Partial power operation

Partial power operation takes place over a continuum and is constrained by the load schedule. The load schedule specifies the value of each process variable as a function of plant power. Good operability as characterised by minimal thermal stresses during power change is achieved by developing a load schedule that maintains temperatures constant with respect to load at the hottest points in the plant (e.g. reactor outlet). 

Thermal-Hydraulic Stability at Partial Power Operations at 25 MPa... 

Fig. 5.33 Decay ratios of thermal-hydraulic stability in maximum power channel at partial power operations...

Partial power operating conditions are also analyzed to investigate the stability during the power increase phase. The calculated decay ratios at 40% core power with various flow rates are shown in Fig. 5.51 and those at 50% core power are shown in Fig. 5.52. The decay ratio map is shown in Fig. 5.53. Unstable conditions arise when the power to flow rate ratio is high, especially at low power operation. Figure 5.54 shows the flow rate required to satisfy the criterion of coupled neutronic... 

The startup curve for the sliding pressure startup scheme that is designed based on only the thermal considerations (Fig. 5.23) is redrawn taking the stability considerations into account as well. The constant pressure startup is not discussed here because the partial power operating conditions in the constant pressure startup are covered by the temperature increase phase and power increase phase of the sliding pressure startup. 

The partial power operating conditions at 25 MPa after the line switching are divided into the temperature increase phase and the power increase phase with only the thermal considerations as shown in Fig. 5.23. In the temperature increase phase, the power is gradually increased from 20 to 35% of the rated value, while the flow rate is fixed at 35% of the rated flow so that the core outlet temperature reaches the normal operating point (500°C). Then, both the power and flow rate are increased... 

FIG. 11-84 Typical power-refrigeration capacity data for different types of compressors during partial, unloaded operation. 

The performance of the reference interface is characterised in Vilim (2007). In that work the GPASS/H code was used to determine the full power condition, the combined plant efficiency and the partial power load schedule. The values of the main operating parameters are summarised in Table 1. 

Reserve Shutdown Requirements and Reactivity Worths The primary reactivity requirement for the reserve shutdown control (RSC) is to maintain shutdown (k < 0.99) indefinitely at or below the refueling temperature 192 C (377 F). Any partially inserted control rods or other fully withdrawn control rods are assumed not to be inserted in determining the RSC capability to meet this requirement, i.e., the maximum core operating excess reactivity is assumed to be held down by control rods and this excess reactivity is not a component of the requirement for the RSC. The reserve shutdown control equipment (RSCE) is also required to trip following the trip of the outer bank of control rods, and after some delay, for transients initiated by moisture ingress during power operation. 

The number of events occurring during LPS conditions is considerably higher than might be expected compared to the number of events occurring during power operational modes. In many cases higher probability of an LPS event is partially compensated for by the slowly... 

Unit substations can be either single-ended, fed by a single primary feed, or double-ended, fed from either end by a separate primary feed. Double-ended substations are usually designed so that either transformer can assume two thirds of the load in the event of a failure of one primary feeder. This is accomplished by the inclusion of a normally open tie circuit breaker in the switchgear lineup. The apphcation of double-ended substations to industrial plants increases the rehabUity of the system and allows partial operation in the event of partial power failures. Plant operators must have a plan for immediate dumping of nonessential loads before closing the tie circuit breaker. This plan will keep essential processes functioning while power is down. 

A short-term performance test demonstrated that the 10-kW class module is capable of meeting the design specifications for full load and partial load operations. Figure 9.13 shows the various data recorded during the test. The DC power output of 12.7 kW is obtained under full load operation at 76% fuel utilization, analogous to the electrical efficiency of 50% HHV. The operational characteristics during the thermally self-sustained operation are listed in Table 9.3. 

As a part of the power demonstration program of the AFC in the 1950s, the Enrico Fermi fast breeder reactor (Fermi-1) was built near Detroit by a consortium of companies led by Detroit Edison. Fermi-1 used enriched uranium as fuel and sodium as coolant, and produced 61 MWe. It suffered a partial fuel melting accident in 1966 as the result of a blockage of core coolant flow by a metal plate. The reactor was repaired but shut down permanently in November 1972 because of lack of binding. Valuable experience was gained from its operation, however (58). 

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