Procedures, personnel and equipment used for determining the quantities of nuclear material received, produced, shipped, lost or otherwise removed from inventory, and the quantities on inventory. This system should provide for:

• Identification of key measurement points and the characteristics of the nuclear material to be measured
• Specification of the measurement performance desired
• Specification of the measurement technique(s) employed
• Specifications for measurement equipment
• Equipment maintenance provisions and procedures
• Operator's qualifications and provisions for training
• Calibration standards and procedures
• Routine measurement and data analysis procedures
• Procedures for controlling measurement quality and maintaining performance at the desired level
• Procedures for generating sample plans and obtaining representative samples
• Procedures for combining measurements and measurement uncertainties so as to calculate material unaccounted for (MUF) and MUF uncertainty (σMUF).

The system of measurements on which the facility records are based "shall either conform to the latest international standards or be equivalent in quality to such standards." (INFCIRC 153*)