Patent Number: 042636540
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the fundamental construction of a normal value determining system according to the present invention. In FIG. 1, numeral 1 indicates a plant status deciding unit, numeral 2 indicates a normal value deciding unit, numeral 11 designates the present value signal of at least one type of plant data (digital or analog data), numeral 12 designates a signal corresponding to the present operation status and numeral 13 designates the normal value signal of at least one type of plant data. When one or more types of plant data represented by a signal or signals 11 are supplied to the plant status deciding unit 1, the present operation status of the plant is determined by comparing predetermined data values representing various operation steps with the plant data signal 11, and the signal 12 corresponding to the present operation step is supplied to the normal value deciding unit 2. One or more normal values are determined by the deciding unit 2 in response to the signal 12 from the deciding unit 1 and one or more signals 13 corresponding to the normal values are derived from the deciding unit 2. Two exemplary embodiments of a specific construction of the normal value determining system shown in FIG. 1 will be explained for a system adapted for use in a nuclear power plant using a boiling water reactor (BWR). The first embodiment relates to the situation in which a normal value of one type of plant data is determined on the basis of present values of a plurality of types of plant data. FIG. 2 illustrates the characteristic change of reactor pressure in the pressurization mode of operation during the start-up of the nuclear power plant. In this figure, the abscissa represents the different operation steps of the plant and the ordinate represents the reactor pressure. As seen from the drawing, the reactor pressure increases with the increase of step number, as shown by the solid line P. The steps of various operations to be executed in the pressurization mode are predetermined on the basis of the reactor pressure in the pressurizaton mode. Therefore, the present normal value of the reactor pressure can be determined on the basis of the progress of the operation step. That is, the normal value such as shown along dotted line Q is obtained by detecting the change of data corresponding to the operation step. Although this value changes stepwise, it is a satisfying value to give to the operator. FIG. 3 shows a schematic block diagram of the first embodiment of the present invention. In FIG. 3 numerals 11a to 11h indicate the present value signals of digital data, as shown in Table 1, numerals 3a to 3h data decision circuits for determining the status of the digital data 11a to 11h, respectively, numerals 14a to 14h signals representing the status of digital data, numeral 4 a code converter for producing a signal 12 corresponding to the operation status of the plant, numeral 5 a memory for storing a plurality of normal values of the reactor pressure, and numeral 6 a selector for selecting one normal value corresponding to the signal 12 from the memory 5 and for producing a normal value signal 13. TABLE 1 ______________________________________ signal classification of digital data status ______________________________________ 11a reactor pressure vessel vent valve closed 11b steam packing exhauster blower ON 11c mechanical vacuum pump OFF 11d clean-up auxiliary pump OFF 11e feedwater pump ON 11f clean-up recirculation pump ON 11g direction by supervisor OK 11h turbine turning motor stopped ______________________________________ The values of the digital data shown in the Table 1 change in response to the steps of the operation in the pressurization mode. These values of digital data are supplied to the data decision circuits 3a to 3h, which may be provided as simple comparator circuits, as signals 11a to 11h. It is determined by the data decision circuits 3a to 3h whether or not the present status represented by the digital data signals 11a to 11h coincide with the predetermined status shown in Table 1. In response to the presence or absence of such coincidence, a binary "1" or "0" signal, respectively, is produced as each of the signals 14a to 14h. For example, when the reactor pressure vessel vent valve is closed, a binary "1" signal is produced as the signal 14a. In the code converter 4, which may be a simple digital summing circuit, a singal 12 corresponding to the present operation status of the plant is produced according to Table 2. TABLE 2 ______________________________________ Signal 14 a b c d e f g h Signal 12 ______________________________________ 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 2 1 1 1 0 0 0 0 0 3 1 1 1 1 0 0 0 0 4 1 1 1 1 1 0 0 0 5 1 1 1 1 1 1 0 0 6 1 1 1 1 1 1 1 0 7 1 1 1 1 1 1 1 1 8 ______________________________________ For example, when only signal 14a is "1" and other signals 14b to 14h are all "0", signal "1" is produced as the signal 12. This signal 12 is supplied to the selector 6 of the normal value deciding unit 2. The normal values of the reactor pressure corresponding to respective operation steps of the plant have been stored at the respective addresses of the memory 5 corresponding to the values of signal 12, as shown in FIG. 4. The normal value of the reactor pressure is read out by the selector 6 from the address corresponding to the value of signal 12 and is outputted as a signal 13. Although signals 11a to 11h are provided in digital form in the above-mentioned embodiment, analog data can be used for the signals 11a to 11h. In FIG. 3, each of the data decision circuits 3a to 3h may be comprised of a register for storing the predetermined status of the corresponding plant data and a comparator for comparing the present status represented by each of the signals 11a to 11h with the predetermined status. The code converter is comprised of a converter for converting the combination of signals 14a to 14h to the corresponding signal 12. A general memory selecting circuit for reading out the information at the address corresponding to signal 12 can be used as the selector 6. A read only memory (ROM) can be used as the memory 5. A second embodiment of the present invention relates to the situation in which the normal values of a plurality of types of plant data are determined on the basis of the present value of one type of plant data. FIG. 5 shows the relationship between the reactor power and the feedwater flow. As seen from FIG. 5, the feedwater flow changes in proportion to the reactor power during the power-up mode at the start-up of the nuclear power plant of the BWR type. In like manner, such plant data as the main steam flow and the generator power change in the same proportion to the rector power in the power-up mode. Therefore, if a ratio of the present value of the reactor power to the rated value thereof is obtained, the present normal value of the feedwater flow, the main steam flow and the generator power, can be obtained by multiplying the rated value of the plant data by the appropriate ratio. FIG. 6 shows a specific example of a system in accordance with this second embodiment of the invention. In the drawing numeral 7 indicates a normalization circuit for calculating the ratio of the present value of the signal 11A representing the reactor power to the rated value thereof and for outputting a signal 12 corresponding to the ratio of the values, and numerals 8a, 8b, 8c identify multipliers for multiplying the rated value of the main steam flow, the feedwater flow, and the generator power by the ratio corresponding to the signal 12. In such construction, the present value of the reactor power is supplied as an analog signal 11A to the normalization device 7. A ratio of the present value 11A of the reactor power to the rated value thereof is calculated by the normalization device 7 and a signal 12 corresponding to the ratio is supplied to the multipliers 8a, 8b, and 8c. The rated values of the main steam flow, the feedwater flow and the generator power are multiplied by the ratio represented by signal 12. The normal values corresponding to the present operation step are thus obtained as signals 13a, 13b, and 13c. Although the normal values of three types of plant data are obtained in the above-mentioned embodiment, the number of types of plant data is not limited thereto and may be one or more than one. In FIG. 6, the normalization device 7 can be comprised of a register for storing the rated value of the reactor power and a divider for calculating the ratio of the present value of the reactor power, represented by the signal 11A, to the rated value stored in the register. Depending on the normal value determining system according to the present invention, the normal value of plant data which continuously changes in the transient operational mode can be determined by a system of simple construction and with high accuracy. By adding a display device, it is also possible to display the normal value of plant data. While we have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.