Radiation consequences of hypothetical accidents associated with transportation of spent nuclear fuel of nuclear submarines aboard floating technical base S.Bogatov, V.Vysotsky, V.Kiselev, O.Sorokovikova Nuclear Safety Institute of Russian Academy of Science, 115191, 52 B.Tulskaya, Moscow, Russia Reload of spent nuclear fuel of nuclear submarines and its subsequent transportation for reprocessing may be carried out by the vessel – floating technical base (FTB). Up to 4 reactor cores can be taken aboard, transportation can occur for distance of dozens and thousands kilometers. In case of the accidents with infringement of protective barriers, FTB may occur to be a significant source of radiation hazard. Two hypothetical accidents associated with explosion aboard and sinking the FTB are analyzed in the report. In the first case a source term for the release and aerial radionuclide spreading out have been estimated, in second case radiation consequences have been estimated for water way taking into account remaining protective barriers. Main task of the assessments was radiation impact at long distances from the source. Source term calculations took into account liquid radioactive waste (LRW, ~10 13 Bq) and spent nuclear fuel (SNF, ~10 16 Bq) on board of FTB. Conservative assumptions have been done for aerial release combining dispersal of SNF due to internal explosion and release elevation due to large fire. Full dispersal and elevation of 2% of SNF in one tank was taken, initial distribution of radionuclides along height of release was considered. “Low” part of release was associated with fume column, “high” part was associated with ascending high temperature cloud. Calculations were performed for “dry” and “wet” (atmospheric precipitations during cloud propagation) sediments. The results of radiation consequences expected for severe accident due to aerial release at pass of FTB from Kamchatka to Primorye are presented in following table for several points. Calculations have been done by computer code “Nostradamus”. Main results of calculation of radiation consequences due to explosion on board of FTB Assessment Parameter Western part of Aleutian islands Petropavlovsk- Kamchatsky city Northern shore of Hokkaido Distance from the place of accident, km 1000 20 50 Time of cloud arrival, hour 25 1,25 3 Time of inhalation, hour 35 0,25 0,5 Effective inhalation dose, micro Sv 1,7 1400 55 “dry” deposition 900 110 6 310 4 Surface contamination (max.), Bq/m 2 “wet” deposition 6500 210 6 1,810 5 “dry” deposition <2 1800 60 Maximal effective annual dose, micro Sv “wet” deposition 2,5 1800 100