A NEW MONITORING MICROSYSTEM FOR RADIATION MEASUREMENT BASED ON VSLI TECHNIQUE

During the researches performed at CERN in high energy physics a new s emiconductor gamma detector, based on VSLI electronics was developed a t INFN. This device is little, cheap reliable and presents high perfor mances. In the frame of a collaboration work, performed between DITEC, Ansaldo Ricerche, and INFN, was proposed, as possible, a new use of t his detector, different from high energy experiments, namely, the ''AV ERAGE AXIAL POWER DISTRIBUTION MEASUREMENT IN A NUCLEAR FISSION REACTO R, 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 mo nitors the ex-core neutron flux at one specific elevation.The new prop osed Ex-core NIS concepts, is based on the presence of a large number of puntiform silicon detectors axially and radially arranged out of th e Reactor Vessel and the concrete primary shield. The presence of a la rge number of detectors and the use of a fast charge preamplifier, con nected to the silicon detectors(both of low cost), allows the use of a computer for on line direct control and protection system enhancing s afety and economic characteristics of the nuclear reactor. In this pap er, after description of the semiconductor detector, of the preamplifi er, and of their performances, the above indicated application are des cribed, stressing the safety and economics advantages to be reached th rough its use.