Measurement of neutron capture cross section of 187W for production of 188W

PubMed: 309786552-s2.0-85064014804Tungsten-188 (t1/2 = 69.4 d) is routinely produced by double neutron capture using highly enriched 186W target, 186W(n,?)187W(n,?)188W reaction, at the ORNL 85 MWt High Flux Isotope Reactor. While the thermal neutron cross section for the first reaction, 186W(n,?)187W, is well known, the single reported 64 b cross-section for the second reaction, 187W(n,?)188W, cannot be validated by experimental results that yield lower than expected activities of 188W. In this study, we report a new value for the thermal neutron capture cross section of 187W. After confirming the neutron capture cross section of 186W (?0 = 37.8 ± 1.8 b for thermal and I0 = 476 ± 25 b for resonance integrals with ?0/I0 = 12.6 ± 0.4) in two short irradiations, longer irradiations (1–10 d) were performed to obtain a value of 6.5 ± 0.8 b for the ?0 of 187W, which is lower than the adopted value by a factor of 10. Due to the short half-life of 187W (t1/2 = 23.7 d), the ?0 for 187W was obtained empirically by comparing the 188W experimental yields with the theoretical yields generated by code IsoChain and varying the 187W cross section while keeping all other parameters constant. © 2019U.S. Department of Energy, USDOE Nuclear Physics, NP: DE-AC05-00OR22725 Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAK: 1059B141600608This research was supported by DOE , Office of Nuclear Physics, Isotope Program, under contract DE-AC05-00OR22725 and TÜBITAK (The Scientific and Technological Research Council of Turkey) and Project Number: 1059B141600608 . The authors acknowledge the efforts and support of the High Flux Isotope Reactor staff, especially Greg Hirtz, for scheduling the irradiations of the targets, and staff of Nuclear and Radiochemistry Group for help in many aspects of this project, especially Allison Peacock and Lance Wyant for handling the irradiated targets in the hot cell. The authors thank James Gaugler II and Riley Hunley for their critical review of the manuscript