IAEAInternational Atomic Energy Agency

Nuclear Reference Materials for Safeguards: Challenges for Users and

Producers Alike

S.Balsley

IAEA

Safeguards- What is it?

• Most countries participate in international initiatives designed to limit the proliferation of nuclear weapons.

• The Nuclear Non-Proliferation Treaty (NPT) has been a success.

• The IAEA is responsible for the verification aspect of the NPT.

• Detection of undeclared nuclear material or activity is a relatively new role for the IAEA

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Safeguards- How is it done?

• The Nuclear Fuel Cycle is the focus of attention.

• The IAEA undertakes regular inspections of civil bulk handling facilities

• Audit the quantity of material within, and the movement of materials through, the facilities.

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IAEA Inspections

• IAEA inspectors must

independently verify

nuclear material

inventories using…

• Containment and

surveillance,

• Counting and

measurement of items,

• Sample analysis

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Verification by Sample Analysis

• Verification of declared

materials by nuclear

material analysis

• Verification of absence

of undeclared activity

by environmental

swipe sample analysis,

or forensic analysis of

nuclear material

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Correctness: Nuclear Material Sample Analysis

• Actinides (mainly U and Pu) from nuclear material samples of all varieties

• Precision and accuracy of analytical results is driven by a “fit-for-intended use” philosophy

• Nuclear material accountancy requires a “state-of-the-practice”level of analytical performance

• Sampling and measurement requirements for both facility operator and safeguards laboratories are guided by an International Target Values document

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Completeness: Environmental Swipe Sample Analysis

• High instrument U, Pu sensitivity is needed to detect small releases

• High selectivity is needed, enhanced by high precision and accuracy

• Bulk analysis by ashing and dissolving the whole swipe sample

• Particle analysis involves removal from swipe, location and analysis

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Certified Reference Materials

• Certified reference materials are critical to the

success of safeguards

• Chemistry process control,

instrument calibration and

establishing detection limits, measurement

quality control

• Nuclear CRMs present

special challenges to users and producers

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IRMM CRMs in Use at the IAEA

• TIMS QC on environmental and nuclear material

samples

• IRMM-18x U Series (IRMM-184 through -187, nat. U

through 5 % enriched)

• IRMM-072/15 (50 % enriched)

• IRMM-075 (1-5) U Series (natural U with U-236/U-238

from 1E-4 through 1E-8)

• IRMM-040/1 (U-233 spike)

• IRMM-044 (Pu-242 spike)

• Uranium assay QC on nuclear samples

• EC-110 UO2 sintered pellets

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Percent Difference from Certificate

U Concentration

(EC-110)

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

2007 2008 2009

EC-110

2007 = 151

2008 = 150

2009 = 121

Example: Uranium Concentration

Target Value (ITV)

Lab Uncertainty (GUM)

Certificate Uncertainty

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Example: Pu Isotopics

Percent Difference From Certificate

(CRM 137)

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

2005 2006 2007 2008 2009 2005 2006 2007 2008 2009

Number of items

2005 = 152

2006 = 117

2007 = 105

2008 = 64

2009 = 70

240-Pu / 239-Pu 242-Pu / 239-Pu

Certificate Uncertainty (& ITV)

Lab Uncertainty

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New Directions for SG- Nuclear Forensics

• Nuclear material samples contain much more information than what SG inspectors have traditionally requested

• Supplementary analytical interrogation of NM accountancy samples is being applied to answer SG relevant questions

• More non-accountancy NM samples are being submitted to for analysis

• RM Producers are feeling these changes, too

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Impurities in Uranium Samples

• Trace levels of metallic elements in nuclear U samples may be used for source attribution, facility characterization, etc.

• ICP-MS is the favoured analytical technique

• Clean lab like conditions needed to mitigate cross contamination

• New reference materials and round robins are needed

Bulyha 2010

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Impurity Analysis in U Samples

×××××××× ××××

×××× ××××××××

××××

××××××××

××××××××

×××× Elements of interest; concentrations are not certified in available CRMs

×××× ×××× ×××× ×××× ×××× ×××× ×××× ×××××××××××× ××××

×××× ×××× ×××× ×××× ×××× ×××× ×××× ×××× ×××× ××××

×××× ×××× ×××××××× ×××× ×××× ×××× ××××

Elements of interest; concentrations are certified in available CRMs

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Age Determination of HEU and Pu

• HEU and LEU CRMs

are needed with

certified 230Th/234U

ratios ranging from ca.

10-5 to ca. 10-4

• Plutonium CRMs are

needed with certified 241Am/241Pu ratios

ranging from ca. 0.1 - 5

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High-Precision Minor U Isotopes

• Determination of the minor isotopes of U (236, 234U) with high precision is possible with latest generation TIMS, using the modified total evaporation protocol (MTE)

• SG target of 1 ppm absolute accuracy can be met in all cases for 234U and 236U

0.001%0.010%0.100%1.000%10.000%100.000%1E-08 1E-06 1E-04 1E-02 1E+00isotope ratioisotope ratioisotope ratioisotope ratiorelative accura

cyrelative accuracyrelative accuracyrelative accuracy and precision and precision and precision and precision U-234/U-238U-235/U-238U-236/U-238U-234/U-238U-235/U-238U-236/U-238

Buerger et al., 2010

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Recent Collaborations with IRMM

• Implementation of Triton modified total evaporation (MTE) at IAEA labs with support by S. Richter (joint publication on

MTE by S. Richter submitted)

• Training of IAEA staff in the Triton MTE

• Application of IAEA Triton MTE to IRMM-3100a Quad spike verification, published in Richter et al., Int. Journal of Mass

Spectrometry 295 (2010) 94

• Application of IAEA Triton MTE to contribute to a new

assessment of natural U standards (published in Richter et

al., Int. Journal of Mass Spectrometry, in press)

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CRM Needs for Safeguards

• LEU (> 5% enriched), HEU CRMs with uncertainties equivalent to presently available CRMs like IRMM-18x Series

• Recertification of some existing Pu CRMs is needed• Pu isotope CRMs with various Pu-239/Pu-240 ratios

• Radiochronometry CRMs with certified ages (e.g., U-234-Th-230, Pu-241-Am-241)

• Trace impurity natural U oxide CRMs for trace elements different to existing CRMs (NBL 123 & 124, CEA).

• Np assay plus Np-236/Np-237 CRM, and Am assay plus Am-241/Am-243 CRM for mass spectrometry

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Other Needs for Safeguards

• Large-size dried spikes produced by IRMM

• Mixed U-Pu nitrate used to measure the U & Pu

content of spent fuel in

reprocessing plants

• Demand is high on 239Pu

CRM metal (~2 g / y)

• IRMM working on ways to

reduce the amount of Pu CRM needed

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Interlaboratory Comparisons

• The IRMM REIMEP and NUSIMEP programs are important for external quality control

• Plutonium programs should be regularly scheduled for the SG measurement community

• Nuclear shipments will become more difficult and costly- challenge for RM producers. Maybe the IAEA can help.

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Conclusions

• The nuclear safeguards measurement community depends on certified reference materials for verifying the correctness and completeness of State inventories.

• Improvements in mass spectrometry require re-certification of older CRMs (esp. Pu).

• The growing emphasis on nuclear forensicmeasurements for safeguards will require development of new CRMs.

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Conclusions

• Interlaboratory comparison programs are extremely important and should be continued, with more emphasis on thenuclear forensic measurement area.

• The IAEA works closely with the European Commission Support Programme to the IAEA to facilitate CRM needs now and in the future.

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Congratulations IRMM!