Use of Eichrom Resins for Bioassay Pa23

1
Use of Eichrom Resins for Bioassay Pa-231

• Bob Timm - GEL
• Tim Chandler - GEL
• Bill Burnett - FSU
• Mike Schultz - PerkinElmer Instuments, ORTEC

2
Outline

• What is Protactinium
• Pa-231 procedure development
• Conclusions

3
Protactinium

• Originally called "protoactinium", Pa is one of
  the rarest and most expensive naturally-occurring
  elements
• Pa-231 has a fast fission cross section nearly
  the same as 239Pu
• Pa(V) forms a very stable, water-soluble complex
  with fluoride
• Pa(IV) forms insoluble fluorides
• Two naturally-occurring isotopes 234Pa and 231Pa

4
Pa-231

• PARENT
• U-235 half-life 7x108 yrs decays to Th-231
• Th-231 half-life 25.52 hrs decays to Pa-231
• Pa-231 half-life 3.3x104 yrs
• DAUGHTER
• Ac-227 Actinium 100.0

5
History

• Method for Environmental developed by Burnett and
  Yeh. (1995)
• The earlier procedure was only concerned with
  interferences from naturally occuring
  radionuclides.
• A method for Bioassay was required. Bioassay
  samples could contain artificial radionuclides.
• Made the decision to try developing method using
  a single column method.

6
Development Objectives

• Try an analysis on TRU Resin and start
  determining corrective steps.
• Begin making corrections to procedure based on
  results of testing.
• Finalize procedure.

7
Load Solution for Test 1

• Perform a Ca(PO4) Precipitation on DI water
  containing Nat Th, Nat U, Pu-239, Am-241 and
  Pa-231.
• Followed procedure on next slide.

8
Test-1
2 mL 9M HCl
3
10 mL 2M HNO3
2
4
10 mL 4M HCL
1
20 mL 8M HNO3 - 1M Al(NO3)3
5
20 mL 0.1M HCl
Pa Elution 20 mL 0.1M HCL - 0.1M HF
6
1-4 (discard)
6
Th
(90-95)
5
Pa
9
Test 1 Results

• Only about 50 Protactinium recoveries with 100
  Plutonium and small amounts of Thorium (Up to
  10) visible in spectrum.
• Analyzed the fractions just before the
  Protactinium Elution and determined the remainder
  of the Protactinium was in the Thorium elution.

10
Test 2

• Decision made to elute Thorium with 1M HCL
  instead of 0.1M HCL to increase Protactinium
  recovery.
• Decision to use a TiCl3 solution to elute
  Plutonium when eluting Americium. Added 0.5 mL of
  TiCl3 to 20 mL of 4M HCL.
• Followed procedure on next slide.

11
Test-2
2 mL 9M HCl
3
10 mL 2M HNO3
2
20 mL 4M HCL - 0.5 mL TiCl3
4
1
20 mL 8M HNO3 - 1M Al(NO3)3
5
20 mL 1M HCl
Pa Elution 20 mL 0.1M HCL - 0.1M HF
6
1-4 (discard)
6
Th
(90-95)
5
Pa
12
Test - 2 Results

• Plutonium was separated as expected and
  Protactinium recoveries increased to near 90.
• We tested the procedure one additional time
  adding the same actinides as before but added
  Np-237 as well. Unfortunately Np-237 followed Pa
  through the procedure and gave a new challenge.

13
Test 3

• Added UTEVA column to remove Neptunium and
  provide additional Uranium and Thorium clean up.
• Load solution changed to 2.5M HNO3 / 0.1M Ferrous
  Sulfamate. Added 1 mL of 1.0 M Ascorbic Acid to
  reduce Fe. This is optimal for Neptunium (IV)
  retention on UTEVA while Protactinium stays in
  the 5 oxidation state.
• Followed procedure on next slide.

14
Test-3
2 mL 9M HCl
20 mL 2.5M HNO3 / 0.1 M FeS / Asc Acid
10 mL 2.5 M HNO3 (2x)
20 mL 4M HCL - 0.5 mL TiCl3
3
4
5
20 mL 1M HCl
1
2
6
Pa Elution 20 mL 0.1M HCL - 0.1M HF
2
1
1-5 (discard)
6
Pa
15
Test - 3 Results

• 80 to 90 of the Neptunium was removed by the
  UTEVA.
• We have not identified exactly why the Neptunium
  is not fully separated by the UTEVA resin. We
  have ruled out column overloading of any sort by
  adding a TEVA column to the sequence and still
  seeing Neptunium interferance.
• One possibility is phosphate interferance with
  Neptuniums retention on UTEVA. (see next slide)

16
Sensitivity to PO4
TRU.Resin
UTEVA.Resin
17
Test - 3 Results contd

• Another thought was to separate Neptunium using
  spectral separation.
• 84 of the energy lines can be used which do not
  have Neptunium interferance with them.

18
Spectral Separation of Np-237 from Pa-231
19
Oxalic Acid rinse

• Began testing to see if the separation of
  Neptunium and Protactinium on TRUResin was
  possible using oxalic acid.
• We loaded Neptunium and Protactinium onto a TRU
  Column and performed a rinse with 1M HCL/0.015 M
  Oxalic acid.
• Neptunium did not show up in the Protactinium
  rinse. We proceeded with Test-4.

20
Test-4
3
2 mL 9M HCl
10 mL 2M HNO3
2
4
20 mL 4M HCL - 0.5 mL TiCl3
1
20 mL 8M HNO3 - 1M Al(NO3)3
5
15 mL 1M HCl / 0.015 M Oxalic Acid
6
10 mL 1M HCl
7
Pa Elution 20 mL 0.1M HCL - 0.1M HF
(Pa)
7
1-6 (discard)
21
Test - 4 Results

• Tracer yields were 50 and spectrums were free
  of interfering actinides.
• Approximately 15 of the Pa tracer came off with
  the 10 mL rinse of 1M HCL. No other actinides
  were detected. This rinse can be combined with
  the Pa elution to obtain tracer yields of 65.
• The remaining Protactinium tracer came off with
  the oxalic acid rinse containing Neptunium.

22
Test 5

• Increased the molarity of HCL with the Oxalic
  acid rinse to 2M HCL. Our thought was that maybe
  the total volume of 1M HCL rinses was causing
  the Protactinium to elute early. The Thorium will
  still elute with the 2M HCL rinse.

23
Test-5
3
2 mL 9M HCl
10 mL 2M HNO3
2
4
20 mL 4M HCL - 0.5 mL TiCl3
1
20 mL 8M HNO3 - 1M Al(NO3)3
5
15 mL 2M HCl / 0.015 M Oxalic Acid
6
10 mL 1M HCl
7
Pa Elution 20 mL 0.1M HCL - 0.1M HF
(Pa)
7
1-6 (discard)
24
Test - 5 Results

• Tracer yields were 95. Spectrums had 1 of the
  Np-237 added. No other actinides were present.
• Two tests are currently in progress.
• a.) Increase the Oxalic rinse to 0.03M Oxalic
  acid.
• b.) Perform the oxalic acid rinse under HNO3
  conditions.

25
Conclusions

• Eichrom Resins can be effectively utilized to
  separate Protactinium from other actinides for
  alpha measurements.
• Np-237 if present may interfere. We can resolve
  this interference with spectral separation or by
  using an oxalic acid rinse.
• A Ce(OH) method of co-precipitation is necessary
  for alpha counting. Flouride co-precipitations
  will not work with Pa(V).