ENTRY 23256 20150610 22442325600000001 SUBENT 23256001 20150610 22442325600100001 BIB 19 112 2325600100002 TITLE Integral cross section measurement of the 2325600100003 235U(n,n')235mU reaction in a pulsed reactor. 2325600100004 AUTHOR (G.Belier,E.M.Bond,D.J.Vieira,N.Authier,J.A.Becker, 2325600100005 D.Hyneck,X.Jacquet,Y.Jansen,J.Legendre,R.Macri,V.Meot, 2325600100006 P.Romain) 2325600100007 INSTITUTE (2FR ITL) N.Authier,D.Hyneck,X.Jacquet,Y.Jansen, 2325600100008 J.Legendre 2325600100009 (2FR BRC) G.Belier,V.Meot,P.Romain 2325600100010 (1USALAS) E.M.Bond,D.J.Vieira 2325600100011 (1USALRL) J.A.Becker,R.Macri 2325600100012 REFERENCE (J,PR/C,91,044605,2015) 2325600100013 #doi:10.1103/PhysRevC.91.044605 2325600100014 FACILITY (REAC,2FR ITL) Pulsed critical reactor CALIBAN located 2325600100015 at the CEA/VALDUC, France. 2325600100016 INC-SOURCE (REAC) 2325600100017 INC-SPECT Fission-like neutron spectrum in the central cavity. 2325600100018 The integrated flux in one 'shot' is typically 2325600100019 3.E+14 n/cm2 . 2325600100020 Cavity spectrum average energy 1.44 MeV. 2325600100021 Moderated spectrum average energy 0.29 MeV - for 2325600100022 additional testing measurement. 2325600100023 Spectra calculated by TRIPOLI 4.4 code are on Fig.6. 2325600100024 SAMPLE Uranium samples of isotope-enriched 235U, 236U, 238U 2325600100025 and various blank samples. 2325600100026 The isotopic content determined by mass spectroscopy: 2325600100027 U-235 sample: U-233 - 0.0001%, U-234 - 0.0342%, 2325600100028 U-235 - 99.84%, U-236 - 0.0249%, U-238 - 0.1052%. 2325600100029 Samples for additional testing measurement: 2325600100030 U-236 sample: U-233 - 0.082%, U-235 - 0.205%, 2325600100031 U-236 - 99.68%. 2325600100032 U-238 sample: U-234 - 0.0054%, U-235 - 0.7204%, 2325600100033 U-238 - 99.2742%. 2325600100034 The U samples ( 19mm diameter, masses 7 to 20 microg) 2325600100035 were prepared from solutions that were dried dropwise 2325600100036 (stippled) onto Ti backing foils. 2325600100037 The U mass of each sample was determined by alpha 2325600100038 counting using an alpha spectrometer (Eurisys Mesures- 2325600100039 EM 7184). It's detection efficiency was determined by 2325600100040 a calibrated alpha source (containing 239Pu, 241Am, 2325600100041 244Cm, diameter 15mm, total activity 459 alpha/s) with 2325600100042 uncertainty of 3% at the 2sigma confidence level. 2325600100043 Indium foils were co-irradiated with the U or blank 2325600100044 samples for flux monitoring. 2325600100045 DETECTOR Dedicated electron detector based on an 2325600100046 electrostatic deflecting system and a channeltron 2325600100047 electron multiplier (Photonics X9551BL). 2325600100048 (HPGE) Irradiated samples were gamma-counted using 2325600100049 three separate HPGe detectors which were energy and 2325600100050 efficiency calibrated using sources of 152Eu and 133Ba 2325600100051 whose activity were known to a precision of 2% at the 2325600100052 1sigma confidence level. 2325600100053 To characterize the 235mU detection efficiency, 2325600100054 samples of different masses were prepared and traced 2325600100055 with a known amount of isomer obtained by alpha-recoil 2325600100056 collection from an electrodeposited 239Pu mother 2325600100057 source. An alpha-recoil collection efficiency of 2325600100058 0.31 +- 0.03 was determined,which agrees with 2325600100059 calculated value 0.31 . 2325600100060 For the calibration of the U-235m conversion electron 2325600100061 detection efficiency, several samples were made by 2325600100062 collecting a known amount of U-235m recoils from the 2325600100063 239Pu-241Pu mother source, adding varying amounts of 2325600100064 235U. The 235mU isomer detection efficiency EPS against2325600100065 the 235U mass for each sample was fitted as: 2325600100066 EPS=eps1+eps2*m, where 2325600100067 eps1=4.14+-0.35, eps2=-0.125+-0.03%/microg, m - mass of2325600100068 U-235 sample in microg. 2325600100069 PART-DET (E) Low-energy conversion electrons . 2325600100070 METHOD (ACTIV,CHSEP) After irradiation, the U was dissolved 2325600100071 off of the backing foil and radiochemically processed 2325600100072 to remove fission products. The samples were then 2325600100073 electroplated onto a stainless steel disk or a fresh Ti2325600100074 backing foil and then counted. Cooling time was 2325600100075 typically 90min. 2325600100076 ANALYSIS Fit of the time spectrum showing U-235m isomer decay 2325600100077 was performed by exponential decay plus a constant 2325600100078 background, and the HL of 25.33min was obtained. 2325600100079 MONITOR (49-IN-115(N,INL)49-IN-115-M,,SIG) 2325600100080 DECAY-MON (49-IN-115-M,4.485HR,DG,497.) 2325600100081 To measure the neutron fluence for each shot. 2325600100082 Counting statistics for the In monitor reaction yielded2325600100083 uncertainties of 1-2%. 2325600100084 DECAY-DATA (92-U-235-M,25.33MIN) 2325600100085 ADD-RES Measured chemical separation factors - Table II of 2325600100086 J,PR/C,91,044605,2015. 2325600100087 Measured U-235m HL : 2325600100088 Backing material Sample form Half-life,min 2325600100089 Al Implanted 26.76 +- 0.04 2325600100090 Ti Implanted 27.4 +- 0.7 2325600100091 Ti Deposited 25.46 +- 0.04 2325600100092 Pt Deposited 26.37 +- 0.05 2325600100093 Ag Implanted 25.7 +- 0.2 2325600100094 NaCl Implanted 29.01 +- 0.24 2325600100095 Stainless steel Deposited 25.62 +- 0.11 2325600100096 CORRECTION For difference of diameter of U sample and calibration 2325600100097 source - 4.4 - 0.3% . 2325600100098 The cooling time correction. 2325600100099 For backgrounds form other activities ( fission product2325600100100 activated backing materials, impurities analyzed)- see 2325600100101 Table V: Averaged half-live and amplitudes for the 2325600100102 U-235m isomer signal and possible backgrounds measured 2325600100103 with a Ti blank and enriched samples of 238U and 236U. 2325600100104 COMMENT The research was carried out under the US-France 2325600100105 Int. Agreement on Cooperation on Fundamental Research 2325600100106 Supporting Stockpile Stewardship. This work was 2325600100107 performed under the auspices of the US Department of 2325600100108 Energy at Los Alamos Nat. Lab. operated by the Los 2325600100109 Alamos National Security, LLCunder Contract 2325600100110 No.DE-AC52-06NA25396 and at Lawrence Livermore Nat.Lab.2325600100111 operated by the Lawrence Livermore National Security, 2325600100112 LLC under Contract No. DE-AC52-07NA27344. 2325600100113 HISTORY (20150610C) M.M. 2325600100114 ENDBIB 112 0 2325600100115 NOCOMMON 0 0 2325600100116 ENDSUBENT 115 0 2325600199999 SUBENT 23256002 20150610 22442325600200001 BIB 4 16 2325600200002 REACTION (92-U-235(N,INL)92-U-235-M,,SIG,,SPA) 2325600200003 Integral cross-section for U-235m isomer activation on 2325600200004 cavity fission-like spectrum. 2325600200005 ANALYSIS The isomer integral cross section was calculated by 2325600200006 Eq. (5) of PR/C,91,044605,2015. 2325600200007 ERR-ANALYS (ERR-1) Electron detection efficiency. 2325600200008 (ERR-2) Uncertainty on isomer HL during cooling . 2325600200009 (ERR-3) Neutron flux measurement. 2325600200010 (ERR-4) 235U mass measurement . 2325600200011 (ERR-5) Isomer P2 amplitude ( see Eq.(1)) . 2325600200012 (ERR-6) Isomer half-life during chemistry and 2325600200013 electrodeposition . 2325600200014 (ERR-T) Total uncertainty obtained by propagation in 2325600200015 Eq. (5) - 13% . 2325600200016 STATUS (TABLE) Text,page 044605-7 of J,PR/C,91,044605,2015, 2325600200017 Table VI - uncertainties. 2325600200018 ENDBIB 16 0 2325600200019 COMMON 6 3 2325600200020 ERR-1 ERR-2 ERR-3 ERR-4 ERR-5 ERR-6 2325600200021 PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT 2325600200022 7.7 0.43 4.7 3.2 1. 10. 2325600200023 ENDCOMMON 3 0 2325600200024 DATA 3 1 2325600200025 EN-MEAN DATA DATA-ERR 2325600200026 MEV B B 2325600200027 1.44 1.00 0.13 2325600200028 ENDDATA 3 0 2325600200029 ENDSUBENT 28 0 2325600299999 ENDENTRY 2 0 2325699999999