Rapid Method for Actinides in Seawater Samples

Sherrod L. MaxwellSenior Fellow Scientist

10-29-14

Need for Rapid Methods

• At a nuclear security summit in 2012, IAEA Director General Yukiya Amano stated:

“A dirty bomb detonated in a major city could cause mass panic, as well as serious economic and environmental consequences”

– “Mexico Finds Stolen Radioactive Material Amid Dirty Bomb Fears” http://www.voanews.com/content/nuclear-materia-stolen-in-mexico/1803195.html,12/4/13

• But there is still uncertainty as to what radioactive elements are actually being leaked in the water. “Most of the radioactive nuclei have been cesium and iodine,” said Horak. “But if you have actinides, the nastier and heavier elements like uranium and plutonium, that would be a whole other thing entirely.”

– “Japan to Spend Over $300M On 'Ice Wall' To Isolate Fukushima Water Leaks,” http://abcnews.go.com/Technology/japan-spend-300m-ice-wall-isolate-fukushima-water/story?id=20144627, 9/3/2013

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SRNL Approach

• Combine innovative sample preparation with rapid column extraction

• Water, air filters, soil, concrete, brick, vegetation, food, milk, fish, urine, feces, etc.

• Stacked cartridge technology• Sequential separation (5X faster than gravity flow)• Rapid flow rates

• Reliable, rapid methods are essential– Rapid assessment of radiological impact– Mitigate dose and protect the public and ecosystems– Maintain public trust

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Could we develop a rapid seawater method for actinides?

• Actinides in Seawater– Challenges– Large volume sample aliquots– Difficult matrix– Low MDA

• Typical preconcentration approaches– Fe (OH)2 ppt, multiple times with rinses– Mn ppt + Fe (OH)2 ppt– Up to 2 weeks, 30-60% chemical yields– Tedious and labor-intensive

• S. Maxwell et al, Rapid Determination of Radiostrontium in Seawater Samples, Journal of Radioanalytical and Nuclear Chemistry, 2013, 298:867-875

– Actinides??

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SRNL Actinides in Seawater Method

• Rapid, rugged, high chemical yields– <8 hours sample preparation– Uses Fe/Ti and LaF3 matrix removal steps• Ti+3 ensure tracer equilibration and valence control

• Reliable, rugged and rapid– Stacked TEVA+TRU cartridges (Pu, Np, U)– Stacked TEVA+DGA cartridges (Pu, Am, Cm)– TEVA cartridge (Pu, Np)

• Enhanced U removal for ICP-MS with DGA Resin

• Versatile– Can be used with alpha spectrometry, ICP-MS or AMS– Emergency or routine seawater samples

Maxwell S, Culligan B, Hutchison J, Utsey R and McAlister D, (2014) Rapid Determination of Actinides in Seawater Samples J Radioanal Nucl Chem, online March, DOI 10.1007/s10967-014-3079-0

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Simple and Fast

• Acidify seawater aliquot (up to 80-100 L)– Chemistry can likely be applied to larger aliquots

• Add tracers, La, Fe and Ti+3

• Adjust pH to 8.8-9.0 with NH4OH• Rinse Fe/Ti OH ppt with ~pH 8.8 water (larger aliquots)• Dissolve in HCl and precipitate LaF3 and CaF2 (removes Fe/Ti)• Load solution in nitric acid +boric acid +Al

– TEVA (Pu, Np) or TEVA+DGA (Pu, Am, Cm) or TEVA (Pu, Np) +TRU(U)

20L

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Rapid Separation for Pu, U, Np (8-10L)

Pu, U, Np by Alpha Spectrometry and/or ICP-MS in hours!

20 mL 4M HCl-0.2M HF 12 mL 10M HNO3

Discard Rinses

Column Load

Solution

TEVA +

TRU

5 mL 3M HNO3 10 mL 3M HNO3

Discard rinses

TEVA (Pu, Np)

TRU (U)

15 mL 9M HCl 5mL 3M HNO3 Discard Rinses

Elute Pu, Np 20 mL 0.1M HCL-0.05M

HF-0.01M TiCl3

Alpha spectrometry or *ICP-MS

Elute U 15 mL 0.1M ammonium

bioxalate

Alpha spectrometry or *ICP-MS

Split Cartridges

*ICP-MS: elute U with 0.01M ammonium

bioxalate or wet-ash with HNO3

*ICP-MS: Elute Pu/Np with 15 ml 0.05M HCl-0.005M HF-0.02M Hydroxlyamine Hydrochloride (HH), wet-ash or ….

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Pu-239 results using TEVA+TRU Method (8L)

Np-237 results using TEVA+TRU Method (8L)

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U-238 results using TEVA+TRU Method (8L)

U-236 can be assayed using AMS/ICP-MS

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80-100+ liter aliquots in <8 hours

80L La, Fe, Ti, NH4OH Settled ppt.

Centrifuge Each 40L: LaF3 Combine: 80L

Rapid Separation for Pu, Np, Am and Cm in Seawater

15 mL 3M HCl (Ca) 4 mL 1M HNO3

30 mL 0.05M HNO3 (La, Ca) 16 ml 3M HNO3-0.25M HF

(Th) 7.5 mL 3M HCl

Column Load

Solution

TEVA +

DGA

5 mL 6M HNO3 10 mL 3M HNO3

Discard rinses

TEVA (Pu)

DGA (3 mL) (Am, Cm)

15-20 mL 9M HCl 12 mL 3M HNO3

Discard Rinses

Elute Pu, Np 20 mL 0.1M HCL-0.05M

HF-0.01M TiCl3

Alpha spectrometry or ICP-MS

Elute Am 18 mL 0.25M HCL

Alpha spectrometry or ICP-MS

Split Cartridges

ICP-MS: U-238 removal very important

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Am, Cm and Cf on DGA resin

10-1 100 101100

101

102

103

104

105

106

Cf(III)

Am(III)

50-100 µm, 1 h contact time, 22(1)oC

k' on TODGA Resin vs. HCl

k'

[HCl], M

Cm(III)

10-1 100 101

101

102

103

104

105

106

Cf(III)

Am(III)

50-100 µm, 1 h contact time, 22(1)oC

k' on TODGA Resin vs. HNO3

k'

[HNO3], M

Cm(III)

Pu, Np results using TEVA (20L)

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Pu-239 results using TEVA+DGA Method (80L)

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Am-241 results using TEVA+DGA Method (80L)

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Cm-244 results using TEVA+DGA Method (80L)

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MDA alpha spectrometry - 16 hour count time

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MDA alpha spectrometry with 7 day count time

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Sr-90 (Y-90) in Seawater

• Rapid collection and purification of Y-90 in <8 hours from 40L• MDA for 90Sr of < 150 µBq/L using a 40 L aliquot and a 1000 minute count with gas

flow proportional counting

0

100

200

300

400

500

600

0 200 400 600 800 1000 1200

MDA

(µBq

/L)

Count Time (min)

MDA(µBq/L) for 40L Aliquotvs. Sample Count Time (min)

Assumes a Detector Background of 1.5 cpm

Maxwell, S., Culligan, B. , Utsey, R. , Hutchison, J. and McAlister, D. Rapid determination of 90Sr in seawater samples, J Radioanal Nucl Chem (Aug. 2014) DOI 10.1007/s10967-014-3391-8

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Summary

• SRNL has developed new rapid method for actinides in seawater samples• Rapid, rugged, high chemical yields

– <8 hours sample preparation– Uses Fe/Ti and LaF3 matrix removal steps– High chemical yields from 80L aliquots o can likely be extended to 100L + aliquots

– Flexible stacked resin cartridge methods– Can use alpha spectrometry or ICP-MS (or AMS)

• Reliable, rapid methods are essential– Rapid assessment of radiological impact– Mitigate dose and protect the public and ecosystems– Maintain public trust

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