Estimating the photo-fission yield of the Trinity Test

In the Trinity Test, the energy was released not only from the fission of Pu-239 core but also from the fast neutron fission of tamper surrounding it. The high energy photons produced from the fissioning core can also induce fission in U-238 tamper. In this work, an effort has been made, for the first time, to develop an approach to investigate the possibility of photon-induced fission in U-238 tamper used in Trinity Test nuclear weapon. GEF nuclear reaction code, version 2018/1.1 is used to calculate the prompt γ-spectrum from the fast fission of Pu-239 core of the device. It is estimated that 14.3 ton (t) of TNT of the total 21 kT yield of the Trinity nuclear device is contributed by the photo-fission of U-238 tamper.