ENTRY 30140 20080208 31263014000000001
SUBENT 30140001 20080208 31263014000100001
BIB 14 43 3014000100002
INSTITUTE (3RUMBUC) 3014000100003
REFERENCE (R,IFA-NR-47-1973,1973) Detailed report 3014000100004
(P,INDC(RUM)-3,17,1972) Short progress-report 3014000100005
(P,INDC(SEC)-28,226,197209) Same as INDC(RUM)-3,17 3014000100006
(R,IFA-NR-22,196507) New method proposed 3014000100007
(R,IFA-NR-33,197007) Experimental method described 3014000100008
AUTHOR (C.Borcea,A.Borza,A.Buta,F.Cirstoiu,L.Marinescu, 3014000100009
I.Mihai,I.M.Mihailescu,M.Petrascu,V.Savu,V.Simion, 3014000100010
T.Nascutiu) 3014000100011
TITLE Absolute determination of U-235 fission cross-section 3014000100012
for 2200 m/sec neutrons 3014000100013
EXP-YEAR (1971) 3014000100014
FACILITY (REAC) VVR-S reactor at Bucharest 3014000100015
INC-SOURCE (REAC) Horizontal channel with thermal neutron chopper 3014000100016
METHOD (TOF) 2200 m/sec neutrons selected by time of flight. 3014000100017
Absolute measurement was performed by determining: 3014000100018
.The neutron flux which was measured by using a thick 3014000100019
B-10 target, the neutron being detected through the3014000100020
477.4 keV gamma rays of Li-7 counted with a NaI 3014000100021
spectrometr (calibrated with the gold 412 keV line)3014000100022
.The detection efficiency of fission fragments, using 3014000100023
2 U-235 targets (a thin and a thick one) in 2 3014000100024
ionization chambers. Density ratio of the targets 3014000100025
and efficiency of 1 ionization chamber(100% 3014000100026
for the thin target) were known. 3014000100027
.The density of nuclei in the target from alpha 3014000100028
activity. 3014000100029
DETECTOR (IOCH,NAICR,D4PI)Ionization chambers 3014000100030
Na-I spectrometer 3014000100031
4*pi beta-gamma counter 3014000100032
MONITOR Absolute measurement, but depending on U-234 3014000100033
half-life, B-10(n,alpha) branching ratio and difference3014000100034
between gamma-energies of Li-7* and activated gold 3014000100035
PART-DET (FF) Fission fragments 3014000100036
COMMENT For similar experiment on Pu-239 see IFA-NR-33-1970 and3014000100037
entry 30089. 3014000100038
STATUS (TABLE) Data from IFA-NR-47, revised in analogy to the 3014000100039
Pu-239 experiment (Exfor-30089) following priv. comm. 3014000100040
(APRVD) approved by Mihailescu (29 Nov 1974) 3014000100041
HISTORY (19720816C) CA. 3014000100042
(19740124A) HDL. Revision after publication of IFA-NR-43014000100043
(19741218U) CA. -Status 'aprvd' added. 3014000100044
(20080208A) BIB section updated 3014000100045
ENDBIB 43 0 3014000100046
COMMON 1 3 3014000100047
EN 3014000100048
EV 3014000100049
2.5300E-02 3014000100050
ENDCOMMON 3 0 3014000100051
ENDSUBENT 50 0 3014000199999
SUBENT 30140002 20080208 31263014000200001
BIB 5 45 3014000200002
REACTION (92-U-235(N,F),,SIG) 3014000200003
SAMPLE 93.8% U-235, 5.3% U-238, .93% U234 electrospraying 3014000200004
of U-acetate on a 20-micron Al-foil, density of U-235 3014000200005
nuclei = 1.805 10**16 atoms/cm2 +-0.82%, assuming 3014000200006
U-234 half-life as 2.47 10**5 Y. 3014000200007
ANALYSIS The result of the experiment is 3014000200008
sigma =(1915.06+-1.32%) * eta * (1.E5 yrs)/hl * 3014000200009
* (1 - 0.002982 dge/keV) barns 3014000200010
where 1915.06 corresponds to the result reported in 3014000200011
IFA-NR-47, but increased by 0.3% for 3014000200012
losses due to threshold fission detection 3014000200013
(priv.Com. Petrascu 1971/5/17) 3014000200014
eta is the B-10(n,alfa) branching ratio 3014000200015
hl is the U-234 alfa-decay half-life 3014000200016
dge is the difference between the gamma-energies 3014000200017
of Li-7* and activated gold. 3014000200018
assuming 3014000200019
eta = 0.93692+-0.00006 from Deruytter+Pelfer 3014000200020
(J.Nucl.En. Ab 21,833,1967) 3014000200021
hl=2.446+-.0024 E5 yrs from De Bievre (Chemical 3014000200022
Nucl.Data,Canterbury 1971,page 221) 3014000200023
dge = 67.3+-1.5 keV from Elliot+Bell (Phys.Rev. 3014000200024
74,1869,1948) 3014000200025
yields sigma = 586.3 +- 7.8 barns 3014000200026
Note= this result follows from correspondence between 3014000200027
A.J.Deruytter,H.D.Lemmel and M.Petrascu. 3014000200028
CORRECTION Following correction-factors were applied 3014000200029
1) attenuation of neutron-beam due to chamber-walls 3014000200030
= 1/1.027 +- 0.25% 3014000200031
2) attenuation of the beam in air between fission- 3014000200032
chamber and boron-target = 1/1.025 3014000200033
3) a fotopeak-correction for the Li-7 gamma-line 3014000200034
= 1.05 +- 0.01% (varying in different runs) 3014000200035
4) losses due to threshold fission detection 3014000200036
= 1.003 (Analog to Pu-239 in entry 30089.) 3014000200037
5) an area correction = Pu/B target area ratio 3014000200038
= 1/1.020 +- 0.2% 3014000200039
plus other corrections smaller than 0.1% 3014000200040
ERR-ANALYS (ERR-T) The error given is the total error which 3014000200041
includes: 3014000200042
0.89% combined error of counting-rates 3014000200043
0.82% U density and uniformity of target 3014000200044
0.4% efficiency of Na-I spectrometer(412keV 3014000200045
0.2% efficiency ratio 477.4keV/412.keV 3014000200046
plus the errors of the corrections given above. 3014000200047
ENDBIB 45 0 3014000200048
NOCOMMON 0 0 3014000200049
DATA 2 1 3014000200050
DATA ERR-T 3014000200051
B B 3014000200052
5.8630E+02 7.8000E+00 3014000200053
ENDDATA 3 0 3014000200054
ENDSUBENT 53 0 3014000299999
ENDENTRY 2 0 3014099999999