ENTRY 21833 20060810 21782183300000001 SUBENT 21833001 20060810 21782183300100001 BIB 14 70 2183300100002 INSTITUTE (2UK HAR) 2183300100003 REFERENCE (J,ANE,9,127,1982) Main reference 2183300100004 AUTHOR (G.EDWARDS,D.J.S.FINDLAY,E.W.LEES) 2183300100005 TITLE -MEASUREMENTS OF PROMPT NU-BAR AND VARIANCE FOR 2183300100006 THE SPONTANEOUS FISSION OF CF-252 AND PU-242. 2183300100007 FACILITY .OIL MODERATED ASSEMBLY OF BF3 COUNTERS. 2183300100008 METHOD .SPONTANEOUS FISSION EVENTS AND FISSION NEUTRONS 2183300100009 WERE COUNTED OVER A PERIOD OF MONTHS. 2183300100010 DETECTOR (FISCH) THE SPONTANEOUS FISSIONING SAMPLE WAS 2183300100011 (BF3 ) INCORPORATED IN AN IONISATION CHAMBER 2183300100012 PLACED AT THE CENTRE OF A HIGH EFFICIENCY 2183300100013 NEUTRON DETECTOR CONSISTING OF 56 BF3 2183300100014 COUNTERS CONNECTED IN 5 RINGS AND 2183300100015 IMMERSED IN AN OIL MODERATOR. 2183300100016 MONITOR .THE EFFICIENCY OF THE NEUTRON DETECTOR 2183300100017 ASSEMBLY WAS DETERMINED USING AM-241/LI, 2183300100018 /F,/B AND /BE SOURCES CALIBRATED AT THE 2183300100019 MANGANESE BATH OF THE NATIONAL PHYSICAL 2183300100020 LABORATORY, TEDDINGTON, ENGLAND. 2183300100021 PART-DET (FF) FISSION FRAGMENTS. 2183300100022 (N) NEUTRONS. 2183300100023 MISC-COL (MISC) THE VARIANCE OF THE PROMPT NEUTRON 2183300100024 MULTIPLICITY DISTRIBUTION. 2183300100025 CORRECTION .BACKGROUND AND DEAD TIME CORRECTIONS. 2183300100026 .CHEMICAL IMPURITIES IN THE MANGANESE BATH 2183300100027 USED TO CALIBRATE THE STANDARD SOURCES. 2183300100028 .ABSORPTION OF NEUTRONS IN THE STRUCTURAL 2183300100029 MATERIALS OF THE FISSION CHAMBERS. THESE 2183300100030 CORRECTIONS TO THE BF3 COUNTER EFFICIENCY 2183300100031 WERE COMPUTED USING THE MONTE CARLO CODE 2183300100032 'MONK',AND WERE FOUND TO BE - 2183300100033 (0.59 +/- 0.11) PER CENT FOR THE CF-252 CHAMBER 2183300100034 (1.01 +/- 0.14) PER CENT FOR THE PU-242 CHAMBER 2183300100035 .VARIATION OF DETECTOR EFFICIENCY DURING THE 2183300100036 EXPERIMENT. ( A PERIOD OF ABOUT 13 MONTHS ). 2183300100037 ERR-ANALYS (ERR-T) TOTAL ERROR, COMPOSED OF - 2183300100038 (ERR-S) STATISTICAL ERROR ( STATISTICAL ERROR 2183300100039 IN THE EXTRAPOLATION FOR PU-242 DATA ) 2183300100040 (ERR-1) ERROR IN BACKGROUND 2183300100041 (ERR-2) ERROR IN FISSION CHAMBER ABSORPTION 2183300100042 (ERR-3) ERROR IN GATING FACTOR 2183300100043 (ERR-4) ERROR IN DETECTOR EFFICIENCY CALIBRATION 2183300100044 (ERR-5) ERROR IN FISSION NEUTRON MEAN ENERGY 2183300100045 (ERR-6) ERROR IN FISSION RATE 2183300100046 (ERR-7) ERROR IN FISSION CHAMBER POSITION 2183300100047 (ERR-8) ERROR IN SAMPLE ORIENTATION. 2183300100048 ERROR QUANTITIES QUOTED AS '0.0', TOGETHER WITH 2183300100049 UNCERTAINTIES ASSOCIATED WITH DETECTOR DEAD TIME 2183300100050 EACH CONTRIBUTED AN ERROR OF LESS THAN 0.001 TO 2183300100051 THE NU-BAR OF BOTH PU-242 AND CF-252. 2183300100052 (MISC-ERR) THE TOTAL ERROR IN THE VARIANCE OF 2183300100053 THE PROMPT NEUTRON MULTIPLICITY DISTRIBUTION (SEE 2183300100054 KEYWORD MISC-COL). IT IS COMPOSED OF THE FOLLOWING - 2183300100055 CF-252 PU-242 2183300100056 STATISTICAL ERROR 0.008 0.004 2183300100057 BACKGROUND 0.002 0 2183300100058 DEADTIME 0.002 0.001 2183300100059 FISSION CHAMBER ABSORPTION 0.002 0.001 2183300100060 GATING FACTOR 0.001 0 2183300100061 DETECTOR EFFICIENCY CALIBRATION 0.004 0.003 2183300100062 FISSION NEUTRON MEAN ENERGY 0.002 0.002 2183300100063 FISSION RATE 0.001 0.001 2183300100064 FISSION CHAMBER POSITION 0 0 2183300100065 SOURCE ORIENTATION 0.006 0.006 2183300100066 '0' INDICATES AN ERROR LESS THAN 0.001. 2183300100067 STATUS .DATA TAKEN FROM REFERENCE. 2183300100068 HISTORY (19830217C) A.P.T. 2183300100069 (19830322E) 2183300100070 (20060810A) DATE AND REFERENCE YEAR corrected 2183300100071 DATA UNITS corrected to PRT/FIS 2183300100072 ENDBIB 70 0 2183300100073 NOCOMMON 0 0 2183300100074 ENDSUBENT 73 0 2183300199999 SUBENT 21833002 20060810 21782183300200001 BIB 4 20 2183300200002 REACTION (94-PU-242(0,F),PR,NU) 2183300200003 SAMPLE .A PU-O2 source containing 1.092E-02 g of 2183300200004 fissionable material on a 0.13 milli-m thick 2183300200005 platinum backing. the isotopic composition was - 2183300200006 PU-242 89.37 % PU-241 0.93 % 2183300200007 PU-240 4.57 % PU-239 5.13 % 2183300200008 ANALYSIS .The data was obtained from an extrapolation 2183300200009 to 100 per cent fission fragment detection 2183300200010 efficiency based on the results of 15 runs. 2183300200011 CORRECTION .The only impurity isotope contributing to 2183300200012 spontaneous fission neutrons was Pu-240. since 2183300200013 this isotope has a nu-bar value very similar to 2183300200014 that of Pu-242 the associated correction is 2183300200015 negligibly small. 2183300200016 .the fission fragment detection efficiency, 2183300200017 deduced from a measurement of the total neutron 2183300200018 output of the sample ( corrected for (alpha,n) 2183300200019 reactions ) varied between 62 and 88 per cent, 2183300200020 as the gas pressure was varied. an extrapolation 2183300200021 to 100 per cent efficiency was made. 2183300200022 ENDBIB 20 0 2183300200023 COMMON 9 6 2183300200024 ERR-S ERR-1 ERR-2 ERR-3 ERR-4 ERR-5 2183300200025 ERR-6 ERR-7 ERR-8 2183300200026 PRT/FIS PRT/FIS PRT/FIS PRT/FIS PRT/FIS PRT/FIS 2183300200027 PRT/FIS PRT/FIS PRT/FIS 2183300200028 3.0000E-03 0.0001E+00 3.0000E-03 1.0000E-03 1.2000E-02 1.0000E-022183300200029 1.0000E-03 1.0000E-03 8.0000E-03 2183300200030 ENDCOMMON 6 0 2183300200031 DATA 4 1 2183300200032 DATA ERR-T MISC MISC-ERR 2183300200033 PRT/FIS PRT/FIS PRT/FIS PRT/FIS 2183300200034 2.1530E+00 1.9000E-02 1.2980E+00 8.0000E-03 2183300200035 ENDDATA 3 0 2183300200036 ENDSUBENT 35 0 2183300299999 SUBENT 21833003 20060810 21782183300300001 BIB 5 17 2183300300002 REACTION (98-CF-252(0,F),PR,NU) 2183300300003 SAMPLE .An oxide sample of high purity containing 2183300300004 7.36e-11 g of fissionable material on a 2183300300005 0.13 milli-m thick platinum backing. 2183300300006 .The sample initially had the following 2183300300007 isotopic composition - 2183300300008 CF-252 74.48 %, CF-250 25.52 % 2183300300009 DECAY-DATA (98-CF-252,2.63YR) 2183300300010 ANALYSIS .The data was obtained from a weighted mean of the 2183300300011 Results of 7 runs. 2183300300012 CORRECTION .The generation of Cm-244, Cm-246 and Cm-248 2183300300013 Daughter impurities in the sample before 2183300300014 Measurement began led to a 0.025 % 2183300300015 Correction in the nu-bar value. 2183300300016 .The fission fragment detection efficiency, deduced 2183300300017 From the measured alpha activity, was in excess of 2183300300018 99 % 2183300300019 ENDBIB 17 0 2183300300020 COMMON 9 6 2183300300021 ERR-S ERR-1 ERR-2 ERR-3 ERR-4 ERR-5 2183300300022 ERR-6 ERR-7 ERR-8 2183300300023 PRT/FIS PRT/FIS PRT/FIS PRT/FIS PRT/FIS PRT/FIS 2183300300024 PRT/FIS PRT/FIS PRT/FIS 2183300300025 3.0000E-03 1.0000E-03 4.0000E-03 2.0000E-03 2.2000E-02 9.0000E-032183300300026 3.0000E-03 2.0000E-03 1.4000E-02 2183300300027 ENDCOMMON 6 0 2183300300028 DATA 4 1 2183300300029 DATA ERR-T MISC MISC-ERR 2183300300030 PRT/FIS PRT/FIS PRT/FIS PRT/FIS 2183300300031 3.7520E+00 2.9000E-02 1.5620E+00 1.1000E-02 2183300300032 ENDDATA 3 0 2183300300033 ENDSUBENT 32 0 2183300399999 ENDENTRY 3 0 2183399999999