A highly enriched 242Pu Isotopic Reference Material (IRMM-049d) has been prepared and certified for the 242Pu isotope amount content. The certified value of 3.666 8(18) x 10-7 mol 242Pu per g of solution was established by Isotope Dilution Mass Spectrometry (IDMS). The plutonium isotopic composition was determined by Thermal Ionization Mass Spectrometry (TIMS) and calibration of these measurements by means of synthetic mixtures.
The IRMM-049d Isotopic Reference Material is supplied in a glass ampoule with a screw cap seals containing about 10 mL of 5 mol x L-1 nitric acid with plutonium. The content of each vial is approximately 1 mg 242Pu.
This Isotopic Reference Material is the product of a systematic IRMM programme to supply Isotopic Reference Materials of various isotopes at different concentrations.JRC.D.2-Reference material

AREGBE Yetunde

EYKENS Roger

JAKOPIC Rozle

KEHOE Frances

KUEHN Heinz

RICHTER Stephan

VERBRUGGEN Andre

JRC Publications Repository

  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
EUR 24915 EN  -  2011 
Preparation and Certification of the 
Isotopic Reference Material IRMM-049d 
 
R. Jakopič, R. Eykens, F. Kehoe, 
H. Kühn, S. Richter, A. Verbruggen, Y. Aregbe 
The mission of the JRC-IRMM is to promote a common and reliable European measurement system in support 
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JRC66016 
 
EUR 24915 EN
 
ISBN 978-92-79-20992-5 (print) 
ISBN 978-92-79-20993-2 (online) 
ISSN 1018-5593 (print) 
ISNN 1831-9424 (online)
 
doi:10.2787/49209 
 
Luxembourg: Publications Office of the European Union 
 
© European Union, 2011 
 
Reproduction is authorised provided the source is acknowledged 
 
Printed in Belgium 
 
European Commission 
 
IRMM information 
REFERENCE MATERIALS 
 
 
 
 
Preparation and Certification of the 
Isotopic Reference Material IRMM-049d 
  
 
IRMM-049d 
 
 
R. Jakopič, R. Eykens, F. Kehoe, H. Kühn, S. Richter, A. Verbruggen, Y. Aregbe 
 
 
 
 
European Commission,  
Joint Research Centre 
Institute for Reference Materials and Measurements 
Retieseweg 111 
2440 Geel, Belgium 
 
 
 
 
 
 
 
 
 
 
 
 
         
European Commission 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Disclaimer 
 
 
Certain commercial equipment, instruments, and materials are identified in 
this report to specify adequately the experimental procedure. In no case does such identification imply 
recommendation or endorsement by the European Commission, nor does it imply that the material or 
equipment is necessarily the best available for the purpose. 
 
1 
Contents 
Contents 1 
Summary 2 
Introduction 2 
Preparation of the 242Pu Isotopic Reference Material 2 
Preparation of a stock 242Pu solution 2 
Purification of a stock 242Pu solution 2 
Dilution and ampouling of 242Pu solution 2 
Plutonium isotopic composition of IRMM-049d 3 
Certification of 242Pu amount content of IRMM-049d 4 
Conclusion 6 
Acknowledgment 6 
References 6 
2 
Summary 
A highly enriched 242Pu Isotopic Reference Material (IRMM-049d) has been prepared 
and certified for the 242Pu isotope amount content. The certified value of 
3.666 8(18) ⋅10-7 mol 242Pu per g of solution was established by Isotope Dilution 
Mass Spectrometry (IDMS). The plutonium isotopic composition was determined by 
Thermal Ionization Mass Spectrometry (TIMS) and calibration of these 
measurements by means of synthetic mixtures. 
The IRMM-049d Isotopic Reference Material is supplied in a glass ampoule with a 
screw cap seals containing about 10 mL of 5 molּL-1 nitric acid with plutonium. The 
content of each ampoule is approximately 1 mg 242Pu. 
This Isotopic Reference Material is the product of a systematic IRMM programme to 
supply Isotopic Reference Materials of various isotopes at different concentrations.  
 
Introduction 
IRMM produces and provides solutions of enriched uranium and plutonium isotopes 
designed for mass-spectrometric isotope dilution measurements of nuclear 
materials. For the measurement of plutonium, the isotope 242Pu is valuable as a 
spike because this isotope is usually found only as a minor component in plutonium 
of the nuclear fuel cycle.  
The original certified spike of this isotope was approaching exhaustion and therefore 
it was decided to replace it by preparing a new stock of the source material and 
certifying the isotope amount content by IDMS using a 239Pu spike. A concentration 
of ca. 0.1 mg/g solution was chosen and deemed to be convenient for many types of 
measurements of plutonium. 
 
Preparation of the 242Pu Isotopic Reference Material 
Preparation of a stock 242Pu solution 
A 242Pu stock solution was prepared by dissolving plutonium metal (BC 975B) of a 
French (CETAMA) origin in 5 molּL-1 HNO3 (p.a., Merck, Darmstadt). This stock 
solution containing about 614 mg 242Pu was purified as described in the following.  
Purification of a stock 242Pu solution 
The plutonium solution was evaporated to dryness and dissolved in 24 mL 2 molּL-1 
HNO3. To achieve valency homogenisation in the Pu+4 state, 4 mL 1.25 molּL-1 FeCl2 
was added to convert all Pu to Pu+3 valency state. Subsequently, 12 mL 1 molּL-1 
NH2OHּHCl and 12 mL 1 molּL-1 NaNO2 were added. Finally, 52 mL concentrated 
nitric acid (65%, Merck, Darmstadt) was added to obtain a Pu+4 8 molּL-1 HNO3 
solution.  
Two glass columns with a diameter of 2.5 cm and a height of 15 cm were used in 
parallel and were filled with Bio-Rad AG1-X4 (100-200 mesh) resin in chloride form 
for the purification. The plutonium solution was transferred onto the columns. After 
both columns were washed with 350 mL 8 molּL-1 HNO3, Pu was eluted from the 
column with 1 L of 0.35 molּL-1 HNO3.   
Dilution and ampouling of 242Pu solution 
The eluted Pu fractions were combined, evaporated to dryness and dissolved in 
61.44 g 5 molּL-1 HNO3 to obtain a 10 mg Pu per g solution. From that purified Pu 
solution, a 10.46 g fraction was taken into a flask and diluted to 1007.1 g with 
5 molּL-1 HNO3 to obtain the final concentration of the 242Pu of 0.1 mg Pu per g 
solution. This solution was dispensed into 93 screw-cap glass ampoules providing 
ca. 10 mL per ampoule. 
3 
 
Plutonium isotopic composition of IRMM-049d 
The isotopic composition of plutonium was established by measuring isotope 
abundance ratios on an ampoule of the IRMM-049d on a Triton TIMS (Thermo 
Fisher Scientific Inc., USA).  
Prior to mass spectrometry measurements a chemical separation was performed to 
obtain a purified Pu solution (RM WI/0352: Separation and purification of plutonium 
samples for measurements of isotopic ratios by TIMS). The purified fraction of Pu 
was prepared in 1 molּL-1 HNO3. About 50 ng of Pu solution was put on an 
evaporation filament using a transfer pipette and dried by passing an electrical 
current through the filament.  
A magazine was loaded with six filaments of IRMM-049d and nine filaments of 
IRMM-290/A3 plutonium isotopic reference material for the calibration of the mass 
spectrometer for mass fractionation. The isotopic composition of the samples was 
measured using the total evaporation technique on a Triton TIMS (RM WI/0360: 
Measurement of Plutonium isotopic ratios by TIMS_TRITON). The measurement 
was continued until the sample has been exhausted. This is done in order to 
minimize mass fractionation effects.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1: Purification of Pu stock solution by anion exchange. 
 
The observed Pu isotope ratios were corrected for mass fractionation by measuring 
the IRMM-290/A3 isotopic standard on the same magazine applying the same 
procedure. The correction factor (K) for mass fractionation was calculated from nine 
replicate measurements of IRMM-290/A3 and was determined to be 
K242/239 = 0.99983(20). Correction factors for all other Pu isotope ratios were derived 
from K242/239 and were in the range of 0.99972 - 1.0001 with a relative standard 
uncertainty of 0.0033-0.017 %.  
4 
 
 
The certified values for the plutonium isotope ratios are listed in Table 1 and are 
valid for 1 July 2010. The expanded uncertainties were estimated according to the 
ISO Guide to the Expression of Uncertainty in Measurement (GUM). They apply to 
the last two digits of the value. 
The main components to the final uncertainty are the IRMM-290/A3 plutonium 
isotopic standard and the K-factor for the respective isotope ratio.  
 
Table 1: Isotope amount ratios and isotopic composition of plutonium in IRMM-049d 
valid for 1 July 2010. Expanded uncertainties are given in brackets (coverage 
factor k=2). 
 
Certified amount ratios 
n(238Pu)/n(242Pu) 0.005 341 8(69) 
n(239Pu)/n(242Pu) 0.002 221 6(13) 
n(240Pu)/n(242Pu) 0.046 070(35) 
n(241Pu)/n(242Pu) 0.002 990 4(21) 
n(244Pu)/n(242Pu) 0.000257 13(84) 
Amount fraction (ּ100) Mass fraction (ּ100) 
n(238Pu)/n(Pu) 0.505 44(64) m(238Pu)/m(Pu) 0.497 30(63) 
n(239Pu)/n(Pu) 0.210 21(12) m(239Pu)/m(Pu) 0.207 69(12) 
n(240Pu)/n(Pu) 4.359 0(31) m(240Pu)/m(Pu) 4.325 0(31) 
n(241Pu)/n(Pu) 0.282 94(19) m(241Pu)/m(Pu) 0.281 91(19) 
n(242Pu)/n(Pu) 94.618 1(36) m(242Pu)/m(Pu) 94.663 6(36) 
n(244Pu)/n(Pu) 0.024 329(79) m(244Pu)/m(Pu) 0.024 543(80) 
The molar mass of the plutonium in this sample is 241.942 417(79) gּmol-1 
 
Certification of 242Pu amount content of IRMM-049d 
The certification of the plutonium amount content of Isotopic Reference Material 
IRMM-049d was achieved by IDMS. Six ampoules of IRMM-049d were randomly 
selected from the batch. The plutonium solution in IRMM-049d was split over two 
vials of IRMM-1027m (239Pu) for IDMS analysis. IRMM-1027m is a large-sized dried 
spike in which approximately 2 mg Pu and 50 mg U, enriched to 20 % 235U, per g 
solution are dried into individual vials. The enriched 239Pu in this spike has been 
certified from the mass of pure plutonium metal and verified by IDMS [1]. The spike 
is primarily designed for measurement of U and Pu amount contents in solutions of 
spent nuclear fuel but the certification of the 239Pu amount content renders it highly 
suitable for the IDMS measurement of IRMM-049d. Furthermore by using IRMM-
1027m the certification of IRMM-049d becomes part of the ongoing compatibility 
study inter-linking selected IRMM plutonium spikes on a metrological basis applying 
state-of-the art measurement procedures [2]. In total 12 blend mixtures were 
prepared.  
 
The series of 12 blend mixtures described above were used to assess the 
homogeneity of the plutonium and to certify the amount content of 242Pu in IRMM-
049d. The blend mixtures were heated to dryness and then chemically conditioned. 
Pu fractions were separated by the standard anion exchange method (RM WI/0354: 
Separation and purification of uranium and plutonium mixtures for measurements of 
isotopic ratios by TIMS). The excess of uranium in the mixed U/Pu spike IRMM-
1027m means that extra separation steps were needed before the measurement of 
5 
the Pu isotope ratios. Three consecutive separations for each blend mixture were 
performed in order to obtain a purified Pu fraction and to avoid interferences with 
uranium coming from IRMM-1027m in mass spectrometric measurements. Three 
magazines were loaded with four filaments for each blend; the remaining positions 
were filled by IRMM-290/A3 standards. The plutonium isotope ratios n(239Pu)/n(242Pu) 
were measured on the Triton TIMS [3] applying a total evaporation technique. The 
results of these IDMS measurements for the 242Pu amount content are given in 
Figure 2. 
IRMM-049d 242Pu (mol/g)
3,660E-07
3,662E-07
3,664E-07
3,666E-07
3,668E-07
3,670E-07
3,672E-07
1 2 3 4 5 6 7 8 9 10 11 12
blends
c 
24
2 P
u
 
(m
o
l/g
)
individual values
average
average + Uc(k=2)
average  - Uc(k=2)
 
Figure 2: The amount content of 242Pu in blends of IRMM-049d measured by IDMS 
(with expanded uncertainties, coverage factor k=2). 
 
Using the 239Pu spike (IRMM-1027m), the 242Pu amount content in IRMM-049d can 
be determined by IDMS through a measurement of the isotope ratio R(b) = 
n(239Pu)/n(242Pu) in a blend via the following equation: 
 
( ) ( ) )(1)()( )()()( )(,, 239242 yRxRbR bRyRxm ymyPucxPuc ⋅−−⋅⋅= , where 
 
c(242Pu, x): amount content of 242Pu in the IRMM-049d  
c(239Pu, y): amount content of 239Pu in the spike  
m(x):  mass of the IRMM-049d 
m(y):  mass of the spike  
R(b):  isotope amount ratio n(239Pu)/n(242Pu) of the blend 
R(x):  isotope amount ratio n(239Pu)/n(242Pu) of the unspiked IRMM-049d 
R(y):  isotope amount ratio n(239Pu)/n(242Pu) of the spike  
 
The certified value for the 242Pu amount content was calculated as the mean value of 
twelve certification measurement results and is 3.666 8(18) ּ10-7 molּg-1. The 
expanded uncertainty with a coverage factor k=2 is given in parentheses and 
corresponds to a level of confidence of about 95 % estimated according to the ISO 
Guide to the Expression of Uncertainty in Measurement (GUM). It applies to the last 
two digits of the value. The major component to the expanded uncertainty comes 
from the spike isotopic reference material IRMM-1027m. Figure 3 shows the relative 
contribution of the main uncertainty components to the overall uncertainty of the 
certified value in IRMM-049d.    
 
6 
63,7%
17,1%
0,7%
18,6%
Pu-239 amount content in the
spike
measurement of Rb
mass of sample
mass of spike
 
Figure 3: The uncertainty budget of the major components for 242Pu amount content 
in IRMM-049d.  
 
The value of the plutonium isotopic amount content in IRMM-049d is traceable to the 
SI via the certified IRMM-1027m spike reference material in combination with 
identification and quantification of the sources of uncertainties for IDMS according to 
the ISO Guide to the Expression of Uncertainty in Measurement (GUM) [4]. 
 
Conclusion 
A new 242Pu Isotopic Reference Material (IRMM0-49d) has been prepared and 
certified for its 242Pu amount content. The certified value of 3.666 8(18) ⋅10-7 mol 
242Pu per g of solution was established by Isotope Dilution Mass Spectrometry 
(IDMS) and is metrologically traceable to the SI. IRMM-049d extends the inter-
calibration campaign using state-of-the art measurement procedures to underpin the 
confidence in the use of IRMM isotopic plutonium reference materials for nuclear 
material and environmental sample measurements.   
 
Acknowledgment 
The authors would like to thank Dr. Roger Wellum for the certification file review.  
 
References 
[1] A. Verbruggen et al., Preparation and certification of IRMM-1027m, Large-Sized 
Dried (LSD) spike, EUR 24119 EN – 2009; 
http://www.irmm.jrc.be/reference_materials_catalogue/catalogue/IRMM_certificates_
and_reports/eur_24119_1027m_report.pdf 
[2] R. Jakopič et al., J Radioanal Nucl Chem 286 (2010) 449–454. 
[3] S. Richter, A. A. Goldberg (2003), Int J Mass Spectrom, 229 (2003) 181-197.  
[4] International Organization for Standardization, Guide to the Expression of 
Uncertainty in Measurement, ISO, ISBN 52-67-10188-9, Geneva, Switzerland 199 
 EUR 24915 EN – Joint Research Centre – Institute for Reference Materials and Measurements 
Title: Preparation and Certification of the Isotopic Reference Material IRMM-049d 
Author(s): R. Jakopič, R. Eykens, F. Kehoe, H. Kühn, S. Richter, A. Verbruggen, Y. Aregbe 
Luxembourg: Publications Office of the European Union 
2011 – 6 pp. – 21.0 x 29.7 cm 
EUR – Scientific and Technical Research series – 1018-5593 (print), 1831-9424 (online)
ISBN 978-92-79-20992-5 (print)
ISBN 978-92-79-20993-2 (online)
doi:10.2787/49209 
 
Abstract 
A highly enriched 242Pu Isotopic Reference Material (IRMM-049d) has been prepared and certified for the 242Pu 
isotope amount content. The certified value of 3.666 8(18) ⋅10-7 mol 242Pu per g of solution was established by 
Isotope Dilution Mass Spectrometry (IDMS). The plutonium isotopic composition was determined by Thermal 
Ionization Mass Spectrometry (TIMS) and calibration of these measurements by means of synthetic mixtures. 
The IRMM-049d Isotopic Reference Material is supplied in a glass ampoule with a screw cap seals containing 
about 10 mL of 5 molּL-1 nitric acid with plutonium. The content of each ampoule is approximately 1 mg 242Pu. 
This Isotopic Reference Material is the product of a systematic IRMM programme to supply Isotopic Reference 
Materials of various isotopes at different concentrations. 
 
 
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Preparation and Certification of the Isotopic Reference Material IRMM-049d

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Preparation and Certification of the Isotopic Reference Material IRMM-049d

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