ENTRY 12448 20220210 14981244800000001 SUBENT 12448001 20220210 14981244800100001 BIB 13 52 1244800100002 TITLE The cross-section for U238 fission by fission neutrons 1244800100003 AUTHOR (R.B.Leachman,H.W.Schmitt) 1244800100004 REFERENCE (J,JNE,4,38,1957) Main reference. 1244800100005 (R,LA-1624,1953) Preliminary results and details. 1244800100006 INSTITUTE (1USALAS) 1244800100007 FACILITY (REAC,1USALAS) Los Alamos homogeneous reactor. 1244800100008 INC-SPECT A thermal-neutron flux of 3*10**7 neutrons/cm2/sec. 1244800100009 DETECTOR (IOCH) Double ionization chamber. 1244800100010 SAMPLE The U238 in the form of U323808 of 110,000:1 isotopic 1244800100011 abundance was on a thin aluminum hemisphere which was 1244800100012 concentric with another thin but larger aluminum 1244800100013 hemisphere. The two aluminum hemispheres constitute 1244800100014 an ionization chamber which detects the U238 fission 1244800100015 fragments. 1244800100016 METHOD By means of measurements with a double ionization 1244800100017 chamber, the average fission cross section of U238 1244800100018 for neutrons from the fission of U235 was determined 1244800100019 in terms of nu, the average number of neutrons per 1244800100020 fission of U235. The number of fissions of U238 was 1244800100021 measured in one of the ionization chambers while the 1244800100022 number of fissions from the fission neutron source of 1244800100023 U235 was measured in the other chamber. 1244800100024 ERR-ANALYS (DATA-ERR) The standard deviations of the mean of the 1244800100025 measurements and does not include uncertainties in 1244800100026 neutron scattering calculations, in the calculations 1244800100027 of unobserved U238 fissions, or in the method of 1244800100028 background measurements. The largest uncertainty in 1244800100029 these measurements is 235U mass and number of 235U 1244800100030 fission neutrons. 1244800100031 CORRECTION Several corrections of several percent or less for 1244800100032 neutron absorption and neutron scattering must be 1244800100033 applied. Corrections are necessary for absorption and 1244800100034 scattering of thermal neutrons in the platinum and 1244800100035 Dural between the U deposit and the U235 disc. 1244800100036 Corrections are necessary because fission neutrons 1244800100037 were, in addition, scattered to the U238 by the 1244800100038 reactor face, the outside case of the chamber, and 1244800100039 the various hemispheres within the case. In addition, 1244800100040 the absorption of the fission neutrons by the cadmium 1244800100041 and the inner aluminum hemisphere was taken into 1244800100042 account. The largest of these corrections is 2 to 3% 1244800100043 for the scattering of neutrons from the hemisphere 1244800100044 containing U238; that is, a greater effective 1244800100045 thickness of U238 is "seen" by the deflected fission 1244800100046 neutrons than is "seen" by the unscattered neutrons. 1244800100047 DECAY-DATA (92-U-238,4.59E9YR,A) Measured by authors. 1244800100048 HISTORY (19760804T) Translated from SCISRS. 1244800100049 (19830809A) Converted to reaction formalism 1244800100050 (20220210A) BP: Updated to new date formats, lower 1244800100051 case. corrections according last EXFOR rules and 1244800100052 Dict. Added LA report, facility, incoming spectrum, 1244800100053 status, sample, method, corrections, error-analysis. 1244800100054 ENDBIB 52 0 1244800100055 NOCOMMON 0 0 1244800100056 ENDSUBENT 55 0 1244800199999 SUBENT 12448002 20220210 14981244800200001 BIB 5 9 1244800200002 REACTION 1((92-U-238(N,F),,SIG,,FIS)* 1244800200003 (92-U-235(N,F),,NU,,FIS)) 1244800200004 2(92-U-238(N,F),,SIG,,FIS) 1244800200005 ASSUMED (ASSUM,92-U-235(N,F),,NU) 1244800200006 REL-REF (R,,D.J.Hughes+,R,BNL-325,1955) U-235 nubar values. 1244800200007 STATUS (TABLE) page 43 of the main reference. 1244800200008 HISTORY (20220210A) BP: Corrected fission neutron energies 1244800200009 from 1 to 2 MeV, added monitor reference. Corrected 1244800200010 first reaction from ratio to product and updated data. 1244800200011 ENDBIB 9 0 1244800200012 NOCOMMON 0 0 1244800200013 DATA 6 1 1244800200014 EN-DUMMY DATA 1DATA-ERR 1DATA 2DATA-ERR 2ASSUM 1244800200015 MEV B B B B NO-DIM 1244800200016 2. 0.756 0.008 1.86 5.E-03 2.461244800200017 ENDDATA 3 0 1244800200018 ENDSUBENT 17 0 1244800299999 ENDENTRY 2 0 1244899999999