Patent Number: 051184613
Section: claims

1. A flow measuring apparatus for coolant flow in a boiling-water-reactor which is composed of a pressure vessel; the pressure vessel containing a core, a shroud and a shroud support leg; coolant circulation internal pumps being located in a flow path defined between the outer peripheries of the shroud and shroud support legs and the inner wall of the pressure vessel; and the shroud support leg having a plurality of leg openings, said apparatus comprising: rotational speed detecting means for detecting the rotational speed of the internal pumps;  pipe network model calculation means for receiving a rotational speed signal from the rotational speed detecting means and for calculating a flow rate of the coolant at any portion of the flow path on the basis of the rotational speed signal, said model calculation means initially storing a program for a closed pipe network model, corresponding to a flow from a pump outlet of the internal pump the the core,  and said model calculation means being responsive to the rotational speed signal to set constants for the model and analytically calculate a flow rate of the coolant at any required portion of that model; and  control means for controlling at least one of a coolant flow and a control rod position to control an output power of the reactor, said control means containing said pipe network model calculation means and controlling an output power of the reactor on the basis of a flow signal from the model calculation means.  rotational speed detecting means for detecting the rotational speed of the internal pump;  pipe network model calculation means for receiving a rotational speed signal from the rotational speed detecting means and for calculating a flow rate of the coolant at any portion of the flow path on the basis of the rotational speed signal, said model calculation means initially storing a program for a closed pipe network model, corresponding to a flow from a pump outlet of the internal pump to a corresponding leg opening, a flow from the pump outlet of the internal pump to a middle point between two adjacent internal pumps in the passage and a flow from the middle point to the leg openings,  and said model calculation means being responsive to the rotational speed signal to set constants for the model and analytically calculate a flow rate of the coolant at any require portion of that model; and  control means for controlling at least one of a coolant flow and a control rod position to control an output power of the reactor, said control means containing said pipe network model calculation means and controlling an output power of the reactor on the basis of a flow signal from the model calculation means.  .alpha..sub.1 : a discharge loss of the nozzle of the internal pump;  .alpha..sub.2 : a pressure loss involved from the nozzle section to a middle point between it and two internal pumps in the passage;  .alpha..sub.3 : a pressure loss at the location of the leg opening; and  .alpha..sub.4 : a pressure loss at the core and the lower plenum. 2. A flow measuring apparatus for coolant flow in a boiling-water-reactor which is composed of a pressure vessel; the pressure vessel containing a core, a shroud and a shroud support leg; coolant circulation internal pumps being located in a flow path defined between the outer peripheries of the shroud and shroud support legs and the inner wall of the pressure vessel; and the shroud support leg having a plurality of leg openings, said apparatus comprising: 3. The flow measuring apparatus according to claim 2, wherein said pipe network model programmed in said pipe network model calculation means is prepared by using .alpha..sub.1, .alpha..sub.2, .alpha..sub.3 and .alpha..sub.4 as flow resistances of corresponding closed pipe network of the model with respective flow/pressure loss characteristics of n number of the internal pumps as differential pressure Pn on those locations of the model corresponding pumps, where 4. The flow measuring apparatus according to claim 2, wherein the pipe network model calculation means comprises a plurality of pump deck differential pressure gauges detecting a differential pressure between suction and discharge sides of the internal pump; speed meters detecting the number of rotations of a respective motor for driving the internal pump; pump section calculation means for receiving a differential pressure signal output from the pump section differential pressure gauge and a rotational speed signal output from the speed transducer, for calculating, from initially measured internal pump characteristics, a discharge of each internal pump on the basis of both the signals, and for calculating a total flow rate of coolant summing up discharges of the pumps; and a pipe network model calculating means, programmed in advance, for receiving a rotational speed signal from each speed transducer, for calculating a flow rate of the coolant from the rotational speed signal, and for delivering a result of calculation as an output so as to adjust and back up the pump section calculation means.