CHARACTERIZATION OF THE NEUTRON SOURCE TERM AND MULTIPLICITY OF A SPENT FUEL ASSEMBLY IN SUPPORT OF NDA SAFEGUARDS OF SPENT NUCLEAR FUEL

摘要

The gross neutron signal (GNS) is being considered as part of fingerprinting or neutron balanceapproaches to safeguards of spent nuclear fuel (SNF). Because the GNS is composed of manyderivative components, understanding the time-dependent contribution of these derivativecomponents is crucial to gauging the limitations of these approaches. The major components of theGNS are (?, n), spontaneous fission (SF), and multiplication neutrons. A methodology wasdeveloped to link MCNPX burnup output files to SOURCES4C input files for the purpose ofautomatically generating both the (α, n) and SF signals. Additional linking capabilities weredeveloped to write MCNPX multiplication input files using the data obtained from theSOURCES4C output files. In this paper, the following are presented: (1) the relative contributionsby source nuclide to the (α, n) signal as a function of initial enrichment/burnup/cooling time; (2) therelative contributions by source nuclide to the SF signal as a function of initialenrichment/burnup/cooling time; (3) the relative contributions by reaction type (α,n vs. SF) to theGNS; and (4) the multiplication of the GNS as a function of initial enrichment/burnup/coolingtime/counting environment. By developing these technologies to characterize the GNS, we canbetter evaluate the viability of the GNS fingerprint and neutron balance concepts for SNF.