Year
2016
Abstract
Physical start of pulse liquid fuel reactor IIN-3M was in December 1075. Up to 1981 reactor operated in normal mode and there were about 850 starts in different modes (pulse or up to 1-2 hours in 30 kW power). After mounting a new tank of reactor in July 1981 discharged fuel was loaded again and made physical start of reactor. Since 1981 there were about 2150 reactor starts in different modes. IIN-3M reactor operated in low intensity last years, with the frequency of about 1 start in a month. Planned technological shutdown of reactor occurred in June 1, 2013. 235U burnup is less than 1% and less than 40,32 g of 235U has burned. It accords to 36 MW*day energy release. For the calculations of isotopic activity in LSNF ORIGEN software was used. Nuclear constants were calculated using WIMS code. Isotopes activities were calculated with assumption that reactor operated 36 MW*day uninterruptedly, but in reality reactor operated in different modes about 3000 times in 33 years, This reason calculated data are higher, because the activities of decay products, appeared earlier, decrease according to exponential law. To determine the amount of accumulated isotopes of plutonium in LSNF of IIN-3M reactor operation data on fuel burnup was used with an account of calculated dependencies of plutonium accumulation from 235U and 238U burnup. Error in detection of accumulated plutonium, also as 235U, 238U isotopes mass changes, mainly, defined by accuracy of burnup depth detection in LSNF and don’t exceed 10-15%.