ENTRY 14807 20230413 1480700000001 SUBENT 14807001 20230413 20231011 1480700100001 BIB 10 28 1480700100002 TITLE Thermal neutron fission properties of Np237 1480700100003 AUTHOR (A.Ghiorso,D.W.Osborne,L.B.Magnusson) 1480700100004 REFERENCE (B,TRANSU.EL.,,1639,1949) 1480700100005 REL-REF (I,,A.Ghiorso+,R,ANL-4048,1947) High-sensitivity 1480700100006 apparatus for fission counting, ionization chamber. 1480700100007 INSTITUTE (1USAANL) 1480700100008 FACILITY (REAC,1USAANL) Thermal column of Argonne heavy-water 1480700100009 reactor. 1480700100010 DETECTOR (IOCH) A fissionability was measured in a sensitive 1480700100011 ionization chamber inserted into thermal column of 1480700100012 Argonne reactor. 1480700100013 SAMPLE A thin sample was prepared by electroplating of 1480700100014 platinum foil. The mass of neptunium was determined 1480700100015 by alpha counting to be 142*10**-6 g. 1480700100016 METHOD The fission rate of 237Np was compared under 1480700100017 identical neutron-flux conditions with that of a 1480700100018 standard thin sample of 239Pu. A fission rate of 6, 1480700100019 000 fission per minute was observed in neptunium 1480700100020 sample. Assuming that all fissions are due to 237Np 1480700100021 and using the known thermal neutron cross section of 1480700100022 239Pu, the thermal neutron cross section for 237Np 1480700100023 was determined. This cross section is for fission by 1480700100024 neutrons with a Maxwellian distribution of energy 1480700100025 corresponding to a temperature of 293 degree K. The 1480700100026 thermal nature of neutrons was confirmed by a 1480700100027 measurement with cadmium shield that reduced counting 1480700100028 rate by a factor of 100 or more. 1480700100029 HISTORY (20230413C) BP 1480700100030 ENDBIB 28 0 1480700100031 NOCOMMON 0 0 1480700100032 ENDSUBENT 31 0 1480700199999 SUBENT 14807002 20230413 20231011 1480700200001 BIB 3 8 1480700200002 REACTION (93-NP-237(N,F),,SIG,,MXW) 1480700200003 ERR-ANALYS (DATA-ERR) Conservative limit of errors, rather 1480700200004 arbitrarily. 1480700200005 (ERR-S,,3.) Not greater than a few percent. 1480700200006 (ERR-1) Error due plutonium present in neptunium. 1480700200007 (ERR-2,,3.) Self absorption of fission particles. 1480700200008 STATUS (TABLE,,A.Ghiorso+,B,TRANSU.EL.,,1639,1949) 1480700200009 page 1640 of B,TRANSU.EL.,,1639,1949. 1480700200010 ENDBIB 8 0 1480700200011 COMMON 1 3 1480700200012 ERR-1 1480700200013 B 1480700200014 0.001 1480700200015 ENDCOMMON 3 0 1480700200016 DATA 3 1 1480700200017 EN-DUMMY DATA DATA-ERR 1480700200018 EV B B 1480700200019 0.0253 0.019 0.003 1480700200020 ENDDATA 3 0 1480700200021 ENDSUBENT 20 0 1480700299999 ENDENTRY 2 0 1480799999999