Year
2011
Abstract
The Next Generation Safeguard Initiative (NGSI) is currently sponsoring a mulitlab/university research effort to investigate different nondestructive assay techniques for quantifying the elemental plutonium mass in spent nuclear fuel assemblies. One instrument being studied is Californium Interrogation of Prompt Neutrons (CIPN). This instrument primarily measures a mixture of the three main fissile isotopes in spent fuel ( 235 U, 239 Pu and 241 Pu). The CIPN signal, which measures the prompt neutron emission, preferentially weights a unit mass of 239 Pu and 241 Pu relative to a unit mass of 235 U due to the elevated fission cross section of the 239 Pu and 241 Pu as well as the larger number of neutrons emitted per fission from 239 Pu and 241 Pu. The detection of delayed neutrons (DN) complements the CIPN technique. A DN technique also primarily measured a mixture of the three main fissile isotopes in spent fuel ( 235 U, 239 Pu and 241 Pu). However, a DN instrument preferentially weights a unit mass of 235 U relative to a unit mass of 239 Pu since 235 U emits around twice as many DN per unit mass as 239 Pu does. The main purpose of this paper is to investigate whether the same hardware used for the CIPN instrument can work as a DN instrument. To quantify the integration of these two techniques, this study analyzed the DN signal from the following 16 virtual spent fuel assemblies: Four burnups (15, 30, 45, and 60 GWd/tU), each at four different initial enrichments (2, 3, 4, and 5 wt%). All assemblies were cooled for 5 years