Detection device UDPN-04 is intended for monitoring of density of thermal neutron flux of ionization chambers during physical start-up in composition of neutron flux monitoring equipment (NFME).
UDPN-04 ensures the monitoring of thermal neutron flux density within the range from 3.0·10-3 to 5.0·102 cm-2·s-1 (neutr.·(cm2·s)-1) at the dose rate of background gamma-radiation absorbed in the air at the place of detection unit location of not more than 0.1 Gy·h-1 (10 R·h-1) at nominal power of reactor plant (100 %).
UDPN-04 sensitivity for thermal neutrons is (60 ± 10) cm2 (pulses during 1 s at the flux density of 1 neutron via 1 cm2 during 1 s).
Detection device UDPN-04 consists of:
- Detection unit BDPN-04, implemented in the form of casing (thin-wall cylinder made of stainless steel). BDPN-04 converts neutron radiation into current pulses.
The appearance of detection unit BDPN-04 is presented on the picture:
- Conversion unit BPH-04, implemented in the form of flat housing, inside of which electromagnetic shield with electronic modules is located. BPH-04 performs the following:
- amplification of current pulses from BDPN-04;
- discrimination of noise pulses;
- generation of output pulses which frequency is proportional to neutron flux density.
The appearance of conversion unit BPH-04 is presented on the picture:
UDPN-04 is based on helium corona counters of neutrons SNM18-1 with radiofrequency flexible cable KAGE-HF. Length of BDPN-04 cable is 22.5 meters.