Nuclear power failure modes

Characteristics of Pipe System Failures in Light Water Reactors Nuclear Approximately 100 records of pipe failure rates in a wide variety of failure modes Nuclear Power Plant Piping 114. 

A risk equation for nuclear power may be derived by imagining a world with a very large nuclear power plant population. All plants are identical with the same demography and meteorology. The plants are separated such that one does not affect the other. Each year, n, plants fail in the ith failure mode, causing a population dose tf,. If the effects are additive, the population dose (other risk measures could be used) is linearly proportional to the number failing (Equation 1.4-4), where ( is... 

If the containment holds, nuclear power plants present no risk to the public. Overpressurization of the containment is the failure mode that could allow direct release of radioactivity to the public. Design a risk reduction investigation of the benefits of releasing the gas pressure through an offgas processing system that removes the particulates. 

The failure description is the third part of the taxonomy structure and involves the modes, severities, and types of failures. These are based on models in the In-Plant Reliability Data Base for Nuclear Power Plant Components Data Collection and Methodology Report (IPRDS) and IEEE Std. 500-1984,2 which are discussed in Chapter 2. 

The data are very comprehensive with direct applications to reliability, risk, and event analysis of nuclear power plants. Information has been assembled on failure frequency, modes, repairs, and maintenance. Rate Information is based on demands calculated. The time period covered varies from the early 1970 s to the present. Using real time access, the output format if the event can be varied by selection of 20 generic and detailed categories. 

Three reports have been issued containing IPRDS failure data. Information on pumps, valves, and major components in NPP electrical distribution systems has been encoded and analyzed. All three reports provide introductions to the IPRDS, explain failure data collections, discuss the type of failure data in the data base, and summarize the findings. They all contain comprehensive breakdowns of failure rates by failure modes with the results compared with WASH-1400 and the corresponding LER summaries. Statistical tables and plant-specific data are found in the appendixes. Because the data base was developed from only four nuclear power stations, caution should be used for other than generic application. 

The total cost of material fracture is about 4% of gross domestic product in the United States and Europe (88,89). Fracture modes included in the cost estimates were stress-induced failures (tension, compression, flexure, and shear), overload, deformation, and time-dependent modes, such as fatigue, creep, SCC, and embrittlement. The environmentally assisted corrosion problem is very much involved in the maintenance of the safety and reliability of potentially dangerous engineering systems, such as nuclear power plants, fossil fuel power plants, oil and gas pipelines, oil production platforms, aircraft and aerospace technologies, chemical plants, and so on. Losses because of environmentally assisted cracking (EAC) of materials amount to many billions of dollars annually and is on the increase globally (87). 

In addition, it should be demonstrated analytically that the mechanical systems can withstand a single active failure including failure of any auxiliary electric power source and not prevent delivery of sufficient cooling water to maintain the plant in a safe shutdown condition. A technique suitable for this analysis is a Failure, Modes, and Effects Analysis (FMEA). IEEE Std. 353-1975, "Guide for General Principles of Reliability Analysis of Nuclear Power Generating Station Protection Systems," provides additional guidance on the preparation of FMEAs. 

This paper deals with the classification of an error type and the characteristics of human errors by each error type for the test and maintenance failures that have led to implanned reactor trips in Korean nuclear power plants. The classification of hmnan errors was basically performed on the taxonomy of Reason s basic error types (Reason 1990). Characteristics of the test and maintenance errors include the major contributing factors or error modes, and predictivity or identifiabil-ity of a potential erroneous action from the viewpoint of a human error prevention or management. 

The main aim of this appendix is to bring readers attention to this powerful process language, which is very useful and helpful in automating hazard analysis and failure mode identifications. With this, the discussions on Little JIL is completed to look into another important issues of embedded controls which are now used in process control application including nuclear installations. 

For each hardware assessment of PFDavg, there should be some consideration of dependent failure (ie common cause or common mode types of dependent failure) with other layers. For each of the human error probability assessments there should again be some consideration of dependent failure. Further guidance on this may be found in Handbook of Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications NUREG/CR-1278. ... 

We have presented methodology for modelling failures. The methodology serves as a framework for the verification of the fault-tolerance of the plant by taking into account the hardware configuration of the system and the various failure modes of the hardware components. We used a PRA model of a nuclear power plant as reference and created a corresponding model that can be used for model checking. We then verified the fault-tolerance of the model with respect to several properties. 

The LA template of the locations that correspond to most likely failure sites along tubes in a steam generator of a pressurized water nuclear power plant (Fig. 7.8) is detailed in Table 7.4 for the main failure modes and submodes considered in such analysis. Maintenance and inspection actions can be decided upon by following developing trends monitored in each LA matrix thus produced. 

FTA is based on the premise that many of the conponent failure modes that would be studied in the FMEA technique would not contribute to any system failure. FTA is a top-down analysis of the system failures. First, the catastrophic system failures to be avoided are identified. Then contributing failures of subsystems and individual conponents are considered. FTA is widely used in the nuclear power industry, where catastrophic system failures are clearly defined. 

---