ABSTRACT
Reliable neutron capture cross sections of lead isotopes are necessary for the development of lead or lead-bismuth cooled fast reactors. Although 204Pb has the smallest natural abundance in stable Pb isotopes, its neutron capture cross-section data are important because a long-lived radionuclide 205Pb (T1/2 = 17.3 million years) is produced by a neutron capture reaction on 204Pb. This study applied a mass spectrometry method to measure the neutron capture cross section of 204Pb. An enriched 204Pb sample was irradiated for 24 days with a neutron flux on the order of 1013 n/cm2/sec at the Japan Research Reactor-3. The irradiated 204Pb sample was analyzed by thermal ionization mass spectrometry to obtain the isotopic ratio between 205Pb and 204Pb. Consequently, the thermal-neutron capture cross-section of 204Pb was found to be 0.536 ± 0.030 barns.
Acknowledgments
The authors would like to greatly appreciate the staff working in the JRR-3 for their cooperation and acknowledge Mrs. Atsushi Yamaguchi, Toshiyuki Takahashi, Masayuki Fujita, and Yuji Sekiya of the facility management section, and Katsuhiko Ishizaki of the JRR3 management section. One of the authors (S.N.) would also like to express gratitude to Dr Osamu Iwamoto of JAEA for their constructive comments and for carefully proofreading the manuscript.