Comparing Measurement Methods for 226Ra on Mnfiber A quantitative comparison between Rn Emanation Li

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Comparing Measurement Methods for 226Ra on
Mn-fiberA quantitative comparison between
Rn Emanation
Line (Lucas Cell), RAD7,
RaDeCC, and g-spectrometry techniques

• Richard Peterson, William Burnett, Natasha
  Dimova, and Isaac Santos
• Department of Oceanography, Florida State
  University, Tallahassee, Florida, 32306 USA

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Oceanographic Uses of 226Ra
Mn-fiber
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Oceanographic Uses of 226Ra
Yellow River Delta
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Oceanographic Uses of 226Ra
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Traditional 226Ra Measurements

• Acid leach of 226Ra from fibers
• Co-precipitation of 226Ra
• Transfer to
  g-spectrometer
• Time-consuming counting
  procedure

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General Approach

• Seal Mn-fiber in air-tight cartridge
• Allow 1 T1/2 for 222Rn ingrowth from the 226Ra
  on the fiber
• Mount the cartridge directly to the air loop of a
  measurement system
• Transfer the built-up 222Rn into the measurement
  system for quantification

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Cartridge Design

• 15 cm long 1 ¼ clear PVC
• End cap
• 1 ¼ PVC union with O-ring
• Plug
• 2 brass ¼ MNPT x ¼ barbed ball valves

• One can use a leak test to ensure air tight

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RAD7 Method

• Must measure background 222Rn in carrier gas
  prior to measurement
• Use carrier gas to evenly distribute built-up
  222Rn in cartridge throughout air loop
• Measure 222Rn in air loop for 15 hours
• Alpha detector in RAD7 measures 222Rn activity
  concentration

Procedure adopted from Dimova et al., 2007.
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Rn Emanation Line Method

• Count Lucas cell background
• Quantitatively transfer built-up 222Rn from
  cartridge to cold trap
• Transfer cold trap 222Rn to Lucas Cell, then
  allow 3 hours for daughter ingrowth
• Count total 222Rn on PMT for 1 hour

Procedure from Mathieu et al., 1988

Stringer and Burnett, 2004.
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RaDeCC Method

• A large Lucas Cell
• Use pump and He carrier gas to distribute
  built-up 222Rn throughout air loop
• Seal for daughter ingrowth (3 hours)
• Count for 4 hours with delayed coincidence
  counting software

Procedure adopted from Waska et al., 2008.
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Gamma Spectrometry Method

• Ash Mn-fiber in muffle furnace (550C, 6 hours)
• Cover with epoxy, store for 21 days
• Count for 2 days on our gamma spectrometer
• Analyze peaks at 295.1, 351.9, and 609.3 keV to
  quantify 226Ra
• IG Detector with a relative efficiency of 20
  calibrated to various IAEA Mn-fiber standards

Procedure and figure from Dulaiova and Burnett,
2004.
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East Japan Sea Sample Set
Error bars represent average 1-s measurement
uncertainties
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Method Parameter Comparison
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Relative Uncertainty
MDA
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So, what is the best method for measuring 226Ra
on Mn-fiber?
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Acknowledgements

• Guebuem Kim, Hannelore Waska
• Supplied sample set
• Dave Oliff
• Assisted in construction of cartridges
• Mark Peterson
• Helped run standards, samples

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East Japan Sea Sample Set
Error bars represent standard deviation of 2
measurements
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Rn Emanation Line Sparging Time
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RAD7 Sparging Time
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RaDeCC Sparging Time
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Mn-fiber Emanation