ENTRY 23515 20230517 231723515 0 1 SUBENT 23515001 20230517 231723515 1 1 BIB 12 41 23515 1 2 TITLE A measurement of the thermal neutron radiative 23515 1 3 capture cross section of 238U 23515 1 4 AUTHOR (J.B.Hunt, J.C.Robertson, T.B.Ryves) 23515 1 5 REFERENCE (J,JNE,23,705,1969) 23515 1 6 REL-REF (I,,T.B.Ryves+,J,JNE,22,759,1968) 23515 1 7 Facility details. 23515 1 8 (R,,K.J.Blinowska+,J,NP,55,331,1964) 23515 1 9 Decay scheme 23515 1 10 (modified to take into account data of Mackenzie+) 23515 1 11 (R,,D.R.Mackenzie+,J,NP/A,108,81,1968) U-239 decay data23515 1 12 (R,11525001,W.H.Walker+,J,CJP,38,57,1960) 23515 1 13 Correction term W 23515 1 14 INSTITUTE (2UK NPL) 23515 1 15 FACILITY (VDG,2UK NPL) NPL standard thermal neutron flux 23515 1 16 facility. 23515 1 17 INC-SOURCE (D-BE) 23515 1 18 INC-SPECT Thermal neutrons. 23515 1 19 Neutron flux was measured by Au foils of 2.2 cm 23515 1 20 diameter, 10 mg/cm2 thickness irradiated in 2 cm 23515 1 21 position simultaneously with U to be 23515 1 22 (4.46+-0.40%) x10**7 n/sec/cm2 in position 2, 23515 1 23 (3.98+-0.55%) x10**7 n/cm2/sec in position 22. 23515 1 24 DETECTOR (D4PI) 4PI beta proportional counter. 23515 1 25 Efficiency of 1.21 MeV beta decay branch was determined23515 1 26 by counting coincidences between beta and 75 keV gamma.23515 1 27 Stability of beta counter was checked by standard Co-6023515 1 28 source. 75 keV gamma-ray gate was checked and reset 23515 1 29 daily by gamma-ray spectrum of irradiated natural U . 23515 1 30 (FISCH) Two fission chambers for further monitoring of 23515 1 31 the flux variation. 23515 1 32 METHOD (ACTIV) Irradiation in 22 cm position, with foils and 23515 1 33 under 1 mm Cd . 23515 1 34 (COINC) 23515 1 35 CORRECTION For background due to decay during irradiation - ~ 6.%.23515 1 36 For fission products activity contribution 0.20+-0.1%. 23515 1 37 Effects due to the sellotape were assumed to be 23515 1 38 negligible. 23515 1 39 For flux variation. 23515 1 40 Correction term for Au - 0.027. 23515 1 41 HISTORY (20190605C) M.M. 23515 1 42 (20230517U) SD: Correction in Subent 002. 23515 1 43 ENDBIB 41 0 23515 1 44 NOCOMMON 0 0 23515 1 45 ENDSUBENT 44 0 23515 199999 SUBENT 23515002 20230517 231723515 2 1 BIB 9 60 23515 2 2 REACTION (92-U-238(N,G)92-U-239,,SIG) 23515 2 3 REL-REF (A,12470003,S.P.Harris+,R,ANL-5032,1953) 23515 2 4 2.71+-0.05 b . Mentioned as from ANL-LAT-109,1954 23515 2 5 (A,21179005,P.A.Egelstaff,J,JNE,1,92,1954) 23515 2 6 2.8+-0.10 b 23515 2 7 (A,21181003,V.S.Crocker,J,JNE,1,234,1955) 23515 2 8 2.72+-0.10 b (corrected for fission activity) 23515 2 9 (A,21182003,V.G.Small,J,JNE,1,319,1955) 23515 2 10 2.72+-0.06 b (revised assuming CS MnSO(4) 13.73 b) 23515 2 11 (A,,S.J.Cocking+,R,NRDC-84,1955) Part 2. 23515 2 12 2.69+-0.04 b 23515 2 13 (A,,P.A.Egelstaff+,R,NRDC-84,1955) Part2. 23515 2 14 2.69+-0.04 b 23515 2 15 (A,12446002,H.Palevsky,C,55GENEVA,4,147,1955) 23515 2 16 2.73+-0.07 23515 2 17 Unpublished, Quoted in Proc.Geneva Conf. 23515 2 18 (A,12444003,C.B.Bigham+,R,EANDC(CAN)-34,1968) 23515 2 19 2.721+-0.016 b 23515 2 20 SAMPLE U(3)O(8) powder, 0.005% U235 in the form of foils. 23515 2 21 Two samples: 14680 mg/cm2 and 12435 mg/cm2 of U oxide 23515 2 22 in 36 mg/cm2 and 26 mg/cm2 sellotape. 23515 2 23 foil 1 foil2 23515 2 24 Thermal factor Gth 0.9995 0.9996 23515 2 25 Westcott function g 1.0023 1.0023 23515 2 26 Cd ratio for ideal detector R 558 558 23515 2 27 Epithermal flux fraction f 0.00482 0.00482 23515 2 28 Renormalization correction C 1.230 1.230 23515 2 29 Correction term W 0.000 0.000 23515 2 30 Transmission factor for res. 23515 2 31 neutrons through 1mm Cd , F 0.992 0.992 23515 2 32 Cd ratio R 4.081+-0.10% 3.873+-0.62%23515 2 33 ANALYSIS Weighted mean of six measurements. 23515 2 34 DECAY-DATA (92-U-239,23.40MIN) 23.40+-0.05 min measured. 23515 2 35 MONITOR (79-AU-197(N,G)79-AU-198,,SIG) 23515 2 36 ERR-ANALYS (ERR-T) Total error (added linearly). 23515 2 37 (ERR-S) Total random error(added in quadrature), 23515 2 38 Sources of random error 23515 2 39 flux determination - 0.25%, 23515 2 40 activity/beta-detection-efficiency ratio - 0.56% 23515 2 41 cadmium ratio - 0.16% . 23515 2 42 (ERR-SYS) Total systematical - 0.59% (added in 23515 2 43 quadrature). 23515 2 44 Sources of systematical errors: 23515 2 45 (ERR-1,,0.1) U-239 HL 23515 2 46 (ERR-2) U-239 decay scheme 23515 2 47 (ERR-3) Weight of U foils 23515 2 48 (ERR-4) Thermal factor for U 23515 2 49 (ERR-5) Sellotape flux depression 23515 2 50 (ERR-6) Transmission factor F for U 23515 2 51 (ERR-7) Fission correction 23515 2 52 (ERR-8) Westcott factor g 23515 2 53 (ERR-9,,0.1) Neptunium correction 23515 2 54 (ERR-10) Au monitors cross section 23515 2 55 (ERR-11) Thermal factor for Au 23515 2 56 (ERR-12) Transmission factor F for Au 23515 2 57 (ERR-13) Corrections for Au 23515 2 58 STATUS (TABLE) Text of abstract, text on page 711, Table 1 of 23515 2 59 J.of Nucl.Energy,v.23,p.705,1969 23515 2 60 HISTORY (20230517U) SD: Value of ERR-T deleted from 23515 2 61 COMMON section. 23515 2 62 ENDBIB 60 0 23515 2 63 COMMON 13 9 23515 2 64 ERR-S ERR-SYS ERR-2 ERR-3 ERR-4 ERR-5 23515 2 65 ERR-6 ERR-7 ERR-8 ERR-10 ERR-11 ERR-12 23515 2 66 ERR-13 23515 2 67 PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT 23515 2 68 PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT 23515 2 69 PER-CENT 23515 2 70 0.63 0.59 0.3 0.2 0.1 0.223515 2 71 0.1 0.1 0.1 0.3 0.1 0.123515 2 72 0.1 23515 2 73 ENDCOMMON 9 0 23515 2 74 DATA 5 1 23515 2 75 EN DATA ERR-T MONIT MONIT-ERR 23515 2 76 EV B B B B 23515 2 77 0.0253 2.69 0.03 98.8 0.3 23515 2 78 ENDDATA 3 0 23515 2 79 ENDSUBENT 78 0 23515 299999 ENDENTRY 2 0 2351599999999