be it doesn’t always mean that it is be · what 7be is used for blake et al. (1999) applied...
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If it looks like 7Be and says it’s 7Be it doesn’t always mean that
it is 7Be
Robert Hardy
Jackie Pates
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Overview
• Context of the work
– 7Be as a environmental tracer
• Data that was recorded
– Looking good
– Wait that can’t be 7Be…
• What was really measured
– The mystery nuclide
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7Be Production
7Be N2 O2
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What 7Be is used for
Blake et al. (1999) Applied Radiation and Isotopes. 51, 599–605
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Clean-up of Tracer
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Gamma spectrum
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Resin binding experiments
• Used tracer to investigate how “Be” binds under different acid concentrations
Horwitz and McAlister (2005) Solvent Extraction and Ion Exchange. 23, 611-629
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“Let’s just check”
Recounted vials after ~300 day. All Be should be gone
Some 54Mn in tracer so recounted to assess 54Mn contribution to count rate
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It’s not 7Be but what is it? Let’s make a model
When optimised model includes NO Be and half-life of X of ~340 days
Model Variables: Counts of Be, Counts of X, Half-life of X
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Possible candidates
Searched every element with half-life 300-360 days
Element Z N Decay Half-life (days)49V 23 26 ε 330
54Mn 25 29 ε+β+, β- 312.3
145Sm 62 83 ε 340
248Cf 98 150 α, SF 333.5
249Bk 97 152 β-,α, SF 320
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Back to Gamma Spectroscopy 145Sm, 61 keV, 12%
54Mn, 835 keV, 99%
7Be, 477 keV, 10%
49V no gamma
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Conclusion
• 7Be not easily detected with LS
– Counting efficiency too low
• Contamination may be present
– Issues with safety
• What are you really handling/disposing of
– Calibration problems
• Counting efficiency
RH funded by studentship from NERC and ACTF Resins supplied by Steffen Happel (Triskem)