Optimizing Radiochemical Methods at SRS (Ni-63, I-129, Actinides)

Sherrod L. Maxwell, III

Westinghouse Savannah River Company

Recent Improvements

• Ni-63 in water method– increase Ni Resin capacity for gravimetric recovery

• I-129 in water method– adapt to vacuum box for rapid flow

• Actinides– TEVA+ TRU for waters, air filters, vegetation, soils

• Pu+Np in same fraction

• Less Th and Po-210 problems

• New soil method

– Alpha resolution: Am/Cm and Th w/o ashing

Ni-63 in Water• Ni resin columns limited in Ni capacity (3 mg )

– Need more Ni capacity for reliable gravimetric carrier recovery

– Ni carrier limited to ICP levels

– Ni-dimethylglyoxime complex bleeds off resin

• Adjust pH to 10 instead of 8-9 for higher retention

• Added prefilter cartridge to catch bleed-off

• Can use up to ~10 mg Ni carrier

• Used 8 mg Ni carrier: 10.21 mg NiO

Ni-63 in Water

Evaporation

Sample loading

Load complete, Ni complex color at bottom of column

During column rising:Ni complex bleed-off caught on prefilter cartridge

Ni column stripping Evaporate/ash

NiO

Ni Cartridge Option

Ni Resin cartridges instead of columns +disposable reservoirs

10 mg Ni carrier

Ni-63 Method Data

LCSSMP-1SMP-2 DUPSMP-3 MSSMP-4SMP-5 MSSMP-6SMP-7 MSBLK

300 mL groundwater samplesNi-63 Spk= 50 pCi Ni carrier = 10.21 mg NiO NiO

Recovery

99.9 %98.9 %98.9 %97.9 %101.9%99.9 %97.4 %98.9 %98.9 %

Ni-63 Spk Recovery

92.0 %

97.2 %

89.5%

90.4 %

avg = 92.3 % (3.4% rsd)

I-129 Method

• 1 pCi/L MDA; 1.5 liter samples• pH adjust /reduce to iodide ion with NaHSO3• Anion exchange-1X8, 100-200 mesh• Flow rate ~25 mL/min• Vacuum box loading with inner liner

– ~ 1 to 1.5 hour loading

– speed & ability to deal with slow samples

• Resin to petri dish• Low energy x-ray

I-129 Method Data

Typical batch of 1.5L samples

I-129 Standard Added Measured

LCS =16.7 pCi/L 15.5 pCi/L

MS = 16.7 pCi/L 16.0 pCi/L

% Recovery LCS 93%

% Recovery MS 96%

TEVA-TRU Separations(Pu, Np, Am, Cm, U)

Alpha Resolution Improvements

• Resolve™ filters-Eichrom– reduced FWHM, from about 50-60 keV to about 40-50 keV– eliminated a lot of filter problems and rework from “bad” lots of

filters from other suppliers

• Strong HCl causes more extractant bleed-off– added small, 3M nitric rinse after strong HCL Th removal and

before Pu strip from TEVA– added small, 3M nitric rinse after strong HCL Th removal and

before U strip from TRU Resin

• What about Am-Cm and Th strong HCl solutions containing organic?– Had tried Am/Cm micro-precipitation from 4M HCL with extra

HF and no ashing but too often had poor resolution/rework

Alpha Resolution Improvements

• Am/Cm and Th HCL strip solutions contain organic bleed-off that can affect alpha peak resolution

• Ashing takes time– Th samples (3-4 hrs) and Am/Cm samples (2-3 hrs)– Prolongs sample preparation

• Solution:– Use prefilter cartridges when stripping Th or Am/Cm– No ashing required– Dilute Am/Cm to 30 mL with water + 3mL con HF– Dilute Th to 45 mL + 5 mL con HF

Resolution with Filters from “Bad” Lot

Resolution with RESOLVE ™ Filters

Resolve Filters-No Ashing

Resolve Filters-No Ashing

Summary

• Ni Resin– Ni capacity expanded using prefilter resin– gravimetric carrier

• I-129 method-vacuum box– reduced loading times

• TEVA-TRU Separations for all matrices– Eliminated cerium fluoride filter problems – Am/Cm and Th alpha resolution-no ashing/prefilter

cartridge