Skip navigation
Nuclear Safeguards Education Portal
  

Nuclear Material Inventory (cont.)

IAEA Safeguard inspectors doing a physical inventory of fuel assemblies stored on a fresh fuel rack. (Source: Dean Calma/IAEA)
IAEA Safeguard inspectors doing a physical inventory of fuel assemblies stored on a fresh fuel rack. (Source: Dean Calma/IAEA) 

There are two different types of inventory for a facility: physical inventory and book inventory.

Physical inventory is the sum of all the measured or derived estimates of batch quantities of nuclear material on hand at a given time within an MBA.  The physical inventory is determined by the facility operator as a result of physical inventory measurements.  This physical inventory is then verified by the IAEA during a physical inventory verification inspection.  A physical inventory inspection represents the end of the current MBP and the start of the next one.

Book inventory (of an MBA) is the algebraic sum of the most recent physical inventory of MBA and of all inventory changes that have occurred since that physical inventory.  The book inventory can be calculated by a simple algebraic equation:

BI = PB + X - Y

where, BI is the book inventory, PB is the physical inventory at the beginning of a material balance period, X is the sum of increases to inventory, and Y is the sum of decreases from inventory.

Page 6 / 17