ANALYTICAL METHODS FOR OBTAINIG„FINGERPRINTS“ OF NUCLEAR MATERIALS IN ILLICIT TRAFICKING: A CASE OF HIGH

ENRICHED URANIUM SEIZED IN PRAGUE IN 1994

A REVIEW

Miloš BERAN, František SUS *

Nuclear Physics Institute, Czech Academy of Sciences

250 68 Rez near Prague, Czech Republic

Nuclear Research Institute Rez plc *

250 68 Rez near Prague

Czech Republic

From the newspaper article in The Prague Post:

Outer and inner packaging of the seized material:

The Certificate as attached to the Material:

After the event, the International Technical Working Group

(ITWG) for assisting to state and international safety offices

and agencies in suppresing an illicit nuclear trafficking, was

established in a short series of international meetings:

• International Conference on Nuclear Smuggling Forensic Analysis,

LLNL, Livermore (U.S.A)

November 7-9, 1995

• First Meeting of the Nuclear Smuggling International Technical

Working Group, ITU, Karlsruhe (Germany)

January 31-February 1, 1996

• International Workshop on Nuclear Material Illicit Trafficking,

Institute of Physics and Power Ingeneering, Obninsk (Russia)

December 2-4, 1996

Basic analytical methods recommended by ITWG for forensic analyses of seized illicit nuclear material to

attribute its origin and possible use:

• High resolution gamma (for detection of enriched U-235 and/orPu) and alpha spectrometry

• Potentiometric oxidation-reduction titration to determine stoichiometric composition (U-content) of material

• Mass spectrometric methods for determination of isotopic com-position, e.g. ID-TI-MS, GD-MS or ICP-MS ( determination of enrichment, impurities, …)

• Optical and electron (scanning or transmision) microscopy fordetermination of structure and microstructure

• X-ray diffraction analysis (homogeneity of material)

• Determination of age of material from ratio of some generic radionuclide pairs ( e.g. U-235/Pa/231, U-232/Th-228,Pu-239/U-235, Pu-240/U/236,… )

SELECTED ANALYTICAL RESULTS FOR THE

MATERIAL SEIZED IN PRAGUE IN

DECEMBER, 1994

Mass Spectrometric (TI-MS) Determination of Isotopic Composition of the Material

Test Parameter Batch A Batch B

U-content (wt. %) 86,799 +- 0,001 86,735 +- 0,001

IC-NRI 232 U

232 U

234 U

235 U

236 U

238 U

<0,000002

< 0,000002

1,0781 +- 0,0003

87,731 +- 0,046

0,2108 +- 0,0001

10,9797 +- 0,004

<0,000002

<0,000002

1,0778 +- 0,0004

87,737 +- 0,035

0,2102 +- 0,0004

10,9438 +- 0,004

IC-ITU

(comparison in

collaboration)

234 U

235 U

236 U

238 U

1,078 +- 0,070

87,766 +- 0,046

0,210 +- 0,00

10,946 +- 0,046

Determination of Trace Impurities by ICP-MS

Test Element Batch A Batch B

Impurities (μg/g)

IC-MS

Elan 6000

(without

chem.

separation)

Ag

Al

Ba

Be

Cd

Cr

Cu

Fe

Li

Mg

Mn

Mo

Ni

Pb

Sb

Sn

Sr

Th

Ti

V

W

Zr

0,19

7,8

0,65

0,005

0,015

8,9

1,25

58,5

0,03

10,4

0,91

3,2

2,9

4,1

0,010

0,70

0,45

0,22

0,82

0,14

0,39

18,6

0,15

8,5

0,49

0,004

0,018

9,5

1,15

65,4

0,04

12,0

1,05

2,8

3,5

3,2

0,018

0,82

0,55

0,26

0,99

0,19

0,46

16,1

Radionuclide Impurities

Method Spike Isotope Batch A Batch B Unit

AS-ID 236Pu 239+ 240Pu < 1 < 1 (Bq/g)

ICP-

MS

99mTc 99Tc < 0,02 < 0,02 (Bq/g)

Age Determination

Pair of

isotopes Spike

Batch A

(year)

Batch B

(year)

234U- 230Th

235U- 231Pa

228Th

237Np

26,9

25,6

27,3

26,4

Appearance of Samples in Optical Microscope

Structure of the Material

Pictures of material by scanning electron microscopy

C o n c l u s i o n s:

• The material seized in Prague in December 1994 was according to high resolution gamma spectrometry, potentiometric titration and mass spectrometric measurement high enriched UO2 (87,7 % of 235U)

• The material consisted of irregular porous particles (size under1 mm) with microcrystal structure according to scanning electron microscopy

• Very low content of radionuclide (99Tc, 239+240Pu) and chemical impurities (excepting traces of common construction materials of production equipment – Fe, Cr, Al and Zr) vere found in the material

• According to determination of „age“, 26-27 years elapsed from last retreatment (separation or purification) of the material to the moment of analysis

C o n c l u s i o n s:

• High chemical reactivity (e.g easy solubility in mineral acids) suggests the material to be an intermediate product for production of other products in nuclear technology

• The described case represent a most significant seizure of weapon utilizable illicit shipment of nuclear matererial

• Radioanalytical chemistry can provide tools to retrace illicit nuclear shipment to its source, supposing that nuclear material database exists