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