ISO 18256-2:2019 PDF

Nuclear fuel technology — Dissolution of plutonium dioxide-containing materials — Part 2: Dissolution of MOX pellets and powders

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Title (English):

ISO 18256-2:2019

Nuclear fuel technology — Dissolution of plutonium dioxide-containing materials — Part 2: Dissolution of MOX pellets and powders

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 7
Publication date:: January 15, 2019
Edition:: ISO IS 18256 edition 1 version 1
ICS:: 27.120.30

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Description (English):

This document specifies the dissolution of samples consisting of MOX pellets or powders to provide suitable aliquots for subsequent analysis of elemental concentration and isotopic composition.

Technical details

Technical committee: ISO/TC 85/SC 5 - Nuclear installations, processes and technologies
SKU: ISO 18256-2:2019

Abstract

Overview

ISO 18256-2:2019 specifies a validated procedure for the dissolution of MOX pellets and powders (mixed oxide fuels containing plutonium dioxide) to produce aliquots suitable for subsequent elemental concentration and isotopic composition analysis. The standard addresses sample size, reagent selection, apparatus, dissolution conditions and safety measures needed in plutonium-bearing sample preparation for nuclear fuel technology and radiochemical laboratories.

Key topics and technical requirements

Scope and purpose: Dissolution methods tailored to MOX pellets or powders to generate representative solutions for Pu/U assay and isotopic measurements.
Sample mass: Typical sample masses recommended are 0.1 g to 10 g depending on radiological hazards and analysis needs.
Reagents: Use analytical-grade reagents. Recommended dissolving media include mixed nitric–hydrofluoric acid (≈8–14 mol/L HNO3 with HF ≈0.05–0.1 mol/L) or nitric–ammonium bifluoride (≈14.4 mol/L HNO3 with ~2 g/L NH4HF2 producing ~0.07 mol/L HF).
Apparatus: Analytical balance (0.001 g), PTFE-lined vials or glass vessels, reflux caps or condensers, shielded hotplates and fume hood. Handling in glove boxes or hot cells is mandatory.
Dissolution conditions:
- Powders: heat at 70–110 °C; add acid slowly due to rapid reaction.
- Pellets: dissolve under reflux/boiling; dissolution may require ≈18 h or more.
Container material trade-offs:
- Glass: attacked by fluoride (tare mass changes) but volatile SiF4 formation can reduce final fluoride and limit PuF precipitation.
- PTFE/HDPE: inert to HF (tare stable) but higher risk of insoluble plutonium fluoride if oxidation state changes.
Quality control: Gravimetric dissolution recommended for highest assay accuracy; volumetric methods acceptable for less critical assays. Mass-loss checks (e.g.,

Related standards

Other ISO standards

Overview

Key topics and technical requirements

Scope and purpose: Dissolution methods tailored to MOX pellets or powders to generate representative solutions for Pu/U assay and isotopic measurements.
Sample mass: Typical sample masses recommended are 0.1 g to 10 g depending on radiological hazards and analysis needs.
Reagents: Use analytical-grade reagents. Recommended dissolving media include mixed nitric–hydrofluoric acid (≈8–14 mol/L HNO3 with HF ≈0.05–0.1 mol/L) or nitric–ammonium bifluoride (≈14.4 mol/L HNO3 with ~2 g/L NH4HF2 producing ~0.07 mol/L HF).
Apparatus: Analytical balance (0.001 g), PTFE-lined vials or glass vessels, reflux caps or condensers, shielded hotplates and fume hood. Handling in glove boxes or hot cells is mandatory.
Dissolution conditions:
- Powders: heat at 70–110 °C; add acid slowly due to rapid reaction.
- Pellets: dissolve under reflux/boiling; dissolution may require ≈18 h or more.
Container material trade-offs:
- Glass: attacked by fluoride (tare mass changes) but volatile SiF4 formation can reduce final fluoride and limit PuF precipitation.
- PTFE/HDPE: inert to HF (tare stable) but higher risk of insoluble plutonium fluoride if oxidation state changes.
Quality control: Gravimetric dissolution recommended for highest assay accuracy; volumetric methods acceptable for less critical assays. Mass-loss checks (e.g.,

ISO 18256-2:2019 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

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Abstract

Overview

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