ENTRY 30753 20090908 31413075300000001 SUBENT 30753001 20090908 31413075300100001 BIB 15 86 3075300100002 TITLE Measurement of the 235-U/238-U fission cross section 3075300100003 ratio in the 235-U fission neutron spectrum 3075300100004 AUTHOR (D.Azimi-Garakani,M.Bagheri-Darbandi) 3075300100005 INSTITUTE (3IRNTEH) 3075300100006 REFERENCE (R,INDC(IRN)-003,198306) 3075300100007 FACILITY (REAC,3IRNTEH) 3075300100008 INC-SOURCE The neutrons originated from the reactor core are 3075300100009 slowed down in a graphite thermal column and collimated3075300100010 The collimated neutron beam impinges on a 235-U fission3075300100011 plate and produces fast fission neutrons which are used3075300100012 as source to hit the sample 3075300100013 SAMPLE Six fissionable deposits were used as samples.The 3075300100014 deposits were 20-mm-diam vacuum evaporated on backings 3075300100015 of 32 mm diam polished platinum 0.125 mm thick.The mass3075300100016 assay of the deposits is as follows: 3075300100017 Foil Principal Mass of 3075300100018 identification isotope principal isotope 3075300100019 UT-51 235-U 79.7 +- 0.4 3075300100020 UT-52 235-U 264.8 +- 1.3 3075300100021 UT-53 235-U 729.5 +- 4.0 3075300100022 UT-81 238-U 81.9 +- 2.5 3075300100023 UT-82 238-U 276.1 +- 8.3 3075300100024 UT-83 238-U 777.0 +- 23.0 3075300100025 The isotopic concentration of the deposits UT-51,UT-52 3075300100026 and UT-53 is as follows 3075300100027 1.179 % of 234-U 3075300100028 93.197 % of 235-U 3075300100029 0.250 % of 236-U 3075300100030 5.435 % of 238-U 3075300100031 The isotopic concentration of the deposits UT-81,UT-82 3075300100032 and UT-83 is as follows 3075300100033 0.005 % of 235-U 3075300100034 99.995 % of 238-U 3075300100035 INC-SPECT The incident-projectile beam is a product of the 3075300100036 reaction 235-U(n,f) as explained under INC-SOURCE 3075300100037 DETECTOR (TRD) 12 Makrofol solid state nuclear track 3075300100038 detectors were used. Six of the Makrofol films were 3075300100039 0.025 mm thick (thin films) and the rest were 0.06 mm 3075300100040 thick (thick films) 3075300100041 METHOD The 235-U/238-U fission cross section ratio was 3075300100042 measured in the fast neutron field using Makrofol 3075300100043 solid state nuclear track detectors.The track detectors3075300100044 were irradiated with the UT enriched and depleted 3075300100045 deposits, and after the etching they were counted by an3075300100046 optical microscope 3075300100047 CORRECTION The corrections applied to the isotopic fission rates 3075300100048 include the absorption of fission fragments in the 3075300100049 deposits, fission in other isotopes where the 3075300100050 corrections are 0.9863 and 0.9998 for 235-U and 238-U 3075300100051 respectively,neutron scattering and absorption and flux3075300100052 perturbation caused by the hydrogen in the Makrofol 3075300100053 ERR-ANALYS (DATA-ERR) The combined uncertainty ascribed to the 3075300100054 observed number of tracks per unit area arises from 3075300100055 the possible sources of systematic errors which are 3075300100056 track counting statistics,background,exposure 3075300100057 timing,irradiation positioning,imperfect contact 3075300100058 between deposit and the solid state nuclear track 3075300100059 detector,radial uniformity of the fission sources 3075300100060 and calibration of the microscope field of view. 3075300100061 Other possible systematic errors such as integrity 3075300100062 of the deposits,flux perturbation by the specimen 3075300100063 holder, track overlap, variation of track density 3075300100064 with etching time and temperature and uncertainty 3075300100065 in the etchant concentration are all assumed to be 3075300100066 negligible. The uncertainties assigned to the 3075300100067 235-U/238-U fission ratios include uncertainties in 3075300100068 mass per unit area(mass assay errors, deposit area), 3075300100069 uncertainties in corrections (see under correction) 3075300100070 and uncertainties in count ratios 3075300100071 COMMENT The following values of the 235-U/238-U fission cross 3075300100072 section ratio show that there is no significant 3075300100073 difference with the thin and the thick films. 3075300100074 Detector Foil 235-U/238-U fission 3075300100075 identification cross section ratio 3075300100076 Thin Makrofol UT-51/UT-81 3.78 +- 0.3 3075300100077 Thin Makrofol UT-52/UT-82 3.48 +- 0.2 3075300100078 Thin Makrofol UT-53/UT-83 4.15 +- 0.23 3075300100079 Thick Makrofol UT-51/UT-81 3.79 +- 0.32 3075300100080 Thick Makrofol UT-52/UT-82 3.70 +- 0.19 3075300100081 Thick Makrofol UT-53/UT-83 4.10 +- 0.2 3075300100082 The average 235-U/238-U fission cross section ratio is 3075300100083 3.83 +- 0.25 3075300100084 STATUS (TABLE) Data averaged taken from Table V, page 7 in 3075300100085 report INDC(IRN)-003, 1983 3075300100086 HISTORY (19870715C)MR- 3075300100087 (20090725A) SD:Updated to new date formats,lower case. 3075300100088 ENDBIB 86 0 3075300100089 COMMON 1 3 3075300100090 EN-DUMMY 3075300100091 MEV 3075300100092 1.5 3075300100093 ENDCOMMON 3 0 3075300100094 ENDSUBENT 93 0 3075300199999 SUBENT 30753002 20090908 31413075300200001 BIB 1 1 3075300200002 REACTION ((92-U-235(N,F),,SIG,,SPA)/(92-U-238(N,F),,SIG,,SPA)) 3075300200003 ENDBIB 1 0 3075300200004 NOCOMMON 0 0 3075300200005 DATA 2 1 3075300200006 DATA DATA-ERR 3075300200007 NO-DIM NO-DIM 3075300200008 3.83 0.25 3075300200009 ENDDATA 3 0 3075300200010 ENDSUBENT 9 0 3075300299999 ENDENTRY 2 0 3075399999999