Collection of high-resolution gamma spectra of certified Pu reference materials.
Date: 2017-01-10
Institutions: Joint Research Centre
Subjects: ionising radiation, metrology, nuclear research, nuclear technology, research report, spectrometry

Collection of high-resolution gamma 
spectra of certified Pu reference 
materials  

Jozsef Zsigrai 
Artur Mühleisen 

2016 

EUR 28390 EN 

 
 
 
 
 
Collection of high-resolution gamma 
spectra of certified Pu reference 
materials  

 
 
 
 
This publication is a Technical report by the Joint Research Centre, the European Commission’s in-house science 
service. It aims to provide evidence-based scientific support to the European policy-making process. The scientific 
output  expressed  does  not  imply  a  policy  position  of  the  European  Commission.  Neither  the  European 
Commission nor any person acting on behalf of the Commission is responsible for the use which might be made 
of this publication. 

Contact information 

Name: 

Jozsef Zsigrai, Artur Mühleisen 

Address:  European Commission, Joint Research Centre, Directorate for Nuclear Safety and Security, G.II.6  

E-mail:   Jozsef.Zsigrai@ec.europa.eu 

Tel.:  

+49 (0)7247-951-871 

JRC Science Hub 
https://ec.europa.eu/jrc 

JRC103886 

EUR 28390 EN 

ISBN 978-92-79-64836-6 (PDF) 

ISSN 1831-9424 (online) 

doi: 10.2789/359955 (online) 

All images © European Atomic Energy Community 2016 

Cover image © European Atomic Energy Community, 2016: 
Spectrum of PIDIE7 reference material measured with HPGe COAX detector. 

© European Atomic Energy Community, 2016 

Reproduction is authorised provided the source is acknowledged. 

How  to  cite:  Jozsef  Zsigrai,  Artur  Mühleisen:    Collection  of  high-resolution  gamma  spectra  of  certified  Pu 
reference materials, JRC103886; European Atomic Energy Community, 2016 

1 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table of contents  

Abstract ............................................................................................................... 3 

1. Introduction ................................................................................................... 4 

2. Experimental setup for Pu measurements .......................................................... 5 

3. Pu reference materials..................................................................................... 7 

4. Measurements and experimental conditions ....................................................... 9 

5. Conclusion ................................................................................................... 10 

References ......................................................................................................... 11 

List of spectra: .................................................................................................... 12 

List of abbreviations and definitions ....................................................................... 14 

List of figures ...................................................................................................... 14 

List of tables ....................................................................................................... 14 

2 

 
 
 
 
 
 
Abstract  

A  collection  of  high  resolution  gamma-ray  spectra  from  well-characterized  Pu  certified 
reference  materials  has  been  recorded  using  a  coaxial  HPGe  detector  in  the  energy 
range  up  to  2.8  MeV.  The  spectra  were  measured  for  long  acquisition  times,  ensuring 
very  good  counting  statistics.  The  experimental  setup  assures  that  the  measurement 
geometry is stable and reproducible, and that the spectra have minimum influence from 
background radiation and pile-up effects. The spectra will fill a gap in the data library of 
the  International  working  group  on  gamma  spectroscopy  techniques  for  U  and  Pu 
isotopics.  They  can  be  used  for  testing  different  software  algorithms  for  spectrum 
evaluation. They will also serve for comparison with spectra taken by medium-resolution 
detectors.  

3 

 
 
 
 
 
 
1. Introduction 

The data library of the International working group on gamma spectrometry techniques 
for U and Pu isotopics (Ref. 1) contains spectra of U and Pu taken with various detectors 
under  various  conditions.  These  spectra  are  useful  for  testing  the  performance  of 
software  codes  for  spectrum  evaluation.  Recently  spectra  from  medium-resolution 
detectors  (LaBr3  and  CdZnTe)  have  been  added  to  the  library  (Ref.  2).  The  high-
resolution  spectra  described in  the  current  report  were  recorded  by  a  HPGe  detector  in 
order to compare them to the medium-resolution spectra. However, they are also useful 
on  their  own  for  testing  the  performance  of  software  codes  for  coaxial  detectors  in  the 
energy range up to 2.8 MeV. The spectra are available upon request at JRC Directorate 
G,  Department  of  Nuclear  Safety  and  Security,  Nuclear  Safeguards  and  Forensics  Unit, 
and  will  be  offered  to  the  data  library  of  International  working  group  on  gamma 
spectroscopy techniques for U and Pu isotopics. 

4 

 
 
 
 
 
 
2. Experimental setup for Pu measurements  

The spectra have been measured at EC JRC Directorate G in Karlsruhe (former Institute 
for Transuranium Elements), in a lab dedicated to HRGS (therefore with a slightly lower 
background  radiation  as  in  the  case  of  MRGS  measurements  (Ref.  2)  that  have  been 
performed  in  a  lab  where  also  other  measurements  take  place).  The  equipment 
consisted  of  Canberra  HPGe  COAX  detector  (model  GEM-50195-P),  absorbers  (3mm 
steel  and/or  1mm  Cd),  Canberra  Lynx  electronics  and  PC  with  installed  GENIE2000 
software.  The  recorded  spectra  have  8192  channels  with  energy  range  up  to  2.8  MeV. 
The  electronics  has  been  set  up  accordingly  (see  Attachment).  Intentionally,  instead  of 
optimizing  absorbers  for  HRGS,  the  same  absorbers  with  the  same  thickness  as  for 
MRGS have been used.  

A  shielded  experimental  setup  with  well-defined  geometry  has  been  used  for  the 
gamma-spectrometric measurements (Figure  1 and Figure 2). The shield consists of 10 
cm  Pb,  2  mm  of  Cu  and  4.5  mm  PMMA.  PMMA  stands  for  poly(methyl  methacrylate) 
(“plexiglass”)  with  chemical  composition  (C5O2H8)n.  Mechanical  setup  for  holding  the 
Plutonium samples at a fixed distance above the detector has been manufactured at the 
in-house  workshop.  The  setup  allows  for  introduction  of  absorbers  of  different 
thicknesses  between  the  source  and  the  detector  without  affecting  the  source-to-
detector  distance.  The  distances  between  elements  of  the  experimental  setup  and  the 
thicknesses of materials are presented in Table 1. The sample-to-detector distances are 
distances  between  the  top  of  the  detector  and  the  lowest  point  of  the  sample's 
encapsulation.  The  sample  holder  plates  ("top"  in  Table  1)  have  a  round  engraving  at 
their  middle  to  facilitate  centred  sample  positioning  on  the  detector  axis.  "Base  plate" 
and  "spacer"  are  PMMA  tubing  with inner  diameter  slightly  smaller  than  outer  diameter 
of  the  detector  (but  larger  then  active  detector  diameter).  "Absorber  cover"  is  PMMA 
element with a hole in the middle (the diameter of that hole is the same as for "spacer"). 
Both "top" and  "absorber support plate" have  a finite thickness across their widths and 
are made of machined PMMA. 

Table 1: Setup distances and the thicknesses of materials (*PMMA="plexiglass") 

 PMMA elements 

base plate 
spacer 
absorber support plate 
absorber cover (1mmCd) 
absorber cover (Cd+Fe) 
top 
sum (1mm Cd) 
sum (1mmCd+3mmFe) 

distance 
4 
195 
5.2 
10 
10 
10 
224.2 
224.2 

mm 

PMMA 
0 
0 
3.4 
0 
0 
3 

air 
4 
195 
1.8 
9 
6 
7 
216.8  6.4 
213.8  6.4 

Cd  Fe 
0 
0 
0 
0 
0 
0 
0 
1 
3 
1 
0 
0 
0 
1 
3 
1 

5 

 
 
 
 
  
 
 
Figure 1: Schematics of experimental setup for the measurements.  

b. 

c. 

a. 

Figure 2: Fig. 2 presents the photos of the experimental setup for COAX detector and Pu 
samples: a. outside view of the experimental setup (enclosure open and PMMA support 
for sample next to it), b. measurement enclosure as setup for measurements with 1mm 
Cd absorber and c. only enclosure with HPGe detector. 

6 

 
 
 
 
 
 
 
 
 
 
3. Pu reference materials   

The reference materials measured have been PIDIE-1, 3, 5 and 7 (described in Refs. 3-
5) and items Pu-61, 70, 84 and 93 from the CBNM Nuclear Reference Material set "271" 
(described in Refs. 6-7).  

The  PIDIE  samples  consist  of  ca.  0.425g  Pu  each  in  the  form  of  a  PuO2  pressed  pellet 
encapsulated in a welded steel container. The measured samples are from set number 4. 
The  samples  have  been  manufactured  specifically  for  inter-comparison  of  the 
measurement capabilities of gamma spectrometry (Ref 4). The results of accompanying 
destructive  analyses  performed  during  that  exercise  are  presented  in  Ref.  3. 
Unfortunately  the  exact  mass  of  the  pellets  has  not  been  recorded  (Ref.  5).  Isotopic 
composition of PIDIE samples based on data from Appendix A  in Ref. 4, recalculated to 
weight % and renormalized to total Pu is presented in Table 2. The samples’ drawing is 
presented in Figure 3. 

Table  2:  Isotopic composition of PIDIE samples in weight % (normalized to sum of Pu 
isotopes) with 2s absolute uncertainty for reference date 1.1.1988. 

Reference 
sample 

PIDIE 1 

PIDIE 3 

PIDIE 5 

PIDIE 7 

238Pu 

239Pu 

240Pu 

241Pu 

242Pu 

241Am 

Isotope 

2s 

weight %  0.01101 
0.00033 
weight %  0.04716 
0.00038 
0.1314 
0.0011 
1.253 
0.016 

2s 
weight % 
2s 
weight % 
2s 

93.7650 
0.0065 
84.5795 
0.0094 
75.8862 
0.0147 
61.9848 
0.0420 

5.99025  0.19920  0.0346  0.2304 
0.0052  0.00255  0.0015  0.0060 
0.9953  0.2338  0.6282 
0.0036  0.0075  0.0151 
2.0638  0.7017  1.7488 
0.0042  0.0015  0.0387 
6.4919  4.6763  3.5287 
0.0132  0.0081  0.1111 

14.1442 
0.0052 
21.2169 
0.0115 
25.5941 
0.0195 

Figure 3: Drawing of a PIDIE sample (reproduced based on Ref. 3). 

7 

 
 
 
 
 
  
 
 
 
The  CBNM  Nuclear  Reference  Material  "271"  (Refs.  6  and  7)  has  been  produced  by 
Central Bureau for Nuclear Measurements of EC JRC. It consists of four plutonium oxide 
sintered  pellets  encased  in  stainless  steel  and  protected  by  a  plastic  cap.  Each  pellet 
contains  6.65±0.06  g  of  PuO2.  The  protective  cap  has  been  left  on  during  the 
measurements. Plastic cap has a thickness of 2 mm, in addition there is a ca. 1mm air 
gap  between  the  plastic  and  the  metallic  bottom  of  the  sample  (overall  height  of  the 
sample  is  24.1±0.1  mm).  The  samples’  drawing  and  description  are  also  presented  in 
Refs.  6-7.  The  reference  sample  Pu93  is  from  set  no.  0/10  and  the  reference  samples 
Pu61,  Pu70  and  Pu84  are  from  set  no.  0/12.  The  isotopic  composition  of  the  reference 
samples from Ref. 6 is for convenience presented in Table 3 and the samples’ drawing in 
Figure 4. 

Table  3:  Isotopic composition  of CBNM standard’s reference samples  in weight % with 
2s absolute uncertainty and reference date 20.6.1986. 

Reference 
sample 

CBNM Pu93 

CBNM Pu84 

CBNM Pu70 

CBNM Pu61 

weight % 
2s 
weight % 
2s 
weight % 
2s 
weight % 
2s 

238Pu 

239Pu 

240Pu 

241Pu 

242Pu 

241Am 

Isotope 

0.00003 

0.0117  93.4123 
0.004 

6.3131  0.2235  0.0395  0.1047 
0.0039  0.0004  0.0003  0.0021 
0.0703  84.3377  14.2069  1.0275  0.3576  0.2173 
0.0006 
0.001  0.0022 
0.8458  73.3191  18.2945  5.4634  2.0772  1.1705 
0.0087  0.0034  0.0023  0.0117 
0.0018 
1.1969  62.5255  25.4058  6.6793  4.1925  1.4452 
0.0241  0.0087  0.0064  0.0144 
0.0025 

0.0085  0.0018 

0.0084 

0.0098 

0.0283 

Figure 4: Drawing of a CBNM reference sample. (Reproduced based on Ref. 7) 

8 

 
 
 
 
  
 
 
 
 
 
4. Measurements and experimental conditions  

Spectra of each reference sample with 50.000 to 150.000s live time per spectrum have 
been recorded. The logbook in the Attachment provides names of the recorded spectra, 
dates of the measurements, live time per particular spectrum, detector dead time as well 
as data on absorbers and detector-to-sample distances used. The spectra, converted to 
Ortec CHN format, are proposed for introduction to the data library of  the International 
working group on gamma spectroscopy techniques for U and Pu isotopics (Ref. 1).   

9 

 
 
 
 
 
 
 
5. Conclusion  

High  quality  high-resolution  gamma  spectra  of  Pu  reference  samples  have  been 
measured by HPGe detector. They will be used in support of phase I of the international 
exercise  on  medium  resolution  gamma  spectrometry.  The  measured  spectra  are  also 
suitable for validation of HRGS analysis software. 

10 

 
 
 
 
 
 
References 

1.  ESARDA website, Data library of The international working group on gamma 

spectroscopy techniques for U and Pu isotopics, 
https://esarda.jrc.ec.europa.eu/index.php?option=com_content&view=article&id
=117&Itemid=255  

2.  J. Zsigrai, A. Mühleisen, M. R. Pascual: Collection of medium-resolution gamma 

spectra of certified Pu reference materials, JRC technical report 98337, 
http://publications.jrc.ec.europa.eu/repository/handle/JRC98337, 2015 

3.  R.J.S. Harry: PIDIE, plutonium isotopic determination inter-comparison exercise, 
Annual Meeting of the Institute of Nuclear Materials Management, Los Angeles 
(USA), ECN-RX--90-044, 1990; 
https://inis.iaea.org/search/search.aspx?orig_q=RN:22045752 

4.  J. Morel, B. Chauvenet: Intercomparaison des mesures de composition isotopique 
du plutonium par spectrometrie X et gamma. Resultats de l'action 'Pidie', rapport 
final,  CEA Centre d'Etudes de Saclay, Gif-sur-Yvette (France). Dept. des 
Applications et de la Metrologie des Rayonnements Ionisants, 1991; 
https://inis.iaea.org/search/search.aspx?orig_q=RN:23077811 

5.  P.M.J. Chard, S. Croft, P.B. Sharp : Characterisation of the Harwell N95 high 
efficiency passive neutron counter, 17th annual ESARDA symposium, p. 551, 
Aachen, 1995; 
https://esarda.jrc.ec.europa.eu/index.php?option=com_jifile&filename=NzkwNzY
wMjQyYTEwMzQ3OWYyN2ZjYWE5MThhODAyMDA= 

6.  CBNM Nuclear Reference Material 271, Certificate of Analysis, Commission of the 

European Communities, Joint Research Centre, Central Bureau for Nuclear 
Measurements, Geel, 1989 

7.  R.J. Friar, T.E. Sampson: Plutonium isotopic abundance measurements on CBNM 

NRM 271 analyzed with the FRAM and MGA codes, Los Alamos National 
Laboratory report LA 12309-MS, 1992; 
http://www.osti.gov/scitech/biblio/10140268 

Attachment: List of spectra 

11 

 
 
 
 
 
 
 
 
 
 
List of spectra:  Measurements of CBNM 271 and Pidie reference materials with HPGe COAX detector 

Meas # 

Sample 

Replicate 
# 

Distance, 
mm 

Shield 

LT, sec  DT, % 

224.2 

1 mm Cd + 3 mm steel 

50000 

18.42 

Pu61_COAX_1mmC_50000s.cnf 

Meas date           

YYYY-MM-DD 
09/12/2014 

Spectrum name 

1 

2 

3 

4 
5 
6 
7 

8 

9 

10 

11 

Pu-61 

Bkg 

Pu-70 

PIDIE-7 
PIDIE-7 
PIDIE-7 
PIDIE-7 

PIDIE-1 

Bkg 

Pu-84 

Pu-93 

12 

PIDIE-3 

13 

PIDIE-5 

14 

Bkg 

1 

1 

1 

1 
2 
3 
4 

1 

2 

1 

1 

1 

1 

3 

- 

1 mm Cd + 3 mm steel 

64000 

0.02 

10/12/2014 

Bkg1_COAX_1mmCd.cnf 

224.2 

1 mm Cd + 3 mm steel 

50000 

15.77 

11/12/2014 

Pu70_COAX_1mmCd_50000s.cnf 

224.2 
224.2 
224.2 
224.2 

224.2 

224.2 

224.2 

224.2 

224.2 

224.2 

1 mm Cd + 3 mm steel 
1 mm Cd + 3 mm steel 
1 mm Cd + 3 mm steel 
1 mm Cd + 3 mm steel 

50000 
50000 
50000 
50000 

3.38 
3.39 
3.38 
3.39 

12/12/2014 
13/12/2014 
13/12/2014 
14/12/2014 

Pidie7_COAX1_1mmCd3mmSteel_50000s.cnf 
Pidie7_COAX2_1mmCd3mmSteel_50000s.cnf 
Pidie7_COAX3_1mmCd3mmSteel_50000s.cnf 
Pidie7_COAX4_1mmCd3mmSteel_50000s.cnf 

1 mm Cd 

150000 

0.92 

15/12/2014 

Pidie1_COAX_1mmCd_150000s.cnf 

1 mm Cd 

50000 

0.02 

14/01/2015 

Bkg2_COAX_1mmCd.cnf 

1 mm Cd 

50000 

9.44 

15/01/2015 

Pu84_COAX_1mmCd_50000s.cnf 

1 mm Cd 

150000 

6.61 

19/01/2015 

Pu93_COAX_1mmCd_150000s.cnf 

1 mm Cd 

150000 

1.68 

21/01/2015 

Pidie3_COAX_1mmC_150000s.cnf 

1 mm Cd 

150000 

3.29 

23/01/2015 

Pidie5_COAX_1mmCd_150000s.cnf 

- 

1 mm Cd 

150000 

0.02 

26/01/2015 

Bkg3_COAX_1mmCd.cnf 

12 

 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Notes to List of spectra: 

Date of measurement is date of start of the measurement (the same as stated within the spectrum) 

Requirements: Pu240 peak at 642.37 keV should be measured with 1% uncertainty (not always possible)   

Settings: 

Detector HV:  3300 

Amplifier polarity 

positive 

gain 

x2 

fine gain 

1.10326 

PUR guard 

1.10x   

offset   

0 

CBNM standards' dose rates at contact 

Pu-61  15 

mSv/h  

Pu-70  10 

mSv/h  

Pu-84  3 

Pu-93  1 

mSv/h  

mSv/h  

Measured reference materials are from: 

Pu-61   

Pu-70   

Pu-84   

Pu-93   

PIDIEs  

CBNM 271 set 0/12 

CBNM 271 set 0/12 

CBNM 271 set 0/12 

CBNM 271 set 0/10 

are from set number 4 

For all measurements the distance between the detector and reference material is the same  

Overall distance: 

of which PMMA: 

224.2 mm 

6.4 mm 

air = overall distance - PMMA distance - absorber thickness 

absorbers (=shield) used are the same as for MRGS measurements 

13 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
List of abbreviations and definitions  

HPGe COAX  High Purity Germanium Co-axial  
HRGS   
ITU 
MRGS   
NDA 
PMMA   

High Resolution Gamma Spectrometry 
Institute for Transuranium Elements 
Medium Resolution Gamma Spectrometry 
Non Destructive Analysis 
Poly(Methyl MethAcrylate)  

List of figures 

Figure 1: Experimental setup for the COAX detector inside lead shielding. .................... 6 

Figure 2: Fig. 2 presents the photos of the experimental setup for COAX detector and Pu 
samples: a. outside view of the experimental setup (enclosure open and PMMA support 
for sample next to it), b. measurement enclosure as setup for measurements with 1mm 
Cd absorber and c. only enclosure with HPGe detector. .............................................. 6 

Figure 3: Drawing of a PIDIE sample (reproduced based on Ref. 3). ............................. 7 

Figure 4: Drawing of a CBNM reference sample. (Reproduced based on Ref. 7) .............. 8 

List of tables  

Table 1: Setup distances and the thicknesses of materials (*PMMA="plexiglass") .......... 5 

Table  2:  Isotopic  composition  of  PIDIE  samples  in  weight  %  (normalized  to  sum  of  Pu 
isotopes) with 2s absolute uncertainty for reference date 1.1.1988. ............................ 7 

Table 3:  Isotopic composition of CBNM standard’s reference samples in weight % with 2s 
absolute uncertainty and reference date 20.6.1986. .................................................. 8 

14 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
Europe Direct is a service to help you find answers to your questions about the European Union 
Free phone number (*): 00 800 6 7 8 9 10 11 
(*) Certain mobile telephone operators do not allow access to 00 800 numbers or these calls may be billed. 

A great deal of additional information on the European Union is available on the Internet. 
It can be accessed through the Europa server http://europa.eu 

How to obtain EU publications 

Our publications are available from EU Bookshop (http://bookshop.europa.eu), 
where you can place an order with the sales agent of your choice. 

The Publications Office has a worldwide network of sales agents. 
You can obtain their contact details by sending a fax to (352) 29 29-42758. 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
L
C
-
N
A
-
2
8
3
9
0
-
E
N
-
N

JRC Mission 

doi: 10.2789/359955 

ISBN 978-92-79-64836-6 

16