Year
2012
Abstract
The goal of Next Generation Safeguards Initiative (NGSI) Spent Fuel project is to determine the amount of plutonium in spent fuel assemblies. Plutonium content in spent fuel is a function of many variables including: initial enrichment (IE), burnup (BU), and cooling time (CT). In the first phase of the NGSI initiative libraries of virtual Pressurized Water Reactor (PWR) spent fuel assemblies were developed as a function of various reactor conditions (IE, BU and CT). Simulated passive gamma ray spectra and neutron count rate from the spent fuel libraries were analyzed to investigate a methodology to determine IE, BU, and CT. A set of 4 equations that quantify the 137 Cs count rate, 134 Cs/ 137 Cs count rate ratio, 154 Eu/ 137 Cs count rate ratio, and the passive neutron count rate were constructed. Based on this model two approaches were introduced: in the first one IE and BU were determined knowing cooling time from operator declaration; and a second one, where the cooling time is unknown (or not trusted); in both cases IE, BU, and CT are calculated. The effectiveness of the two approaches is evaluated by means of the spent fuel libraries introduced. The model, its assumptions, and the results obtained will be discussed in the details in the presentation. Further, the application of information derived from the IE, BU, and CT to the plutonium compositions of the assembly will be discussed. The inverse problem is being addressed of measuring a count rate, IE, BU, and CT from NDA instruments, and determining the expected fissile quantity