Accurate measurement of plutonium, uranium and americium are particularly challenging when the lungs in question also contain depositions of higher energy nuclides such as 137Cs or 60Co. For more than 20 years Mirion has designed and fabricated the systems and components to meet this challenge. Mirion is constantly surveying technological advances that improve system ergonomics and detection capability. The 2270 Lung Counter is one of the company's two resulting standard Lung Counting systems.
The Model 2270 Lung Counter provides accurate and reliable measurements of uranium, plutonium and americium in the lungs. The standard system design includes two Mirion ACT-II cryostat assemblies, a detector positioning mechanism that provides six degrees of freedom, digital spectrum analyzers, Apex-InVivo body counting software with the lung counting software option, and a comfortable subject positioning chair.
Each of the system's ACT-II Crysotats can accommodate two low or broad energy crystals with surface areas of 2000 mm2, 2800 mm2, or 3800 mm2 each. Mirion will work with the user during the proposal process to recommend the optimal crystal size and type based on the customer's detection requirements and budget. Please refer to the Mirion low and broad energy germanium detector specification sheets for additional detailed information on detector performance and design.
The 2270 Lung Counter also includes complete system integration, calibration, installation and training. The result is a complete turnkey system specifically tailored to the measurement and analysis of U/Pu lung burdens on a routine basis. System integration is completed at the factory. If one of the optional system shield assemblies is purchased then the calibration is also performed at the factory.
The installation and training are provided at the customer's site. If the customer elects to supply the shield or shielded room for the system, then the calibration will be provided at the customer's site after installation in the shield. The combination of hardware, software and services included in this system ensures that the system is ready for operation once the system has been installed at the customer's site.
Mirion offers both a standard 10 and a 15 cm thick, low background steel shield as an option for the 2270 Lung Counter. These shields come with overlapping double entry/exit doors, internal lighting, an oxygen sensor, and a subject panic button, as wells as shield penetrations for detector cables, liquid nitrogen fill lines, music system cables and closed circuit video cables. The customer must provide a shield or shielded room for use with the Model 2270 system which provides external environment shielding equivalent to that provided by the 10 cm thick shield room in order to achieve system detection performance similar to that defined in this specification sheet.
Mirion can also option a set of detector anti-Compton shields, an automatic liquid nitrogen filling system, a music system and a closed circuit television system for use with the 2270 Lung Counter. Mirion highly recommends the use of the anti-Compton shields around the germanium detectors. These lead shields significantly reduce spectral background due to bremsstrahlung interactions from the naturally occurring 40K within the subject. This background reduction can be used to improve detection capability and lower counting time.
The 2270 Lung Counting system is designed to make routine radiation protection monitoring for actinides in the lungs fast, reliable and accurate. The chair and detector positioning mechanism are designed to allow optimal positioning of the detectors over the lungs to increase operational efficiency and lower detection limits.
The subject or patient is seated in a semi-reclining position in the chair for routine counts. The chair geometry minimizes the chest wall thickness, which improves detection limits, and is more comfortable for the patient than a fully reclining position. The detector positioning mechanism slides on a rail assembly on the side of the chair. This allows the detectors to be moved out of the way making it easy for the patient to enter and exit the chair.
The chair can be positioned to a nearly fully reclining position. The combination of the sliding detector positioner mechanism and the reclining chair allows the system to be used to count individual organs such as the liver or thyroid. Such counting geometries that may be of interest in research operations and accident scenarios.