prEN ISO 18256-2

SLOVENSKI STANDARD
oSIST prEN ISO 18256-2:2020
01-november-2020

Tehnologija jedrskih goriv - Raztapljanje materialov, ki vsebujejo plutonijev dioksid

Nuclear fuel technology - Dissolution of plutonium dioxide-containing materials - Part 2:

Technologie du combustible nucléaire - Dissolution des matériaux contenant du dioxyde

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Summary of the method ............................................................................................................................................................................... 1

5 Apparatus and reagents ................................................................................................................................................................................ 2

5.1 Apparatus .................................................................................................................................................................................................... 2

5.2 Reagents........................................................................................................................................................................................................ 2

6 Sample dissolution ............................................................................................................................................................................................. 3

6.1 Procedure for common plutonium containing materials ................................................................................... 3

6.2 Solution adjustment (optional) ................................................................................................................................................ 5

7 Quality control ........................................................................................................................................................................................................ 6

Bibliography ................................................................................................................................................................................................................................ 7

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This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies,

and radiological protection, Subcommittee SC 5, Nuclear installations, processes and technologies.

Any feedback or questions on this document should be directed to the user’s national standards body. A

This document describes a method to dissolve samples consisting of MOX pellets or powders to provide

suitable aliquots for subsequent analysis of elemental concentration and isotopic composition.

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.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Among the factors affecting the formation of solid solution and hence, the ease of dissolution are:

— the method of fuel fabrication (i.e. mechanically blended oxides, co-precipitated oxides, microwave

Therefore, different dissolution methods are applied depending on the type of MOX sample to be

The radiological hazard of plutonium and the need to minimize the waste shall be taken into account

when choosing the mass of the sample to be dissolved. A MOX mass of 0,1 g to 10 g should be sufficient

For the highest possible assay accuracy only gravimetric dissolution methods are recommended.

For grain-size powders, the sample is transferred in a pre-weighed flask or vial made of glass, high-

density polyethylene (HDPE), polytetrafluoroethylene (PTFE), Nalgene or other container types,

— When using a glass dissolution vessel, the added fluoride will attack the glass (resulting in a

falsification of the pre-weighed tare) but with the benefit that the fluoride is ultimately removed

from the solution via release of volatile SiF . The resulting reduction in fluoride content of the final

solution guards against the formation of insoluble plutonium fluoride (especially below 8 M), which

would negatively bias the plutonium element content up to 0,1 % [or more when large quantities of

hydrofluoric acid (HF) are used). The tare mass of the etched glass vessel may be re-established by

— HDPE, PTFE or Nalgene dissolution vessels are not reactive to HF, therefore tare mass remains

unaffected. However, these materials have the disadvantage that fluoride ions in the dissolution

liquor promote the precipitation of insoluble plutonium fluoride when the oxidation state of

plutonium is reduced from IV to III (e.g. by later volume adjustments using a low molarity acid).

An aqueous dissolving mixture comprising nitric acid (about 8 mol/l to 14 mol/l) and an effective