NAA using Kayzero: from peak areas to element concentration

19/04/23www.kayzero.com

NAMLS-8, Rio de Janeiro, April 17th-22nd 2005

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NAA using Kayzero: from peak areas to element concentration

NAA using Kayzero:from peak areas to element

concentration

R. van Sluijs, k0-ware, Heerlen, the Netherlands

D. Bossus, DSM Geleen, the NetherlandsF. De Corte, RUG, Ghent, Belgium



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Problem? No problem!?

k0-methodPeak area, A

Element concentration, ρ

Simple? Perhaps not, but very well documented! nowadays there are many programs to help!



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No problem,but ..... (1)

How to get the correct peak area?

Use a perfect gamma spectrometry system and keep it in the best possible condition!

Use the perfect gamma spectrum deconvolution program!

However: who has this perfect set-up?



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No problem, but......... (2)

How to select the analytical line K0-library has data for 68 elements, 144 nuclides and

more than 700 gamma-lines For a panoramic analysis you use preferably 2

irradiations (short and long) each followed by 2-3 measurements

A single element will give data for several nuclides and probably tens of gamma lines.

All we want one single list:Containing the all elements with their concentrations and/or limits of detection.



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DSM’s/Kayzero’s method

Optimise the peak table! Peak Table: Area’s and Energies from gamma

spectrum deconvolution program

Calculation Concentrations for all lines in the k0- library

EvaluationIdentify the nuclides in the sample Correct for gamma interferencesCalculate averages per nuclide and per element Average over all measurements

Refine the results

User Input

Automatic



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Optimise the peak table!

Peak Areas: Broadened peaks (due to count rate effects, bad

pile-up correction, etc..) can be split by the gammaspectrum deconvolution program into two separate peaks.

Sum the false/artificial peaks for a correct result Peak locations:

Linear energy calibration, non-linear is often better

Re-do the energy calibrationHypermet shifts data 1 channel to the left Shift back



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Measurement Input screen



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Peak summation screen



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Re-do energy calibration



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k0-calculations

Calculate concentrations for all library linesIncluding Corrections for:

background, dead-time, gamma-absorption, burn-up, neutron self absorption, True-coincidence correction

No matching peak: the LD concentration is calculated using the spectrum base line.

No result if calculated concentration >100%



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Evaluation of the results: Check the presence of a nuclide

0

20

40

60

80

100

1 2 3 4

Energy

Con

cent

ratio

n

Limit of Detection

positive

negative

positive neutral

4 energies of nuclide X



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Evaluation of the results:Check the presence of an

element

0

20

40

60

80

100

Nucl. A/Meas.1

Nucl. A/Meas.2

Nucl. B/Meas.1

Nucl. B/Meas.2

Nuclide data from 2 measurements

Co

nce

ntr

atio

n

Limit of Detection

positive

negative

positive neutral

Nuclide data of Element X



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Evaluation of the resultsCorrect for gamma interferences

0

20

40

1 E 2 3Energy

Co

nce

ntr

atio

n

Average this nuclide is producing 50% of the area in line E =Cn, aver./Cn,E

)1(1 ,

.,,,,

N

n En

avernEacorrectedEa C

CCC N=number of interfering

nuclides on line E



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Evaluation of all results Calculate averages and standard

deviations • over the lines of a nuclide

• weighing factor wi= 1/σ2i

• σobserved should be approx. equal to σexpected

w1)-(n

)-(w=

i

2ii

obs

)w(

)w(= 2i

2ii

exp

w

w=

i

ii



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Refine the resultsselect the analytical lines

Select by hand:gamma’s to be used correct for threshold, fission,

second-order reaction interferences,

blank correction,

Alarm for high epi-thermal self shielding



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Ba-131: large observed SD



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Deselect Ba-131 line



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Fission Correction for La-140



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Fission Correction



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Blank subtraction



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The goal of all our work:a (digital) list of concentrations



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Conclusion

k0-method (DeCorte/Simonits) is a very complete method, all

aspects of INAA are taken into account, elaborate calculations are needed but this is no problem nowadays

The method presented to handle k0-data is based on almost

20 years of experience, analysing all kinds of samples

Evaluation of the data of a panoramic elemental analysis of an unknown sample takes less than half an hour

Although very much automated: the analyst is in control

The competition in our lab is though, NAA is the most expensive technique so quality and reliability is a prerequisite

Documents

NAA using Kayzero: from peak areas to element concentration