Reactor Power Control System

The reactor power is controlled by the control rods. The control logic is based on what is widely used in nuclear reactors, including LWRs, and it is shown in Fig. 4.22. The speed of the control rod drive is calculated as (4.15). 

As shown in Fig. 4.23, the speed of the control rod drive is proportional to the deviation of the power from the setpoint if the deviation is below a certain value b while the control rods keep the maximum speed Vmax with larger deviation from the viewpoint of safety. The maximum speed is 1.9 cm/s taken from PWRs. 

Sensitivity analysis is carried out with various b when the setpoint of the reactor power decreases stepwise by 5%. Operation of the pressure control system and the 

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One is the secondary- coolant reduction test by partial secondary loss of coolant flow in order to simulate the load change of the nuclear heat utilization system. This test will demonstrate that the both of negative reactivity feedback effect and the reactor power control system brings the reactor power safely to a stable level without a reactor scram, and that the temperature transient of the reactor core is slow in a decrease of the secondary coolant flow rate. The test will be perfonned at a rated operation and parallel-loaded operation mode. The maximum reactor power during the test will limit within 30 MW (100%). In this test, the rotation rate of the secondary helium circulator will be changed to simulate a temperature transient of the heat utilisation system in addition to cutting off the reactor-inlet temperature control system. This test will be performed under anticipated transients without reactor scram (ATWS). 

Fig. 4.24 Calculation results for tuning maximum deviation for proportional control in reactor power control system...

The reactor power control system consists of a reactivity control system, the linear power monitoring channels of the neutron instrumentation system and the reactor shut-down (control rod system) It is designed to automatically operate control rods to compensate reactivity changes caused by loading and unloading of irradiation samples, accumulation of Xenon, changes of coolant temperature, bum-up of fuels and so on in reactor operation... 

Our present discussions relate only to the laboratory testing of safety-related secondary systems, as are employed in critical areas such as areas of emergency power supply and reactor power control supply etc. of a nuclear power plant (NPP) according to IEEE 344 and lEC 60980. There are other codes also but IEEE 344 is referred to more commonly. Basically, all such codes are meant for an NPP but they can be applied to other critical applications or installations that are prone to earthquakes. 

P P Po PCHE PCR PCS PDF PDMS Pe PEM PEMFC PET pH Power output Pressure Pressure drop of one SAR step Printed circuit heat-exchanger Printed circuit reactor Process control system Probability density function Poly-dimethylsiloxane Peclet-number Proton exchange membrane Proton exchange membrane fuel cell Poly-ethylene terephthalate Potentia Hydrogenii (measure for acid and base strength)... 

The power density distribution is controlled by the 12 LAC and 24 LS rods. The average power control system is used as standby in the 20-100% power range and is switched on automatically when the LAC system malfunctions. The automatic control system holds reactor power to within 1 % of the required output in the range 20-100% full power and to within 3% in the range 3-5-20% full power. 

The ARTS will initiate a reactor trip when pressurizer pressure exceeds a predetermined value (see CESSAR-DC, Table 7.7.1). Turbine trip signals can also initiate ARTS if the Reactor Power Cutback System is out of service. The ARTS turbine trip input is manually enabled from the main control panel. 

Negative temperature reactivity coefficients and negative coolant void reactivity effect, provided by an appropriate selection of the design parameters the incorporation of negative temperature reactivity coefficients facilitates realization of passive safety features [XV-2] and also simplifies the power control system so that only feed water control in the power circuit can regulate reactor power ... 

For small power reductions (less than a 10% change in load), the turbine bypass system is not actuated. Instead, it is accommodated by the reactor power control, the pressuriser level control, the pressuriser pressure control and the steam generator level control systems. 

The plant control system provides the fimctions necessary for normal operation of the plant, from cold shutdown through to full power. This system controls the duty systems in the plant, which are operated from the main eontrol room or remote shutdown woikstation. The plant control system contains the control and instmmentation needed to change reactor power, control pressuriser pressure and level, eontrol feed water flow, turbine control and perform other plant fimetions associated with power generation. 

To ensure the function of reactor power control, two independent systems based on diverse drive mechanisms are provided for reactor shutdown. One system acts as an accident protection system, while the actuated second system is designed to provide guaranteed subcriticality for an unlimited period of time and to be able to account for any reactivity effects including those in accidental states. Either system can operate under the failure of a minimum of one rod with maximum worth. In case of loss of power to the reactor control and protection system (RCP), all rods of this system can be inserted in the core under the effect of gravity. 

Fig. 3 Simplified schematic of reactor and power control systems...

Reactivity control during and after the external event allowing, either automatically or through operator action, the power of the research reactor to be reduced to a sufficiently low level to maintain a suitable margin to deal with later events or an evolution in the emergency. Redundancy and diversity in the reactor reactivity control system should be demonstrated. 

A.813. This section should include a description of the instrumentation systems which are provided in the reactor control room for indicating the status of the protection system, the reactor power regulation system and other important systems. 

PWR Reactor following turbine Turbine control valves Reactor power Control rods. Chemical and volume control system... 

In order to clarify the characteristics of the reference control system, the plant dynamics is analyzed with the designed control system against the 10% stepwise decrease in the setpoint of the reactor power. The results are shown in Fig. 7.71 [31]. The pressure control system and the power control system work well. However, the change in the main steam temperature is still considerable. 

The plant response shown for this transient is similar to an alternator load reduction if the Brayton is operated without a speed control system. That is, vtrithout a speed control system, the Brayton speed will increase when electrical load is decreased. This speed increase produces a number of cascading effects that change the plant heat balance resulting in an increase in reactor power. Since the load reduction results in an increase in reactor power, the system is referred to as non-load following. This characteristic is a major reason that a Bra on shaft speed controi system is employed. The following transient description explains what happens in the overall plant as alternator load decreases and Brayton shaft speed increases. The effects are shown based on a load reduction in one loop only. If the transient was not due to a casualty, it is likely that a load reduction would be shared by both (all) operating Brayton loops. 

The reactor power regulation system is implemented as a software module within the Supervision and Control system. This system, when active, is responsible of regulating reactor power to its setpoint, compensating reactivity changes (temperature effects. Xenon, sample insertion, fuel bumup, etc.) and to perform power changes to new levels upon modification of the power setpoint... 

The Reactor Power Regulating System (RPRS) controls reactor power from source level to 125% of full power level, using neutron and gamma instrumentation ... 

The instrumentation and control system of the JRR-3M consists of its constituent systems of neutron instrumentation, process instrumentation, reactor power control, reactor protection, engineered safety feature stating and process radioactivity monitoring The system is designed and constructed under the laws, standards and criteria of those days with a satisfactory quality assurance program A specific feature of the system is an extensive introduction of computer systems with a process computer and a management computer This contributes to lightening operators loads satisfactorily... 

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Boron, in the form of boric acid, is used in the PWR primary system water to compensate for fuel consumption and to control reactor power (3). The concentration is varied over the fuel cycle. Small amounts of the isotope lithium-7 are added in the form of lithium hydroxide to increase pH and to reduce corrosion rates of primary system materials (4). Primary-side corrosion problems are much less than those encountered on the secondary side of the steam generators. 

Power reactors are similar to transformers. However, they have only one winding per phase and can be represented as shown in Figure 27.1. They are employed to perform a number of functions, primarily to control and regulate the reactive power of a power system by supplying the inductive and absorbing the capacitive power. Control can be achieved in different ways as noted later. The reactors, depending upon their design and l-(p characteristics, can be classified as follows ... 

Figure 5.2. Two of the more common types of low pressure CVD reactor, (a) Hot Filament Reactor - these utilise a continually pumped vacuum chamber, while process gases are metered in at carefully controlled rates (typically a total flow rate of a few hundred cubic centimetres per minute). Throttle valves maintain the pressure in the chamber at typically 20-30 torr, while a heater is used to bring the substrate up to a temperature of 700-900°C. The substrate to be coated - e.g. a piece of silicon or molybdenum - sits on the heater, a few millimetres beneath a tungsten filament, which is electrically heated to temperatures in excess of 2200 °C. (b) Microwave Plasma Reactor - in these systems, microwave power is coupled into the process gases via an antenna pointing into the chamber. The size of the chamber is altered by a sliding barrier to achieve maximum microwave power transfer, which results in a ball of hot, ionised gas (a plasma ball) sitting on top of the heated substrate, onto which the diamond film is deposited.

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