JP2008014705A - Nuclear reactor monitoring unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nuclear reactor monitoring unit seldom giving a wrong alarm by a simple constitution. <P>SOLUTION: The nuclear reactor monitoring unit monitors a nuclear reactor (30) for an abnormality by output signals of a neutron detector of a start-up system installed inside the nuclear reactor (29), a neutron detector of an operation system and a γ-ray detector of a safety system. The unit includes detectors of the same types A1, A2 and B1, B2 symmetrically arranged with respect to a core 30 to obtain outputs of the same level, and has the function of making a judgment of an abnormality in a measuring system and giving an alarm if the outputs k1, k2 of the detectors of the same type satisfy the relationship of ¾(k1-k2)/(k1+k2)¾>α, wherein α represents a predetermined value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reactor monitoring apparatus for monitoring an abnormality of a small nuclear reactor.

  Test and research reactors are reactors designed and constructed for test and research, and can be broadly divided into research reactors and critical test equipment. A research reactor is a reactor that performs radiation tests on nuclear materials and fuels, manufactures radioisotopes for medical and industrial use, education and training for students and engineers, etc. using radiation generated by nuclear reactions. . The criticality test apparatus is a nuclear reactor whose core structure can be easily changed, and is provided exclusively for measuring nuclear characteristics of the nuclear reactor, such as the critical amount of nuclear fuel material. The reactor is provided with a monitor device that measures the neutron flux and monitors the reactor output (Patent Document 1).

Small reactor monitoring devices such as test and research reactors have a small number of measurement systems and are not as reliable as power generation reactors. The alarm signal is output with the OR of the signal at the time of exceeding) and scrammed. However, it has simplified earthquake resistance, noise resistance, environmental resistance, etc. compared to power reactors. In each measurement system, false signals due to vibration, false signals due to external noise, minute discharge due to moisture, etc. In addition, there is a possibility of an erroneous signal due to, and since an alarm signal is output by OR of a plurality of measurement system signals, there is a high possibility of scram due to an erroneous signal.
JP-A-1-301196

  As described above, the monitoring device for the test and research reactor is different from the power generation reactor in that the system is simple and the number of measurement systems is small. There is a high possibility of scramming due to false alarms. When a scrum occurs, a great deal of effort is required to promptly report it to local governments and countries, and then identify the cause of the occurrence.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a reactor monitoring apparatus with a simple configuration and few false alarms.

  In order to solve the above-mentioned problems, claim 1 of the present invention is characterized in that the atomic neutron detector, the neutron detector for the operating system, and the γ-ray detector for the safety system installed in the nuclear reactor are used to output the atoms. In a reactor monitoring device that monitors reactor abnormalities, the same kind of detectors are arranged at symmetrical positions with respect to the core so that the same level of output can be obtained, and the outputs k1 and k2 of the same kind of detectors are When | (k1−k2) / (k1 + k2) |> α with respect to the predetermined value α, the measurement system is judged to be abnormal and has a function of issuing an alarm.

  Claim 2 is a reactor monitoring apparatus for monitoring an abnormality of the reactor by output signals of an activation system neutron detector, an operation system neutron detector and a safety system γ-ray detector installed in the reactor. A first comparison circuit for outputting an abnormal signal when the output signal of the detector continuously exceeds a set value for a predetermined time, and a determination time shorter than the predetermined time with a value larger than the set value as a set value. And a second comparison circuit that branches and inputs the output signal.

  According to a third aspect of the present invention, there is provided a reactor monitoring apparatus for monitoring an abnormality of the nuclear reactor based on output signals of a starting neutron detector, an operating neutron detector, and a safety γ-ray detector installed in the nuclear reactor. The operating neutron measurement system includes a pulse counting circuit that counts neutron detection signal pulses and a determination circuit that outputs a signal when the pulses exceed a predetermined count rate.

  According to the present invention, it is possible to provide a reactor monitoring apparatus with few false alarms with a simple configuration.

  Compared to the nuclear power reactor, the utilization rate of the test and research reactor is not much of a problem. Rather, the scram caused by a false signal has a greater effect. For this reason, in the reactor monitoring device of the present invention, the soundness confirmation function of the circuit system is strengthened, the preventive maintenance function is strengthened by measuring the predictive phenomenon of a failure that will occur in the future, and an alarm is issued when there is a problem. Prevent the occurrence of scrum due to false signals by stopping the system by human system and checking the part. In addition, an abnormality determination means is introduced in each measurement system so that it functions effectively against an initial burst signal due to a rapid increase in the in-core neutron flux, in addition to preventing false alarms due to false signals.

  FIG. 1 shows a basic configuration of a reactor monitoring apparatus according to an embodiment of the present invention. This system consists of 3 startup systems with neutron detectors A1, A2 and A3, 3 operating systems with neutron detectors B1, B2 and B3, 1 safety system with γ-ray detector C1, alarm A generator 15 and an alarm generator 17 are provided.

  The starting system is composed of two systems (neutron detectors A1 and A2) of neutron counting circuits and one system of neutron pulse logarithmic period circuits (neutron detector A3). The operation system is composed of two systems (neutron detectors B1 and B2) of neutron micro DC amplification circuits and one system (neutron detector B3) of neutron current log period circuits. The safety system is composed of a gamma ray detector counting circuit of one system (γ ray detector B3) for measuring the gamma dose in the core.

  The above-mentioned seven systems of abnormal signals are processed by the logic circuit 22 in the alarm generator 15 shown in FIG. 2 under the OR condition. When the condition is satisfied, an alarm signal is generated and a scram signal is output to the control rod drive controller 16. Then, a signal is output from the alarm generator drive circuit 26 to the alarm generator 17.

  When the counting rate of the two pulse counting circuits of the starting system is equal to or greater than a predetermined set value, the logarithmic period circuit of one system is determined by the determination circuits 13-1 and 13- when the period value falls below a predetermined value (several seconds). 2 or 13-3 gives an alarm signal. Similarly, in the case of the operation system, when the current values of the two micro DC current amplifier circuits are equal to or greater than a predetermined value, and when the period value of the current log period circuit is equal to or less than the predetermined value, the determination circuit 13-4, An abnormal signal is output by 13-5 or 13-6. In the safety system, the determination circuit 13-7 outputs an abnormal signal when the γ-ray level becomes a predetermined multiple (several times) or more of the background. The period is the time required to reach e times when the number of neutrons increases exponentially.

  In order to check the soundness of this apparatus, when the power supply voltage of the low voltage power supply 10-1 to 10-7 or the high voltage power supply 3-1 to 3-7 deviates from a predetermined range, the monitor signal is sent to the alarm generation device. 15 is transmitted to the computer 24 via the interface 23 in the system 15, and an alarm is displayed on the display unit 27. Further, the confirmation of the gain of the circuit system is made between the detectors A1 to C1 and the amplifiers 5-1, 5-2, 5-7, 6-3, 7-4, 7-5 and 8-6. 2-1 to 2-7 are provided, and a changeover signal is transmitted from the computer 24 in the alarm generation device 15 to the changeover switches 2-1 to 2-7 via the interface 23, and periodically, the reference pulse generator 4 -1,4-2,4-3 (starting system) and reference minute current generators 9-4, 9-5, 9-6 (operating system) are driven, the gain of the measuring system with respect to the input is confirmed, and predetermined If it deviates from the range, an alarm is issued and inspection can be performed.

(Example 1)
The reactor monitoring apparatus of the present embodiment further enhances the soundness check function of the measurement system, issues an alarm when there is a problem with soundness in any of the measurement systems, stops the reactor and stops the measurement system. Perform the inspection. This improves the reliability of the measurement system and prevents the occurrence of an event that leads to scram due to an error signal.

  That is, as shown in FIG. 3, the same type of detectors (A1 and A2, B1 and B2) are arranged symmetrically with respect to the core 30 so that the same level of output can be obtained. When the outputs a1 and a2 of the detectors A1 and A2 or the outputs b1 and b2 of the two detectors B1 and B2 in the operating system satisfy the following expression (1) or (2), it is determined that the measurement system is abnormal. An alarm is issued, the furnace operation is stopped, the gain of the circuit system is confirmed by the reference pulse generator and the reference minute current generator, the sensitivity calibration of the detectors A1, A2, B1, and B2 is performed to identify and repair the problem. I do.

| (A1-a2) / (a1 + a2) |> α (1)
| (B1-b2) / (b1 + b2) |> β (2)
(Α and β depend on the device and test method, but values such as 0.1)

(Example 2)
If the same type of detectors cannot be placed symmetrically with respect to the core and the signal levels are different, the ratio of the signal levels of the two detectors is the following formula (2) or (3): If it deviates from such a certain range, it is determined that the measurement system is abnormal, and the problem is identified and repaired in the same manner as described above.

α1 <a1 / a2 <α2 (3)
β1 <b1 / b1 <β2 (4)
(Although α1, α2, β1, and β2 depend on the apparatus test method, for example, when a1 / a2 is 0.5, α1 = 0.4 and α2 = 0.6. The same applies to β1 and β2.)

(Example 3)
In general, a reactor monitor device outputs a signal when a plurality of detector signal levels exceed a set value, and issues a scram by scoring with an OR. In order to prevent false alarms, a signal is generated under an OR condition established within a predetermined time. In addition, transient signals such as external noise (does not continue with a single pulse) may enter the measurement system and exceed the set value. Only signals that have exceeded the set value for a predetermined time must be monitored. And measures are taken. The problem in this case is that the initial burst that generates large neutrons in a relatively short time is overlooked if the duration is short.

  In the reactor monitoring apparatus of the present embodiment, this time interval is variable according to the input signal level. That is, as shown in FIG. 4, in addition to the normal setting value comparison circuit 32, for example, a voltage comparison circuit 36 several times (for example, three times) the setting value is added to the determination circuits 13-1 to 13-7. Assuming that the normal set value duration time condition is the delay time ΔT1, and the set time value is several times the duration time condition of the comparison circuit 36, the delay time ΔT2, for example, ΔT1 = 4 seconds and ΔT2 = 0.5 seconds. Allow setting.

  Specifically, the signal from the detector is branched, and for example, when the normal setting value of the comparison circuit 32 is 1 V and the latter continues for 0.5 seconds or more, it is determined that there is an abnormality. The duration condition creates a pulse signal whose duration is the pulse width when the set value is exceeded, generates a reference signal when the set value falls below the set value, and takes the AND of the reference signal and the duration pulse, and the AND signal If this occurs, the generation of an “abnormal” signal is prevented.

Example 4
As a predictive phenomenon of an event leading to a scrum, there may be a case where a pulse-like signal appears in the current output of the minute DC current amplifiers 7-4 and 7-5 of the neutron detectors B1 and B2 in the operating system. The cause is creepage discharge at the high voltage application portions of the detectors B1 and B2 and the cable connector due to environmental conditions (mainly humidity), disturbance of the outputs of the high voltage power supplies 3-4 and 3-5, external noise, and the like.

  Normally, the current amplifier is not provided with a pulse measurement system. In this embodiment, as shown in FIG. 5, a pulse amplifier circuit 41 and a pulse counter circuit 42 are provided in parallel with the current amplifier circuit 40 to detect the current amplifier. The detector signal is branched and the pulses are counted. When the determination circuit 43 exceeds a predetermined count rate, an alarm is issued, the furnace is stopped, the relevant part is inspected and repaired, and the occurrence of a scram event is prevented.

1 is a block diagram showing a basic configuration of a reactor monitoring apparatus according to an embodiment of the present invention. The horizontal sectional view which shows the arrangement | positioning in the reactor of the neutron detector with which the reactor monitoring apparatus of embodiment of this invention is equipped. The block diagram (a) which shows the structure of the alarm generator with which the reactor monitoring apparatus of embodiment of this invention is equipped, and the time chart (b) which show operation | movement. The block diagram which shows the structure of the determination circuit with which the reactor monitoring apparatus of embodiment of this invention is equipped. The block diagram which shows the structure of the micro direct current amplifier with which the nuclear reactor monitoring apparatus of embodiment of this invention is equipped, and the determination circuit.

Explanation of symbols

  A1, A2, A3, B1, B2, B3 ... neutron detector, C1 ... γ-ray detector, 2-1 to 2-7 ... changeover switch, 3-1 to 3-7 ... high voltage power supply, 4-1, 4-2, 4-3, reference pulse generator, 5-1, 5-2, 5-7, pulse amplifier, 6-3, pulse logarithmic period amplifier, 7-4, 7-5, minute DC current amplifier, 8-6... Current logarithmic period amplifier, 9-4, 9-5, 9-6... Reference minute current generator, 10-1 to 10-7... Low voltage power supply, 11-1, 11-2. , 12-1 to 12-7 ... power supply voltage monitor circuit, 13-1 to 13-7 ... determination circuit, 15 ... alarm generator, 16 ... control rod drive controller, 17 ... alarm generator, 20, 21 ... ADC (Analog / digital conversion) circuit, 22 ... logic circuit, 23 ... interface, 24 ... computer, 2 Reference pulse / current generator drive circuit, 26 Alarm generator drive circuit, 27 Display unit, 29 Reactor pressure vessel, 30 Core, 31 Water-tight pipe, 32, 36 Comparison circuit, 33, 37 Setting voltage generation circuit, 34, 38 ... delay pulse generation circuit, 35 ... AND circuit, 40 ... current amplifier, 41 ... pulse amplification circuit, 42 ... pulse counting circuit, 43 ... determination circuit.

Claims (3)

  In a reactor monitoring apparatus that monitors abnormalities of the reactor by output signals of a starting neutron detector, an operating neutron detector, and a safety γ-ray detector installed in the reactor, The same kind of detectors are arranged at symmetrical positions so that the same level of output is obtained, and the outputs k1 and k2 of the same kind of detectors are | (k1−k2) / (k1 + k2) with respect to a predetermined value α. A reactor monitoring device characterized by having a function of judging that the measurement system is abnormal and issuing an alarm when |> α.   In a reactor monitoring apparatus that monitors an abnormality of the reactor by output signals of a starting neutron detector, an operating neutron detector, and a safety γ-ray detector installed in a nuclear reactor, the detector A first comparison circuit that outputs an abnormal signal when the output signal continuously exceeds the first set value for a predetermined time, and a value larger than the first set value is set as a second set value, which is longer than the predetermined time. A reactor monitoring apparatus comprising: a second comparison circuit that branches and outputs the output signal with a short discrimination time.   In a reactor monitoring apparatus that monitors an abnormality of the reactor by output signals of a starting neutron detector, an operating neutron detector, and a safety γ-ray detector installed in a nuclear reactor, the operating system A reactor monitoring apparatus comprising: a pulse counting circuit that counts neutron detection signal pulses in a neutron measurement system; and a determination circuit that outputs a signal when the pulses exceed a predetermined count rate.

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