Power plants limitations

Furnaces of this type, such as the steam locomotive furnace—boHet design, had the obvious disadvantage that pressure was limited to ca 1 MPa (150 psi). The development of seamless, thick-waH tubing for stationary power plants (ie, water-tube furnaces) and other engines for motive power, such as diesel—electric, has in many cases ecHpsed the fire-tube boHet. For appHcations calling for moderate amounts of lower pressure steam, however, the modern fire-tube boHet continues to be the indicated choice (5). 

The safety principles and criteria used ia the design and constmction of the faciUties which implement the nuclear fuel cycle are analogous to those which govern the nuclear power plant. The principles of multiple barriers and defense-ia-depth are appHed with rigorous self-checking and regulatory overview (17,34). However, the operational and regulatory experience is more limited. 

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. 

CAAA Impact on Nonutility Power Producers. The SO2 and NO regulations being implemented as part of the CAAA of 1990 primarily target electric utiHty power plants. However, under Phase II of the CAAA, nonutiHty power producers will be requited to acquire emissions allowances for any SO2 being emitted from new faciHties. Although industrial emitters of SO2 and NO are not directly affected, the EPA did undertake a study to estimate what contribution industrial producers have on annual estimated SO2 production in the United States (10). The report found that annual industrial SO2 emissions would remain below the predeterrnined critical limit of 5.6 x 10 tons/yr until at least 2015 (10). Thus, the agency recommended no new controls for industrial SO2 emissions at this time. 

After the final designs are complete it is recommended that the actual touch (actual) and step voltage (actual) are rechecked for both power plant and switchyard areas separately, to ensure that they are within the tolerable limits as determined above. After the ground stations have been finally installed the actual step and touch voltages must be measured to verify the designs. 

In a combined cycle plant, high steam pressures do not necessarily convert to a high thermal efficiency for a combined cycle power plant. Expanding the steam at higher steam pressure causes an increase in the moisture content at the exit of the steam turbine. The increase in moisture content creates major erosion and corrosion problems in the later stages of the turbine. A limit is set at about 10% (90% steam quality) moisture content. 

The gas turbines major limitations on the life are the eombustor eans, first stage turbine nozzles and first stage turbine blades as seen in Figure 21-6. The effeet of dry Low NO eombustors have been very negative on the availability of Combined Cyele Power Plants, espeeially those with dual fuel eapability. Flash baek problems are a very major problem as they tend to ereate burning in the pre-mix seetion of the eombustor, and eause failure of the pre-mix tubes. These pre-mix tubes are also very suseeptible to resonanee vibrations. 

New low-NO, burners are effective in reducing emissions from both new power plants and existing plants that are being retrofitted. Low NO, burners limit the formation of nitrogen oxides by controlling the mixing of fuel and air, in effect... 

Loss of offsite power at nuclear power plants is addressed in EPRI NP-2301, 1982 giving data on the frequency of offsite power loss and subsequent recoveiy at nuclear power plants. Data analysis includes point estimate frequency with confidence limits, assuming a constant rate of occurrence. Recovery time is analyzed with a lognormal distribution for the time to recover. 

Chernobyl may represent the upper limit that is possible in a nuclear power plant accident. 

The confidence limits of a measurement are the limits between which the measurement error is with a probability P. The probability P is the confidence level and a = 1 - P is the risk level related to the confidence limits. The confidence level is chosen according to the application. A normal value in ventilation would be P = 95%, which means that there is a risk of a = 5 /o for the measurement error to be larger than the confidence limits. In applications such as nuclear power plants, where security is of prime importance, the risk level selected should be much lower. The confidence limits contain the random errors plus the re.sidual of the systematic error after calibration, but not the actual systematic errors, which are assumed to have been eliminated. 

If all the heat absorbed were converted into work, the efficiency would be 1, or 100 percent. If none of the heat absorbed was converted into work, the efficiency would be 0. The first law of thermodynamics limits the efficiency of any heat engine to 1 but does not prevent an efficiency of 1. The efficiency of practical heat engines is always less than 1. For example, the efficiency of a large steam turbine in an electric power plant is about 0.5, which is considerably more efficient than the typical 0.35 efficiency of an auto engine. When two objects at different temperatures are m... 

For a heat engine like a steam turbine in an electric power plant the low temperature is determined by the outdoor environment. This temperature is about 300 K. Engineering considerations limit the high temperature to about 800 K. The maximum efficiency according to Carnot is 0.63 or 63 percent. No matter how skilled the builders of a steam turbine, if the temperatures are 300 K and 800 K, the efficiency will never exceed 63 percent. When you realize that the efficiency can never be larger than about 63 percent, a realizable efficiency of 50 percent looks quite good. 

Uranium is used as the primai-y source of nuclear energy in a nuclear reactor, although one-third to one-half of the power will be produced from plutonium before the power plant is refueled. Plutonium is created during the uranium fission cycle, and after being created will also fission, contributing heat to make steam in the nuclear power plant. These two nuclear fuels are discussed separately in order to explore their similarities and differences. Mixed oxide fuel, a combination of uranium and recovered plutonium, also has limited application in nuclear fuel, and will be briefly discussed. 

In large power plants, precoat filters are traditionally used only when freshwater condenser cooling is employed because brine or seawater condenser leaks would quickly overwhelm the limited ion-exchange capacity available. They also are commonly used for continuous filtering of suspended corrosion products under variable power load conditions and when frequent boiler startups are necessary. 

Zirconium carbide is a highly refractory compound with excellent properties but, unlike titanium carbide, it has found only limited industrial importance except as coating for atomic-fuel particles (thoria and urania) for nuclear-fission power plants.l " ] This lack of applications may be due to its high price and difficulty in obtaining it free of impurities. 

Eor (1), MSWIs, the maximum bonus is limited by the calorific value of the plastics waste (about 40 MJ/kg). Eurthermore, the energy recovery is relatively low due to technical limitations in comparison to normal power plants. Normally, at best some 20% electrical energy is recovered (or some 50%-70% calculated as primary energy). 

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