ENTRY 21643 20130427 22362164300000001 SUBENT 21643001 20130427 22362164300100001 BIB 15 48 2164300100002 TITLE Delayed neutron yield and decay constants for thermal 2164300100003 neutron induced fission of U-235 2164300100004 AUTHOR (S.Synetos, J.G.Williams) 2164300100005 INSTITUTE (2UK LON) Univ. of London Reactor centre, Imperial 2164300100006 College 2164300100007 REFERENCE (S,INDC(NDS)-107,183,197908) 2164300100008 Proceedings of the Consultants Meeting on delayed 2164300100009 neutron properties, Vienna, 26-30 March 1979 2164300100010 FACILITY (REAC,2UK LON) Thermal research reactor 2164300100011 INC-SOURCE (THCOL) Thermal column 2164300100012 INC-SPECT Thermal Maxwellian neutron spectrum 2164300100013 SAMPLE (92-U-235,ENR=0.9554) 2164300100014 Metal foils of 7.5 mm diameter, 35 mg in weight. 2164300100015 METHOD Samples transferred pneumatically to and from the 2164300100016 irradiation position where a constant thermal flux 2164300100017 was maintained. 2164300100018 After each irradiation the delayed neutron emission 2164300100019 rate was measured in a detector consisting of a water 2164300100020 bath containing BF3 counters. 2164300100021 DETECTOR (BF3) Water bath containing BF3 counters in cylindrical2164300100022 aluminium tubes of O.D. 26 mm, active length 310 mm 2164300100023 filled with 96% B-10. 2164300100024 The efficiency was calibrated with a standard Am/Li 2164300100025 source from National Physical Laboratory which was 2164300100026 itself calibrated to 0.5% using a manganese sulphate 2164300100027 bath. 2164300100028 ANALYSIS Measured neutron decay curve was fitted to the sum of 2164300100029 five exponential decaying groups by a least square 2164300100030 method. 2164300100031 MONITOR (92-U-235(N,F)57-LA-140,CUM,FY,,MXW) 2164300100032 The number of fission in the U-235 source was monitored2164300100033 by measuring the activity of La-140 relative to a 2164300100034 calibration foil in an absolute ionisation chamber. 2164300100035 No value given. 2164300100036 CORRECTION Corrections made for 2164300100037 - volume of Am/Li calibration source, 2164300100038 - neutron self-absorption in calibration source 2164300100039 (ANISN calc.), 2164300100040 - anisotropy of neutron emission, 2164300100041 of delayed neutrons (Table 1.). 2164300100042 The total yield was corrected for the absence of the 2164300100043 sixth group. 2164300100044 ERR-ANALYS (DATA-ERR) Quoted error includes statistical 2164300100045 uncertainty plus errors on corrections and in 2164300100046 detector efficiency. 2164300100047 HISTORY (19800825C) 2164300100048 (19800829E) 2164300100049 (20130427U) On. DETECTOR: SCIN -> BF3 2164300100050 ENDBIB 48 0 2164300100051 COMMON 1 3 2164300100052 EN-DUMMY 2164300100053 EV 2164300100054 0.0253 2164300100055 ENDCOMMON 3 0 2164300100056 ENDSUBENT 55 0 2164300199999 SUBENT 21643002 20130427 22362164300200001 BIB 6 16 2164300200002 REACTION (92-U-235(N,F),DL/GRP,NU,,MXW/REL) 2164300200003 Yields are normalised to a sum of unity. 2164300200004 HALF-LIFE The half-life fitted to each delayed group is 2164300200005 given in the table. 2164300200006 COMMENT No 6th group was observed because of the transfer time 2164300200007 of 380 ms before counting commenced. 2164300200008 COVARIANCE There are strong correlations between the yields for 2164300200009 the five measured groups. 2164300200010 Group Correlation coefficients 2164300200011 1. 1. 2164300200012 2. 0.63 1. 2164300200013 3. -0.42 -0.54 1. 2164300200014 4. 0.27 0.32 -0.62 1. 2164300200015 5. -0.15 -0.20 -0.38 -0.38 1. 2164300200016 STATUS (TABLE) Table 3 of INDC(NDS)-107, 183 (1979) 2164300200017 HISTORY (20130427A) On. REACTION: DL/PAR,NU -> DL/GRP,NU 2164300200018 ENDBIB 16 0 2164300200019 NOCOMMON 0 0 2164300200020 DATA 4 5 2164300200021 HL HL-ERR DATA DATA-ERR 2164300200022 SEC SEC ARB-UNITS ARB-UNITS 2164300200023 5.6530E+01 5.5000E-01 0.035 0.002 2164300200024 2.2350E+01 2.5000E-01 0.227 0.009 2164300200025 7.0000E+00 6.3000E-01 0.148 0.023 2164300200026 2.7200E+00 2.2000E-01 0.403 0.017 2164300200027 7.7000E-01 1.0000E-01 0.187 0.017 2164300200028 ENDDATA 7 0 2164300200029 ENDSUBENT 28 0 2164300299999 SUBENT 21643003 20130427 22362164300300001 BIB 6 14 2164300300002 REACTION (92-U-235(N,F),DL,NU,,MXW) 2164300300003 COMMENT Total measured yield was 0.0151 +/- 0.007, 2164300300004 which is 0.0156 +/- 0.0010 when corrected for the six 2164300300005 group structure of Keepin et al. 2164300300006 REL-REF (R,,G.R.Keepin+,J,JNE,6,1,1957) 2164300300007 ERR-ANALYS Contributions to total uncertainty are 2164300300008 (ERR-S) Counting statistics (0.9%) 2164300300009 (ERR-1) Fission measurement (2.2%) 2164300300010 (ERR-2) Detector efficiency (2.4%) 2164300300011 (ERR-3) Decay parameters (3.1%) 2164300300012 STATUS (TABLE) Text and Table 4 of INDC(NDS)-107, 183 (1979) 2164300300013 HISTORY (19800826C) 2164300300014 (19800829E) 2164300300015 (20130427A) On. NO-DIM -> PRT/FIS 2164300300016 ENDBIB 14 0 2164300300017 COMMON 4 3 2164300300018 ERR-S ERR-1 ERR-2 ERR-3 2164300300019 PER-CENT PER-CENT PER-CENT PER-CENT 2164300300020 0.9 2.2 2.4 3.1 2164300300021 ENDCOMMON 3 0 2164300300022 DATA 2 1 2164300300023 DATA ERR-T 2164300300024 PRT/FIS PRT/FIS 2164300300025 0.0156 0.0010 2164300300026 ENDDATA 3 0 2164300300027 ENDSUBENT 26 0 2164300399999 ENDENTRY 3 0 2164399999999