Operational Control Criteria

The operational control system must meet the following requirements  

Adequate strength to maintain the reactor suhcrltlcal under all normal operating and shutdown conditions. 

Adjustment at rates fast enou to override all normal operational reactivity transients and to minimize delays at startup. However, the system must be limited to its withdrawal rate to that rate which, In coincidence with simultaneous failure of the Primary Safety System, would not result In fuel melting. 

3 Precision positioning and movement to permit establishing and maintaining the reactor power level within desired limits. 

Adequacy of geometrical coverage and flexibility to permit attaining adequate power-flattening efficiencies and satisfactory control over sj tlal power cycling. 

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The operational control criteria and part of the safety control criteria are re-statements of the Hanford Total control Criterion As far as the operational control criteria are concerned the horizontal control rods have adequate strength in the operating reactor (minimum of 7 7 per cent cold) to control any fore-... 

The operational control criteria (Section 1.5 1 1) and part of the eefety control criteria (Section 1 5 1 2) are restatements of the Hanford Total Control Criterion As far as the operational control... 

The second safety control criterion (Section 1.5.1.2) is a reatatsnent of the Hanford Speed-of Control Criterion. Since the water-loss accident in N Reactor does not result in a rapid increase in reactivity as is the case in the present reactors, the accident governing the response of the safety systems is one associated with rod-withdrawal. Since the horisontal rods combine both operational and safety functions, the limitation on withdrawal rate specified in the operational control criteria can alao be included in this discussion. 

Optimal control of reaction generally involves two contradictory criteria the operating time and the conversion. In this paper, the study amounts in the determination of the optimal profiles of temperature and reactants addition for an operating time criterion with an acid conversion constraint set up to 95.5%. Within the context of an industrial reactor, the considered temperature consists in the heat transfer fluid temperature. 

While the physicists failed to validate their models and therefore could not be certain that they caught the right processes their efforts were still seen as useful to the control project by the consultancy. Although the models fell short with regards to physics internal assessment criteria such had no consequences for the models usefulness to the control project. The fact that the control project used the physicists models, despite their inability to validate them, shows that the usefulness to process control -criterion required significantly less representational accuracy and certainty than that aimed for by the physicists. The domain of work in which the physicists representational modeling formed part, was engineering of process control that operated after a unique set of success criteria that were based on operational usefulness and impact on production yields. ... 

Control philosophies for clarifiers are based on the idea that the overflow is the most important performance criterion. Underflow density or suspended sohds content is a consideration, as is optimal use of flocculation and pH control reagents. Automated controls are of three basic types (I) control loops that optimize coagulant, flocculant, and pH control reagent additions (2) those that regulate underflow removal and (3) rake drive controls. Equahzation of the feed is provided in some installations, but the clarifier feed is usually not a controlled variable with respect to the clarifier operation. 

As previously indicated, most bag-type filters require a pre-coat of particulates before they can effectively remove airborne contaminates. However, particles can completely block air flow if the filter material becomes overloaded. Therefore, the primary operating criterion is to maintain the efficiency of the filter media by controlling the cleaning frequency. 

Businesses require funds for day-to-day operations ( working capital ) and for expansion by acquisition and for the provision of plant and machinery, buildings, etc. Most working capital needs are normally (and should be) met from the company s own cash generated from its own operations. Indeed, the need to meet this criterion serves as a discipline upon the company s standard of cash management in relation to credit control, payment of suppliers, etc. 

Management systems - the operator needs to have an effective management system in place to control the production process. Registration under EMAS or ISO 14001 would meet this criterion although this is not a specified requirement. 

The setting of a boundary around a research area, is achieved by selecting a part of the operational process against a selection criterion which is established by the researcher in accordance with the request of the company s management. Moreover, the tertiary process and the process controlling the selected operational processes are also identified. 

Target control charts are control charts with fixed quality criterions. In the contrary to classical control charts of the Shewhart-type these control charts operate without statistically evaluated values. 

In the construction of the wet oxidation unit, several areas of safety were considered. Of utmost importance was that of personal safety. Since this type of operation demands the use of high pressures and temperatures, operator contact with the high pressure vessels had to be limited. To accommodate this criterion, a barrier was constructed to shield the operator from any unforeseen releases from the reactor. This barrier was constructed from 1/4 inch steel and is desig ied in a manner that will fully contain any releases. This barrier is also equipped with two explosion vents to direct the force of any explosions away from the main walls and into a safe area. To further maximize personnel safety, all operator assisted controls are mounted on the outside of the unit. 

Let us establish a criterion whereby we conclude that the reactor is not in control if the mean of five measurements of yield is more than three standard deviations away from the population mean (as determined by the earlier 11 runs). Then we can establish upper and lower control limits on a control range X 3a, outside of which we initiate corrective action on the reactor operation. 

The optimal control of a process can be defined as a control sequence in time, which when applied to the process over a specified control interval, will cause it to operate in some optimal manner. The criterion for optimality is defined in terms of an objective function and constraints and the process is characterised by a dynamic model. The optimality criterion in batch distillation may have a number of forms, maximising a profit function, maximising the amount of product, minimising the batch time, etc. subject to any constraints on the system. The most common constraints in batch distillation are on the amount and on the purity of the product at the end of the process or at some intermediate point in time. The most common control variable of the process is the reflux ratio for a conventional column and reboil ratio for an inverted column and both for an MVC column. 

A general approach to the analysis of low amplitude periodic operation based on the so-called Il-criterion is described in Refs. 11. The shape of the optimal control function can be found numerically using an algorithm by Horn and Lin [12]. In Refs. 9 and 13, this technique was extended to the simultaneous optimization of a forcing function shape and cycle period. The technique is based on periodic solution of the original system for state variables coupled with the solution of equations for adjoin variables [Aj, A2,..., A ], These adjoin equations are... 

Sequential optimisation methods are used for multi-parameter optimisation. The simplex method starts with some initial experiments, evaluates from them the values of a sum optimisation criterion (COF), on the basis of these results determines the next combination of operation parameters to be used for running a new chromatographic experiment and compares the value of the COF obtained from the new experiment with the old one. On the basis of this prediction, a new combination of the operation parameters is calculated which is expected to yield an improved value of the COF, the separation is run at these new conditions and the procedure is repeated until maximum COF with no further improvement is eventually obtained, for which — hopefully — the optimum combination of operation parameters has been obtained (Fig. 1.22). Any combination of operation parameters can be optimised in this way and no knowledge about the nature of the chromatographic process is necessary ( black-box philosophy). Some HPLC control systems allow the simplex optimisation to run unattended. 

It is expected that results will fall within normally anticipated operating levels (Table 1) with 95% confidence, if randomness in critical environments and operations is sufficiently controlled. If data from successful PQ runs (when the process is demonstrated to be under control) do not meet this criterion, the monitoring methods may not measure a phenomenon that relates directly to process control, may not be sufficiently reproducible to provide useful information, or may have been incorrectly conducted. Every effort should be made to develop monitoring methods that comply with this performance expectation so that data will be useful. 

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