Patent GB-918537-A (GB)
Title: Improvements in methods and devices for the automatic monitoring of the variations of a physical magnitude at a multiplicity of distinct points and in particular for detecting can leaks in the channels of a heterogeneous nuclear reactor
Inventor: PICARD ETIENNE
IPC: G21C17/04
Filed: 1960-02-17
Abstract: 918,537. Nuclear reactors. COMMISSARIAT A L'ENERGIE ATOMIQUE. Feb. 17, 1960 [Feb. 12, 1959], No. 5576/60. Class 39 (4). [Also in Groups XIX and XXIX] A method of monitoring the variations of a physical magnitude at a multiplicity of distinct points by means of a single instrument capable of measuring this magnitude, a multiplicity of ways being provided for transmitting this magnitude from the respective points to the instrument and a number of switch means being mounted in the ways, the group formed by the ways being divided into a plurality of subgroups, comprises operating the switch means cyclically to transmit to the instrument the mean value of the magnitude for each of the sub-groups successively and modifying the programme of switch control when a defect is detected in one sub-group by intercalating the magnitude at the respective points of the defective sub-group. The method may be applied to monitoring the fuel channels of a nuclear reactor and in Fig. 2 the reactor contains 1000 channels divided into 10 groups A-K each containing 20 sub-groups I-XX (of which the first two of group A are shown in Fig. 2) of five channels. The gas sampling pipes 1 of the channels are connected through valves 42 to a sub-collecting conduit 5 for each sub-group, and the conduits 5 are connected through valves 7 to a collecting conduit 8 for each group, the conduit 8 being connected to a radio-activity detector 2 which may be a scintillation counter. The output of the detector 2 is fed to a calculating unit 20 which, in conjunction with a memory unit 21, determines whether the ratio of radioactivity to reactor power (measured by unit 23) has increased since the previous cycle of monitoring. Normally the sub-groups are monitored cyclically from I to XX, but if a fault is indicated say in sub-group II, then after sub-group III has been monitored channel IIa is tested and after sub-group IV channel IIb and so on until the faulty channel is located, or if the fault clears itself the operator sets the apparatus to revert to its original programme. If a faulty channel is detected, say channel IIc, this channel is monitored after every fourth sub-group and when it is the turn of sub-group II the output of all the channels in sub-group II except IIc is monitored. Fig. 11 shows a diagram of a digital computer used to programme the operation of valves 4 2  and 7. When starting unit 38 is operated a signal I is sent through OR gate 43 into register 40, and when clock 39 sends a reading order this signal is sent to decoding unit 28 which opens the valve 7 of sub-group I. Further actuation of unit 38 sends a signal II into decoding unit 28 and at the same time a signal II is sent to compartment 35 1  of memory 35 through gate 45x which is open. During this time arithmetic unit 20 determines whether the radioactivity of subgroup I is normal and if it is sends a pulse through normally open gate 48x (gates 48y and 48z are normally closed) and OR unit 49 to open gates 47x and 45x. Gate 47x allows the contents of compartment 35 1  of memory 35 to pass to adding element 51 which adds n units to it to give a signal representative of the next sub-group which passes to the register 40, and so the programme continues. If the radioactivity is excessive a pulse from unit 20 operates flipflop 54 which sends a pulse from 54 1  to open gate 48y, close gate 48x, and operate flip-flop 60 through OR unit 59. Flip-flop 60 sends a pulse to open gate 62 to allow the signal stored in 35 1  of memory 35, after subtraction of n pulses in unit 63, to enter at 35 2  the signal representative of the faulty sub-group. It also sends a re-setting pulse to itself through unit 59 and thus sends a second pulse which opens gate 66 and transfers the contents of compartment 35 2  to 35 3  and to decoding unit 31 which closes the valves 4 2  of the defective sub-group. This second pulse also passes through OR unit 68 to open gates 45y and 47y and allow the signal representative of the defective subgroup to pass from compartment 35 2  to adding element 70 which transforms the sub-group signal, e.g. II, to a signal representative of channel IIa. On the next clock pulse the signal IIa is sent from register 40 to decoding unit 28 to open the corresponding valves and through gate 45y to compartment 35 2  Pulses from unit 20 now pass through gate 48y to flip-flop 73 which sends pulses alternatively to gates 47x and 47y so that the programme tests sub-groups and channels within the faulty sub-group alternately. When the faulty channel is detected unit 20 sends a second pulse to flip-flop 54 which sends a pulse from 54 2  which closes gate 48y, opens gate 48z, and operates flip-flop 80 through CR unit 81. Flip-flop 80 sends e pulse which opens gate 83 to transfer from compartment 35 2  to compartment 35 4  the signal representative of the faulty channel, for example IIC; unit 80 also resets itself through OR unit 81 and produces a second pulse which opens gate 86 to transfer from compartment 35 4  to 35 5  a signal complementary to signal IIc, that is to say representative of all the channels of sub-group II except IIc, by backward displacement in unit 87. The second pulse from unit 80 also opens gates 45z and 47z and allows the contents of compartment 35 4  (the signal IIc) to pass into the register 40 When the next clock pulse occurs the signal IIc is sent from the register 40 to unit 28 and to compartment 35 4 . Pulses from unit 20 now pass through gate 48z to a scale of five ring counter 91 so that the first four pulses pass through gate 47x and continue monitoring the subgroups whilst the fifth pulse passes through gate 47 z  and monitors the suspected channel. The second pulse from flip-flop 80 controls unit 20 through line 95 to prevent further pulses due to the faulty channel already detected from passing to flip-flop 54 whereas a new fault can cause a repetition of the fault programme. When next it is the turn of the faulty subgroup to be monitored a coincidence unit 96 is actuated by the contents of compartment 35 3  and that of 35 1  to which n pulses are added in unit 99; the pulse from unit 96 closes gate 52 and opens gate 102 to allow the complementary signal from 35 5  to pass into the register 40. Specifications 899,747 and 918,536 are referred to.