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Nuclear Safeguards Education Portal

Nuclear material accountancy

Photo related to the term with caption below

Comprehensive Inspection Exercise of IAEA Safeguard inspectors at Mochovce Nuclear Power Plant in Levice, Slovakia.

(Source: Dean Calma/IAEA)

The practice of nuclear material accounting as implemented by the facility operator and the State system of accounting for and control of nuclear material (SSAC) to satisfy the requirements in the safeguards agreement between the IAEA and the State (or group of States); and as implemented by the IAEA to independently verify the correctness of the nuclear material accounting information in the facility records and the reports provided by the SSAC to the IAEA. Nuclear material accountancy may include the following:

Facility Level

  • Dividing operations involving nuclear material into material balance areas (MBAs)
  • Maintaining records on the quantities of nuclear material held within each MBA
  • Measuring and recording all transfers of nuclear material from one MBA to another or changes in the amount of nuclear material within MBAs due to, for example, nuclear production or nuclear loss
  • Determining periodically the quantities of nuclear material present within each MBA through the taking of the physical inventory
  • Closing the material balance over the period between two successive physical inventory takings and computing the material unaccounted for (MUF) for that period
  • Providing for a measurement control program to determine the accuracy of calibrations and measurements and the correctness of recorded source data and batch data
  • Testing the computed MUF against its limits of error for indications of any unrecorded nuclear loss or accidental gain
  • Analyzing the accounting information to determine the cause and magnitude of mistakes in recording unmeasured losses, accidental losses and unmeasured inventory (hold-up)

State Authority Level

  • Preparing and submitting nuclear material accounting reports to the IAEA, as appropriate
  • Ensuring that nuclear material accounting procedures and arrangements are adhered to
  • Providing for IAEA inspector access and co-ordination arrangements, as necessary, to enable the IAEA to carry out its verification activities
  • Verifying facility operators' nuclear material accountancy performance, as provided for in the SSAC regulations.

IAEA Level

  • Independently verifying nuclear material accounting information in facility records and State reports, and conducting activities as provided for in the safeguards agreement
  • Determining the effectiveness of the SSAC
  • Providing statements to the State on the IAEA's verification activities