SIST EN ISO 16795:2025 PDF

Overview

EN ISO 16795:2025 (adopted from ISO 16795:2024) specifies a validated method for the determination of Gd2O3 (gadolinium oxide) mass fraction in UO2 fuel pellets by X‑ray fluorescence spectrometry (XRF). The document defines a procedure using wavelength-dispersive XRF (WD‑XRF)-measuring the Gd Lα line-as the stated method, while also noting that energy‑dispersive XRF (ED‑XRF) is applicable. The method has been tested for Gd2O3 mass fractions from 2% to 10% and covers sample preparation, calibration, measurement and reporting requirements.

Key Topics

• Scope and principle
  • Determination of Gd2O3 content in sintered (U,Gd)O2 pellets by XRF; signal intensity of the selected L X‑ray line is proportional to Gd concentration.
• Apparatus and instrumentation
  • Sequential X‑ray spectrometer with precision goniometer, LiF 200 analyzer crystal, scintillation/flow detectors, multi‑channel analyser, ~3 kW X‑ray generator.
  • Supporting equipment: pellet press, analytical balance (±0.1 mg), powder blender/shaker, sintering furnace (≈1 800 °C).
• Standards and calibration
  • Preparation of standard pellets (UO2 + Gd2O3) sintered and fabricated under controlled conditions; calibration curve established across 2–10% Gd2O3.
  • Requirements for metrological traceability of reference materials per ISO 17034 or ASTM C1128 for working standards.
• Sample preparation
  • Blending dried powders, pressing and sintering pellets under the same conditions as fuel production, polishing the pellet face (e.g., 800‑grit SiC), and cleaning prior to analysis.
• Measurement controls
  • Angle calibration (example 2θ ≈ 61.115°), pulse‑height distribution, background correction and stability/sensitivity checks; automatic data acquisition and evaluation.
• Precision, accuracy and reporting
  • Clauses include precision/accuracy evaluation and required content of the test report.

Applications

• Quality control in nuclear fuel fabrication for verifying Gd2O3 loading in UO2 pellets.
• Production process control for laboratories performing acceptance testing of doped fuel pellets.
• Metrology and accreditation labs establishing calibration curves and traceable reference materials for fuel analysis. Who uses this standard: nuclear fuel manufacturers, analytical laboratories in the nuclear industry, regulatory bodies, and metrology institutes involved in nuclear material characterization.

Related Standards

• ISO 16795:2024 (original ISO text)
• ISO 17034 - competence of reference material producers
• ASTM C1128 - guide for preparation of working reference materials for nuclear fuel cycle analyses

Keywords: EN ISO 16795:2025, ISO 16795:2024, Gd2O3 determination, UO2 fuel pellets, X‑ray fluorescence spectrometry, WD‑XRF, Gd Lα line, calibration curve, nuclear fuel quality control.