The Model 2340-20 Mobile Packet Monitor is a Passive Neutron Coincidence Counter (PNCC) Assay System which makes quantitative measurements of the plutonium-240 effective (240Pueff) content of Pu/MOX fuel samples. It can detect and measure from a few grams up to kilogram quantities of plutonium in Pu/MOX fuel items. The system is capable of assaying fissile materials such as plutonium and americium within various matrices. The results obtained can be used as the definitive nuclear material declaration value of packages for safety, criticality control and nuclear materials safeguards purposes. This information can be combined with the isotopic information from the Gamma Spectrometer to provide a complete isotopic inventory of plutonium present in each package.
Two pieces of equipment make up the integrated system:
The PNCC consists of an array of 30 x 3He detectors arranged in two annular rings around the outside of the chamber in a polyethylene moderator. The detectors are grouped into six (6) channels, with each channel connected to an Amptek A111 high count rate amplifier. The output from each amplifier connects to an ANTECH A2000 TTL-LVDS convertor to provide a single output train to the neutron counting electronics for true lossless counting, which is particularly important for high count-rate applications. The system is designed for flexibility and can easily be converted into an Active Well Coincidence Counter by exchanging the removable chamber liners and inserting of a pair of interrogation sources in the plug units.
The High Purity Germanium (HPGe) Gamma Spectrometer consists of a high resolution gamma spectrometry data acquisition and analysis system and is designed primarily for isotopic analysis of Pu/MOX fuel. However, it can easily be configured to assay other isotopic materials.
The Workstation consists of an enclosure which houses the system main computer and the neutron counting electronics, which operates the neutron system and acquires raw measurement data. It is fitted with a worktop onto which an LCD monitor and keyboard/mouse can be mounted. A gland plate at the rear of the cabinet provides connection points for power to the Workstation, power and signal to the Neutron Assay System and signal from the Gamma Spectrometer. Both instruments can be fitted with additional data take-off points for independent safeguards monitoring and surveillance.
The sample measurement time for each instrument is typically between 10 to 20 minutes. The analysis software terminates a measurement at a pre-set time configured by the user. Should the accuracy not be reached within this period, the user can extend the count time for an additional pre-set time.