COMPARISION OF PERFORMANCE
COMPARISION OF PERFORMANCE
PARAMETERS FOR DIFFERENT TYPES
PARAMETERS FOR DIFFERENT TYPES
OF LIQUID SCINTILLATION COCKTAILS
OF LIQUID SCINTILLATION COCKTAILS
Funda B. ŞİMŞEK
Funda B. ŞİMŞEK
funda.simsek@taek.gov.tr
funda.simsek@taek.gov.tr
TAEA-Çekmece Nuclear Research and
TAEA-Çekmece Nuclear Research and
Training Center
Training Center
S
S
election of
election of
an
an
optimal liquid scintillation cocktail
optimal liquid scintillation cocktail
O
O
verall
verall
C
C
ocktail
ocktail
P
P
erformance
erformance
counting efficiency counting efficiency
background contributionbackground contribution
sample stabilitysample stability
figure of meritfigure of merit
quench resistancequench resistance
α/β discriminationα/β discrimination
S
S
pecific
pecific
L
L
aboratory
aboratory
N
N
eeds
eeds
detection limitdetection limit
measurement uncertainity measurement uncertainity
sample volumesample volume
waste treatment regulations waste treatment regulations
The LS
The LS
cocktails used in the test
cocktails used in the test
s
s
are all commercially
are all commercially
available:
available:
Optiphase Hisafe-3,
Optiphase Hisafe-3,
Ultimagold LLT,
Ultimagold LLT,
Mineral Oil,
Mineral Oil,
Ultima Flo-M.
Ultima Flo-M.
Influence of Sample Load Capacity on
Influence of Sample Load Capacity on
Counting Efficiency
Counting Efficiency
To determine the effect of maximum amount of sample, a set
To determine the effect of maximum amount of sample, a set
of 19 polyethylene vials were prepared by mixing the
of 19 polyethylene vials were prepared by mixing the
appropriate volumes of each possible combination of LS
appropriate volumes of each possible combination of LS
cocktail and sample solution with a known amount of a
cocktail and sample solution with a known amount of a
certified reference solution of
certified reference solution of 33H. H.
Sample solutions were prepared with
Sample solutions were prepared with DDWDDW. The volume of . The volume of sample solution in each series of vials increases in steps of
sample solution in each series of vials increases in steps of
1mL starting at 1mL in the first vial, up to 19 mL in the last
1mL starting at 1mL in the first vial, up to 19 mL in the last
one. Scintillation cocktail is finally added to obtain a final
one. Scintillation cocktail is finally added to obtain a final
volume of 20 mL.
volume of 20 mL.
E
Each vial was counted for 30 minutes and the resulting count ach vial was counted for 30 minutes and the resulting count rates were used to calculate the counting efficiency and
rates were used to calculate the counting efficiency and
relation between sample load
Background Count Rate and Figure of Merit
Background Count Rate and Figure of Merit
To obtain the FOM values for each scintillation cocktail, a set of
To obtain the FOM values for each scintillation cocktail, a set of
four polyethylene vials was prepared.
four polyethylene vials was prepared.
To eliminate the instrumental and other effects only one proper
To eliminate the instrumental and other effects only one proper
counting
counting channel intervalchannel interval was used to determine the observed was used to determine the observed count rates
count rates
E, B and FOM
Quench Resistance
Quench Resistance
Quenching is the most important factor responsible for a reduction in counting efficiency for a given sample/ cocktail mixture in LSC
Adding small quantities of CCl4 to the prepared standard samples showed the effect of quenching on the SQP.
All vials were counted for 30 minutes and the obtained count rates were used to calculate counting efficiencies.
Quench standard curve were plotted for each scintillation cocktail.
Sample Stability
Sample Stability
A possible reason for sample instability can be evaporation
A possible reason for sample instability can be evaporation
of solvent through the vial.
of solvent through the vial.
20 mL of each cocktail was transferred in both a glass and
20 mL of each cocktail was transferred in both a glass and
a polyethylene vial.
a polyethylene vial.
V
V
ials were then closed and stored in the sample changer
ials were then closed and stored in the sample changer
unit of the LSC and the weight of the vials
unit of the LSC and the weight of the vials
was recorded
was
recorded
over a period of two months
α/β Discrimination
α/β Discrimination
The discrimination of alpha and beta pulses is based on the
The discrimination of alpha and beta pulses is based on the
well-known difference between the delayed component of their
well-known difference between the delayed component of their
fluorescent decay.
fluorescent decay.
The working discriminator setting is chosen in such a way that
The working discriminator setting is chosen in such a way that
alpha spillover (τ
alpha spillover (ταα) and beta spillover (τ) and beta spillover (τββ) are both at a ) are both at a
minimum: minimum: T T
C
C
T
C
C
T
/
/
PSD
PSD depends to some extent on alpha and beta particles energy. depends to some extent on alpha and beta particles energy. PSA value depends on vial and scintillator type
PSA value depends on vial and scintillator type
PSA values were tried to determine for each scintillation cocktail
PSA values were tried to determine for each scintillation cocktail
by using glass vials.
by using glass vials. 241
241Am and Am and 3636Cl reference solutions were used as alpha and beta Cl reference solutions were used as alpha and beta
sources
sources..
For different PSA values between 40 and 150 optimum PSA
For different PSA values between 40 and 150 optimum PSA
values were obtained for each scintillation cocktail
Results and Discussion
Results and Discussion
Effects of Sample Load on Counting Efficiency
Effects of Sample Load on Counting Efficiency
The expected decrease in counting efficiency with increasing sample The expected decrease in counting efficiency with increasing sample load is caused by two different possibilities.
load is caused by two different possibilities. quenching and
quenching and
stability of the mixture. stability of the mixture.
If the sample to cocktail ratio exceeds the sample load capacity, a If the sample to cocktail ratio exceeds the sample load capacity, a sudden change in counting efficiency occurs
sudden change in counting efficiency occurs
Results and Discussion
Results and Discussion
Background Count Rate and Figure of Merit (FOM)
Background Count Rate and Figure of Merit (FOM)
Calculated FOM and measured background count rate values for different cocktails Calculated FOM and measured background count rate values for different cocktails
Cocktail FOM BG (cpm)
OptiPhase Hisafe-3 1101.84 0.816 Ultima Gold LLT 1334.63 0.885
Ultima Flo-M 242.60 0.920
Quench Resistance
Quench Resistance
Relationship between SQP and Eff
Sample spectrums for
3H spiked samples for
each cocktail
Results and Discussion
Results and Discussion
Results and Discussion
Sample StabilitySample Stability
The weighted values of each cocktailThe weighted values of each cocktail in both a glass and a polyethylene vials in both a glass and a polyethylene vials over time are listed
over time are listed in Table below in Table below. .
Weighted data shows that there is no significant loss for any of the cocktails in Weighted data shows that there is no significant loss for any of the cocktails in either glass or polyethylene vials.
either glass or polyethylene vials.
Elapsed
Time (Day) UF-M poly. UF-M glass HiSafe-3poly. HiSafe-3glass MO poly. MO glass UG poly. UG glass
1 18.081 24.471 18.051 24.629 18.018 24.552 17.956 24.642 5 18.079 24.469 18.048 24.623 18.018 24.549 17.955 24.639 10 18.075 24.469 18.044 24.623 18.012 24.548 17.951 24.639 15 18.077 24.467 18.043 24.624 18.011 24.548 17.952 24.637 20 18.074 24.464 18.044 24.625 18.009 24.545 17.954 24.638 25 18.075 24.464 18.043 24.625 18.010 24.546 17.951 24.638 30 18.073 24.461 18.044 24.626 18.011 24.543 17.949 24.637 40 18.070 24.460 18.042 24.625 18.008 24.544 17.950 24.636 50 18.067 24.456 18.041 24.621 18.002 24.540 17.948 24.633 60 18.065 24.453 18.039 24.620 18.001 24.540 17.945 24.629
Results and Discussion
Results and Discussion
α/β Discrimination
α/β Discrimination
PSA setting optimization was done and alpha and beta sources PSA setting optimization was done and alpha and beta sources were analyzed by LSC at different PSA settings.
were analyzed by LSC at different PSA settings.
The graph: spillover of alpha in beta and beta in alpha versus PSA The graph: spillover of alpha in beta and beta in alpha versus PSA setting was built. The lowest spillover gave the optimal PSA setting was built. The lowest spillover gave the optimal PSA setting. PSA setting optimization was done for each cocktail and setting. PSA setting optimization was done for each cocktail and the data are presented in the Table
the data are presented in the Table below. below.
Cocktail Optimal PSA setting OptiPhase HiSafe-3 110-120
Ultimagold LLT 90-100 Ultima Flo-M 120-130 Mineral Oil 30-40
