A new monitoring microsystem for radiation measurement based on VSLI technique

During the researches performed at CERN in high energy physics a new semiconductor gamma detector, based on VSLI electronics was developed at INFN. This device is little, cheap reliable and presents high performances. In the frame of a collaboration work, performed between DITEC, Ansaldo Ricerche, and INFN, was proposed, as possible, a new use of this detector, different from high energy experiments, namely, the “AVERAGE AXIAL POWER DISTRIBUTION MEASUREMENT IN A NUCLEAR FISSION REACTOR, USING MANY EXCORE DETECTORS”. At present, the current PWR Ex-Core Nuclear Instrumentation System (NIS), is based on a detection facility, composed of four/six axial ionization chambers, each one of which monitors the ex-core neutron flux at one specific elevation. The new proposed Ex-core NIS concepts, is based on the presence of a large number of puntiform silicon detectors axially and radially arranged out of the Reactor Vessel and the concrete primary shield. The presence of a large number of detectors and the use of a fast charge preamplifier, connected to the silicon detectors (both of low cost), allows the use of a computer for on line direct control and protection system enhancing safety and economic characteristics of the nuclear reactor. In this paper, after description of the semiconductor detector, of the preamplifier, and of their performances, the above indicated application are described, stressing the safety and economics advantages to be reached through its use.