ISO 18213-1:2007

Overview - What ISO 18213-1:2007 covers

ISO 18213-1:2007, "Nuclear fuel technology - Tank calibration and volume determination for nuclear materials accountancy - Part 1: Procedural overview," provides procedural guidance for planning and performing tank calibrations and subsequent volume determinations for nuclear process tanks equipped with bubbler probe pressure-measurement systems. The standard explains the calibration objective: to collect the data needed to estimate a tank’s volume-measurement equation (the inverse of the calibration equation) so that liquid volumes can be derived from pressure or height measurements. The methods apply only to clear, homogeneous liquids at thermal and static equilibrium.

Key topics and technical requirements

• Physical principle: Hydrostatic law (P = g·H·ρ) relating pressure, liquid height and density.
• Scope limitations: Methods are specific to tanks using bubbler probe systems and are reliable only for liquids without suspended solids and under equilibrium conditions.
• Calibration model: Defines calibration and measurement (volume vs. height) equations and the inverse relationship needed to compute volume from probe pressure or height.
• Equipment and inputs: Guidance on tank measurement systems, prover systems, calibration liquid selection, manometers, and calibration software.
• Planning and procedures: Steps for a typical calibration exercise including a calibration plan, measurement requirements, pre-calibration checks, data acquisition, and data standardization to reference conditions.
• Standardization and corrections: Need to standardize measurements for temperature, density and other factors that affect comparability.
• Statistical treatment and uncertainty: Directions to assess data consistency, derive calibration equations and compute uncertainty bounds (see related parts for detailed statistical methods).
• Special topics: Procedures for determining reference heights, computing volumes, handling heel volume, and notes on bubbling rate effects.

Practical applications and users

ISO 18213-1 is intended for organizations involved in nuclear materials accountancy and process control where accurate liquid volume measurement is critical, such as:

• Nuclear fuel fabrication and reprocessing plants
• Safeguards and regulatory laboratories
• Measurement engineers responsible for accountability tanks and inventory control
• Calibration teams planning in-tank calibration campaigns

Users will apply the procedural framework to design calibration campaigns, select equipment and software, standardize collected data, and produce defensible volume determinations with quantified uncertainties.

Related standards

Part 1 complements the other parts of ISO 18213:

• ISO 18213-2: Data standardization for tank calibration
• ISO 18213-3: Statistical methods (uncertainty analysis)
• ISO 18213-4 / -5: Height determination for slow/fast bubbling rates
• ISO 18213-6: In-tank density determination

Keywords: ISO 18213-1, tank calibration, volume determination, bubbler probe, nuclear materials accountancy, pressure-measurement systems, calibration equation, data standardization, uncertainty.