Year
2003
Abstract
In previous studies the use of the Nuclear Materials Identification System (NMIS) for passive measurements on plutonium metal samples was investigated. The technique is based on the detection of correlated particles from the spontaneous fission of Pu-240 and from the subsequent induced fission on Pu-239. Past measurements and analyses showed the sensitivity of the acquired signature to the emission, attenuation, and multiplication properties of the shells. In particular, measurements were performed at VNIIEF for a variety of shell thicknesses ranging from 6 to 30 mm, and masses varying from 1829 to 4468 g. In the present paper, the effect of placing the fissile material being investigated inside a specifically designed container (AT-400R) is investigated. The container is designed to shield the radiation emitted by the fissile sample, and is therefore expected to reduce the correlated signal greatly. A number of simulations were performed with the MCNPPoliMi code to quantify this reduction and to assess the feasibility of conducting measurements using large liquid scintillators on the plutonium samples placed inside the AT-400R container.