ISO 13464:1998

Overview

ISO 13464:1998 specifies a nondestructive, combined K‑absorption edge (K‑edge) and X‑ray fluorescence (XRF) method for the simultaneous determination of uranium (U) and plutonium (Pu) volumetric concentrations in nitric‑acid dissolver/feed solutions from reprocessing plants. The procedure is designed to operate directly on original feed solutions (typical ranges ~150–300 g·L−1 U and ~1–2.5 g·L−1 Pu) in the presence of fission products (up to ~10 TBq·L−1 β,γ activity).

Keywords: ISO 13464:1998, K‑absorption edge, K‑edge densitometry, X‑ray fluorescence (XRF), uranium plutonium determination, nondestructive assay, reprocessing plant dissolver solutions.

Key topics and technical requirements

• Measurement principle: irradiate a small sample (≈3–5 mL) with a high‑energy X‑ray continuum (up to ≈150 keV).
  • K‑edge densitometry (KED) measures abrupt attenuation change across the uranium K‑absorption edge (E ≈ 115.6 keV) to determine uranium concentration.
  • XRF measures the U/Pu Kα X‑ray intensity ratio to obtain the U/Pu mass ratio; plutonium concentration is then calculated from the uranium result and the ratio.
• Instrumentation: two high‑resolution HPGe detectors, fast pulse processing, computer‑based MCA, and a 3 kW X‑ray tube (typical rating ~150 kV/10–15 mA). HPGe specs: active area ~100–200 mm2, depletion depth ~10–13 mm, resolution ≤0.6 keV FWHM at 122 keV.
• Geometry & shielding: tightly controlled tube‑to‑sample distance (≈6.5 cm), specific detector/collimator angles (Θ ≥ 150°), and limited K‑edge detector solid angle (Ω < 10−4 sr) to reduce scattering and self‑radiation effects.
• Sample handling: thin‑walled cuvettes or cylindrical vials (pathlength ≈1.5–2.5 cm) with strict control of effective pathlength and lateral positioning.
• Calibration & quality: procedure includes instrument calibration, bias correction factors and uncertainty evaluation. Counting time and tube settings are chosen to meet required repeatability.

Practical applications and users

• Process monitoring and control in nuclear reprocessing plants - rapid, nondestructive assays of dissolver feed solutions.
• Nuclear material accountancy and safeguards - independent verification of U and Pu mass in feed streams.
• Hot‑cell or glovebox assay laboratories and providers of nondestructive assay (NDA) instrumentation.
• Regulatory and safeguards agencies that require standardized, traceable measurement methods for U/Pu in reprocessing contexts.

Related standards

• Prepared by ISO/TC 85 (Nuclear energy), Subcommittee 5 (Nuclear fuel technology). For broader context, refer to other ISO standards and guidance on nuclear fuel assay, nondestructive assay methods and uncertainty evaluation published by ISO/TC 85 and IAEA documents on safeguards (consult respective catalogs).

ISO 13464:1998 is a practical reference when implementing high‑precision, nondestructive U/Pu assays using combined K‑edge densitometry + XRF techniques in reprocessing and safeguards environments.