RADIATION HARDNESS TEST OF A SILICON DETECTOR AND PREAMPLIFIER OVER THE DESIGN LIFETIME FOR A REACTOR COOLANT LEAKAGE MONITORING SYSTEM

Abstract

Radiation hardness tests were condusted on a silicon detector and preamplifier to develop a reactor.coolant leakage monitoring system, which detects high-energy beta particles from 16N in the primary reactor coolant of nuclear power plants. Monte Carlo simulations were used to calculate the doses that would be absorbed on components over a 60-year design lifetime. The components were exposed to a 6 degrees Co gamma source with an activity of 2.4 kCi for 54 hours. The absorbed doses accumulated during the test were determined to be 0.99 kGy for the de- tector and 1.37 kGy for the preamplifier. During the test, the alpha count from a check source in the high-channel range disappeared in a high-dose-rate environment, and the gross gamma count decreased as the accumulated dose increased. The performance degradation of the de- tector and preamplifier was evaluated by comparing the alpha signals and background noise before and after irradiation. The energy resolution of the alpha signals in the high-channel range exhibited slight changes, whereas the electronic noise in the low-channel range in- creased by approximately 773% for the irradiated detector and 17% for the irradiated pre-amp. A method employing various low-level discriminator channels is proposed to miti- gate noise effects in the monitoring system.

Testovi ~vrsto}e na radijaciju sprovedeni su na silicijumskom detektoru ipretpoja~ava~u kako bi se razvio sistem za pra}ewe curewa rashladne te~nosti reaktora, kojidetektuje visokoenergetske beta ~estice iz 16 u primarnom hladiocu reaktora nuklearnih elektrana. Monte Karlo simulacije kori{}ene su za izra~unavawe doza koje bi se apsorbovale na komponentama tokom 60-godi{weg projektovanog veka trajawa. Komponente su bile izlo`ene 60 gama izvoru aktivnosti od 2.4 tokom 54 ~asa. Utvr|eno je da su apsorbovane doze akumulirane tokom testa bile 0.99 za detektor i 1.37 za pretpoja~ava~. Tokom testa, alfa odbroj iz test izvora u opsegu visokih kanala nestajao je u okru`ewu sa velikom ja~inom doze, a bruto gama broj smawivao se kako se akumulirana doza pove}avala. Degradacija performansi detektora ipretpoja~ava~a procewena je pore|ewem alfa signala i pozadinskog {uma pre i posle zra~ewa. Energetska rezolucija alfa signala u visoko-kanalnom opsegu pokazala je male promene, dok je elektronski {um u niskokanalnom opsegu pove}an za pribli`no 773 % za ozra~eni detektor i 17 %za ozra~eni pretpoja~ava~. Predlo`ena je metoda koja koristi razli~ite diskriminatorske kanale niskog nivoa za ubla`avawe efekata }uma u sistemu za pra~ewe.