SIST EN ISO 6863:2026

• Abstract:

  This document specifies a method which applies to the preparation and validation of the standard materials generally called “large size spikes” with an uncertainty suitable for international nuclear safeguards used for measuring the content of plutonium and/or uranium by isotope dilution mass spectrometry. ; This measurement methodology can be applied to input solutions of irradiated Magnox and light water reactor fuels (boiling water reactor or pressurized water reactor); in final products at spent-fuel reprocessing plants; in feed and products of mixed oxide of plutonium and uranium (MOX); and in uranium fuel fabrication

• Status: Published
• Public Enquiry End Date: 04-Jul-2026
• Publication Date: 01-Sep-2026
• ICS: 27.120.30 - Fissile materials and nuclear fuel technology
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 27-Aug-2026
• Due Date: 01-Nov-2026
• Completion Date: 02-Sep-2026
• Ref Project: EN ISO 6863:2026 - Nuclear fuel technology - Preparation of spikes for isotope dilution mass spectrometry (IDMS) (ISO 6863:2024)

SIST EN ISO 6863:2026 is the CEN adoption of ISO 6863:2024 for nuclear fuel technology. It specifies how to prepare and validate spikes for isotope dilution mass spectrometry (IDMS) so uranium and/or plutonium content can be measured for nuclear safeguards and fuel-cycle work. The document is written for laboratories and technical staff who prepare, check, store, and use these spike materials.

What does SIST EN ISO 6863:2026 specify?

SIST EN ISO 6863:2026 specifies a method for preparing and validating standard materials called large size spikes for measuring plutonium and/or uranium by IDMS. The scope covers work in international nuclear safeguards and applies to several nuclear fuel-cycle situations, including irradiated Magnox and light water reactor fuel input solutions, spent-fuel reprocessing products, MOX feed and products, and uranium fuel fabrication.

The document is organized into these main parts:

• Clause 1 Scope
• Clause 2 Normative references
• Clause 3 Terms and definitions
• Clause 4 Principle
• Clause 5 Design of spikes
• Clause 6 Reference materials and reagents
• Clause 7 Apparatus
• Clause 8 Preparation of spikes
• Clause 9 Validation of spikes
• Clause 10 Storage of spikes
• Bibliography

What are the key requirements of SIST EN ISO 6863:2026?

SIST EN ISO 6863:2026 focuses on getting the spike composition right, making it reproducible, checking it against measured values, and keeping it stable in storage. In practice, the document is about controlling mass, isotopic composition, uncertainty, and evaporation at every step.

Design and uncertainty

The document says spikes should be designed for the sample to be analysed so that IDMS can reach the appropriate International Target Values (ITV) for safeguards. That matters because the wrong spike composition can reduce accuracy or make the result less useful for the intended material.

The principle in Clause 4 is that the sample and spike should have significantly different isotopic compositions, with spike isotopes ideally absent or only minimally present in the unspiked sample. This is what makes IDMS work and is why the spike composition has to be chosen deliberately.

Clause 5 also says there are two basic spike types - solution spikes and dry spikes - and either may be used depending on user needs. Clause 5.2 says spike uncertainty should combine the uncertainty contributions from the Certified Reference Material (CRM), analytical balance, equipment, and tracer used for characterization or standardization, and it should be reported as expanded uncertainty with coverage factor k = 2.

Materials and apparatus

Clause 6 requires reference materials with certified elemental content of ±0.05 % (k = 2) or better for uranium and plutonium starting materials, and major isotope abundance of at least 80 % for the uranium and plutonium materials named in the document. It also allows secondary standard materials that are traceable to CRMs or verified by laboratory intercomparison. In practice, this means the starting material has to be well characterized before it becomes a spike.

The reagents listed include nitric acid, hydrochloric acid, hydrofluoric acid, potassium carbonate solution, water meeting at least grade 1 of ISO 3696, ethanol, and acetone. Clause 7 requires mass spectrometry apparatus in accordance with ISO 8299, glove boxes for safe handling, and an analytical balance with 0.1 mg capability for most weighings. Those controls matter because small mass errors and contamination directly affect the final spike value.

Preparation, validation, and storage

Clause 8 gives separate procedures for large-sized dried (LSD) spikes, uranium spikes, plutonium spikes, and uranium-plutonium mixed spikes. The general method is to dissolve uranium and plutonium CRMs to stock solutions, mix them to the desired composition, take measured aliquots, and dry them if a dried spike is required. The document also gives methods for uranium-only and plutonium-only liquid spikes and for dried versions of each.

Clause 8.1.5 says the aliquots should be dried carefully to form a glassy film at the bottom of the vial without material loss. Clause 8.1.6 allows coating materials such as cellulose acetate butyrate (CAB) or carboxymethyl cellulose (CMC) to improve longer-term stability, provided the effect on IDMS is checked. That matters in practice because dried spikes can crystallize or flake if they are not handled and dried properly.

Clause 9 requires validation of the spike content and isotopic composition against the make-up values derived from the certified values, the masses used, and any dilution or evaporation factors. It points to IDMS, mass spectrometry, controlled-potential coulometry, and titration methods such as ISO 12183, ISO 7097-1, ISO 7097-2, and ISO 8298 as suitable supporting methods. Clause 10 then sets the storage approach: solution spikes in sealed or tightly capped ampoules or vials, and dried spikes in a stable place, with reconditioning allowed if crystallization appears.

What terms does SIST EN ISO 6863:2026 define?

• Solution spike - a nitric acid solution with accurately quantified uranium and/or plutonium content and isotopic composition.
• Dried spike - a solution spike aliquoted into glass vessels and then dried.
• Large-sized dried spike (LSD spike) - a dried spike containing both uranium and plutonium in milligram size, developed for high-concentration input solutions.
• Isotope dilution mass spectrometry (IDMS) - a method that determines element content from the change in isotopic composition after adding a spike.
• Thermal ionization mass spectrometry (TIMS) - the mass spectrometric method used here to measure elemental content and isotopic composition.
• Certified Reference Material (CRM) - a reference material with certified values used as the basis for spike preparation and validation.

Who uses SIST EN ISO 6863:2026?

SIST EN ISO 6863:2026 is used by laboratories working in nuclear fuel technology, nuclear safeguards, and reference material preparation. Typical users include analytical chemists, metrology staff, quality managers, and producers or users of uranium and plutonium reference materials.

It is relevant to spent-fuel reprocessing plants, MOX fuel feed and product control, and uranium fuel fabrication. These users need it when they prepare IDMS spikes, check their content, compare measured values with certified values, and manage stability during storage and shipment.

What changed in SIST EN ISO 6863:2026 from the previous edition?

SIST EN ISO 6863:2026 takes over ISO 6863:2024 as EN ISO 6863:2026 without any modification.

Which standards are used with SIST EN ISO 6863:2026?

The document normatively references ISO 3696, which supplies the water quality needed for analytical laboratory use, and ISO 8299, which covers the mass-spectrometric determination of uranium and plutonium in nitric acid solutions and the apparatus basis for this work.

It also cites ISO/IEC Guide 98-3 for uncertainty evaluation, ISO 12183, ISO 7097-1, ISO 7097-2, and ISO 8298 for uranium and plutonium titration, ISO 17034 and ISO Guide 35 for reference material production, characterization, homogeneity, and stability, and ASTM C1128 for preparation of working reference materials.

What does the SIST EN ISO 6863:2026 document contain?

The document contains the full preparation workflow for uranium, plutonium, and mixed spikes, including dissolution of metal reference materials, mass control, aliquoting, drying, stabilization, and reconditioning. It also provides calculation formulas for spike design, uncertainty, and evaporation correction, so the user can track how the final spike value is obtained.

It gives practical guidance on reference materials, reagent grades, apparatus, and storage conditions, which makes it useful for method setup and laboratory procedure writing. Clause 9 is especially important for validation work because it shows how to compare measured values with make-up values and how to support homogeneity and stability assessment.

SLOVENSKI STANDARD
01-oktober-2026
Tehnologija jedrskega goriva - Priprava konic za masno spektrometrijo z
izotopskim redčenjem (IDMS) (ISO 6863:2024)
Nuclear fuel technology - Preparation of spikes for isotope dilution mass spectrometry
(IDMS) (ISO 6863:2024)
Kernbrennstofftechnologie - Vorbereitung von Spikes für die
Isotopenverdünnungsmassenspektrometrie (IDMS) (ISO 6863:2024)
Technologie du combustible nucléaire - Préparation de traceurs pour les analyses par
spectrométrie de masse avec dilution isotopique (IDMS) (ISO 6863:2024)
Ta slovenski standard je istoveten z: EN ISO 6863:2026
ICS:
27.120.30 Cepljivi materiali in jedrska Fissile materials and nuclear
gorivna tehnologija fuel technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 6863
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2026
EUROPÄISCHE NORM
ICS 27.120.30
English Version
Nuclear fuel technology - Preparation of spikes for isotope
dilution mass spectrometry (IDMS) (ISO 6863:2024)
Technologie du combustible nucléaire - Préparation de Kernbrennstofftechnologie - Vorbereitung von Spikes
traceurs pour les analyses par spectrométrie de masse für die Isotopenverdünnungsmassenspektrometrie
avec dilution isotopique (IDMS) (ISO 6863:2024) (IDMS) (ISO 6863:2024)
This European Standard was approved by CEN on 10 August 2026.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6863:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 6863:2024 has been prepared by Technical Committee ISO/TC 85 "Nuclear energy,
nuclear technologies, and radiological protection” of the International Organization for Standardization
(ISO) and has been taken over as EN ISO 6863:2026 by Technical Committee CEN/TC 430 “Nuclear
energy, nuclear technologies, and radiological protection” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by February 2027, and conflicting national standards
shall be withdrawn at the latest by February 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 6863:2024 has been approved by CEN as EN ISO 6863:2026 without any modification.

International
Standard
ISO 6863
First edition
Nuclear fuel technology —
2024-11
Preparation of spikes for isotope
dilution mass spectrometry (IDMS)
Technologie du combustible nucléaire — Préparation de traceurs
pour les analyses par spectrométrie de masse avec dilution
isotopique (IDMS)
Reference number
ISO 6863:2024(en) © ISO 2024
ISO 6863:2024(en)
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 6863:2024(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Design of spikes . 2
5.1 Optimization of spikes .2
5.2 Uncertainty of spikes .3
6 Reference materials and reagents . 3
6.1 Reference materials .3
6.1.1 Uranium reference materials .3
6.1.2 Plutonium reference materials .3
6.1.3 Secondary standard materials.4
6.2 Other chemical reagents .4
7 Apparatus . 4
8 Preparation of spikes . 5
8.1 Large-sized dried (LSD) spikes .5
8.1.1 Preparation of uranium stock solution .5
8.1.2 Preparation of plutonium stock solution .6
8.1.3 Preparation of mixed stock solution . .7
8.1.4 Taking mixed solution aliquots .8
8.1.5 Drying .9
8.1.6 Stabilization of LSD spike .9
8.2 Uranium spikes .9
8.2.1 Uranium liquid spikes .9
8.2.2 Uranium dried spikes .10
8.3 Plutonium spikes .10
8.3.1 Plutonium liquid spikes .10
8.3.2 Plutonium dried spikes .10
8.4 Uranium – plutonium mixed spikes .10
9 Validation of spikes .11
9.1 General .11
9.2 LSD spikes .11
9.3 Uranium spikes .11
9.4 Plutonium spikes . 12
9.5 Uranium-plutonium mixed spikes. 12
10 Storage of spikes .12
10.1 Storing solution spikes . 12
10.2 Storing dried spikes . 12
10.3 Reconditioning of dried spikes . 12
Bibliography .13

iii
ISO 6863:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
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
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 6863:2024(en)
Nuclear fuel technology — Preparation of spikes for isotope
dilution mass spectrometry (IDMS)
1 Scope
This document specifies a method which applies to the preparation and validation of the standard materials
generally called “large size spikes” with an uncertainty suitable for international nuclear safeguards used
for measuring the content of plutonium and/or uranium by isotope dilution mass spectrometry.
This measurement methodology can be applied to input solutions of irradiated Magnox and light
water reactor fuels (boiling water reactor or pressurized water reactor); in final products at spent-fuel
reprocessing plants; in feed and products of mixed oxide of plutonium and uranium (MOX); and in uranium
fuel fabrication.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 8299, Nuclear fuel technology — Determination of the isotopic and elemental uranium and plutonium
concentrations of nuclear materials in nitric acid solutions by thermal-ionization mass spectrometry
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
solution spike
nitric acid solutions with accurately quantified uranium and/or plutonium content and isotopic composition
Note 1 to entry: One of the reference materials for IDMS.
3.2
dried spike
prepared by aliquoting solution spikes (3.1) into glass vessels and then drying
Note 1 to entry: One of the reference materials for IDMS.
3.3
large-sized dried spike
LSD spike
dried spike containing both uranium and plutonium in milligram size, were originally developed to analyse
high concentrated input solution
Note 1 to entry: One of the reference materials for IDMS.

ISO 6863:2024(en)
Note 2 to entry: The LSD spikes can simplify the sample preparation process with only one spiking step to the sample,
which also contains uranium and plutonium, and reduce measurement uncertainty by less dilution factor than smaller
sized spikes.
4 Principle
Element content measurement using thermal ionization mass spectrometry (TIMS) is made on a sample
and mixture of the sample and a spike, consisting of an enriched isotope of the element to be analysed and
determine element content by calculating the difference of isotopic composition before and after spike
mixture. This method of measuring an element’s content is called isotope dilution mass spectrometry (IDMS).
The isotopic compositions of the sample and spike is required to be significantly different. Therefore, it
is desirable that spikes are composed of isotopes that are not present, or only minimally present, in the
unspiked sample. It is necessary that the isotopic composition and the content of spikes be known or
measured accurately and has small uncertainties because it reflects to the uncertainty of the final results,
element content.
Chemically-pure compounds of separated plutonium or uranium isotopes are dissolved to prepare stock
solutions of spikes, in general terms, in 3 mol/l to 7 mol/l nitric acid to obtain an optimized content based
on its design to obtain reliable results. Aliquots of the plutonium and uranium spike stock solutions can be
mixed to prepare mixed spikes. Aliquoted spikes are used for IDMS in solution state or after dried.
5 Design of spikes
As the uncertainty to be considered in determining the reliability of nuclear fuel material analysis techniques
[1]
for safeguards, International Target value (ITV) is decided for IDMS. It is desirable that spikes are used for
IDMS after being optimized for the sample to be analysed. Different target values are set depending on the
environment to be measured and spikes used. Spikes shall be designed so that measurement by IDMS can
achieve the appropriate ITVs.
There are two types of spikes: solution spikes and dry spikes. Basically, either spike is fine. In general, choose
which spike to prepare according to user needs.
5.1 Optimization of spikes
In IDMS, when the isotopic composition in the unknown sample and in the spike are significantly different,
the measurement accuracy become higher. On the other hand, the isotopic composition of available certified
reference materials for preparing spikes are limited. Therefore, it is important to design the plutonium and/
or uranium composition of spikes by evaluating, in advance, the isotopic composition and the amounts of
elements of spikes that can be obtained sufficient accuracy. The following sentences describe an example of
calculations for optimizing spikes.
The following Formula (1) can be obtained by partially differentiating the theoretical equation of IDMS with
[2]
sample to spike mass ratio, p .
2 22 2 2
1+ppK1+γ R
σγ()p 1 ()11+pK()+ R () ()
 
22 S 22
T
=⋅ ⋅+ε R ⋅ε R
S T
 
2 22 2 2
p
 
p
()RR− ()1+γKR ()RR− ()1+γKR
ST S ST T
[]pR ()11+γγKR ++RK()Rp[]()11+γγKR ++()KR
TS ST ST 2
+⋅ ⋅ε
2 22 2 2
p RR− 11+γγKR + KR
() () ()
ST TS
γ RR−
()
TS
+ ⋅σ (1)
K
2 2
()11+γγKR ()+ KR
TS
ISO 6863:2024(en)
where
σ ()p
is the standard deviation of p;
R is the isotopic ratio of sample;
S
R is the isotopic ratio of spike;
T
γ is absolute mass ratio of second to first major isotope;
K is mass discrimination factor;
ε
is standard deviation of for isotopic ratio measurement.
By replace p to sample to spike number of atoms ratio, q and putting γ equal to unity. If K equal to 1,
Formula (1) is described as following Formula (2):
2 22 2 2
σ ()q ()11+qR()+ ()1+q ()11+R
  1
T 22 S 22
=⋅ ⋅+ε R ⋅ε R
S T
 
2 22 2 2
q
  q
()RR− ()1+R ()RR− ()1+R
ST S ST T
qR 11+RR++Rq 11+RR++
1 []() () []() ()
TS ST ST 2
+⋅ ⋅ε (2)
2 2 2 2
q
()RR− ()1+R ()11+R
ST T S
2 2
Where, the value “[σ(q)/q] /ε ” means the size of the error depending on the mixing ratio of spike and sample,
and from this, the amount of spike to sample and/or isotopic ratio is calculated and able to be optimized.
5.2 Uncertainty of spikes
The uncertainty of spikes can be combined from the Certified Reference Material (CRM), analytical balance,
and also from the equipment and tracer used for instrumental analysis for the purpose of characterization
or standardization. These individual uncertainties should be combined and should be given as expanded
uncertainty when the coverage factor k = 2. The uncertainty can be calculated in accordance to the
[3]
ISO/IEC Guide 98-3 .
6 Reference materials and reagents
The reagents listed below are prepared from analytical grade reagents unless it is specified otherwise.
6.1 Reference materials
Examples of reference material for preparing spike are shown below.
6.1.1 Uranium reference materials
a) natural uranium metal CRM of purity with an elemental content certified to ±0,05 % (k = 2) or better,
such as NBL-CRM-112A (e.g. NBS-960D), EC-101, CETAMA-MU2.
b) other uranium metal, powder or pellet CRM of purity with an elemental content certified to ±0,05 %
(k = 2) or better, such as NBL-CRM-116A (HEU metal), CRM-125A (UO pellet) and CRM-129 (U O
2 3 8
powder). CRM solution can also be available as a source. Abundance of the major isotope of uranium
shall be greater than or equal to 80 %.
6.1.2 Plutonium reference materials
Plutonium metal CRM with an elemental content certified to ±0,05 % (k = 2) or better, such as NBL-CRM-126
or 126A, EC-201 or CETAMA-MP2. Abundance of the major isotope of plutonium shall be greater than or
equal to 80 %.
ISO 6863:2024(en)
6.1.3 Secondary standard materials
For both plutonium and uranium, secondary standard materials in solution or in solid and traceable to CRMs
or verified by means of a laboratory intercomparison can also be used. The values should be certified to
±0,05 % (k = 2) or better.
6.2 Other chemical reagents
The reagents listed below are in analytical grade and other reagents could also be used if results are
confirmed to be equivalent.
6.2.1 Nitric acid solutions, c(HNO ) = 1 mol/l, 3 mol/l, 4 mol/l, 7 mol/l to 8 mol/l and other.
6.2.2 Hydrochloric acid solutions, c(HCl) = 0,1 mol/l, 3 mol/l, 4 mol/l, 12 mol/l and other are applicable
for dissolution and etching for uranium metal and/or plutonium metal.
6.2.3 Hydrofluoric acid, c(HF) = 27 mol/l. HF can mix with nitric acid solution before use.
WARNING — Hydrofluoric acid is strongly corrosiv
...