiffness, as a function of the different vehicle suspension components. On the other hand, there is the dry friction at the centre plate. Such yaw resistance of the car´s bogies, has a two-contradictory effect on railway performance, as a flexible bogie reduces the level of the steering forces, but at the same time, it increases the probability of having hunting instability. A variable yaw resistance, with high values at straight track segments and low values at curved tracks, seems to be an interesting design. In this paper, a variable friction Center plate is proposed, aiming at maximizing the yaw resistance on straight track segments, and minimizing such resistance at curved tracks. The conceptual design of this device is described, together with its ability to reduce the yaw torque. Benefits of this device, regarding the transport energy consumption and the magnitude of the steering forces, are estimated on the order of 1 to 10, when comparing the proposed design with the standard center plate design.
For the long-term storage of spent nuclear fuel and other high-Level radioactive waste, dual purpose casks for the transportation and storage are widely used. Usually, these casks consist of a thick-walled monolithic cask body and a bolted double barrier lid System equipped with metal seals (consisting of an inner helical spring and two outer metal layers with a total cross-section diameter between 5 and 10 mm) to ensure the long-term safe confinement of the radioactive inventory.
Based on analytical and experimental studies, such metallic Systems have been qualified of storage periods of up to four decades so far as long as proper manufacturing and assembling conditions are met. More than 20 years of Operation experience with a permanently increasing number of casks has shown full compliance with the expectations.
In the meantime many countries have to face a significant delay of establishing a high-level radioactive waste repository what leads to Need for extending interim storage periods for probably 60, 80 or 100 years.
For that reason the long-term performance of metal seals for such time periods is of specific internst to demonstrate their sufficient safety function and specific investigations have already been launched, e.g. by BAM, to gain more experimental data and to develop validated models to extrapolate the seal performance to longer periods of time and or requested temperature levels.
Spent fuel storage periods well beyond those originally foreseen are a reality. This publication offers several ideas and approaches that may be considered to address the increasingly longer storage times. The aim is to raise awareness, encourage dialogue and provide ideas on how to manage spent fuel. Key messages include the following:
- Delays in reprocessing or disposal could result in spent fuel being stored for 100 years or longer. Safe, secure and effective storage of spent fuel manages fuel degradation while preserving future fuel cycle options.
- Ageing management programmes apply engineering, operations and maintenance actions to ensure safety is maintained during storage, future handling and transport.
- Site selection and facility and equipment design can significantly reduce the risks and costs of spent fuel storage over longer periods.
- Spent fuel storage configurations can be selected to accommodate uncertain storage periods, to facilitate ageing management and to provide flexibility needed to accommodate the uncertainty of future end points, such as reprocessing or disposal.
- By considering multiple licence renewals, regulatory frameworks can be designed to ensure safe storage until an acceptable end point is achieved.
- Safety can be assured by maintaining shielding, containment, decay heat removal and criticality control. Navigating the complexity of societal beliefs and values, as well as political systems, has proven to be a greater challenge for the management of spent fuel than maintaining its safety and security or addressing the technical and economic aspects.
- Sustainable spent fuel management requires policies and strategies to provide a clear, consistent and stable direction because they drive the need for spent fuel storage as well as the available options and timing for achieving an acceptable end point. Unless States address spent fuel reprocessing and disposal on a sufficient scale to accommodate their spent fuel discharges, then storage for longer and longer periods becomes the de facto end point — which is not considered to be consistent with the responsibility to protect human health and the environment.
An effective, periodic licence renewal process can ensure effective ageing management and strong institutional control. Hence, spent fuel can be safely and securely stored for as long as it may be necessary until transport for reprocessing or disposal. However, the risks and costs of storing the growing inventory of spent fuel will continue to increase; and in the absence of an end point, it will eventually become a significant societal burden.