MCNP-POLIMI Evaluation of Time Dependent Coincidence Between Detectors for Fissile Metal Vs. Oxide Determination

Conference · Mon Jun 03 04:00:00 EDT 2002

OSTI ID:799509

Pozzi, Sara A. ^[1]; Mihalczo, John T. ^[1]

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1. Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)

In the past, passive Nuclear Materials Identification System (NMIS) measurements on plutonium metal shells at VNIIEF have shown the sensitivity of the acquired covariance functions to shell mass and thickness for a variety of shell thicknesses from 6 to 30 mm and masses varying from 1829 to 4468g. The technique acquires the time-dependent coincidence distribution between plastic scintillators detecting radiation from the Pu. The measurements showed the sensitivity of the acquired signature to the different spontaneous emission, attenuation, and multiplication properties of the shells. In this work, the MCNP-POLIMI neutron and photon transport code was used to simulate passive measurements on plutonium metal and oxide. The code is a modified version of MCNP, which attempts to calculate more correctly quantities that depend on the second moment of the neutron and gamma distributions, and attempts to model detector pulses as closely as possible. MCNP-POLIMI, together with a post-processing code, can simulate all the time-dependent coincidence distributions measured by NMIS. In particular, the simulations evaluate the time-dependent coincidence distributions between detectors for plutonium samples having mass 2 and 4 kg, in metal and oxide form. This work shows that the time-dependent coincidence distributions between two scintillators measured by NMIS can be used to distinguish metal from oxide.

• Research Organization: Oak Ridge Y-12 Plant (Y-12), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)
• DOE Contract Number: AC05-00OR22800
• OSTI ID: 799509
• Report Number(s): Y/LB--16,131
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ATTENUATION
DISTRIBUTION
EVALUATION
IDENTIFICATION SYSTEMS
MCNP-POLIMI
NEUTRONS
NUCLEAR MATERIALS MANAGEMENT
Nuclear Criticality Safety Program (NCSP)
Nuclear Materials Identification System (NMIS)
OXIDES
PHOTON TRANSPORT
PLASTIC SCINTILLATORS
PLUTONIUM
Passive
RADIATIONS
SENSITIVITY
THICKNESS
VNIIEF