1. NAA using Kayzero: from peak areas to element concentration
R. van Sluijs, k0-ware, Heerlen, the Netherlands
D. Bossus, DSM Geleen, the Netherlands
F. De Corte, RUG, Ghent, Belgium
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

2. Problem? No problem!? Peak area, A Element concentration, ρ k0-method
Okay, k0 method is well documented, all is clear, but is this all?
No!
Simple? Perhaps not, but very well documented!
nowadays there are many programs to help!
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

3. 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?
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

4. 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.
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

5. DSM’s/Kayzero’s method
User Input
Automatic
Optimise the peak table!
Peak Table: Area’s and Energies from gamma spectrum deconvolution program
Calculation
Concentrations for all lines in the k0- library
Evaluation
Identify the nuclides in the sample
Correct for gamma interferences
Calculate averages per nuclide and per element
Average over all measurements
Refine the results
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

6. 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 calibration
Hypermet shifts data 1 channel to the left
Shift back
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

7. Measurement Input screen
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

8. Peak summation screen 22/11/2018 www.kayzero.com
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

9. Re-do energy calibration
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

10. k0-calculations Calculate concentrations for all library lines
Including 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%
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

11. Evaluation of the results: Check the presence of a nuclide
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

12. Evaluation of the results: Check the presence of an element
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

13. Evaluation of the results Correct for gamma interferences
N=number of interfering
nuclides on line E
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

14. 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
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

15. Refine the results select 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
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

16. Ba-131: large observed SD 22/11/2018 www.kayzero.com
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

17. Deselect Ba-131 line 22/11/2018 www.kayzero.com
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

18. Fission Correction for La-140
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

19. Fission Correction 22/11/2018 www.kayzero.com NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

20. Blank subtraction 22/11/2018 www.kayzero.com NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

21. The goal of all our work:a (digital) list of concentrations
51 elements reported:
30 with concentration,
21 only detection limit
Final result
51 elements reported:
- 30 concentrations
- 21 only detection limit
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005

22. 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
22/11/2018
NAMLS-8, Rio de Janeiro,
April 17th-22nd 2005