Level Reactor Operating Range

Ry definition the lov level reactor operating range shall -12 -7 

Trips shall be provided to alarm (audible and visual) for exponential power level rate increases having periods of 13 seconds or less. Trips and Instrumentation ranges shall be fixed when the reactor power level is in this range (10 to 10 ). 

The response time N of the system shall be If. seconds or less. Geometric distribution of transducers Is relatively unimportant In this range. ( ) All transducers shall be located In one general area. 

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By definition the Intemediate level reactor operating range shall be from 10 T decades to 10" decades vlth two decades overlap to 10 decade totaling six decades. 

Different reactor networks can give rise to the same residence time distribution function. For example, a CSTR characterized by a space time Tj followed by a PFR characterized by a space time t2 has an F(t) curve that is identical to that of these two reactors operated in the reverse order. Consequently, the F(t) curve alone is not sufficient, in general, to permit one to determine the conversion in a nonideal reactor. As a result, several mathematical models of reactor performance have been developed to provide estimates of the conversion levels in nonideal reactors. These models vary in their degree of complexity and range of applicability. In this textbook we will confine the discussion to models in which a single parameter is used to characterize the nonideal flow pattern. Multiparameter models have been developed for handling more complex situations (e.g., that which prevails in a fluidized bed reactor), but these are beyond the scope of this textbook. [See Levenspiel (2) and Himmelblau and Bischoff (4).]... 

Three ranges are used to monitor the power level of a reactor throughout the full range of reactor operation. The source range makes use of a proportional counter. 

The load schedule specifies for normal at-power operation a unique plant steady state at each power level over the normal operating range, typically from 25 to 100% of full power. This includes the values of all plant forcing functions such as turbo-machine power inputs and reactor and cooler heat rates. For normal operating transients the load schedule gives conditions at which a transient begins and ends. If the transient is an upset event, then while it begins from a point on the load schedule it may terminate at some stable off-normal condition not found on the load schedule. 

Reactor operating conditions vary over a considerable range depending upon the particular catalyst, feed stock, and desired conversion level. Once-through motor-gasoline operations are typically at conversions of 45 to 60% in partial-recycle operations, conversions up to 75% are commonly obtained (53,236). 

The model has been used to analyze and improve performance for a range of emulsion processes. The substantial level of details (e.g., kinetics, PSD, MWD) that can be incorporated into reactor operation and control algorithms. ... 

The gas-oil cracking was carried out in a fixed-bed tubular reactor at atmospheric pressure and 482°C. The yields of the different reaction products, i.e., diesel (300°C), gasoline (210°C), methane, ethane, ethylene, propane, propylene, i-butene, n-butane, butenes and coke, were measured at total conversion levels in the range 30-80% wt/wt. The different conversions were achieved by varying the catalyst oil ratio in the range 0.025-0.40 g.g, but always at 60 seconds the time on stream. The operational procedure is given elsewhere (4). 

Our analysis of enzyme membrane reactors will range from systems proposed at bench scale to equipment already in operation at the industrial level, and from systems where enzymes are bound to membranes to apparatus where enzymes are simply confined in well-defined regions of the reaction vessel. In the following sections, we will refer to five main reactor configurations ... 

The -importance of having proper instruments for control purposes is made evident by consideration of Table 5.2.B, which shows the relation, of power (or neutron) level considered in four definite ranges to the choice of instru- ment and control action. These ranges, as suggested- by H. W. Newson or as applied to the MTR, serve as convenient divisions of the entire range of reactor operation. At the lowest level is the source range which lies below... 

Generic Safety Issue (GSI) I.D.5 (4) in NUREG-0933 (Reference 1), addresses the benefit to plant safety and operations of improved measurement of certain reactor parameters (e.g., reactor vessel water level and relief valve flow), and parameters outside of their normal operating range. 

The feedstock, which may range from natural gas to naphtha, is heated and desulfurized (usually in a conventional ZnO/CoMoX bed ) to levels below 1 ppm after which steam is added and the combined feed is introduced into the ATR. The upper part of the reactor basically consists of a burner, mounted on the reactor shell the burner itself is the key item of the autothermal reactor and is critical for the reactor operation. In this part of the reactor, temperatures until 1,400°C are reached. The burner design is a proprietary design of the technology supplier. Flame stability, in combination with a sootless operation, is the key requirement for proper burner operation. This is accomplished with the correct ratio of feedstock, oxygen, and steam. 

The nuclear flux level and rate of change of flux is monitored in the sub-critical range, in the intermediate power level range, and in the operating range by multiple sensing and control systems, each consisting of multiple fail-safe components. Any one of these systems, except for the subcritical instruments, will automatically shut down the reactor complex in the event that process limits are exceeded. 

The TMI-2 accident reinforced the need to supply the NPP operators with pressure, temperature, radiation and humidity measurements that have a measuring scale beyond the normal operating range. In case of a design basis accident or a beyond design basis accident these measurements have to provide reliable information of the conditions inside the reactor pressure vessel and the containment. The accident monitoring instrumentation in some reactors is not adequate. For example, the reactor pressure vessel level indication is currently not provided, and the level can be estimated only by indirect means. A further example is that the effluent from the ventilation duct is not properly monitored in terms of radioactivity. The information obtained on the effluent from ventilation ducts during accidents is not reliable and accurate and this can lead to an overirradiation of plant personnel and inhabitants in the vicinity. 

To improve unit performance, the existing reactor internals were replaced by high performance vortex t) e mixing chambers to optimize liquid-liquid mixing and VLT distribution trays to increase the number of drip points and minimize the dead flow zones adjacent to the reactor wall (Figure 6). The VLT distribution trays also offered low sensitivity to tray levelness and improved stability over a wide operating range. 

The control of the primary coolant inventory is shown in Figures C-62 and C-63. The coolant liquid level in the pressurizer must be maintained essentially constant under various phases of reactor operation to assure surge capacity and pressure control capability Liquid level changes in the pressurizer will operate the primary loop Injection flow control valves Indirectly controlling the liquid level in the pressurizer. Surges in level above the normal control ranges will result in operation of the spill system and will initiate a reactor power setback. Drops in the pressurizer level below the normal control range may lead to serious consequences if not arrested Efforts have been made to avoid excessively low levels or to minimize their consequences If the level drops below the normal control point an alarm sounds If, in spite of corrective actions taken after the alarm, the level continues to drop, a power setback trip will occur. The purpose of the setback is to reduce power before the pressurizer is depleted and losa of pressure control is threatened. In case of a still further drop in level, a reactor scram trip will be incurred automatically. 

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