Type of neutron detector BF3 Type of signal cable Triaxial

Location of pulse preamplifier At top of detector instrument well Location of pulse amplifier In amplifier cabinet at control room Distance between pulse amplifier and preamplifier 220 ft Distance between neutron detector and preamplifier 35 ft

Method of grounding A single-point grounding system is used The neutron detector is grounded to the building ground at its point of installation The inner and outer shields of the triaxial cable are grounded at the neutron detector One electrode of the neutron detector is connected to the inner shield The inner shield to the preamplifier is connected to the preamplifier signal ground The outer conductor is insulated and floated above ground back to the amplifier cabinet The signal ground of the preamplifier and amplifier are likewise insulated and floated above building ground, being grounded at the detector Operating problems and modifications During the initial installation and preoperational testing, it was discovered that the start-up channels were excessively noisy, which prevented further operation of the plant These problems were corrected by installing LR filters in the signal lead at the preamplifier output Other noise problems were isolated and corrected at the source, such as faulty switches, relays, and motor starters

See Secs 10 5 5(b) and 10 5 5(c)