NFA-05.06: Neutron Flux Data Processor

The signals from analogue modules are further processed in the Neutron Flux Data Processor (NFDP) type NFA-05.06. The signal exchange between analogue modules and NFDP is performed by two manners:

  1. Via galvanic isolated parallel signals (analogue and digital) without inherent intelligence;
  2. Via serial communication link (RS485/ANSI protocol).

The conditioned detector signals (pulse, AC and DC) are led to the NFDP. Then these signals are combined to form a continuous extended wide range signal using an overlapping algorithm. A sliding transition from the pulse signal to the ac current signal and from the ac signal to the dc current signal is guaranteed by overlapping algorithm. The following values are calculated from the extended wide range signal:

  1. In the percent power function the linear power level from 0,1 % to 125% is measured in two ranges. This function is scoped to accurate measurement of power in nominal power range.
  2. In the wide range logarithmic power function the power signal in logarithmic scale is presented. This function provides for the reading of ten-decade power magnitude in a single range.
  3. In the multirange function the equipment converts the wide range power signal into 16 linear power ranges. This feature provides more precise reading of linear power level over the entire range of reactor power. The multirange function is either auto range or slaved to an operator switch on control console. Automatic range selection is performed in the NF computer.
  4. Period time and reactivity.
  5. It generates alarms and emergency shutdown signals if the neutron flux is too high or if the flux changes rapidly. The NFDP provides isolated digital output signals for the safety logic through SAFETY connector. ALARM or WARNING lamps on the front panel lights if any of the alarm or warning situations has occurred.
  6. NFDP also produces a number of values which, when transmitted to the control room, provide the operator with information on the state of the reactor. The signals are led to REMOTE connector as isolated 0/4 to 20 mA outputs.

Primary function of the built-in computer, in addition to the mentioned level excess monitoring, is to establish man-machine connection, and to produce accessibility of the measured data via a serial interface. Operator interface comprises a 4x20 character wide vacuum fluorescent display and a keyboard of 21 push buttons.

In LOCAL mode by means of the keyboard one can control the operation of the whole channel, set measuring range, changing display picture, controlling test, power etc. In remote mode the trip reset and range control can be implemented through REMOTE rear panel connectors.

The NFA-05.06 type NFDP has testing and calibration functions. Watchdog unit supervises the proper operation of the whole digital processing hardware. The WORK lamp shows the state of the watchdog unit.

The modules of NFDP are situated in a 19" rack. On the front panel, the operator interface comprises a 4x20 character wide vacuum fluorescent display, keyboard of 21 push buttons, and indicator lamps (WORK, ALARM, WARNING). The power switch, mains connector and fuse are on the back panel. Analogue module connectors are also placed on the back panel. In addition, there are still several terminals on the back panel, which are mainly important for servicing.