Pierre Funk (IRSN)

Nuclear non destructive assay and security

Table of contents

� 1. Nuclear security in France

• Regulatory framework

• Provision related to measurement

� 2. Non Destructive Assay: description of the techniques used

• Passive neutron measurement

• Gamma spectrometry measurement

� 3. Examples

1. Nuclear security in France: regulatory framework

Defense CodeL1332 L1333

Security of installationsof vital importance

Protection and controlof nuclear materials

SAIV Decree PCMNIT Decree

10 Orders4 Orders DNS

VIGIPIRATEPlan

SAIV: Activity Sector of Vital ImportanceDNS: National Security Directive

Pillars of the protection and control of nuclear materials

Nuclear Materials protection in facilities is based on three complementary independent layers

� 1 - Physical protection

Provisions aimed at preventing, detecting or delaying any unauthorized or unjustified access to the nuclear materials and any unjustified movement of these materials out of the zones where they should be located. These provisions include alert procedures allowing for intervention of response forces.

Pillars of the protection and control of nuclear materials

� 2 - Physical follow-up

Provisions aimed at authorizing nuclear material movements and controlling nuclear material when necessary in order to detect any attempt of fraud when moving material. They are based on a permanent and precise (quantity and quality) knowledge of all the entries /exits of nuclear materials and on the knowledge of their location, their use, their movements and transformations.

� 3 – Nuclear Material accounting

Provisions for data control performed independently of physical follow-up / tracking systems. Accounting provisions are based on the daily knowledge of the book inventory in every material balance area (MBA), and on the variations of this inventory, especially entries and exits.

Provision related to measurement

Defense Code - Art. R. 1333-11…

� 1/ Always know the exact quantity and quality, all inputs and outputs of nuclear material in facility or installation"

� 2/ To monitor the nuclear material present in facility in order to know their location, use, movement and transformation"

The objectives of measuring nuclear materialfor the operator

� Control at entry => detection of difference

� Characterization => knowledge

� Internal controls => detection of difference

� Control before shipping => detection of difference

� To acquire knowledge

� Quantitative and qualitative measurement

� As soon as integrity of an article is modified

� => Continuity of the follow-up

� In any event: before shipping

Inspections by the Ministry in charge of energy with the help of the IRSN

� Annual program

� Aim at verifying operators obligations and commitments.

� Inspections can be :– Routine inspections

– Comprehensive inspections or focused on specific themes

– Reactive (following an event)

� Control operations performed during inspections :– are conducted independently by sworn and accredited inspectors

– are conducted on-field

– concern technical provisions and organization

– can imply independent measurements (NDA)

– are second level controls

– are not aimed to be exhaustive

Inspections including independent measurement

� Objective 1: control of implementation of commitments - refering to the documentary reference framework - for the detection of discrepancy on the authorized movements

� Objective 2: control of quality and quantity of nuclear material – within the uncertainties described in the documentary reference framework

� Verification of operators declarations, using independent methods

� Inventory verification– in addition to check tags

– rapid measures on many items

� Precise control of the quantities of nuclear material– non-destructive measurements on a limited number of articles

• mass of uranium, plutonium, thorium

• U and Pu isotopic composition

Measuring the isotopic composition of natural uranium by different techniques

0

0.2

0.4

0.6

0.8

1

1.2

gamma spectrometry gamma spectrometry alpha spectrometry mass spectrometry

enrichment (%

)

15 mn 2 h 5 d 10 d

Inspections including independent measurement

� Constraints

– Non destructive Assay

– Quick measurement

� Means : realization of NDA measurement by inspectors from IRSN, in the operator plant

– Passive neutron measurements

– Gamma spectrometry

– Weighting

� Qualitative and quantitative measurement

Description of a typical inspection

Preparation meeting

S M T W T F S

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

S M T W T F S

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Packaging

Measurement (4+1 days)

Packaging, Conclusion meeting

TransportReport

, Transport , Setting , Sampling

Announced inspection

Inspection with current devices (~ 23)

PLUMFUNEHOTRANSINSPECTORFRAMJCC51AMATHORTHEMIS…

Feedback from the field

Research and development

Request for a new inspection

New devices

Link between R&D and inspections

2. Non destructive assay: description of the techniques used

� Passive neutron measurement

� Gamma spectrometry measurement

Passive neutron measurement

� Measure neutrons emitted naturally by the nuclear material

� The total mass of plutonium contributes to the measure because the neutrons easily penetrate the nuclear material

� Therefore a measure of high masses is possible

� No spectrometry (simply counting)

� Requires knowledge of the isotopic composition

Gamma spectrometry measurement

� characteristic gamma-rays of the isotopes

� identification

� Intensity of the gamma-ray

� proportional to the mass of isotope

Computer with software acquisition and processing of spectrum

Analyser Detector Sampleto characterize

Quantitative measures: parameters to be considered

� Background

� Efficiency of the detector

� Distance of measurement

� Screen between source and detector

� Self-absorption

� Nuclear data

BkGcefficiencyfcactivityfn screenectorabsorptionselfsource −××==

− )()),((

system detection theby detected count of Number n

det

Energy (keV)

Nombre de coups 185,7 keV

Pic caract é ristique

de l ’uranium 235

de surface Si

Number of counts

Energy (keV)

185,7 keV

Characteristic gamma-rayfor U-235

i

Plutonium mass

3. Examples

� Check of waste containing nuclear material (plutonium)

– 2 measurements devices: FUNE and PLUM

� Search for biases

– quantitative uranium measurements with improper consideration by the operator of self-absorption processes for a uranium mass measuring system, leading to under-estimating declared amounts of nuclear material.

– the use of contradictory measuring system allows showing biases in the operator’s measuring, as the search for such biases based on a review of the operator’s practices alone is often difficult.

Check of waste containing nuclear material (plutonium)

� Kind of Waste

– Low active plutonium waste drum

– 100-liter/200-liter drum

– ~ 30 kg

– Light matrix: combustible, metallic

� Range of measurement

– [50 mg - 100 g] of plutonium

FUNE

� Based on passive neutron coincidence counting

� Measurement of 238Pu, 240Pu, 242Pu

PLUM

� Based on infinite energy extrapolation method

� Characterization of 239Pu, 241Pu

Strategy to declare an anomaly (1)

� Two results are obtained for each drum :

1. FUNE result (~30 min)

2. PLUM result (~30 min)

+ the declared value

� How to compare them to the declared value?

� What happens if they are different?

� What criteria to use?

Strategy to declare an anomaly (2)

Several cases…

Declared value

PLUM value (γγγγ)

FUNE value (n)

« Good »case

Anomaly

?

Strategy to declare an anomaly (3)

Several cases… -> interest of complementary methods

Declared value

PLUM value (γγγγ)

FUNE value (n)

« Good »case

high self-absorption ?Presence of other neutron emitters(ex: Curium)

In summary

� The nuclear security regulation provides

– physical protection, follow-up, and accoutancy

– Shipper / receiver protocols

• "first level“ control

• "second level“ control

– Periodic physical inventories

– Realization of measures:

• to acquire knowledge

• Continuity of the follow-up

� The holder of nuclear material should always know the qualities and quantities of nuclear material held

For the operator

In summary

� Measurement done in nuclear facilities by national control inspectors

� Control of implementation of commitments - refering to the the documentary reference framework - for the detection of discrepancy on the authorized movements

� Control of quality and quantity of nuclear material – within the uncertainties described in the documentary reference framework

� Common methods used rely on passive neutron measurement techniques and gamma spectrometry.

� Enables to ensure the credibility of the control in full independence from operators.

Inspections including independent measurement