Concrete Containment Structures Research Articles

Non-linear response of reinforced concrete containment structure under blast loading

The paper demonstrates the effect of an external explosion on the outer reinforced concrete shell of a typical nuclear containment structure. The analysis has been made using appropriate non-linear material models till the ultimate stages. The generation and the propagation of blast wave and its effect on a cylindrical structure are discussed. Parametric studies have also been performed for surface detonations of different amount of blast charges at a distance of 100 m from a nuclear containment shell. Critical distances have been evaluated for different amount of blast charges for nuclear containment shell.

Numerical models for prestressing tendons in containment structures

Two modified stress–strain relations for bonded and unbonded internal tendons are proposed. The proposed relations can simulate the post-cracking behavior and tension stiffening effect in prestressed concrete containment structures. In the case of the bonded tendon, tensile forces between adjacent cracks are transmitted from a bonded tendon to concrete by bond forces. Therefore, the constitutive law of a bonded tendon stiffened by grout needs to be determined from the bond–slip relationship. On the other hand, a stress increase beyond the effective prestress in an unbonded tendon is not section-dependent but member-dependent. It means that the tendon stress unequivocally represents a uniform distribution along the length when the friction loss is excluded. Thus, using a strain reduction factor, the modified stress–strain curve of an unbonded tendon is derived by successive iterations. In advance, the prediction of cracking behavior and ultimate resisting capacity of prestressed concrete containment structures using the introduced numerical models are succeeded, and the need for the consideration of many influencing factors such as the tension stiffening effect, plastic hinge length and modification of stress–strain relation of tendon is emphasized. Finally, the developed numerical models are applied to prestressed concrete containment structures to verify the efficiency and applicability in simulating the structural behavior with bonded and/or unbonded tendons.

05/02662 Penetration resistance of reinforced concrete containment structures

05/02662 Penetration resistance of reinforced concrete containment structures

Penetration resistance of reinforced concrete containment structures

Containment structures not only provide a leak tight barrier, but also play a role in ensuring that the structures can withstand the impact load from projectile impacts or internal plant accidents. In assessing the containment structures of nuclear power plants, predicting the characteristics of impact resistance in relation to design and safety considerations is relevant. This investigation proposes a simple but effective method of performing numerical analysis on perforation resistance of reinforced concrete containment structures. In this work, normal and oblique impacting is considered to examine the residual velocity and impact phenomena of an ogive-nose steel projectile with various impact velocities against a reinforced concrete slab. Additionally, a phase diagram is devised to describe the ballistic terminal phenomena of projectile and target. This model could assess the resistance to penetration to results in the optimum design of the containment structures in nuclear power plants.

Creep prediction of concrete for reactor containment structures

Since the biggest time-dependent prestress loss of a prestressed concrete nuclear reactor containment structure is due to the creep of concrete, creep is one of the most important structural factors to be considered for the safety of a reactor containment structure during design, construction and maintenance. Creep in concrete has also recently been considered in evaluation of the crack resistance of concrete at an early-age in the durability examination of massive concrete structures like reactor containment structures. Existing empirical formulas on creep prediction show errors in their predictions due to simplified consideration of mixture proportions, and they also show large discrepancy among their predictions. In addition, they do not consider early-age behaviors of concrete and thus are mainly for the prediction of long-term creep at hardened concrete. In this paper, the creep characteristics of the reactor's both early-age and hardened reactor concrete made of type V cement are examined by carrying out both early-age and long-term creep tests. Then, the creep of the reactor concrete is predicted by using major creep-prediction equations of the AASHTO LRFD design specification, the Japanese standard specification for concrete structure, the ACI Committee 209 and the CEB/FIP model code and the Bazant and Panula's model, and the predicted results are compared with the test results. From the comparison, the applicability of the creep-prediction equations for the concrete of a reactor containment structure at both early-age and hardened stages is discussed.

Improvement in the design of prestressed concrete containment structures

Improvement in the design of prestressed concrete containment structures

Containment Inservice Inspection, Repair, Replacement, and Testing

Section XI, Subsections IWE and IWL, of the ASME Boiler and Pressure Vessel Code provide requirements to assure that the critical areas of steel and concrete primary containment structures are inspected to detect degradation that could compromise structural and leak-tight integrity. They also specify requirements for preservice examination, acceptance standards, repairs, replacements, and pressure testing. Each nuclear utility in the United States is required to develop and implement a containment inservice inspection program by September 9, 2001, 5 yr after the initial approval in Title 10, Part 50, of the U.S. Code of Federal Regulations. This paper discusses the Code requirements and also provides an insight into the development process and philosophy for containment inservice inspection. [S0094-9930(00)01903-X]

Inspection of nuclear power plant containment structures

Safety-related nuclear power plant (NPP) structures are designed to withstand loadings from a number of low-probability external and interval events, such as earthquakes, tornadoes, and loss-of-coolant accidents. Loadings incurred during normal plant operation, therefore, generally are not significant enough to cause appreciable degradation. However, these structures are susceptible to aging by various processes depending on the operating environment and service conditions. The effects of these processes may accumulate within these structures over time to cause failure under design conditions, or lead to repair. Steel and concrete containment structures in nuclear power plants are described and their potential degradation factors identified. Reported incidences of containment degradation are summarized. Current regulatory in-service inspection requirements are reviewed. Nondestructive examination techniques commonly used to inspect NPP steel and concrete structures to identify and quantify the amount of damage present are described, and their capabilities and limitations identified. Finally, areas where nondestructive evaluation techniques require development (i.e. inaccessible portions of the containment pressure boundary, and thick heavily reinforced concrete sections) are identified and prior research addressing these needed developments summarized.

Reliability assessment and design load factors for reinforced concrete containment structures

Abstract The current ASME code for reinforced concrete containment structures is not based on probability concepts. This paper develops reliability assessment and probability-based design load factors for reinforced concrete containment structures. The purpose of constructing reinforced concrete containment structures is to protect against radioactive release, and so the use of a serviceability limit state related to cracking that can cause the emission of radioactive materials is suggested as a critical limit state for reinforced concrete containment structures. Load factors for the design of reinforced concrete containment structures are proposed. The proposed load factors are also examined in terms of a set of code performance objectives and consistency in limit state probability.

Serviceability design load factors and reliability assessments for reinforced concrete containment structures

A reinforced concrete nuclear power plant containment structure is subjected to various random static and stochastic loads during its lifetime. Since these loads involve inherent randomness and other uncertainties, an appropriate probabilistic model for each load must be established in order to perform reliability analysis. The current ASME code for reinforced concrete containment structures are not based on probability concepts. The stochastic nature of natural hazard or accidental loads and the variations of material properties require a probabilistic approach for a rational assessment of structural safety and performance. The paper develops probability-based load factors for the limit state design of reinforced concrete containment structures. The purpose of constructing reinforced concrete containment structure is to protect against radioactive release, and so the use of a serviceability limit state against crack failure that can cause the emission of radioactive materials is suggested as a critical limit state for reinforced concrete containment structures. Load factors for the design of reinforced concrete containment structures are proposed and carried out the reliability assessments.

Reliability-based assessment of integrity of bonded prestressed concrete containment structures

The main function of a nuclear containment structure is to prevent the leakage of radioactive materials from the reactor in the event of a serious failure in the process system. To maintain a high level of leak integrity, prestressed concrete is widely utilized in containment construction. In bonded prestressing systems, excessive prestressing losses caused by unexpected material deformations and degradation of tendons could result in the loss of leak integrity under an accident. To safeguard against this, the Canadian Standard, CSA N287.7 (1995), recommends periodic inspection and evaluation of prestressing systems of CANDU containments. As bonded tendons are not amenable to direct inspection, the evaluation is based on the testing of a set of beams with features identical to the containment. The paper presents a quantitative reliability-based approach to evaluate the containment integrity in terms of the condition of bonded prestressing systems. The proposed approach utilizes the results of lift-off, destructive, and flexural tests to update the probability distribution of prestressing force, and to revise the calculated reliability against through-wall cracking of containment elements. An acceptable criterion for the results of beam tests is established on the basis of maintaining adequate reliability throughout the service life of the containment.

Secondary Containment: Choosing the Right Coating

This article discusses the placement of treatment tanks within concrete vaults or walled structures in order to provide secondary containment in the event of a leak. Some of the regulatory requirements for concrete containment structures are briefly discussed. Although there are many types of coatings and fillers to provide an impervious surface to a structure, this article limits itself to a discussion of liquid‐applied coating systems and uses an example of an effective phenolic‐novolac epoxy medium film coating system. The article provides a table outlining chemical effects on concrete secondary containment units.

Reliability of Reinforced-Concrete Cylindrical Shells

Reinforced concrete shells are structurally complex and closed-form models for their various limit states of serviceability and strength either are not available or may be based on approximations and idealizations of behavior. Nonlinear finite-element techniques have made it possible to account for the complexities of reinforced concrete behavior in the inelastic range, to identify these limit states more accurately, and to assess the safety and reliability of concrete shells. Traditional reliability analysis methods are more convenient to apply when closed-form mechanical models of limit states are available. In the absence of such models, the reliability analysis can be performed by response surface methods that approximate the limit states by polynomial surfaces obtained through finite-element analyses of the system at a set of predetermined experimental points. This paper presents the reliability analysis of a reinforced concrete containment structure by the response surface method. Axisymmetric nonlinear finite-element analyses were performed to define the limit surfaces and importance sampling was used for the calculation of limit state probabilities.

Numerical studies of impact on reinforced concrete beam of hard missile

The safety design of concrete containment structures in nuclear power stations has thus far covered only accidents due to internal pressure, temperature loading and earthquake loading. Recently, designers and researchers have become interested in the important effects of the impact load of a projectile on nuclear power stations. This paper develops an FEM model for analyzing the collision of a hard missile against reinforced concrete structures and compares the results with impact tests conducted at our institute.

The Long-Term Properties of Concrete Used in Prestressed Concrete Pressure Vessels

Data are presented on the late-life properties of concretes used in prestressed concrete pressure vessels (PCPV) and containment structures. The effects of ageing under simulated PCPV conditions are discussed.

Testing Reinforced Concrete Structures for Watertightnes

The American Concrete Institute Committee 350, Environmental Engineering Concrete Structures, recognized a need for standardized criteria as well as a standardized method of testing reinforced concrete structures for watertightness. AWWA's Committee 400, Waterproofing, was also interested in documenting the state‐of‐the‐art of watertightness testing and criteria for reinforced concrete tanks. A joint subcommittee was subsequently formed to prepare a report containing recommendations on watertightness for reinforced concrete containment structures. This article presents the findings of the joint report.

Design Considerations and Criteria for Pesticide and Liquid Fertilizer Handling and Storage Facilities with Modular Concrete Containment Structures

Protection of groundwater and surface-water resources from point-source pesticide and liquid fertilizer leaks and spills during storage and handling requires watertight containment facility design. Functional requirements of mixing, loading, storage, and containment are reviewed. Design specifications for watertight concrete criteria are documented.

Reliability-based design code calibration for concrete containment structures

The safety of concrete nuclear containment structures should be secured against all kinds of loading due to various natural disasters or extraordinary accidental loads. Furthermore, the current design criteria or load combination criteria of concrete containment structures in Korea are not based on the probability-based design concept but rely on the conventional design concept. In this study, a load combination criteria for design and a probability-based reliability analysis were proposed on the basis of a FEM-based random vibration analysis. The limit state model defined for the study is a serviceability limit state of the crack failure that causes the emission of radioactive materials, and the results are compared with the case of strength limit state. More accurate reliability analyses under various dynamic loads such as earthquake loads were made possible by incorporating the FEM and random vibration theory, which is different from the conventional reliability analysis method. The uncertainties in loads and resistance available in Korea and the references were adapted to the situation of Korea, and especially in case of earthquake, the design earthquake was assessed based on the available data for the probabilistic description of earthquake ground acceleration in the Korea peninsula. The SAP V-2 is used for a three-dimensional finite element analysis of concrete containment structure, and the reliability analysis is carried out by modifying HRAS reliability analysis program for this study. In this study, the load factors for the design of concrete containment structures in Korea are proposed by considering appropriate load combination criteria for design, and the results are compared to the present those of ASME code.

A large-scale soil-structure interaction experiment: Design and construction

This paper describes the design and construction phase of the Large-Scale Soil-Structure Interaction Experiment project jointly sponsored by the Electric Power Research Institute (EPRI) and the Taiwan Power Company (Taipower). The project has two objectives: (1) to obtain an earthquake database which can be used to substantiate soil-structure interaction (SSI) models and analysis methods; and (2) to quantify nuclear power plant reactor containment and internal components seismic margin based on earthquake experience data. These objectives were accomplished by recording and analyzing data from two instrumented, scaled down, reinforced concrete containment structures during seismic events. The two model structures are sited in a high seismic region in Taiwan. A strong-motion seismic array network is located at the site. The containment models ( 1 4 - and sol1 12 - scale ) were constructed and instrumented specially for this experiment. Construction was completed and data recording began in September 1985. By November 1986, 18 strong motion earthquakes ranging from Richter magnitude 4.5 to 7.0 were recorded.

Plastic analysis of concrete containment structure

Overpressure capacity of a box type concrete containment structure is evaluated. Plastic analysis of the finite element model is performed using a quadrilateral plate element of homogeneous material. A special approach is used to represent nonlinear properties of reinforced concrete, such as concrete cracking and crushing and steel yielding. Those properties are represented by a set of idealized stress-strain curves of equivalent homogeneous sections. The analysis allows for a better estimate of the overpressure capacity of the containment structure while keeping the computer cost low by avoiding the use of the more expensive reinforced concrete brick element.