Metrology is defined as the science of measurement and its application, encompassing amongst others the accuracy, traceability, reliability and comparability of measurement results, linking them to reference standards and conformity assessment tools.
Confidence in the analytical results provided by laboratories carrying out measurements for independent safeguards verification, is on the basis of international political decisions in view of the peaceful use of nuclear energy in any geopolitical context. Independent accurate measurement results are equally required for special and environmental sample analysis.
Quality assurance (QA) and quality control (QC) comprise different aspects:
• Method validation via Certified Reference Materials (CRM) and instrument calibration.
• Traceability and Comparability of measurement results.
• Uncertainty of measurement results (Guide to the expression of uncertainty in measurement).
• External performance evaluation.
• Document/data control and deployment of a quality system.
Confidence in results
Accountancy and control of nuclear material require analytical measurements that “shall either conform to the latest international standards or be equivalent in quality to such standards” IAEA INFCIRC/153. This equally applies to verifying the absence of undeclared nuclear materials and activities under the Additional Protocol (AP) INFCIRC/540 (Corr). Nuclear safeguards conclusions are based to a large extent on comparison of obtained measurement results with the declarations of the operator.
More recently, safeguards have become increasingly investigative and deals with consistency of measurable material properties with declared processes. In nuclear forensics, characteristic parameters (also referred to as “signatures”) are used for re establishing the history of nuclear material found out of regulatory control. QA and QC in destructive sample analysis in nuclear safeguards and security are the means to comply with the requirements to provide accurate and reliable measurement results.
Conformity assesment
Laboratories performing measurements in nuclear safeguards and nuclear security have to demonstrate their competence and increasingly their proficiency in compliance with ISO/IEC 17025 on an international level and to their respective accreditation bodies through internal and external quality control measures. The JRC is accredited by the Belgian Accreditation Body (BELAC) according to ISO/IEC 17043:2010 Conformity assessment — General requirements for proficiency testing.
• In the JRC’s Regular European Inter-laboratory Measurement Evaluation Programme (REIMEP), samples matching materials analysed routinely in the nuclear fuel cycle are sent to participating laboratories for measurements with undisclosed reference values.
• The JRC’s Nuclear Signatures Inter-laboratory Measurement Evaluation Programme (NUSIMEP) is an example of an external quality control programme in the field of environmental sample analysis, involving element and isotopic analysis of trace amounts of nuclear material in the environment.
Uranium particle reference materials for environmental swipe sample analysis
Environmental swipe samples collected at nuclear facilities during inspections are used by (inter)national safeguards authorities to verify the absence of undeclared nuclear material and/or activities in nuclear facilities under safeguards.
Nuclear security authorities also use environmental samples for evidence collection in cases of border interdictions of nuclear material, and seizures or discoveries of nuclear material in the public domain.
Uranium particle analysis is a powerful tool to this end:
• The JRC, the Forschungszentrum Jülich (FZJ), Germany, and the International Atomic Energy Agency (IAEA) joined forces to release the first uranium oxide microparticle reference materials for nuclear safeguards and security, IRMM-2329P and IRMM-2331P.
International target values (ITV) network
ITV represent estimates of achievable uncertainties under routine measurement conditions. They are used as a reference by nuclear plant operators, State and regional authorities, safeguards inspectors, safeguards laboratories and other safeguards practitioners. The proper application of metrological quality control and conformity assessment tools is indispensable to the achievement of measurement accuracy in compliance with the International target values (ITV) network.
Future objectives and challenges
- Quality control and quality assurance remain indispensable for providing reliable, high quality measurement results to safeguards authorities.
- An essential part of a quality system is to assure that analytical staff is well trained, that infrastructure and equipment is operational and that an appropriate project management system with data and document control is implemented.
- Guaranteeing tailor-made quality control tools for future nuclear fuel cycles.
- Assessment of measurement capabilities of Network of Analytical Laboratories in nuclear safeguards & security.
- ITV review in a continuous way by an extended ITV Expert Network.