Nuclear plants

Repeatability. This refers to two aspects of inspection similarity between objects that are inspected and possibility of maintaining constant inspection conditions (settings) for all the inspections performed. Obviously, interpretation of data in repeatable conditions is significantly simplified. Usually, inspection during or after manufacturing process will be repeatable. Another example of repeatable inspection is inspection of heat exchangers in power nuclear plants, inspection of aircrafts as these are well standardised. However, a large part of the NDT inspection done is not repeatable. 

Our main application domain is the steam generator tubes of pressurized water nuclear plant. These tubes have 22.22 mm outer diameter and 1 27 mm thickness. 

MAPPscan is a manual ultrasonic testing system connected to an acoustic positioning system.. The system is developed as a consequence of the increased radiation doses in nuclear plants The system has the same flexibility as manual scanning with the same accuracy and the possibilties to collect, store and evaluate the UT data as with mechanised Ultrasonic systems The positioning system is based on spatial acoustic triangulation and have an accuracy of better than 1.0 mm within its recommended range. 

The system is to be qualified under the new regulations for ISI in Swedish nuclear plants, SKIPS, during the spring of 98 and the pre-trials for these qualifications has produced very promising results. 

Many problems have plagued steam generators of nuclear power plants over the last decades. Therefore, Laborelec developed its own inspection equipment and services. These were extended to other components of nuclear plants like thimbles, guide cards and baffle bolts and to classical parts of power stations like turbines, alternators, heat exchangers and piping. 

The American Society of Mechanical Engineers (ASME) United Engineering Center 345 East 47th Street New York, NY 10017 The ASME Boiler and Pressure Vessel Code, under the cognisance of the ASME PoHcy Board, Codes, and Standards, considers the interdependence of design procedures, material selection, fabrication procedures, inspection, and test methods that affect the safety of boilers, pressure vessels, and nuclear-plant components, whose failures could endanger the operators or the pubHc (see Nuclearreactors). It does not cover other aspects of these topics that affect operation, maintenance, or nonha2ardous deterioration. 

Spent nuclear fuel has fission products, uranium, and transuranic elements. Plans call for permanent disposal in underground repositories. Geological studies are in progress at the Yucca Mountain site in Nevada. Until a repository is completed, spent fuel must be stored in water pools or in dry storage casks at nuclear plant sites. 

As a consequence, there is a general reluctance in the financial community to support the construction of new nuclear plants. 

All processes in a nuclear plant, in a treatment facility, or at a disposal site are governed by rules of the U.S. Nuclear Regulatory Commission (NRC)... 

The World Association of Nuclear Operators (WANO) has been formed, consisting of nuclear plant operators over the entire world who have pledged to assist each other in the achievement of safe operations (25). There are four centers from which this international program is adrninistered one in the United States in Atlanta, Georgia, operated by INPO one in Paris operated by Electricitir de Prance one in Moscow operated by the Ministry of Nuclear Power and one in Tokyo operated by the Central Research Institute for the Electric Power Industry (CRIEPI). Through this mechanism, teams of operators from the U.S., Western Europe, and Asia visit CIS plants to share safety experience and know-how, and similarly, plant personnel from Russian and Eastern European nuclear units visit European, Asian, and U.S. plants. 

If possible comparisons are focused on energy systems, nuclear power safety is also estimated to be superior to all electricity generation methods except for natural gas (30). Figure 3 is a plot of that comparison in terms of estimated total deaths to workers and the pubHc and includes deaths associated with secondary processes in the entire fuel cycle. The poorer safety record of the alternatives to nuclear power can be attributed to fataUties in transportation, where comparatively enormous amounts of fossil fuel transport are involved. Continuous or daily refueling of fossil fuel plants is required as compared to refueling a nuclear plant from a few tmckloads only once over a period of one to two years. This disadvantage appHes to solar and wind as well because of the necessary assumption that their backup power in periods of no or Httie wind or sun is from fossil-fuel generation. Now death or serious injury has resulted from radiation exposure from commercial nuclear power plants in the United States (31). 

PWRs operate differendy from BWRs. In PWRs, no boiling takes place in the primary heat-transfer loop. Instead, only heating of highly pressurized water occurs. In a separate heat-exchanger vessel, heat is transferred from the pressurized water circuit to a secondary water circuit that operates at a lower pressure and therefore enables boiling. Because of thermal transfer limitations, ultimate steam conditions in PWR power plants ate similar to those in BWR plants. For this reason, materials used in nuclear plant steam turbines and piping must be more resistant to erosion and thermal stresses than those used in conventional units. 

Nuclear Reactors. Nuclear power faciUties account for about 20% of the power generated in the United States. Although no new plants are plaimed in the United States, many other countries, particularly those that would otherwise rely heavily on imported fuel, continue to increase their nuclear plant generation capacity. Many industry observers predict that nuclear power may become more attractive in future years as the price of fossil fuels continues to rise and environmental regulations become more stringent. In addition, advanced passive-safety reactor designs may help allay concerns over potential safety issues. 

The accident at the Three Mile Island nuclear plant clearly demonstrated that an alarm system can be counterprociuc tive. An excessive number of alarms can distract the operator s attention from the real problem that needs to be addressed. Alarms that merely tell the operator something that is already known do the same. In fac t, a very good definition of a nuisance alarm is one that informs the operator of a situation of which the operator is already aware. The only problem with applying this definition is determining what the operator already knows. 

Nuclear Plant Reliability Data System Annual Reports of Cumulative System and Component Reliability for Period from July 1, 1974, through December 31, 1982, NPRD A02/A03 (INPO 83-034), Institute of Nuclear Power Operations, Atlanta, GA, October 1983. 

Figure 1.4.3-1 from WASH-1400 compares the risk of 100 nuclear plants with other man-caused risks. This is a CCDF that gives the frequency per year that accidents will L-xcccd a value on the abscissa. For example, for 100 fatalities, the frequency that 100 nuclear power plants could do this is lE-4, air crashes to persons on the ground lE-2, chlorine releases 1. IE-2, dam failures 7E-2, explosions SF-2, fires 1. IE-1, air crashes (total) 5E-1, and total man-caused 9E-1,... 

The fraction 0.1% is chosen to be so low that individuals living near a nuclear plant should have no special concern because of the closeness. Uncertainties in the analysis of risk are not caused by the "quantitative methodology" but are highlighted by it. Uncertainty reduction will be achieved by methodological improvements mean values should be calculated. As a guideline for rcinilatory implementation, the following is recommended ... 

It is important to note that the chi-squared estimator provides upper bounds on A for the case of zero failures. For example, a certain type of nuclear plant may have 115 plant-years of experience using 61 control rods. If there has never been a failure of a control rod, what is A for 50% (median) and 90% confidence ... 

Markov analysis (Sec. 2.5.4) Evaluation of components systems, or functions Quantitative, time-dependent modeling process complc.s. success oriented has pcicniial for modeling complete nuclear plant... 

CER50.65, the Maintenance Rule requires nuclear plant licensees in the U. S. to monitor the condition of structures, systems, or components (SSC) against licensee goals to assure the SSC are fulfilling their intended function. 

IPRDS prepares nuclear plant data under the auspices of the ANSI/Failure and Incidents Reports Review (FIRR) Data Subcommittee. Data collection teams visit plants to e) n... 

Nuclear Plant Reliability Data System (NPRDS), Institute of Nuclear Plant Ofxratlons... 

Table 4.1-5 NUREG 1150 Nuclear Plant Reliability data...

Table 4.J-5 NUREG JI50 Nuclear Plant Reliability Data (cant.)...

According to 10 CFR 50,73, the holder of an operating license for a nuclear power plant (the licensee) must submit an LER for a reportable event, within 30 days after discovery. An event b reportable regardless of the plant mode, power level, structure, system, or component that initiated the event. In addition the licensee must report the completion of any nuclear plant shutdown required by the plant s Technical Specifications or any operation or condition prohibited by the plant s Technical Specifications, or any deviation from the plant s Technical Specifications. LERs are available on the Internet at http //www.nrc.gov/NRR/DAILY/97mmdddr.htm, where inrn is the... 

In addition to these formal studies of human error in the CPI, almost all the major accident investigations in recent years, for example, Texas City, Piper Alpha, Phillips 66, Feyzin, Mexico City, have shown human error as a significant causal factors in design, operations, maintenance or the management of the process. Figures 4.4-1 and 4.4-2 show the effects of human error on nuclear plant operation. 

The AP600 passive safety system includes subsystems for safety injection, residual heat removal, containment cooling, and control room habitability under emergency conditions. Several of these aspects are in existing nuclear plants such as accumulators, isolation condensers as natural-circulation closed loop heat removal systems (in early BWRs), automatic depressurization systems (ADS - in BWRs) and spargers (in BWRs). 

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