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

WOS: 000469892600028PubMed ID: 30978655Tungsten-188 (t(1/2) = 69.4 d) is routinely produced by double neutron capture using highly enriched W-186 target, W-186(n,gamma)W-187(n,gamma)W-188 reaction, at the ORNL 85 MWt High Flux Isotope Reactor. While the thermal neutron cross section for the first reaction, W-186(n,gamma)W-187, is well known, the single reported 64 b cross-section for the second reaction, W-187(n,gamma)W-188, cannot be validated by experimental results that yield lower than expected activities of W-188. In this study, we report a new value for the thermal neutron capture cross section of W-187. After confirming the neutron capture cross section of W-186 (sigma(0) = 37.8 +/- 1.8 b for thermal and I-0 = 476 +/- 25 b for resonance integrals with sigma(0)/I-0 = 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 sigma(0) of W-187, which is lower than the adopted value by a factor of 10. Due to the short half-life of W-187 (t(1/2) = 23.7 d), the sigma(0) for W-187 was obtained empirically by comparing the W-188 experimental yields with the theoretical yields generated by code IsoChain and varying the W-187 cross section while keeping all other parameters constant.DOE, Office of Nuclear Physics, Isotope Program [DE-AC05-00OR22725]; TUBITAK (The Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [1059B141600608]This research was supported by DOE, Office of Nuclear Physics, Isotope Program, under contract DE-AC05-00OR22725 and TUBITAK (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