The spectroscopic methods discussed above are amenable for measuring components in commercial fuel and fuel simulant feeds. Section 4.3.1 dis­cusses work performed using actual spent commercial fuel, including the preparation and dissolution of the fuel and the spectroscopic measurements of these fuel samples. The spectroscopic measurements were compared with ICP-MS analyses and ORIGEN code calculations. Section 4.3.2 describes real-time spectroscopic monitoring tests using a centrifugal contactor system deployed at PNNL. This section contains measurements resulting from “cold” testing of the contactor system containing HNO3, Nd(NO3)3, and NaNO3 and a “hot” demonstration using solutions containing UO2(NO3)2 and Np(V) in nitric acid.