PNNL

Abstract

Isotopes are versions of an element with the same number of protons but a different number of neutrons. Adding neutrons to a stable element usually makes it unstable, or radioactive, and these isotopes radiate particles or light to decay back into a stable form. 135Xe (xenon-135) is a radioactive isotope of great interest to the nuclear physics community because it is produced by nuclear fission, which is how nuclear reactors generate electricity. In reactors, unstable 135Xe often absorbs a neutron, making stable 136Xe (xenon-136). This removes a neutron from the reactor fuel that could otherwise interact with other isotopes and sustain fission, making the fission reaction less efficient, so isotopes in reactors that commonly absorb neutrons to become stable are known as neutron poisons. 135Xe is the biggest neutron poison known, so understanding it directly supports the U.S. Department of Energy’s Office of Nuclear Energy mission to develop more efficient and safe advanced reactors. The 135Xe + neutron reaction cannot be measured directly because neither 135Xe nor neutrons live long enough, so we must use experimental nuclear physics techniques to determine whatever we can for this reaction. We performed an experiment at Argonne National Laboratory using their radioactive ion beam source to generate 136I (iodine-136) and 136Te (tellurium-136). These both decay into 136Xe, and we studied this decay using a specialized detector. We can analyze this data to extract a lot of information, such as how long the isotopes live and how they decay. Information like this will be used to determine more about the key 135Xe + neutron reaction. As part of my internship at PNNL, I started the data analysis by working on data calibration and comparing it to simulations. This internship allowed me to develop my coding and data analysis skills and expand my professional network significantly.