Type of neutron detector BF3 and fission counters

Type of signal cable Coaxial between detector and preamplifier, triaxial between preamplifier and amplifier

Location of pulse preamplifier Top of neutron-detector instrument well Location of pulse amplifier In amplifier cabinet at control room Distance between pulse amplifier and preamplifier 185 ft Distance between neutron detector and preamplifier 25 ft

Method of grounding A single point grounding system is used System ground is made at the amplifier cabinet The signal cabling, preamplifier, and neutron detector are insulated and floated above ground, being grounded at the amplifier cabinet The two shields in the triaxial cable are connected Coaxial fittings are used for both triaxial and coaxial cables The two shields are grounded at the amplifier cabinet The signal ground in the amplifier is grounded at the amplifier cabinet The amplifier cabinet is grounded to building ground through grounding cable and buses Operating problems and modifications During the initial installation and preoperational testing, it was discovered that the start-up channels were subject to transient noise problems from several systems throughout the reactor plant These noise problems were corrected at the source by replacing faulty relays and switches and by providing better shielding for fluorescent lighting After several years of operation, an unusual noise problem showed up at this power reactor site The reactor was shut down in preparation for refueling Just prior to the start of the second fuel-loading program, r-f noise showed up on all the signal buses coming out of the containment sphere The noise was of such magnitude that all operations were suspended After several davs of attempting to isolate the source of r f noise, the breakers at the 2180 kv substation were opened and closed by a planned operation The noise all but disappeared By readjusting the discriminator threshold bias control on the pulse amplifier, the start-up channels were brought within safe operating condition again A technical explanation has not been given as to what caused the severe r-f noise problem