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