UDC: 614.876:621.039.572:539.1.074

Mon i tor ing of ra di a tion lev els in and around the nu clear re search re ac tors is es sen tial to safe-guard ing life and the en vi ron ment. Back ground ra di a tion mon i tor ing at the Pa ki stan In sti tute of Nu clear Sci ence & Tech nol ogy (PINSTECH) has been car ried out since the early six ties, be-fore the crit i cal ity of the 5 MW Pa ki stan Re search Re ac tor, so as to con firm the safe op er a tion of PINSTECH nu clear fa cil i ties. In the pres ent study, am bi ent dose rate lev els were mea sured around PINSTECH by us ing TLD–200 (G-2 cards) in stalled at 15 dif fer ent lo ca tions over a five year pe riod (1998-2002). The mean dose rates for in di vid ual lo ca tions in the said pe riod ranged from 0.14 � 0.01 to 0.19 � 0.03 µSv/h, with a mean value of 0.16 � 0.03 µSv/h. The cu-mu la tive av er age an nual ef fec tive dose equiv a lent spread over 5 years was 204.4 � 17 µSv. The data were com pared with the world and av er ages in other coun tries. It was con cluded that, from the health haz ard point of view, the op er a tion of re search re ac tors and other nu clear fa cil i-ties at PINSTECH pres ents no risk to pub lic health. Key words: en vi ron men tal ra di a tion, am bi ent dose rate, an nual ef fec tive doses, sea sonal vari a tion, re search re ac tors, thermoluminescence do sim e ter IN TRO DUC TIO