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The required range of neutron radiation intensity monitoring of the International Experimental Thermonuclear Reactor (ITER) is from 10 14 to10 21 n/s. One of the systems of neutron diagnostics, called the Divertor Neutron Flux Monitor (DNFM), contains as primary converters fission chambers (FCs) placed in the ITER Vacuum Vessel beneath the Divertor Dom. During the operation the FCs will be exposed to the intense neutron radiation and electromagnetic fields. The expected neutron flux at the location of the DNFM FC is 10 6-10 13 n•cm-2 •s-1. A distinctive feature of the neutron diagnostic channel for ITER is the desired time resolution of 1 ms and a measuring error of 10%. Such a requirement can be realized only at an FC signal registration rate of at least 1•10 5 s-1. Therefore, the pulse mode of processing the FC signals is very limited and it will probably be used only for calibration and diagnostics of the equipment. The working monitoring range of the channel with one FC will be less than 7 orders of magnitude. This explains the necessity of using several FCs with different sensitivity in the DNFM. The hardware of the signal processing equipment will be the same for all FCs. The wide-range channel equipment circuitry development for DNFM recording signals is based on the experience of the MEPhI in the development, implementation and operation of wide-range neutron flux monitoring equipment for control and protection systems (CPS) for various types of nuclear reactors. An important factor in the design of such equipment is the use of the fluctuation (Campbell) mode of fission chamber operation and signal processing equipment. The use of the fluctuation mode made it possible to radically solve the problem of the neutron flux monitoring in CPS channels in the 10-order range using a single FC. The equipment operates in the pulse, fluctuation and current modes. The work which related to the testing of the DNFM detector unit (DU) mockup by the influence of intensive fluxes of neutron and gamma radiation and evaluation of technical decisions of the neutron flux monitoring channel was performed with use of the research reactors. The fission chamber Signals Processing Unit (SPU) was used. This device based on microprocessors with wide application of high integration chips, including complex programmable logic devices (CPLD).Taking into account the requirements for ITER neutron diagnostics and the conditions for DU testing, the SPU circuitry was adjusted and the software of microprocessors and CPLDs was modified to control the temperature of the DU. In addition, a test complex including hardware and software for controlling equipment, processing and recording measurement data is assembled for a detailed research of the DU characteristics. The test complex includes the remote thermo assembly and the control and signal processing equipment. Thermo assembly includes an electric heater (EH) and a thermocouple (TC). Control and signal processing equipment consist of heater power supply (PS), DU signals processing unit ...

No abstract

The required range of neutron radiation intensity monitoring of the International Experimental Thermonuclear Reactor (ITER) is from 10 14 to10 21 n/s. One of the systems of neutron diagnostics, called the Divertor Neutron Flux Monitor (DNFM), contains as primary converters fission chambers (FCs) placed in the ITER Vacuum Vessel beneath the Divertor Dom. During the operation the FCs will be exposed to the intense neutron radiation and electromagnetic fields. The expected neutron flux at the location of the DNFM FC is 10 6 -10 13 n·cm -2 ·s -1 .A distinctive feature of the neutron diagnostic channel for ITER is the desired time resolution of 1 ms and a measuring error of 10%. Such a requirement can be realized only at an FC signal registration rate of at least 1·10 5 s -1 . Therefore, the pulse mode of processing the FC signals is very limited and it will probably be used only for calibration and diagnostics of the equipment. The working monitoring range of the channel with one FC will be less than 7 orders of magnitude. This explains the necessity of using several FCs with different sensitivity in the DNFM. The hardware of the signal processing equipment will be the same for all FCs.The wide-range channel equipment circuitry development for DNFM recording signals is based on the experience of the MEPhI in the development, implementation and operation of wide-range neutron flux monitoring equipment for control and protection systems (CPS) for various types of nuclear reactors. An important factor in the design of such equipment is the use of the fluctuation (Campbell) mode of fission chamber operation and signal processing equipment. The use of the fluctuation mode made it possible to radically solve the problem of the neutron flux monitoring in CPS channels in the 10-order range using a single FC. The equipment operates in the pulse, fluctuation and current modes.The work which related to the testing of the DNFM detector unit (DU) mockup by the influence of intensive fluxes of neutron and gamma radiation and evaluation of technical decisions of the neutron flux monitoring channel was performed with use of the research reactors. The fission chamber Signals Processing Unit (SPU) was used. This device based on microprocessors with wide application of high integration chips, including complex programmable logic devices (CPLD).Taking into account the requirements for ITER neutron diagnostics and the conditions for DU testing, the SPU circuitry was adjusted and the software of microprocessors and CPLDs was modified to control the temperature of the DU. In addition, a test complex including hardware and software for controlling equipment, processing and recording measurement data is assembled for a detailed research of the DU characteristics.The test complex includes the remote thermo assembly and the control and signal processing equipment. Thermo assembly includes an electric heater (EH) and a thermocouple (TC). Control and signal processing equipment consist of heater power supply (PS), DU signals processing un...

The Divertor nuclear flux monitor (DNFM) is one of the ITER neutron diagnostics. This diagnostic consists of the three same subsystems. Each subsystem concludes the detector module with fission chambers (FCs) and the data acquisition system (DAQ). To solve the task of the neutron flux measurements in the range of 7 orders of magnitude and 1 ms of time resolution the multidetector module is used. To confirm the possibility of the neutron flux measurements in a wide range using such a detector module and to evaluate the characteristics of the DAQ prototype a number of tests were carried out under conditions of the intense neutron radiation. The detector module and the DAQ, which are the prototype of the equipment planned for use on site were used for the tests. The tests were carried out at the plasma neutron diagnostic stand based on the NG-24M neutron generator and at the IBR-2 pulsed reactor of the Joint Institute for Nuclear Research. During the tests at the plasma neutron diagnostic stand the data for the calibration of the DNFM DAQ measuring channels were collected. During the tests at the IBR-2 pulsed reactor the signals from the measuring channels of the DNFM subsystem were obtained while the neutron flux was changed. This report shows the test results and the subsystem calibration techniques.