test, it should be performed after the turbine has been operated at 10 % or more of rated power for about 4 hours or more to eliminate the temperature difference of each part.

4. Power increase to rated power

After synchronizing the generator, reactor power is increased by withdrawing control rods and increasing the recirculation pump speed (increase in core flow). During this process, when generator power has increased to the extent that it can stably and sufficiently supply the plant service power, the plant service power is switched from the off-site power (the startup transformer) to the power supply from the main generator side (the unit transformer). Additionally, the motor-driven feedwater pump is switched to the turbine-driven reactor feedwater pump when the latter pump can be used for the feedwater control system.

After this point, reactor power is gradually increased to rated power by increasing core flow and withdrawing control rods. Since margins for various kinds of limits and trip setpoints decrease at high reactor power, it is necessary to increase reactor power while monitoring the following items.

1. Fuel rod thermal limits (minimum critical power ratio (MCPR) and fuel rod maximum linear heat generation rate (MLHGR)) should not be exceeded.

2. Reactor thermal power and core flow should not deviate from the specified operating range. Fuel rod thermal limits should not be exceeded at 30% or less of reactor thermal power (Figure 4.1.3).

3. Margins for power-dependent trip setpoints of various parameters (each process flow rate, radiation monitor output, atmospheric temperature etc.) should not be exceeded.

Specifically, the fuel rod thermal limits are monitored using the output of the reactor core performance calculation performed automatically and periodically by the process computer, and other parameters are monitored using output of the process computer and recorders and indicators. For the actual power increase, control rod operation and core flow change procedures are determined by an off-line three-dimensional core analysis code at the startup program stage. The control rod operation procedure is loaded to the rod worth minimizer

Figure 4.1.3 Operating range of core thermal power and core flow

which outputs a rod operation guide, and when an erroneous rod operation is performed, the rod operation is blocked at low power level.

The Pre-Conditioning Interim Operating Management Recommendations (PCIOMR), which limit rate of power increase to the specified limit or less when the fuel linear power density exceeds the specified threshold when operating at high power levels, was formerly applied to fuel fabricated up to the 1980s in order to reduce pellet clad interaction (PCI). However, recent fuel adopts zirconium liner cladding, which uses pure zirconium, and PCIOMR is not required anymore.

2. Normal Plant Operation

As mentioned at the beginning, operation of a NPP is performed according to various kinds of regulations, standards, procedures, etc., and fundamental matters of which persons involved in its operation should be aware are particularly discussed here.

1. In operating a NPp the following matters should be especially observed in addition to always and correctly monitoring performance and conditions of plant components:

1. To monitor the conditions of the reactor facility, instruments, display devices, etc. in an appropriate and reliable manner;

2. To review the object, procedures, and the results of operation in advance, and check the conditions of plant components; and

3. To take into due consideration the related facilities and effects on the local community.

2. Plant patrols to check the following systems and components should be performed once or more

4-7

NSRA, Japan