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PUNITA

RESEARCH ACTIVITIES

FISSILE MATERIAL ASSAY

The nuclear safeguards application of PUNITA concerns the determination of the mass of fissile material in a sample independent of matrix materials and spatial source distribution. To achieve this aim, intense bursts of thermal neutrons, produced by the neutron generator and a substantial graphite liner, induce fission in the fissile isotopes of the sample. The fission neutrons are detected and analyzed in the time domain. The analysis method consists of a further development of the standard passive neutron correlation technique

DETECTION OF CONTRABAND MATERIALS

A wide range of methods have been proposed in the past for automated, non-destructive detection of hidden dangerous/contraband materials located inside consignments of luggage or goods. In the PUNITA facility we study the methods which apply the detection of characteristic gamma rays subsequent to neutron irradiation. Many types of neutron reactions will cause the emission of characteristic gamma rays from a target material. Among these reactions, known to the method of prompt gamma activation analysis (PGAA), are in-elastic scattering (n, n´γ) by fast neutrons and the neutron capture reaction (n,γ) by thermal neutrons. The gamma energy from such reactions is characteristic for the chemical elements present in the sample. By gamma spectroscopy it is possible to identify elements in the target material and to some extend the element composition by determination of gamma line ratios. An interesting possibility currently being studied in PUNITA consists of combining both inelastic scattering and capture in the same measurement. For this purpose neutrons emitted from the pulsed neutron generator interrogate the sample, first by fast neutrons directly from the neutron generator, and a few hundred microseconds later by thermal neutrons produced by the surrounding graphite liner.