Key takeaways
- NMAC is how a facility keeps an exact record of its nuclear material, so its State authority and the IAEA can verify that none is diverted.
- Records are kept per material balance area (MBA), with every movement recorded at key measurement points.
- Facilities report inventory changes (ICR), physical inventories (PIL) and material balances (MBR) in the format set by Code 10 of the Subsidiary Arrangements.
- Good NMAC software produces these reports from the same records the plant works from, with an audit trail and separate preparers and approvers.
What NMAC is and who needs it
Under a comprehensive safeguards agreement based on IAEA document INFCIRC/153, a State sets up a State system of accounting for and control of nuclear material. Each facility keeps accounting records and sends reports through its State authority to the IAEA, which verifies them through inspections.
This applies to nuclear power plants, research reactors, fuel fabrication plants and storage facilities. At a power plant most material is held in items, mainly fuel assemblies, so accounting is item-based: each assembly is identified and counted, and its uranium and plutonium content is tracked as fuel is used in the reactor.
Key concepts
| Term | Meaning |
|---|---|
| Material balance area (MBA) | An area where the quantity of nuclear material moving in or out, and the physical inventory, can be determined. |
| Key measurement point (KMP) | A location where material appears in a form that can be measured to determine flows or inventory. |
| Book inventory | Beginning inventory plus increases minus decreases, from the accounting records. |
| Physical inventory taking (PIT) | The periodic count and measurement of all nuclear material present in an MBA. |
| MUF (material unaccounted for) | Book inventory minus physical inventory at the end of a balance period. |
| Shipper/receiver difference | The difference between the quantity stated by the shipper and the quantity measured by the receiver. |
| Significant quantity | The approximate amount of material for which a nuclear explosive device cannot be ruled out: 8 kg of plutonium, 25 kg of uranium-235 in high-enriched uranium, or 75 kg of uranium-235 in low-enriched uranium. |
The three reports the IAEA expects
Code 10 of the Subsidiary Arrangements, General Part, sets out the content, format and structure of reports to the IAEA. Facilities report by batch for each MBA.
| Report | What it contains | When it is due |
|---|---|---|
| Inventory Change Report (ICR) | Every increase or decrease in nuclear material in the MBA: receipts, shipments, nuclear production and loss, transfers and corrections. | As soon as possible, and within 30 days after the end of the month in which the changes occurred. |
| Physical Inventory Listing (PIL) | A batch-by-batch list of all nuclear material present at a physical inventory taking. | With the material balance report. |
| Material Balance Report (MBR) | Beginning inventory, inventory changes, ending book inventory, shipper/receiver differences, ending physical inventory and MUF. | As soon as possible, and within 30 days after the physical inventory was taken. |
Concise notes can accompany any report to explain unusual entries. Reports can be corrected later, following the correction rules in Code 10. Code 10 allows labelled and fixed formats, and many States now exchange reports electronically.
What NMAC software must do
- Model your MBAs, KMPs, items and batches the way the plant is organized.
- Record every movement once, with date, location, item identity and quantities by element and isotope.
- Keep ledgers for each MBA and produce the book inventory for any date.
- Support physical inventory taking: generate the lists, record verification and calculate MUF against an alarm threshold.
- Produce ICR, PIL and MBR in Code 10 format, with concise notes and corrections.
- Keep the history of every fuel assembly: receipt, core loading, discharge, spent fuel pool position and transfers.
- Account for nuclear production and loss using the operator’s reactor physics data.
- Separate preparers, reviewers and approvers, and keep a tamper-evident audit trail.
- Run on your own servers, with single sign-on, multi-factor authentication and role-based access.
- Support national formats where they apply. In the United States, for example, that means NRC rules in 10 CFR Parts 74 and 75 and NMMSS reporting on DOE/NRC Forms 741, 742 and 742C.
Why spreadsheets fall short
Many facilities start with spreadsheets. They work until an inspection or a correction exposes their limits:
- Data is typed in more than once, so reports and records can disagree.
- There is no reliable audit trail of who changed what, and when.
- Report formats are rebuilt by hand, which invites errors in codes and batch data.
- Knowledge sits with one or two people, which is a continuity risk.
Questions to ask a vendor
- Can you show an ICR, PIL and MBR generated from your test data in Code 10 format?
- How are corrections handled, and how do they appear in later reports?
- How is MUF calculated, and how are thresholds configured?
- How are core and spent fuel pool positions shown and kept in step with movements?
- Can the system run fully on-premise, without internet access?
- How are national reporting formats configured?
Where Mizan fits
Mizan (ميزان) is Birbal AI’s NMAC software for nuclear power plants. It covers material movements, ledgers per MBA, physical inventory taking, material balance and MUF, core and spent fuel pool maps, and ICR, PIL and MBR reports in Code 10 labelled format, with four-eyes approval and an on-premise deployment. See Mizan.
Questions and answers
What does NMAC stand for?
Nuclear material accounting and control: the records, measurements and procedures a facility uses to know exactly how much nuclear material it holds and where it is.
Which reports do nuclear facilities send to the IAEA?
Inventory Change Reports (ICR), Physical Inventory Listings (PIL) and Material Balance Reports (MBR), sent through the State authority in the format set by Code 10 of the Subsidiary Arrangements.
What is MUF?
Material unaccounted for: the difference between the book inventory and the physical inventory at the end of a material balance period.
What is a significant quantity?
The approximate amount of nuclear material for which a nuclear explosive device cannot be ruled out, for example 8 kg of plutonium or 75 kg of uranium-235 in low-enriched uranium.
Can NMAC software run without internet access?
Yes. NMAC software is normally installed on the facility’s own servers, and can run on an isolated network. Mizan is deployed this way.
Does a facility report directly to the IAEA?
Usually not. The facility keeps the records and sends its reports to the State authority, which reports to the IAEA.
Sources
- IAEA: INFCIRC/153, the structure and content of comprehensive safeguards agreements
- IAEA: Subsidiary Arrangements, Code 10 (labelled format)
- US eCFR: 10 CFR 74.13, material status reports
- NNSA: NMMSS reporting forms 741, 742, 742C and 740M
Birbal AI is an independent company based in Abu Dhabi. Facts about third parties come from the sources above; check them for the latest position.