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4. September 2013 PSI, 4. September 2013 PSI,

Paul Scherrer Institut

Comparison of the Tricarb and Hidex 300 SL technique using

measurements for 241Pu and 90Sr for diverse samples

Maya Jäggi

Question

-Can we use the Hidex 300 SL for routine measurements, concerning 241Pu and 90Sr

Comparison

Hidex 300 SL with guard-

function and Anti-Coincidence

LSC-Detector with BGO-Anti-

Coincidence

Outline

-90Sr activity determination using the Two-window method (Tricarb/Hidex)

-soil samples

-sediment samples

-241Pu activity determination using the / separation mode (Tricarb/Hidex)

-radioactive slurry samples

-IAEA-375 soil sample

-Summary

Two-window LSC technique for 90Sr

-Two windows are set for Hidex 300 SL using the tracers 85Sr and 90Sr (also for Tricarb)

-90Sr is in equilibrium with 90Y and must be separated by Sr-resin (Triskem) and measured

separately

-The figure below shows the three necessary radionuclides and the blank to determine the two

windows

0

100

200

300

400

500

600

700

800

900

1000

0

41

82

123

164

205

246

287

328

369

410

451

492

533

574

615

656

697

738

779

820

861

902

943

984

Counts

Channel

Beta-Backgr

Beta-S-90

Beta-Y-90

Beta-Sr-85

260 705 853

Three-window LSC technique for 90Sr

-The efficiencies per radionuclide and window are determined by dividing the counts per

second (total counts minus background) by the total activity [Bq]

efficiency Sr-85 Sr-90 Y-90

(normal count m.)

window A 0.605 0.103 0.016

window B+C 0.077 0.910 0.963

Hidex

0.995 0.913 0.077 window B+C

0.002 0.071 0.580 window A

(normal count m.)

Y-90 Sr-90 Sr-85 efficiency

Tricarb

E2/B

FOM

440 440/423 429/412 Tricarb: window A+B+C: sed/soil

505/496 540/534 Hidex: window A+B+C: sed/soil

Y-90 Sr-90 E2/B

4. September 2013 PSI,

90Sr in soil samples

4. September 2013 PSI, Seite 7

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Act

ivit

yco

nce

ntr

atio

n [

Bq

/kg]

Soilsamples

Soilsamples: Tricarb - Hidex

Sr-90-Tricarb

Sr-90-Hidex

4. September 2013 PSI,

90Sr in soil samples

4. September 2013 PSI, Seite 8

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

Act

ivit

yco

nce

ntr

atio

n [

Bq

/kg]

Samples

Soilsamples: Tricarb-Hidex

Sr-90 Tricarb

Sr-90 Hidex

4. September 2013 PSI,

90Sr in sediment samples

4. September 2013 PSI, Seite 9

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

KL10-5-24 KL10-5-25 KL10-5-29 KL10-5-30 KL10-5-36 KL10-5-40 KL10-5-44 KL10-5-45 KL10-5-51 KL10-5-52

Act

ivit

yco

nce

ntr

atio

n [

Bq

/kg]

Sedimentsamples

Sedimentsamples: Hidex - TriCarb

Sr-90-TriCarb

Sr-90-Hidex

Tschernobyl

The 70ties

Bomb fallout 60ties

* * * * * * * * *

* The value is below the calculated detection limit

4. September 2013 PSI,

90Sr in sediment samples

4. September 2013 PSI, Seite 10

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

Act

ivit

yco

nce

ntr

atio

n [

Bq

/kg]

Sedimentsamples

Sedimentsamples: Hidex - TriCarb

Sr-90-TriCarb

Sr-90-Hidex

Tschernobyl

The 70ties

Bomb fallout 60ties

* * * * * * * * *

Thoughts about the difference in 90Sr activities:

-aging of the cocktail between two measurments (first Tricarb, then Hidex)

-not optimized window-settings (however the background must also be adjusted)

-Tricarb values seem to be ok, since another lab (ICPMS) found also 4 Bq/kg 90Sr for the fallout

samples

-The FOM is higher for the Hidex, thus the instrument should be more sensitive

4. September 2013 PSI,

Hidex/Tricarb-241Pu: /-Separation – pulse shape – discriminator

4. September 2013 PSI, Seite 11

20 40 60 80 100 120 140 1600

200

400

600

800

1000

1200

alpha-pulse

beta-pulse

rela

tive inte

nsity

pulse decay time [ns]100 110 120 130 140 1500

2

4

6

8

10

12

14

in in

sp

illove

r [%

]

discriminator setting [ns]

Scintillator: Ultima Gold A/B – optimises the difference in alpha-pulse/beta-pulse.

Scintillator: Ultima Gold F – optimises the peak resolution of the /-emitters.

Discriminator

Hidex 300 SL: Pulse shape theory

PLI = Pulse-decay / Pulse-increase

ns

Rel

ativ

e in

ten

sity

4. September 2013 PSI,

Hidex: /-Separation – PLI – ygain

4. September 2013 PSI, Seite 13

PLI

(Pulse length index)

ygain

Background

HL-slurry sample

Alpha

Beta

3D

Plot

4. September 2013 PSI,

241Pu: Efficiency-Curve-Hidex, Quench-Curve-Tricarb, E2/B

4. September 2013 PSI, Seite 14

y = 1.0017x - 0.0395 R² = 0.9967

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.1 0.2 0.3 0.4

Eff

icie

ncy

Pu

-241

TDCR

Efficiency

y = -7E-07x2 + 0.001x - 0.0139 R² = 0.9988

0.25

0.26

0.27

0.28

0.29

0.3

0.31

0.32

0.33

0.34

0.35

350 450 550 650

Eff

icie

ncy P

u-2

41

tSIE

Efficiency Pu-241

Samples

Parameter

Rad. Slurry

Hidex (n=10)

Rad. Slurry

Tricarb (n=10)

Soil-samples

Hidex (n=6)

Soil-samples

Tricarb (n=6)

Efficiency [%] 47 34 36 34

Background CPM 9.6 3.2 9.7 3.6

E2/B - FOM 239 ± 36 362 ± 1 134 ± 8 312 ± 1

4. September 2013 PSI,

241Pu in radioactive slurry samples 1

4. September 2013 PSI, Seite 15

0

200

400

600

800

1000

1200

1400

1600

1800

2000

HL-1 HL-2 HL-3 HL-4 HL-5 HL-6 HL-7 HL-8 HL-9 HL-10

Pu

-24

1 A

ctiv

ityc

on

cen

trat

ion

[B

q/k

g]

Radioactive slurry samples

Pu-241: TriCarb - Hidex

Tricarb 1

Tricarb 2

Hidex 300 SL

4. September 2013 PSI, 4. September 2013 PSI, Seite 16

0

20

40

60

80

100

120

140

160

180

200

HL-1 HL-2 HL-3 HL-4 HL-5 HL-6 HL-7 HL-8 HL-9 HL-10

Pu

-24

1 A

ctiv

ityc

on

cen

trat

ion

[B

q/k

g]

Radioactive slurry samples

Pu-241: TriCarb - Hidex

Tricarb 1

Tricarb 2

Hidex 300 SL

241Pu in radioactive slurry samples 2

4. September 2013 PSI,

241Pu for the IAEA-375 soil sample

4. September 2013 PSI, Seite 17

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

1 2 3 4 5 6

Pu

-24

1 A

ctiv

ityc

on

cen

trat

ion

[B

q/k

g]

IAEA-375 samples

IAEA-375: TriCarb - Hidex

IAEA-375-Tricarb

IAEA-375-Hidex

-The activityconcentrations were backcalculated to 1991 (sampling of the IAEA-standard)

4. September 2013 PSI, 4. September 2013 PSI, Seite 18

Summary

- 90Sr shows good agreement, even at low level measurments (sample weight 30 g; low

detection limit).

- The lower the sample weights of the sediments (6 – 8 g) the higher the fluctuations between

the single 90Sr measurements and the higher the detection limits.

- The Hidex 300 SL is not an absolute low level instrument, however, what really accounts for

the discrepancies of 90Sr activities in the sediments, could not be found.

- For the measured 241Pu samples we find very good agreement for both instruments. All

samples have been corrected for Quench and thus the efficiency has been adjusted.

- The FOM for 90Sr is 22%, and for 90Y 14% higher for the Hidex compared to theTricarb.

- The FOM of 241Pu is 34% (radioactive slurry) and 57% (soil samples) lower for the Hidex,

compared to the Tricarb. Eventhough the Hidex shows higher efficiencies in both cases, the

high beta-background (three times higher than the Tricarb) causes this difference.

Question

-Can we use the Hidex 300 SL for routine measurements, concerning 241Pu and 90Sr

Answer: Yes!

But…low weight, low level measurements might be

excluded

4. September 2013 PSI, 4. September 2013 PSI, Seite 20

Mein Dank geht an

Thanks to Jost Eikenberg for discussion…

…and to you for your attention