The Importance of Destructive Analysis for Nuclear Material Accountancy and Safeguards Verification

Destructive Analysis remains a cornerstone for nuclear material accountancy and its safeguards verification. The basic concept of nuclear material accountancy is simple and has much in common with a financial accounting system, with the IAEA playing the part of an auditor. Operators of bulk handling facilities - such as conversion, enrichment, fuel fabrication and reprocessing plants - are required to have a measurement system in place that ‘shall either conform to the latest international standard or be equivalent in quality to such standards’. Such a system usually comprises various methods of destructive analysis. At the end of a material balance period a facility has to declare the difference between the book inventory and the physical inventory which, in the IAEA’s terminology, is called MUF (‘material unaccounted for’). Using estimates of the operator’s measurement uncertainties the actual MUF value is expected not to be statistically significant. The IAEA, as part of its Safeguards inspections, is taking samples for Destructive Analysis (DA) to independently verify the amount of nuclear material in the flow of material or in the inventory of a facility. The sampling strategy depends on the type of facility and the availability of other verification tools, such as Non-destructive Assay (NDA) techniques. Procedures are in place to combine the use of DA and NDA by calculating optimized sample sizes, considering the actually observed measurement quality for the techniques. The aim of the majority of DA measurements, conducted by the IAEA, is to verify the quality and functioning of the operators’ measurement systems and to verify operator’s declarations on inventories and flows of nuclear materials. Besides describing the importance of DA for both, a facility operator and Safeguards, the paper will summarize the specifics of the IAEA’s system of Destructive Analysis, make reference to the International Target Values and highlight the importance of DA in the certification of NDA calibration standards and working reference materials.