PLANT NORMAL OPERATIONS

In many practical applications, the engineer often has only plant performance data to use to backcalculate kinetic parameters. Data of this type are seldom extensive enough to permit precise calculation of all parameters since the plant normally operates in a fairly narrow window of operating conditions. However, useful simplified kinetics and parameters can often be determined that describe the major kinetics inside this region. Extrapolation outside the region from which the data has been obtained is very risky. 

The fact that these catalysts continue retaining metals under the plant normal operational conditions suggest that the limitation in the performance of the plant at the end of the run is mainly originated by the nature of the coke deposits. 

Ethylene plants normally operate for 4-5 years without turnaround. In such a case, the membrane unit needs to be isolated and membranes replaced on-stream. 

The solid waste treatment and storage system provides treatment, encapsulation and storage for the solid radioactive waste produced during, plant normal operation and maintenance. 

To fulfil the chemistry requirements, the primary coolant has to be treated by the addition of chemicals. The concentrations of the additives needed have been given in specifications elaborated by specialists in detailed discussions and which are continuously re-evaluated based on the current state of knowledge. Table 1.4. shows an overview of the primary coolant specifications established by various vendors and institutions for plant normal operation periods (Mathur and Narasim-han, 1992). From these data, it can be seen that there is a worldwide consensus on the use of LiOH or KOH as a pH control reagent. Different vendors or organizations may recommend minor changes in some of these specifications as, for example, KWU not specifying fluoride, but fundamentally the plant specifications are virtually identical. During startup and shutdown phases, deviations from these specified data are allowed for a limited period of time. 

From these two main groups of the Periodic System of Elements, only the elements bromine, iodine, rubidium and cesium are produced by nuclear fission to an extent worth mentioning. Iodine and cesium are of particular interest during plant normal operation as well as in accident situations, because of their comparatively high fission yields, their enhanced mobility in the fuel at higher temperatures and the radiotoxicity of some of their isotopes. Both elements are often summarized under the term volatile fission products their similar properties justify their treatment in the same context, despite pronounced differences in their basic chemical behavior. 

The coolants that come into contact with the nuclear areas of the reactor plants, primarily the PWR primary coolant and the BWR reactor water, are contaminated even during plant normal operation with radionuclides formed by various nuclear reactions. However, the appearance of these radionuclides in the coolants does not cause any difficulties in plant operation since all the relevant circuits are designed for safe operation in the presence of radioactivity. 

There is no doubt that the generation of radionuclides from the corrosion product elements can only occur in the neutron field, i. e. inside the reactor pressure vessel (RPV). On the other hand, the radionuclides which cause the radiation fields which potentially complicate work during plant normal operation as well as during inspection and repair work are those deposited on the inner surfaces of the out-of-RPV primary circuit piping and components, regions they are transported to by the primary coolant. This means that contamination buildup in the PWR primary circuit is a complex process. It can be roughly divided up into three stages (see Fig. 4.26.), each of which raises its particular questions ... 

The word emergency is used in many different contexts and different areas of human activity. In Ret [4] emergency is defined in part as A nonroutine situation or event that necessitates prompt action primarily to mitigate a hazard or adverse consequences for human health and safety, quality of life, property or the environment . In IAEA safety assessment publications the following terms have been established for identification of different operational states and accident conditions of a nuclear power plant normal operation, anticipated operational occurrences (AOOs) (abnormal operation), design basis accidents (DBAs), beyond design basis accidents (BDBAs) and severe accidents. 

The EDG are ready for immediate startup at any time in their own design conditions, except during maintenance (limited and suitable parts of the maintenance programme is planned and performed during plant normal operation). 

The check valves in the core make-up rank injection lines are designed so thatthey lemain in the open position during the plant normal operation. This design eliminates opening failures and common cause failures with the accumulator check valves. 

The value of Nq in Equation 8.3 is the number of operators required to run the process unit per shift. A sin e operator works on the average 49 weeks a year (3 weeks time off for vacation and sick leave), five 8-hour shifts a week. This amounts to (49 weeks/year x 5 shifts/week) 245 shifts per operator per year. A chemical plant normally operates 24 hours/day. This requires (365 days/year x 3 shifts/day) 1095 operating shifts per year. The number of operators needed to provide this number of shifts is [(1095 shifts/yr)/(245 shifts/operator/yr)] or approximately 4.5 operators. Four and one-half operators are hired for each operator needed in the plant at any time. This provides the needed operating labor but does not include any support or supervisory staff. 

Operational state of the plant Normal operation Anticipated operational occurrences Design basis and conplex operating states Severe accidents beyond die design basis Post-severe accident situation... 

In defining the key attributes, it was necessary to determine the fundamental elements associated with plants that operate safely. Three aspects were addressed — nuclear power plant normal operation, nuclear power plant emergency operation, and the attitude of nuclear power plant personnel towards safety. From these areas, experts isolated three key attributes that are associated with plants that operate safely ... 

ABAQUS is used to rnodei the hot leg piping for a four Brayton system. The model is used to determine the stresses due to thermal expansion during plant normal operation. The model is analyzed at the steady state normal operation point. The beam section moment results are used in spreadsheet calculations to perform ASME B PV code piping stress calculations. 

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