Safeguards Environment and Measurement Conditions

The hardware and software of an NDA system depend on the specific conditions (e.g., environment, sample matrix, etc.) of the measurement task. In most cases, different NDA instruments are required to obtain the total quantity for a given nuclear material sample. Only a combination of the results of several calibrated NDA techniques provides for a credible assessment of the type and quantity of nuclear material. 

The nature of a particular inspection activity may require the customization of equipment and methods applied. The equipment and method should be simple and user firiendly, and should provide results in a short time period, because the available inspection time is usually very limited. Furthermore, emphasis is placed on compact, lightweight, rugged, and reasonably priced equipment, which can be carried by the inspectors and thus remain completely under their control. 

For large and complex facilities, the inspectorates require facility resident and specific safeguards equipment systems with features for attended, unattended, and remotely controlled operations. Some of the safeguards systems are integrated in the process equipment of the facility. The dimensions of the measurement head (the sensor) for these systems are often strongly conditioned by factors like sample geometry, plant requirements and detection efficiency, all of which factors impose boundary conditions that demand an individual design. 

Calibration is necessary in all quantitative NDA measurements to relate measured responses (e.g., neutron coincidence rate or specific gamma intensity) to nuclear material characteristics. An accurate measurement depends crucially on the effective calibration of measurement instrumentation. This calibration is based on similar items whose nuclear material content is very accurately known. The resulting calibration functions including all necessary correction factors (such as those relating to neutron multiplication or gamma-ray 

In some instances, safeguards inspectorates do not own the NDA equipment and need to share the instruments with third parties, e.g., operators. In this case, documented joint-use procedures should define arrangements for data sharing, authentication, recalibration and use of standards and software, maintenance, repair, storage, and transportation. 

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