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The International 7th k0-Users’ Workshop, 3-9 September 2017, Montreal,
Canada
k0- method for Flowing Sample Neutron Activation Analysis
Mohamed A.M. Soliman Head of NAA Laboratory at Egypt Second Research Reactor
soliman.ma@gmail.com
Introduction…
It is a subclass of INAA. It involves the continuous flowing (pumping) of the sample between an irradiation cell and measurement station. It can be operated in 2 modes: 1- cyclic mode: 1- one-way mode: for very short-lived radionuclides
What is Flowing Sample Neutron Activation Analysis (FSNAA)?
Introduction…
Motivation ?
One challenge that currently affects NAA (and all analytical techniques) is the analysis
of liquid samples with low elemental content.
The conventional methods have some drawbacks:
1. Chemical pre-concentration method
- costly and time consuming,
- Potential losses of elements may be occurred, and/or
- cross-contamination problems.
2. Radiochemical process
- costly and time consuming
- not suitable for determining short-lived radionuclides
- analyst may be exposed to a high radiation dose
3. Analysis of large volume
- Almost all reactors aren’t equipped with large volume irradiation facility.
- Not suitable for analysis of elements via short lived isotopes
- radiolysis of water molecules - pressure build-up problems
Introduction…
Advantages of FSNAA?
O Simple and non-destructive
No pre-treatment and/or radio-chemical process
O Analysis of large volume
No pressure build-up
Measuring of short-lived isotopes
Easy to be installed currently available irradiation sites
Analysis of solutions contained suspended matters
No need for filtration and/or dissolution steps
O Constant dead time
More accurate results
Previous work
FSNAA…
What we did……. Optimizing the counting and irradiation configurations using
Monte Carlo simulations (MCNP code)
Testing and Characterizing
Leakage test
Pump (flow rate and its stability)
Repeatability
Stability of dead time
etc….
Applications
Installation @ Reactor neutron beam
Publications
F.S. Abdo, M. Soliman et al. 2016. Arab J Nucl Sci Appl. Accepted for publication
F.S. Abdo, M. Soliman, M. M. Ahmed, R. A. M. Rizk, R. M. Megahid, 2016. J Radioanal Nucl Chem, 307, 1413–1418
M. Soliman, N.M.A. Mohamed, A. M. Osman, A. M. Abdel-Monem, 2014. J Radioanal Nucl Chem, 285, 321-329
M. Soliman, N.M.A. Mohamed, M. A. Abd El-Samad, A. M. Abdel-Monem, A. Hamid, E.A.Saad, 2013. J Radioanal Nucl Chem, 295, 245–254
Optimization Counting geometry
Monte Carlo simulations was carried out to optimize
counting geometry:
U (= Eff. x volume around
The detector)
# tube diameter.
Detector length: 5.5cm
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6
U
Tube Diameter, cm
Previous work
Previous work
Getting more count by:
1- Keeping the irradiation
tube as large as possible
and
2- keeping the decay tube
as narrow as possible
decay line (D 0.2cm)
counting line
From fluid mechanics point of view,
1- extreme difference in tube diameters leads to an increase in the amount of eddies
2- tube diameter controls the type of flow: Laminar or Turbulent
Turbulent flow Laminar flow
Turbulent flow is preferred over Laminar one because it guarantees a homogenous irradiation and counting of the irradiated samples
Previous work
System repeatability
Fifteen measurements of Indium solutions (116m2In, t1/2=2.2sec)
Repeatability<3%
Analysis of solutions containing suspended matters
Analysis of AgNO3 # AgCl3
No significant difference between count obtained with
dissolved and precipitated 110Ag
Previous work
Previous work
0
1000
2000
3000
4000
5000
6000
7000
0
200
400
600
800
1000
1200
0 10 20 30 40
Se
nsitiv
ety
(co
un
t/m
g)
DL
(m
g)
No. of Cycles Cu*
DL S
0
20000
40000
60000
80000
100000
120000
0
50
100
150
200
250
300
350
0 10 20 30 40
Se
nsitiv
ety
(co
un
t/m
g)
DL
(m
g)
No. of Cycles Mn*
DL S
0
500
1000
1500
2000
2500
3000
0
100
200
300
400
500
600
0 10 20 30 40
Se
nsitiv
ety
(co
un
t/m
g)
DL
(m
g)
No. of Cycles Cl-38*
DL S
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
4500000
0
0.5
1
1.5
2
2.5
3
0 10 20 30 Se
nsitiv
ety
(co
un
t/m
g)
DL
(m
g)
No. of Cycles In-116m2*
DL S
Effect of no of cycle
Previous work
Elements detected Sample type
Ag, Dy, In, Mn, Cu, Na, Cd, Ba, F, Se, Cl, K and V Synthetic multi-
elements standard
Na, Cl, K, and Cu Sea water
Al Ismailia Cannel (near
Al2(SO4)3 factory)
Al and Mn Suspension of IAEA-
soil-7
Ca Milk sample
Applications
O The main objective of the present work is to implement the k0-standardization method for FSNAA. To achieve this goal, tools and method have been developed for:
1. detector efficiency calibration for this new counting geometry.
2. characterizing the neutron flux at the port of the neutron beam.
1. correction of neutron and gamma-ray shelf-shielding.
The objective of the current work
FSNAA with neutron beam port
Experimental
OFSNAA has been
installed with a
neutron beam port of
ETRR-2.
Experimental
127
127
127
106.8
104.2
106.8
scm
scm
scm
f
ep
th
O Neutron flux monitors: Au, Zr, In
O Standard solution: Ag, Dy, In, Mn, Cu, Na, Cd, Ba, F, Se,
Cl, K and V
O Radioactive standard solution (in-house):
Co-60, Cs-134 and Eu-152
O
Experimental
O MCNP modeling:
1. F8 tally, which is the pulse height tally, was used to
predict the detector’s efficiency and the correction
factors.
2. F2 tally, which is the surface flux tally, was used to
predict the neutron flux on the tube surface.
3. F4 tally, which is track length estimated of cell flux
tally, was used to predict the neutron flux inside by
the sample.
Experimental
O MCNP modeling:
O Counting geometry
O Irradiation geometry
Experimental
O HPGe calibration:
In-house standard of 60Co (471 Bq) , 134Cs (352 Bq)
and 152Eu (561 Bq) were prepared from stock
radioactive solution and used for calibrating HPGe.
This standard solution was injected in the counting
tube around the HPGe
Results
O HPGe calibration:
Results
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 300 600 900 1200 1500
Eff
icie
ncy
No need for attenuation
correction factor
O HPGe calibration:
O Valid when
Results
Leve
l o
f ra
dio
acti
vit
y
Detector length
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 300 600 900 1200 1500
Eff
icie
ncy
t1/2 >> tc
No need for attenuation
correction factor
O HPGe calibration:
But if t1/2 << tc, then:
In that case, half-life based correction factor (fh) should be estimated
Results
Leve
l o
f ra
dio
acti
vit
y
Detctor length
O HPGe calibration:
Half-life based correction factor (fh):
Where:
εu is the eff. for uniformly distributed activity of the
source.
εh is the eff. for a source with a half-life based
distribution activity.
Results
h
uhf
O HPGe calibration:
Half-life based correction factor (fh):
Using MCNP Code:
Results
0.75
0.80
0.85
0.90
0.95
1.00
1.05
0 1 2 3 4 5 6 7 8
Co
rre
cti
on
fa
cto
r
Half-life (Sec.)
150 ml/min
300 ml/min
450 ml/min
750 ml/min
O Characterization of the irradiation facility:
1- Homogeny of the flux:
Indium foil was applied to study the distribution of the flux over the
sample surface
In foil
Results
O Characterization of
the irradiation facility:
1- Homogeny of the flux:
The count of the central
In foil is 20% less?!
Results
0
5000
10000
15000
20000
25000
30000
-30 -20 -10 0 10 20 30
416 keV
x-axis
y-axis
O Characterization of the irradiation facility:
1- Homogeny of the flux:
The count of the central In foil is 20% less?!
Results
The back scattering
is the main reason
for the lower value
of neutron flux in
the central part
O Characterization of the irradiation facility:
2- Neutron self-shielding correction factor (fn):
Where: ¢surface and ¢inside are the neutron flux at the
surface and inside the sample as calculated using
MCNP Code, respectively.
Results
inside
surface
nf
O Characterization of the irradiation facility:
2- Neutron self-shielding correction factor (fn):
Inside Flux # tube diameter
Results
0.0E+00
5.0E+07
1.0E+08
1.5E+08
2.0E+08
2.5E+08
3.0E+08
3.5E+08
4.0E+08
0 1 2 3 4 5 6 7 8
Ne
utr
on f
lux, cm
-2.s
ec
-1
Tube diameter, cm
Thermal
Epithermal
Fast
O Characterization of the irradiation facility:
3- measuring of (ƒ) and (α) parameters
Triple bare monitors : Zr-Au
After 4 hr irradiation:
Au-198: OK
Zr-97: OK
Zr-95: NO count .
The plan was modified to use Mo-Cr-Au as flux monitor
Results
O Simple procedure for HPGe eff calibration
(complicated geometry) as well as prediction of the
correction factor has been established.
O Neutron self-shielding is strongly dependant on the
sample diameter - be considered
O Zr-Au should be replaced (in our case) by another
flux monitor.
Conclusion
O Designing the FSNAA set-up to fit into the vertical neutron irradiation channel of ETRR-2 with high neuron flux (in order of 1013 cm-2s-1.).
O Analysis of commercially available liquid reference materials and participation in inter-comparison rounds
O Analysis of environmental liquid samples
O Replacing the HPGe with neutron detector and testing the system for determining fissile materials.
O Research on analysis of liquid samples containing suspended matters without any pretreatment; chemical dissolution or filtration.
Future Plan
Recommended